A Glance at microvalves

Presented by Name: Ahmed Mohsen ID: 20121435

Contents State of the Art Introduction to Microvalves Classification of Microvalves Active Microvalves Mechanical Non-Mechanical External Passive Microvalves

State of the Art A primary block for successful miniaturization and commercialization of fully integrated microfluidic system. 'lab On a Chip‘ is capable of shrinking and integrating operations normally performed in a chemical or medical laboratory on to a single chip smaller than a credit card.

State of the art cont’d Microfluidic systems use networks of channels much narrower than a human hair to control the movement of miniscule amounts of fluids. Recent advances in microfluidics technology have proven invaluable for immediate diagnosis of diseases and have greatly improved enzymatic and DNA analysis.

Intro to Microvalves Microvalves consist of a flexible diaphragm sandwiched between a control chamber and liquid chamber. By applying pressure from an external mechanical pump, or through electrostatic or pneumatic forces, the diaphragm can be deformed allowing for the manipulation of fluidic flow within the chamber. Advantages of Microvalves: Best choice to solve liquid, air and gas service design problems. Low probability for leakage of fluid. Fast to short response time depending on application. Smaller size and minimal weight

Classification of Microvalves By their ability to withstand pressure and response time.

Classification of Microvalves cont’d Generally, classified by the number of ports and/or by the number of switching states they can apply

Classification of Microvalves cont’d Active Passive Mechanical Magnetic Check Valve Electric Piezoelectric Non-Mechanical Bistable Capillary Electrochemical External Modular   Pneumatic Can also be categorized by their flow control

Active Microvalves “Mechanical” Most of microvalves couple a flexible membrane to actuation principles. Various actuation principles could be adapted: Electromagnetic Electrostatic Piezoelectric Bimetallic Thermopneumatic Shape Memory Alloy

Active Microvalves “Mechanical” - Magnetic External Magnetic Fields A gas flow regulator is driven by a magnetic field. Can be hybrid integrated to increase magnetic force. Integrated Magnetic Inductors Consists of Integrated inductor Deflectable Silicon Membrane Input/Output Seats

Active Microvalves “Mechanical” - Electric Electrostatic Pair of electrodes NiFe Film Electrokinetic Mobile plugs of lengths and diameter close to 60 um Formed by photo-pattering of polymers within microchannels Controlled by Electrokinetically induced pressure

Active Microvalves “Mechanical” - Piezoelectric Piezoelectricity is the ability of certain crystals to produce mechanical stress or stretching with an applied electric field. Used more often in micropumps because it generates big bending force and small displacement J. Peirs developed a miniature robotic arm manipulator with a piezoelectric and electromagnetic microvalves for an endoscope application.

Active Microvalves “Mechanical” - Bistable Solves a major problem related to microvalves, which is the continuous power it has to be applied to keep the microvalve either open in NC or closed in NO microvalves. Power needed only in transient mode between two stable positions. Bohm designed a bistable electromagnetic microvalve contained Neodymium Magnet.

Active Microvalves “Mechanical” - Bistable cont’d

Active Microvalves “Non-Mechanical” Most recent and cheaper than traditional mechanical active microvalves. Simple in structure and disposability. Thus, they’re well suited for applications in life sciences.

Active Microvalves “Non-Mechanical” - Electrochemical Cristina R. Neagu suggested an electromechanical valving concept with a deflectable membrane due to oxygen gas generation. A pressure of almost 200KPa could be obtained at 1.6 V within seconds. Therefore, membrane deflection ranges from 30 mm up to 70mm. Bubbles are generated and used as an actuation force.

Active Microvalves “Non-Mechanical” – Electrochemical cont’d

Active Microvalves “Non-Mechanical” - Phase Change Hydrogel Microvalves The volume changes can be induced in response to an input such as pH, glucose and temperature. Response time is relatively slow, hydrogel microvalves are more appropriate for drug related applications.

Active Microvalves “Non-Mechanical” - Phase Change cont’d Paraffin Microvalves Paraffin based microvalves are useful in application where rapid valving time is not critical. By use of paraffin materials which is favorable due to its phase change nature. Thus, it can be used either propellant for the membrane or as a meltable plug

Active Microvalves “Non-Mechanical” - Phase Change cont’d Reversible Microvalve With external pneumatic air/vacuum system Irreversible Microvalve Without pneumatic air/vacuum system

Active Microvalves “External” External actuation by means of an external pneumatic air pressure or vacuum. Preferable due to no leakage flows at high input pressures. Only drawback so far is the required additional external systems.

Active Microvalves “External” - MODULAR Built in Microvalves It performs excellently in both sample loading and reagent sealing. Yang & Maeda designed a module specifically for electrophoresis. Up to 200 KPa Rotary Microvalves Hasegawa has developed a rotary switching microvalve with an auto positioning of outlets. He then added a silicone rubber ring within the housing to prevent internal leakage.

Active Microvalves “External” – MODULAR cont’d GeneXpert system, included a microfluidic modular cartridge with a random access rotational valve for sample preparation.

Passive Microvalves “Mechanical” Most of these microvalves include mechanical moving parts such as membrane and spherical balls which allow flow in one direction. Passive mechanical valves are mostly included with micropumps

Passive Microvalves “Mechanical” - Flap Cantilever-Type flaps Made of thin layer of materials Feng and Kim fabricated a Parylene flap valve Parylene’s advantages: Permeability to liquid Low Young’s Modulus; 30 times less than that of silicion

Passive Microvalves “Non-Mechanical” Uses geometry shapes such as nozzles instead of valves Uses functionality of a diffuser for clogging issues. Ahn’s microvalves with a disposable smart LOC for clinical diagnostics.

Passive Microvalves “Non-Mechanical” cont’d It works on the change that occurs to cross-sectional areas. Thus, it would generate pressure drops across the passive valves, resulting in fluidic flow valving.

Thank You!