تخصص هندسة أجهزة الطبية د.نعمان النجار كلية العلوم والهندسة تخصص هندسة أجهزة الطبية الكترونيات حيوية و قياسات (1) إعداد د. نعمان النجار Dr.Eng. Noman AL Najjar Noman_qaed@yahoo.com Qualification : - PhD in biomedical engineering

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Biomedical sensors Chapter 5: Biomedical sensors Outline Introduction & concepts Biomedical sensor using &tech nology Measurements biosystem Optical Measurements are used in biomedical sensors Physical measurements Physiological Transducers Displacement –Inductive –Resistive –Capacitive –Ultrasonic Air flow Temperature Chemical measurements Chemical sensors Oxygen Sensors Transcutaneous pO2 pH electrode ------------ cont.

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Chapter 5: Biomedical sensors cont. Outline ------------------------ CO2 Sensors- The carbon dioxide electrode Transcutaneous carbon dioxide sensor Other Physical Sensors The oximeter catheter system Cardiac output measured by thermodilution Biosensors – Major applications for biosensors -Biosensing Principles Biosensor-Enzymatic biosensors Biosensor -Immunosensors Biosensor -SPR biosensors Biosensor - BIACORE biosensors Biosensor -Fiber optic based biosensors Biosensor - Chemical sensors based biosensors Optical biomedical sensors-Fiber Optics Optical biomedical sensors-Radiation Sources & sensors Pressure Sensors Silicon Pressure Sensors Ultra Low Pressure Sensing Capacitive Pressure Sensors Other Pressure Sensors References

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية د.نعمان النجار Biomedical sensors Introduction • Transducer is a device that converts energy from one form to another • In sensors, a transducer converts an observed change into a measurable signal • Integrated with other parts to “read” out the signal (electrically, optically, chemically) • Some are used in vivo to perform continuous, invasive or non-invasive monitoring of critical physiological variables – pressure, flow, concentration of gas • Some are used in vitro to help clinicians in various diagnostic procedures – electrolytes, enzymes, metabolites in blood concept • in vivo: inside a living body (human or animal) • ex vivo: outside the living body • in vitro: in a test tube • in situ: right in the place where reactions happen (could be in the cells, tissue, test tube , etc.)

Biomedical Sensor Issues in developing a biomedical sensor كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Biomedical Sensor Issues in developing a biomedical sensor 1- Configuration 2- Supply of power 3- Individual sensing of variables 4- Processing of different signals 5-Interconnection to the other modules in the system 6- Manufacturing Biomedical Sensor technology Use of microelectronics Electronic components are incorporated into sensors for signal processing and conversion Use of Optical devices calorimetry, spectrophotometry principles are used to develop biomedical sensors based on optoelectronic systems

Biomedical sensor using force sensors كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Biomedical sensor using force sensors 1- Used to measure force required for grasping at the thumbs and finger tips 2- Sensor based upon variable capacitance priniciple 3- Used in spinal cord injury patients 4- Sensor used as a feedback element in a closed loop control system. Trends in biomedical sensors Key technologies for miniaturization of biomedical sensors and realization of biochips: microfluidics, semiconductor fabrication processes, microelectro mechanical systems (MEMS) Equally important are: the development of more stable and effective biomolecules used for recognition; search for new target analytes that are of diagnostic and/or biological significance

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Measurements biosystem What are the Transduers, Sensors, and Actuators? Transducer is a device that converts energy from one form to another • In principle, Transducers are devices that convert signals in one form of energy into signals in another form of energy. • Sensors • Actuator • Conventional v.s. Intelligent Transducers Transducer - A device that converts energy of one form to another. • Sensor - A device that converts a physical parameter to an electric output. • Actuator - A device that converts an electric signal to a physical output.

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Measurements biosystem

تخصص هندسة أجهزة الطبية د.نعمان النجار كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Measurements biosystem What are the Transduers, Sensors, and Actuators?

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Measurements biosystem Three types of output signal 1- Self-generating (active) transducers: – The electrical signal output of transducer is generated from another form of input energy. 2- Modulating (passive) transducer: – The input signal energy of transducer is used to modulate the electrical energy flow from the power supply to the transducer output. 3-Tandem transducers: – The original input signal energy is converted to a final output of electrical energy through two or three effects or conversions in tandem.

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Measurements biosystem

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Measurements biosystem Physical Quantities for Measurement • Displacement measurement – Resistive sensors: Potentiometers, Strain gages, and Bridge circuit – Inductive sensors: Self-inductance, Mutual inductance, and Differential transformer (LVDT) – Capacitive sensors – Piezoelectric sensors: Piezoelectric effect • Temperature measurement – Thermocouples: Thermoelectric effect (Discovered by Seebeck in 1821), Peltier effect, Thomson effect, • Three empirical thermocouples laws: Homogeneous circuits, Intermediate metals, Successive (Intermediate temperature) – Thermistors – Radiation thermometry – Fiber-optic temperature sensor

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Optical Measurements are used in biomedical sensors Optical Measurement – Optical systems are widely used in medical diagnosis, especially in clinical-chemistry lab. – Application example: Blood or tissue sample analysis, oxygen saturation of hemoglobin, cardiac output. – Radiation sources: Tungsten lamp, Arc discharges, LEDs, LASERS Figure : General block diagram of an optical instrument. Highest efficiency is obtained by using an intense lamp, lenses to gather and focus the light on the sample in the cuvette, and a sensitive detector. Solidstate lamps and detectors may simplify the system.

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Optical Measurements are used in biomedical sensors Light sources and detectors Sources Incandescent bulb Light emitting diode (LED) Gas and solid state lasers Arc lamp Fluorescent source Detectors Thermal detector (pyroelectric) Photodiode Phototransistor Charge-coupled device (CCD) Photoconductive cell Photomultiplier tube

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Optical Measurements are used in biomedical sensors Absorption/Fluorescence Different dyes show peaks of different values at different concentrations when the absorbance or excitation is plotted against wavelength. Phenol Red is a pH sensitive reversible dye whose relative absorbance (indicated by ratio of green and red light transmitted) is used to measure pH. HPTS is an irreversible fluorescent dye used to measure pH. Similarly, there are fluorescent dyes which can be used to measure O2 and CO2 levels.

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Physiological Transducers ناقل الطاقة الفسيولوجي (كهر وحيوي) - CLASSIFICATION OF TRANSDUCERS The transducers can be classified in many ways, such as: (i) By the process used to convert the signal energy into an electrical signal. For this, transducers can be categorized as: Active Transducers—a transducer that converts one form of energy directly into another. For example: photovoltaic cell in which light energy is converted into electrical energy Passive Transducers —a transducer that requires energy to be translate changes due to the measured. For example: a variable resistance placed in a bridge in which the voltage at the output of the circuit reflects the physical variable (ii) By the physical or chemical principles used. For example: variable resistance devices and optical fiber transducers.(ادوات المقاومةِ المتغيّرةِ ناقل الطاقة ذو الليف ضوئيةِ ) (iii) By application for measuring a specific physiological variable. For example: flow transducers, pressure transducers, temperature transducers,

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Physiological Transducers ناقل الطاقة الفسيولوجي (كهر وحيوي) - 1-Dsplacement transducers: 1- 1. Linear Variable Differential Transformer (LVDT) or Inductive Sensors The primary coil P is excited by an AC current. The induced potentials at the 2 secondary coils are canceled due to the opposite polarities. When the core moves toward one coil, the induced potential in the coil increases and the voltage in the other coil decreases An LVDT is used as a sensitive displacement sensor: for example, in a cardiac assist device or a basic research project to study displacement produced by a contracting muscle. Taken from http://www.pages.drexel.edu/~pyo22/mem351-2004/lecture04/pp062-073lvdt.pdf

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Physiological Transducers ناقل الطاقة الفسيولوجي (كهر وحيوي) - 1-Dsplacement transducers: 2- 1. Resistive Sensors - Potentiometers Potentiometer: resistance is proportional to position . If the current through the resistor is constant, the displacement (linear o angular) will be proportional to Taken from www.fyslab.hut.fi/kurssit/Tfy-3.441/ luennot/Luento3.pdf

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Physiological Transducers ناقل الطاقة الفسيولوجي (كهر وحيوي) - 1-Dsplacement transducers: 3- 1. Strain gauge Measures a small change in the length of an object as a result of an applied force. Resistance of a conductive materiel with length / and cross-sectional area A. p is a constant (resistivity) The fractional change in length of an object is called strain Now consider a metal wire as a strain gauge For silicon strain gauges, G > 100 (much more sensitive than metal) Taken from www.fyslab.hut.fi/kurssit/Tfy-3.441/ luennot/Luento3.pdf

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Physiological Transducers ناقل الطاقة الفسيولوجي (كهر وحيوي) - 1-Dsplacement transducers: 3- 1. Strain gauge The types of Strain Gauge Pressure Transducers: a).Unbonded Strain Gauges: Most of the pressure transducers for the direct measurement of blood pressure are of the unbonded wire strain gauge type. The arrangement consists of strain wires of two frames which may move with respect to each other. مقاييس الإجهادِ الغير المرطبِتة: مِنْ هذا النوع هو أغلب ناقلي الطاقة للضغطِ الذي يقوم بقياسِ مباشرِ لضغطِ الدمّ. تتركب بالترتيبُ- من أسلاكِ الإجهادِ ْذات الإطارين التي يمكن ان يتحرّكانِ حركة تتعلق ببعضهم البعض. Taken from www.fyslab.hut.fi/kurssit/Tfy-3.441/ luennot/Luento3.pdf

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Physiological Transducers ناقل الطاقة الفسيولوجي (كهر وحيوي) - 1-Dsplacement transducers: 3- 1. Strain gauge The types of Strain Gauge Pressure Transducers: b). Bonded Strain Gauges: The bonded strain gauge consists of strain-sensitive gauges which are firmly bonded with an adhesive to the membrane or diaphragm whose movement is to be recorded. In practice, it is made by taking a length of very thin wire (for example, 0.025 mm dia) or foil which is formed into a grid pattern (Fig. 3.7 a,b) and bonded to a backing material.

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Physiological Transducers ناقل الطاقة الفسيولوجي (كهر وحيوي) - 1-Dsplacement transducers: 3- 1. Strain gauge The types of Strain Gauge Pressure Transducers: C). Silicon Bonded Strain Gauges: Lead wire resistance and capacitance change with temperature. Compensation for temperature variation in the leads can be provided by using the three lead method. In this method, two of the leads are in adjacent legs of the bridge which cancels their resistance changes and does not disturb the bridge balance. The third lead is in series with the power supply and is, therefore, independent of bridge balance. Diffused p-type strain gauge

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Physiological Transducers ناقل الطاقة الفسيولوجي (كهر وحيوي) - 1-Dsplacement transducers: 4- 1.Capacitive Sensors ( Electrolytic or ceramic capacitors are most common) : change in distance between two parallel plates (an insulating material sandwiched in the middle) results in a change in capacitance A: area d: distance between two conductors where ε0 is the permittivity of vacuum = 8.85×10-12 F/m εr is dielectric constant of the insulating material e.g. An electrolytic capacitor is made of Aluminum evaporated on either side of a very thin plastic film (or electrolyte).

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Physiological Transducers ناقل الطاقة الفسيولوجي (كهر وحيوي) - 1-Dsplacement transducers: 5- 1. Piezoelectric Transducers (PZT) ناقل طاقة ذوإجهاد كهربائي - The piezo-electric effect is a property of natural crystalline substances to develop electric potential along a crystallographic axis in response to the movement of charge as a result of mechanical deformation (التأثيرَ الكهربائي الاجهادي ذو الخاصية الطبيعية لموادِ البلّوريةِ ينمي جهد كهربائي على طول محور المادة البلورية كردّ او استجابة لشحن حركي ناتخ عن تشويهَ ميكانيكيَ.). Thus, piezoelectricity is pressure electricity. On application of pressure, the charge Q developed along a particular axis is given by Q = kF coulomb ((وحدة قياس كمية كهربا where k is the piezoelectric constant (expressed in Coulombs/Newton, i.e. C/N) and F is the applied force. The Piezoelectric Effect ) principle) The principle of operation is that when an asymmetrical crystal lattice is distorted, causing a relative displacement of negative and positive charges. إنّ مبدأَ العمليةِ بأنّ المشبّكِ بلّوريِ لا مُتماثلِ يشوّهُ(يتعرض لضغط خارجي)،هذا يسبّب إزاحة نسبية للشحن السلبة والإموجبة. هذه الإزاحة تترجم الي إشارات كهربائية لغرض القياس.

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Physiological Transducers ناقل الطاقة الفسيولوجي (كهر وحيوي) - 2-The Scand type -Flow Sensors Flow : the motion of a fluid (1) Blood flowmeters : - ultrasonic (doppler, transit time) - electromagnetic (2) Gas flowmeters : - pneumotachometer - spirometer - Wright's respirometer - rotameter ball float meter Flow rate : (1) mass flow rate : mass transferred per unit of time (ex:[kg/sec]) (2) volumetric flow rate : volume of material transferred per unit of time(ex:[cc/sec]) (3) Total flow or flow volume : integration of flowrate

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Physiological Transducers ناقل الطاقة الفسيولوجي (كهر وحيوي) - 2-The Scand type - Air flow 1-1.Fleish pneumotachometer This measures the flow rate of gases during breathing. The breath is passed through a short tube (Fleisch tube) in which there is a fine mesh which presents a small resistance to the flow. --The screen obstruction provides some resistance to the air flow and therefore generates pressure drop across the screen. -The resulting pressure drop across the mesh is in proportion to the flow rate. -The pressure drop is very small (e.g. 2 mmHg) and so the measuring circuit must be of high quality and produce very little drift with time. Fleisch tube : It consists of a wide bore tube in which there is a mesh or screen which slightly restricts the airflow through it. The resistance to flow presented by the screen produces a differential pressure which is proportional to the airflow through the device. Spirometer : These measure the volumes of gases breathed in or out. They are usually displacement (bell) devices, a bellows, or a small turbine device with gears to drive a pointer Flow rate ∝ ΔP Pressure is measured at both sides of the resistive screen

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Physiological Transducers ناقل الطاقة الفسيولوجي (كهر وحيوي) - 2-The Scand type 2-2.Electromagnetic Blood Flowmeter :Faraday's principle of electromagnetic induction can be applied to any electrical conductor (including blood) which moves through a magnetic field. This probe applies an alternating magnetic field (typically at 400 Hz) across the vessel and detects the voltage induced by the flow via small electrodes (microvolt region) in contact with the vessel. where B = magnetic flux density, T L = length between electrodes, m u = instantaneous velocity of blood, m/s

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Physiological Transducers ناقل الطاقة الفسيولوجي (كهر وحيوي) - 2-The Scand type Apply a uniform magnetic field B across blood vessel If velocity of blood flow is v, F is force experienced by charged particles in blood This force causes movement of charges ⇒ distribution of charges generates an electric field E For charged particles, there is a second force qE, at equilibrium: 2-2.Electromagnetic Blood Flowmeter :Blood flow

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Physiological Transducers ناقل الطاقة الفسيولوجي (كهر وحيوي) - 2-The Scand type 3-2.Ultrasonic Blood Flowmeter (1) transit time methods in which the blood velocity is calculated from the time taken to cross the vessel oblique to the direction of flow. (2) The most practical form of ultrasonic blood flowmeter is the continuous wave doppler system with the doppler-shifted components being fed to a zero-crossing detector. Forward and reverse flow is represented by the doppler- shifted components above and below the ultrasonic frequency. Transit Time

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Physiological Transducers ناقل الطاقة الفسيولوجي (كهر وحيوي) - 2-The Scand type 3-2.Ultrasonic Blood Flowmeter

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Physiological Transducers ناقل الطاقة الفسيولوجي (كهر وحيوي) - 2-The Scand type -Flow Sensors

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Physiological Transducers ناقل الطاقة الفسيولوجي (كهر وحيوي) - 3-The third type -Temperature transducer (Temperature Sensors ) 1. Resistance based a. Resistance Temperature Devices (RTDs) b. Thermistors 2. Thermoelectric – Thermocouples 3. Radiation Thermometry 4. Fiber Optic Sensor 3-1. Resistance based a) .RTDs RTDs are made of materials whose resistance changes in accordance with temperature . Metals such as platinum, nickel and copper are commonly used. They exhibit a positive temperature coefficient. A commercial ThermoWorks RTD probe

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Physiological Transducers ناقل الطاقة الفسيولوجي (كهر وحيوي) - 3-The third type -Temperature transducer (Temperature Sensors ) 3-1. Resistance based b).Thermistors :Thermistor: semiconductor; the resistance is a function of temperature. Thermistors are made from semiconductor material. Generally, they have a negative temperature coefficient (NTC), that is NTC thermistors are most commonly used. where R0 is the resistance at a reference temperature, T0, and RT is the resistance at temperature T. β is a material-specific constant. Both temperatures are expressed in degrees K Thermistors: - have high sensitivity (<<1°C) - range is not as great as thermocouples (-50°C – 100°C), but suitable for biological/physiological measurements - need calibration (R vs. temperature curve) - can also be made very small

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Physiological Transducers ناقل الطاقة الفسيولوجي (كهر وحيوي) - 3-The third type -Temperature transducer (Temperature Sensors ) 3-2. Thermoelectric – Thermocouples- : two different metal wires welded together Seebeck (1821)effect: - Thermal to electrical An electromotive force (emf) exists across the junction and is temperature dependent. If we use two such junctions, one is at a known temperature and the other is at the sample Figure -Thermocouple circuits (a) Peltier emf. (b) Law of homogeneous circuits. (c) Law of intermediate metals. (d) Law of intermediate temperatures

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Physiological Transducers ناقل الطاقة الفسيولوجي (كهر وحيوي) - 3-The third type -Temperature transducer (Temperature Sensors ) 3-3. Radiation Thermometry Governed by Wien’s Displacement Law which says that at the peak of the emitted radiant flux per unit area per unit wavelength occurs when lamda maxT=2.898x10-3 moK -Variations of ε with λ is very important in absolute-temperature measurement, but less important in relative temperature measurement. – For T = 300 K and λ = 3 μm, a 5% change in ε is equivalent to a temperature change of approximately 1oC. – Two types of infrared sensors: Thermal and photon (quantum) detectors. – Thermal detector has low sensitivity and responds to all wavelengths, whereas photon (quantum) detector respond only to a limited wavelength band. – Radiation thermometry - A technique that determines the internal or core body temperature of the human by measuring the magnitude of infrared radiation emitted from the tympanic membrane and surrounding ear canal.

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Physiological Transducers ناقل الطاقة الفسيولوجي (كهر وحيوي) - 3-The third type -Temperature transducer (Temperature Sensors ) 4-3. Fiber Optic Temperature Sensors Nortech's fiber-optic temperature sensor probe consists of a gallium arsenide crystal and a dielectric mirror on one end of an optical fiber and a stainless steel connector at the other end. Figure - Details of the fiber/sensor arrangement for the GaAs semiconductor temperature probe.

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Chemical measurements Important analyses and their normal ranges in blood, which indicate the physiological status of the body: gas pressure and related parameters, electrolytes, and metabolites Introductions • Chemical sensors – For recognition of presence of specific substances and their concentration – Sensitive to stimuli produced by various chemical compound or elements – High selectivity – Very small output electrical signal : need high quality interface electronic devices – Gas/liquid phase sensor : ex, O2 in air/ dissolved oxygen

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Chemical measurements Blood Gas Measurement • Blood pressure : arterial BP, CVP, intracardiac BP, PAP, spinal fluid pressure, intraventricular brain pressure. pressures of oxygen (pO2), carbon dioxide (pCO2) as well as the concentration of hydrogen ions (pH) are vital in diagnosis. Oxygen is measured indirectly as a percentage of Haemoglobin which is combined with oxygen (sO2). pO2 can also provide the above value using the oxyhaemoglobin dissociation curve but is a poor estimate. Blood oxygen measurement Measuring arterial blood gases pO2: in operating room and intensive care unit to monitor respiratory and circulatory condition of a patient.

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Chemical sensors -Oxygen Sensors 1- Oxygen Sensors • Oxygen content of gases and liquid – Partial pressure : pressure exerted by one gas in a mixture of gases. – The dissolving process for gases is an equilibrium. The solubility of a gas depends directly on the gas pressure. If the temperature stays constant increasing the pressure will increase the amount of dissolved gas. – O2(g) <--->O2(aq) • Sensor methods - – Paramagnetic properties of oxygen – Clark electrode – Fuel cell, galvanic cell type Figure - PO2 electrode (From R. Hicks, J. R. Schenken, and M. A. Steinrauf, Laboratory Instrumentation. Hagerstown, MD: Harper & Row, 1974. Used with permission of C. A. McWhorter.)

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Chemical sensors -Oxygen Sensors 1- Oxygen Sensors 1-1.Clark electrode: measures partial pressure of O2.The pO2 electrode produces a current at a constant polarizing voltage (0.6 V) which is directly proportional to the partial pressure of oxygen diffusing to the reactive surface of the electrode.

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Chemical sensors -Oxygen Sensors 1- Oxygen Sensors 2-1. Blood oxygenation - Oxygen saturation Oxygen saturation (% of oxygenated hemoglobin) can be measured and used to represent blood oxygenation . Relationship between arterial blood oxygen saturation and partial pressure of O2 Figure - The oxyhemoglobin dissociation curve, showing the effect of pH and temperature on the relationship between SO2 and PO2.

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Chemical sensors -Oxygen Sensors 1- Oxygen Sensors 2-1. Blood oxygenation - Oxygen saturation Oximetry: (color) measures light absorbance at one wavelength where there is a large difference between Hb and HbO2 and at another wavelength (or more wavelengths) Figure - The oxyhemoglobin dissociation curve, showing the effect of pH and temperature on the relationship between SO2 and PO2.

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Chemical sensors -Oxygen Sensors 2-1. Blood oxygenation - Oxygen saturation-Pulse Oximetry The pulse oximeter is a spectrophotometric device that detects and calculates the differential absorption of light by oxygenated and reduced hemoglobin to get sO2. A light source and a photodetector are contained within an ear or finger probe for easy application. Two wavelengths of monochromatic light -- red (660 nm) and infrared (940 nm) -- are used to gauge the presence of oxygenated and reduced hemoglobin in blood. With each pulse beat the device interprets the ratio of the pulse-added red absorbance to the pulse-added infrared absorbance. The calculation requires previously determined calibration curves that relate transcutaneous light absorption to sO2.

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Chemical sensors - Oxygen Sensors 2-1. Blood oxygenation - Oxygen saturation-Pulse Oximetry (b) (a) Figure : (a) Noninvasive patient monitor capable of measuring ECG, noninvasive blood pressure (using automatic oscillometry), respiration (using impedance pneumography), transmission pulse oximetry, and temperature. (b) Disposable transmission So2 sensor in open position. Note the light sources and detector, which can be placed on each side of the finger. [From Y. M. Mendelson, "Blood gas measurement, transcutaneous," in J. G. Webster (ed.). Encyclopedia of Medical Devices and Instrumentation. New York. Wiley, 1988. pp.448-459. Used by permission.]

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Chemical sensors- Oxygen Sensors 2-1. Blood oxygenation - Oxygen saturation-Pulse Oximetry Pulse oximetry: use the pulsatile (AC) component to extract oxygen saturation information and the non-pulsatile (DC) signal as a reference for normalization Light Source Light Detector Cuvette In the Chemistry Lab Physiological Measurement D Spectrophotometer Change in arterial blood volume associated with periodic contraction of the heart Photoplethysmograph Figure - Pulse oximetry this was taken from Medical Instrumentation: Application and Design, edited by John G. Webster

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Chemical sensors - Oxygen Sensors 2-1.Blood oxygenation - Oxygen saturation -Pulse Oximetry Advantages Easy to use Frequent calibration unnecessary Limitations Usually only measured by transillumination Limited to tissues that can transmit light Highly sensitive to motion Venous pulsations can affect results

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Chemical sensors 2-Transcutaneous pO2 The skin is heated to 43°C to increase local blood flow and enhance diffusion of O2 through the skin. Mostly used on newborn babies in the ICU because their skin is thinner Figure - Cross-sectional view of a transcutaneous oxygen sensor. Heating promotes arterialization. (From A. Huch and R. Huch, "Transcutaneous, noninvasive monitoring of PO2," Hospital Practice, 1976, 6, 43-52. Used by permission.)

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Chemical sensors 3-pH electrode: To measure the acidity or alkalinity of solutions determined by activities of [OH-] and [H+] • pH electrode : Ag-AgCl metallic electrode immersed مغَطِس in a chloride buffer with a very thin permeable glass membrane that allows hydrogen ions to diffuse(ينتشر) into the buffer A potentiometric electrode is designed to measure the potential between the sample and a buffer solution. This glass electrode is placed in the blood sample and a potential difference is generated across the glass, which is proportional to the difference in hydrogen ion concentration

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Chemical sensors 3-pH electrode: Figure - pH electrode (From R. Hicks, J. R. Schenken, and M. A. Steinrauf, Laboratory Instrumentation. Hagerstown, MD: Harper & Row, 1974. Used with permission of C. A. McWhorter.)

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Chemical sensors 4-CO2 Sensors- The carbon dioxide electrode : The carbon dioxide electrode is a modified pH electrode in contact with sodium bicarbonate solution and separated from the blood specimen by a rubber or Teflon semi-permeable membrane. • In liquid solutions : pCO2 with a selective pH electrode • In air or other gases : absorption of infrared by CO2 Figure - PCO2 electrode (From R. Hicks, J. R. Schenken, and M. A. Steinrauf, Laboratory Instrumentation. Hagerstown, MD: Harper & Row, 1974. Used with permission of C. A. McWhorter.)

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Chemical sensors 5-Transcutaneous carbon dioxide sensor Figure -Cross-sectional view of a transcutaneous carbon dioxide sensor. Heating the skin promotes arterialization. (From A. Huch, D. W. Lübbers, and R. Huch, "Patientenuberwachung durch transcutane Pco2 Messung bei gleiechzeiliger koutrolle der relatiuen Iokalen perfusion," Anaesthetist, 1973, 22, 379. Used by permission.)

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Other Physical Sensors 1-The oximeter catheter system - The oximeter catheter system measures oxygen saturation in vivo, using red 660 nm and infrared 940 nm light emitting diodes (LEDs) and a photosensor. The red and infrared LEDs are alternately pulsed in order to use a single photosensor. Figure

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Other Physical Sensors 2-Cardiac output measured by thermodilution CVP injection port Thermistor Balloon Transmitting fiber-optic Receiving Sampling and pressure monitoring lumen Balloon inflation lumen Optical module Cardiac output computer connector To oximetry instrument Proximal (CVP) lumen Distal (PA) lumen Figure - The catheter used with the Abbott Opticath Oximetry System transmits light to the blood through a transmitting optical fiber and returns the reflected light through a receiving optical fiber. The catheter is optically connected to the oximetry processor through the optical module. (From Abbott Critical Care Systems. Used by permission.)

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Other Physical Sensors 2-Cardiac output measured by thermodilution Catheter with multiple ports - Inject cold saline into the right atrium (intravenous catheter) - Measure temperature at the pulmonary artery over time - Conservation of energy: The total heat content of the injected saline will be

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية د.نعمان النجار Biosensor What are biosensors? • Biosensor: is a sensor using a living component or a product of a living thing for measurement or indication. Or a biosensor is an analytical device which converts a biological response into an electrical signal. Features of a successful biosensor: 1- Biocatalyst highly specific for the purpose of the analyses, 2-Reaction independent of physical parameters, 3- Response accurate, precise, reproducible and linear, 4-No electrical noise, 5- Biocompatible 6- Cheap, small, portable and capable of being used by operators.

Major applications for biosensors كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Biosensor Major applications for biosensors 1-Medical Applications Suitable for analyzing blood samples using diagnostic sensors monitoring of various medical conditions Glucose level monitoring 2-Wireless solutions for human-implanted sensors 3-Military combat operations can track the soldier movements 4-Civilian applications Temperature change notification Pollution detection Detecting changes in exhaustive systems of the vehicles

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Biosensor Biosensing Principles

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Biosensor Generally a biosensor consists of two parts – A biological recognition element (enzyme, antibody, receptor) to provide selectivity to sense the target of interest (referred to as the analyte) – A supporting element which also acts as a transducer to convert the biochemical reaction into “signal” that can be read out

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Biosensor “Receptor” provides selective molecular recognition For example: enzymes, antibodies, receptors, nucleic acids, polypeptides, etc. Transducer types in biosensors: calorimetric, electrochemical, optical, etc. Biosensor- 1.Enzymatic biosensors Enzymes are catalysts for biochemical reactions; large macromolecules consisting mostly of protein, and usually containing a prosthetic group (metals) Substrate: the target molecule of an enzymatic reaction S: substrate; E: enzyme; ES: enzyme-substrate complex; P: product

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Biosensor- 1.Enzymatic biosensors Advantages – Highly selective – Enzymes are catalytic, thus improving the sensitivity – Fairly fast • Disadvantages – Expensive: cost of extraction, isolation and purification – Activity loss when enzymes are immobilized – Enzymes tend to be deactivated after a relatively short period of time In an enzymatic biosensor, the enzyme is immobilized as the “receptor” Enzymes are specific to their substrates which can be the analyte Example: glucose sensors

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Biosensor- 1.Enzymatic biosensors Enzymatic Approach (Glucose Sensors) Makes use of catalytic (enzymatic) oxidation of glucose. The setup contains an enzyme electrode and an oxygen electrode and the difference in the readings indicates the glucose level. The enzyme electrode has glucose oxidase immobilized on a membrane or a gel matrix. Figure : (a) In the enzyme electrode, when glucose is present it combines with O2, so less O2 arrives at the cathode. (b) In the dual-cathode enzyme electrode, one electrode senses only O2, and the difference signal measures glucose independent of O2 fluctuations. (From S. J. Updike and G. P. Hicks, "The enzyme electrode, a miniature chemical transducer using immobilized enzyme activity," Nature, 1967, 214, 986-988. Used by permission.)

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Biosensor- 1.Enzymatic biosensors Affinity Approach -Glucose Sensors This approach is based on the immobilized competitive binding of a particular metabolite (glucose) and its associated fluorescent label with receptor sites specific to the metabolite (glucose) and the labeled ligand. This change in light intensity is then picked up. Immobilized Con A

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Biosensor-Enzymatic biosensors Alternatively, the reaction product hydrogen peroxide can also be measured through reduction of H2O2 Use a Clark-type electrochemical cell similar to the one for measuring O2, but at a positive bias voltage of 0.65V Problems: 1. The reduction/oxidation potentials are fairly high ⇒ other materials will interfere 2. The concentration of O2 needs to be kept constant, which is difficult since O2 is involved in the reactions

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Biosensor-Enzymatic biosensors Electron mediators in enzymatic biosensors In the membrane: At the anode: Oxygen is consumed and later regenerated, therefore it only serves to transfer electron ⇒ can be replaced by a mediator Example: multi-cycle chemical electrochemical reaction chain for detecting glucose

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Biosensor 2-Immunosensors Immunosensors: based on highly specific antigen-antibody reactions Antibody: works against the foreign body Immunoglobin: globular proteins that participate in the immune response Structure of antibody The Fc end of an antibody can bind to other immune cells and the binding activate these immune cells

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Biosensor 2-Immunosensors Detection of the reaction (binding/association) can be either direct or indirect (labeled) Direct detection: the binding of the analyte (antigen) to the “receptor” (antibody) is detected directly through the presence of the analyte However, most are indirect due to lack of signal from the analyte itself Indirect detection: signal is provided by an exogenous reporter

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Biosensor 2-Immunosensors Indirect detection • Radioimmunoassay (RIA) – The labels are radioactive isotopes (for example 131I) – Highly sensitive and specific but inconvenient and expensive – Less popular now due to safety issues • ELISA (Enzyme-Linked Immunosorbent Assay) – Enzymes are used for labeling and signal is provided by the reaction product – Simple in terms of procedure and equipment • Fluorescent immunoassay – Labeled with fluorescent dyes

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Biosensor 2-Immunosensors

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Biosensor 3-SPR biosensors Direct detection – Surface plasmon resonance. A surface plasma wave (SPW) is an electromagnetic wave (due to charge density oscillation) which propagates along the boundary between a dielectric (e.g. glass) and a metal. A surface plasmon wave can be excited optically: when the propagation constant β of the incident light and the SPW are equal in magnitude and direction for the wavelength. This corresponds to a certain angle of incident light at a fixed wavelength ⇒ the reflected light reaches its minimum. Binding induced change in propagation constant of SPW is proportional to the refractive index change in the sample ⇒ the angle of incident light also changes (fig.)

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Biosensor 3-SPR biosensors Different parameters are measured in SPR biosensors to indicate the refractive index change in the sample (due to binding) Character of SPR biosensors: Direct detection ⇒ no need for labeling • High sensitivity • Fast ⇒ real-time monitoring • Used with sample in liquid ⇒ important for biological samples • Relatively simple device, which makes multichannel parallel detection easier ⇒high throughput. SPR commercialization - BIACORE BIACORE optical system: light from different angle of reflection is imaged onto different position of a photo-detector array. The corner-stones of Biacore technology

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Biosensor 4- BIACORE biosensors BIACORE features • Specificity: different molecules interact with a single partner immobilized on a sensor surface • Kinetics: rates of complex formation (ka) and dissociation (kb) • Affinity: the level of binding at equilibrium (KD, KA) • Concentration: can be determined for purified molecules or for molecules in complex mixtures such as serum (needs a calibration curve) • Multiple interactions during complex formation Multiple flow-cells ⇒ simultaneous detection of reflection intensity

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Biosensor - Fiber optic based biosensors • Fiber optic based biosensors Optical fibers are flexible and compact which are important features for applications that need miniaturization such as in vivo measurements

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Biosensor - Fiber optic based biosensors • Optical fiber sensor – examples • Sensing area along side of an optical fiber • Sensing area located at distal end surface of an optical fiber

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Biosensor - Fiber optic based biosensors • Optical fiber sensor – examples • A fiber optic (imaging) bundle is used for detecting multiple analytes simultaneously - Each latex sphere can specifically binds to one analyte - The analytes can be fluorescently labeled - Use of reference channels could increase the reliability of detection (e.g. spheres without recognition element still bind to some analyte molecules non-specifically, so the measured fluorescence from the reference spheres is considered “background” and should be subtracted)

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Biosensor - Chemical sensors based biosensors Chemical Sensors (Biosensors) Biosensors produce an output (electrical) which is proportional to the concentration of biological analyses. Biosensing Principles • Electrochemical – Potentiometric – Amperometric – FET based – Conductometric • Optical • Piezoelectric • Thermal

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Biosensor - Chemical sensors based biosensors Electrochemical Sensors Potentiometric : These involve the measurement of the emf (potential) of a cell at zero current. The emf is proportional to the logarithm of the concentration of the substance being determined. Amperometric : An increasing (decreasing) potential is applied to the cell until oxidation (reduction) of the substance to be analyzed occurs and there is a sharp rise (fall) in the current to give a peak current. The height of the peak current is directly proportional to the concentration of the electroactive material. If the appropriate oxidation (reduction) potential is known, one may step the potential directly to that value and observe the current. Conductometric. Most reactions involve a change in the composition of the solution. This will normally result in a change in the electrical conductivity of the solution, which can be measured electrically.

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Optical biomedical sensors-Fiber Optics 1-Fiber Optics or Optical fiber Typically made of glass SiO2, and consisting of a core and a cladding layer. Transmits light through the core (total internal reflection). Diameter can be very small ~μm ⇒ very flexible. The angle of light rays that go into the fiber core and can be accepted (transmitted) by the fiber is dependent on the core and cladding materials. Incident angle of light rays going into a fiber must be less than θ Sensing Principle They link changes in light intensity to changes in mass or concentration, hence, fluorescent or colorimetric molecules must be present. Various principles and methods are used : Optical fibres, surface Plasmon resonance, Absorbance, Luminescence

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Optical biomedical sensors-Fiber Optics 1-Fiber Optics or Optical fiber Most of the light is trapped in the core, but if the cladding is temperature sensitive (e.g. due to expansion), it might allow some light to leak through. -> hence the amount of light transmitted would be proportional to temperature -> since you are measuring small changes in light level, this sensor is exquisitely sensitive A fiber optic cable

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Optical biomedical sensors-Fiber Optics 1-Fiber Optics • Geometrical optics – The f number of lens is the ratio of the focal length to diameter. • Fiber optics – Fiber optics are an efficient way of transmitting radiation. It is based on Snell’s law: – Critical angle for reflection: Figure - Fiber optics. The solid line shows refraction of rays that escape through the wall of the fiber. The dashed line shows total internal reflection within a fiber.

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Optical biomedical sensors-Fiber Optics 1-Fiber Optics Geometrical and Fiber Optics • Fiber optics – 50 cm glass fiber: transmission > 60% for wavelength between 400 and 1200 nm. – 50 cm plastic fiber: transmission > 70% for wavelength between 500 and 850 nm. – Most applications use flexible bundles of about 400 fibers. – Noncoherent bundles (light guide) and Coherent bundles • Liquid Crystals – For an application of voltage, liquid crystals may change their passive scattering or absorption of light. – Low power consumption • Filters of FO – Filters are frequently inserted in the optical system to control the distribution of radiant power or wavelength. – Reflection filters or absorption filters – Interference filters – Diffraction gratings

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Optical biomedical sensors-Fiber Optics 1-1.A reversible fiber-optic chemical sensor Figure - A reversible fiber-optic chemical sensor measures light scattered from phenol red indicator dye to yield pH [From J. I. Peterson, "Optical sensors," in J. G. Webster (ed.), Encyclopedia of Medical Devices and Instrumentation. New York: Wiley, 1988, pp. 2121-2133. Used by permission.]

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Optical biomedical sensors-Fiber Optics 2-1.A single fiber intravascular blood-gas sensor Figure - A single fiber intravascular blood-gas sensor excites fluorescent dye at one wavelength and detects emission at a different wavelength. The following modifications are made to the sensor tip: pH: Chemistry – pH-sensitive dye bound to hydrophilic matrix. PCO2: Chemistry – bicarbonate buffer containing pH-sensitive dye with silicone. PO2: Chemistry – Oxygen-sensitive dye in silicone. (From J. L Gehrich, D.W. Lübbers, N. Optoz, D. R. Hansmann. W. W. Miler, J. K. Tusa, and M. Yafuso, "Optical fluorescence and its application to an intravascular blood gas monitoring system," IEEE Trans. Biomed. Eng., 1986, BME-33, 117-132. Used by permission.)

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Optical biomedical sensors-Fiber Optics 3-1.A fiber-optic oxygen sensor Figure - In a fiber-optic oxygen sensor, irradiation of dyes causes fluorescence that decreases with Po2. [From R. Kocache, "Oxygen analyzers," in J. G. Webster (ed.), Encyclopedia of Medical Devices and Instrumentation. New York: Wiley, 1988, pp. 2154-2161. Used by permission.]

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Optical biomedical sensors-Fiber Optics 4-1.An intravascular blood-gas probe measures pH, PCo2, and Po2 Figure - An intravascular blood-gas probe measures pH, PCo2, and Po2 by means of single fiber-optic fluorescent sensors. (From J. L. Gehrich, D. W. Lübbers, N. Opitz, D. R. Hansmann, W. W. Miler, J. K. Tusa, and M. Yafuso, "Optical fluorescence and its application to an intravascular blood gas monitoring system," IEEE Trans. Biomed. Eng., 1986, BME-33, 117-132. Used by permission.)

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Optical biomedical sensors-Fiber Optics 5-1.The affinity sensor Figure - The affinity sensor measures glucose concentration by detecting changes in fluorescent light intensity caused by competitive binding of a fluorescein-labeled indicator. (From J. S. Schultz, S. Manouri, et al., "Affinity sensor: A new technique for developing Implantable sensors for glucose and other metabolites," Diabetes Care, 1982, 5, 245-253. Used by permission)

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Optical biomedical sensors-Fiber Optics 5-1.The affinity sensor - The optical system for a glucose Figure - The optical system for a glucose affinity sensor uses an argon laser and a fiber-optic catheter.

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Optical biomedical sensors-Radiation Sources 2-Radiation Sources 1-2.Tungsten lamps – Incandescent tungsten-wire filament lamps are the most commonly used sources for radiation. – Their output varies with temperature and wavelength, as given by where C1 = 3.74 x 104 (W.μm4/cm2), C2 = 1.44 x 104 (μm4/K), T = blackbody temperature (K), and ε = emissivity, the extent by which a surface deviates from a blackbody (ε = 1) Coiled filaments to increase emissivity and efficiency. - Ribbon filaments for uniform radiation Tungsten-halogen lamps have iodine or bromine to maintain more than 90% of their initial radiant.

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Optical biomedical sensors-Radiation Sources 2- 2.Arc discharges – Low-pressure lamp: Fluorescent lamp filled with Argon-Mercury (Ar-Hg) mixture. Accelerated electron hit the mercury atom and cause the radiation of 250 nm (5 eV) wavelength which is absorbed by phosphor. Phosphor will emits light of longer visible wavelengths. Fluorescent lamp has low radiant so it is not used for optical instrument, but can be turned on in 20 sec and used for tachistoscope to provide brief stimuli to the eye. - High pressure lamp: mercury, sodium, xenon lamps are compact and can provide high radiation per unit area. Used in optical instruments. 3-2.Light-Emitting Diodes (LEDs) A p-n junction devices that are optimized to radiant output. GaAs has a higher band gap and radiate at 900 nm. Switching time 10 nsec. GaP LED has a band gap of 2.26 eV and radiate at 700 nm GaAsP absorb two photons of 940 nm wavelength and emits one photon of 540 nm wavelength. Advantages of LED: compact, rugged, economical, and nearly monochromatic.

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Optical biomedical sensors-Radiation Sources 4-2. LASERS – Laser (Light Amplification by Stimulated Emission of Radiation) – Laser output is highly monochromatic, collimated, and phase-coherent. – Solid-state laser (ruby laser (693 nm, 1 mJ), Nd: YAG laser (1064 nm, 2 W/mm), He-Ne laser (633 nm, -100 mW), CO2 laser (50 -500 W) -He-Ne lasers operate at 633 nm with 100 mW power. Argon laser operates at 515 nm with the highest continuous power level with 1-15 W power. CO2 lasers provide 50-500 W of continuous wave output power. Ruby laser is a solid state lasers operate in pulsed mode and provide 693 nm with 1-mJ energy. The most medical use of the laser is to mend tear in the retina. Figure - Spectral characteristics of sources, (a) Monochromatic outputs from common lasers are shown by dashed lines: Ar, 515 nm; HeNe, 633 nm; ruby, 693 nm; Nd, 1064 nm

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Optical biomedical sensors-Radiation Sensors Radiation Sensors Classifications of Radiation Sensors 1-Thermal sensors Thermal Sensors: absorbs radiation and change the temperature of the sensor. -Change in output could be due to change in the ambient temperature or source temperature. -Sensitivity does not change with wavelength -Slow response – This type of sensor absorbs radiation and transforms it into heat, thus causing a rise in temperature in the sensors. – Thermistors and thermocouple – Pyroelectric sensor absorbs radiation and converts into heat, thus resulting rise in temperature that changes the polarization of the crystals. A current may be produced in proportional to the rate of change of temperature. Example: Pyroelectric sensor: absorbs radiation and convert it to heat which change the electric polarization of the crystals

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Optical biomedical sensors-Radiation Sensors Radiation Sensors Classifications of Radiation Sensors 2-Quantum sensors Quantum Sensors: absorb energy from individual photons and use it to release electrons from the sensor material. – It absorbs energy from individual photons and use it to release electrons from the sensor material. -sensitive over a restricted band of wavelength -Fast response -Less sensitive to ambient temperature Example: Eye, Phototube, photodiode, and photographic emulsion. – Photoemissive sensors, Photoconductive cells, Photojunction sensors, Photovoltaic sensors

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Optical biomedical sensors-Radiation Sensors Radiation Sensors 3-Radiation Thermometry The higher the temperature of a body the higher is the electromagnetic radiation (EM). Electromagnetic Radiation Transducers - Convert energy in the form of EM radiation into an electrical current or potential, or modify an electrical current or potential. Medical thermometry maps the surface temperature of a body with a sensitivity of a few tenths of a Kelvin. Application Breast cancer, determining location and extent of arthritic disturbances, measure the depth of tissue destruction from frostbite and burns, detecting various peripheral circulatory disorders (venous thrombosis, carotid artery occlusions) Measuring the core body temperature of the human by measuring the magnitude of infrared radiation emitted from the tympanic membrane and surrounding ear canal. Response time is 0.1 second Accuracy of 0.1 oC

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Optical biomedical sensors-Radiation Sensors 3-Radiation Thermometry Radiation Thermometer System Figure - Stationary chopped-beam radiation thermometer (From Transducers for Biomedical Measurements: Principles and Applications, by R. S. C. Cobbold. Copyright © 1974, John Wiley and Sons, Inc. Reprinted by permission of John Wiley and sons. Inc.)

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Optical biomedical sensors-Radiation Sensors 3-Radiation Thermometry Radiation Thermometer System Sources of EM radiation: Acceleration of charges can arise from thermal energy. Charges movement cause the radiation of EM waves. The amount of energy in a photon is inversely related to the wavelength: Thermal sources approximate ideal blackbody radiators: Blackbody radiator: an object which absorbs all incident radiation, and emits the maximum possible thermal radiation (0.7 m to 1mm).

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Optical biomedical sensors-Radiation Sensors Anther radiation sensors 1-Photoemissive Sensors a).Phototube: have photocathode coated with alkali metals. A radiation photon with energy cause electron to jump from cathode to anode. Photon energies below 1 eV are not large enough to overcome the work functions, so wavelength over 1200nm cannot be detected. b).Photomultiplier An incoming photon strikes the photocathode and liberates an electron. This electron is accelerated toward the first dynode, which is 100 V more positive than the cathode. The impact liberates several electrons by secondary emission. They are accelerated toward the second dynode, which is 100 V more positive than the first dynode, This electron multiplication continues until it reaches the anode, where currents of about 1 mA flow through RL. Time response < 10 nsec

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Optical biomedical sensors-Radiation Sensors Anther radiation sensors 1–Photoemissive Sensors المضاعفات الضوئية : يتألف من أنبوب مفرغ من الهواء و تحتوي على مجموعة مصاعد(14) و مهبط مطلي بمادة حساسة للضوء حيث أنها تصدر إلكترونات عندما تسقط عليها فوتونات الضوء. إن فرق ألكامن بين المصعد الأول و المهبط ( 100 v ) و نفسه بين المصعد الثاني و الأول . الإلكترونات الصادرة عن المهبط تستقبل من المصعد الأول  و باصطدامها به فإنها تحرر المزيد من الإلكترونات التي تستقبل بالمصعد التالي و تتكرر العملية على عدد المصاعد فتنتج إشارة تتناسب مع الضوء الهابط على المهبط تتميز بتخطيتها و حساسيتها العالية للضوء لذلك يجب أن توضع في ظلام دامس.

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Optical biomedical sensors-Radiation Sensors Anther radiation sensors 2- Photoconductive Cells Photoresistors: a photosensitive crystalline materials such as cadmium Sulfide (CdS) or lead sulfide (PbS) is deposited on a ceramic substance. The resistance decrease of the ceramic material with input radiation. This is true if photons have enough energy to cause electron to move from the valence band to the conduction band.

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Optical biomedical sensors-Radiation Sensors Anther radiation sensors- 3. Photojunction Sensors Photojunction sensors are formed from p-n junctions and are usually made of silicon. If a photon has enough energy to jump the band gap, hole-electron pairs are produced that modify the junction characteristics. Photodiode: With reverse biasing, the reverse photocurrent increases linearly with an increase in radiation. Phototransistor: radiation generate base current which result in the generation of a large current flow from collector to emitter. Response time = 10 microsecond Figure -Voltage-current characteristics of irradiated silicon p-n junction. For 0 irradiance, both forward and reverse characteristics are normal. For 1 mW/cm2, open-circuit voltage is 500 mV and short-circuit current is 8 mA.

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Optical biomedical sensors-Radiation Sensors Anther radiation sensors - 4. Photovoltaic Sensors Photovoltaic sensors is a p-n junction where the voltage increases as the radiation increases. Figure - Spectral characteristics of detectors, Detectors. The S4 response is a typical phototube response. The eye has a relatively narrow response, with colors indicated by VBGYOR. CdS plus a filter has a response that closely matches that of the eye. Si p-n junctions are widely used. PbS is a sensitive infrared detector. InSb is useful in far infrared. Note: These are only relative responses. Peak responses of different detectors differ by 107.

Silicon Pressure Sensors كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Pressure Sensors - Silicon Pressure Sensors Silicon Pressure Sensors Pressure sensors contain sensing elements that consist of four piezoresistors buried in the face of a thin, chemically-etched silicon diaphragm. A pressure change causes the diaphragm to flex, inducing a stress or strain in the diaphragm and the buried resistors. The resistor values change in proportion to the stress applied and produce an electrical output.

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Pressure Sensors - Silicon Pressure Sensors Silicon pressure sensors best used for (Applications ): 1- Medical equipment: respiration, dialysis, infusion pump; data storage, and gas chromatography equipment; process controls; industrial machinery; pumps; robotics; and off-road applications. Costs for extremely accurate sensors can be as low a $50. Pressure sensors are used in almost every industry and is widely used 2-Eye Pressure Testing Called an oculocerebrovasculometer the eye pressure sensor measures the blood pressure in your eye to check to see if you have a glaucoma or stroke. The procedure is non-invasive and is quick and painless. The technician uses a pen sized device with the measuring disk on the end and places it against your eyeball. 3- Pressure Monitoring System Using the 140 PC pressure sensor an intercranial pressure monitoring system was designed where a probe is inserted into the patients skull and a portable pneumatic system monitors the changes of the system. Air enters and leaves the probe at a constant rate. Any changes in the system caused by leaks or other obstructions will set off an alarm so the problem can be addressed. The following pressure sensors can be found at ww.honeywell.com

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Pressure Sensors - Ultra Low Pressure Sensing The Ultra Low Pressure Sensing sensor from Honeywell is one of the most precise pressure sensing elements on the market. The ULPS has the ability to dynamically adjust to changes in temperature thereby reducing the error in the measurements The typical applications of the ULPS are used in medical instrumentation, environmental controls, and portable monitors.

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Pressure Sensors - Capacitive Pressure Sensors Capacitive pressure sensors are made using thin metallic silicon wafers that are spaced apart and when pressure is applied to the sensor the capacitance changes in the sensor thereby allowing the measurement of change in pressure. Capacitive pressure sensors are inherently non-linear, but extensive FEA analysis has improved the linearity of these types of sensors.

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Pressure Sensors - Capacitive Pressure Sensors Applications The medical industry has a wide variety of uses for pressure sensors. The fact that they are used in the medical industry, drives the manufacturers to design more robust and smaller pressure sensors. Smaller design of the pressure sensors allows them to be implanted into patients without the annoyance of noticing that something is there, such as on your arm or wrist. These implanted pressure sensors are a factor in preserving lives. These data can be found at www.mems-issys.com

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Pressure Sensors - Other Pressure Sensors Although almost all pressure sensors now used in industry are electronic, mechanical pressure sensors still exist. The bourdon tube for example is still used in many analog pressure gages and are extremely cheap and easy to make. Shown below is how the bourdon tube pressure sensor works. (e-funda.com)

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Pressure Sensors - Other Pressure Sensors Medical Pressure Measurement Systems • Blood pressure : arterial BP, CVP,intracardiac BP, PAP, spinal fluid pressure, intraventricular brain pressure • Flow measurement : venturi tube, orifice • Different range of measurements • Need to be least invasive, sterile, electrical isolation from ac power mains Units of Pressure

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية Pressure Sensors - Other Pressure Sensors Types of Pressure Sensors

تخصص هندسة أجهزة الطبية كلية العلوم والهندسة تخصص هندسة أجهزة الطبية References • Medical Instrumentation: Application and Design, edited by John G. Webster • Chemical sensors and biosensors, by Brian R. Eggins • Sensors in Biomedical Applications: Fundamentals, Technology & Applications, by Gábor Harsányi – Ch7: Biosensors • Information about glucose meters http://www.diabetesmonitor.com/meters.htm#fcnim • Biomolecular sensors, edited by Electra Gizeli & Christopher R. Lowe