1. NSF-ITR Meeting 10-05 Miniaturized Sensors Air molecules aerosols Water molecules cells, viruses

2. Sensor Operation Sensor Specific Initial event Transduction to a signal Measurement of signal Communication of result

3. Initial Event Binding of analyte Interrogation of free analyte Chemical reaction

4. Binding of Analyte Gas Chemical or physical adsorption Metal oxides & semiconductors Biologicals Antibodies Nucleic acids Ligands

5. Interrogation of free analyte Gas Ionization Spectroscopy Light, microwave, mass Water Spectroscopy Light, microwave, mass

6. Transduction to a Signal Electrical Conductance Impedance spectroscopy voltametry Light & Microwaves Absorption Fluorescence Resonance Oscillators Mechanical motion Surface acoustic waves

7. Gas Ionization Modi, et al., Nature, 424, 171-174, 2003

8. Gas Ionization Modi, et al., Nature, 424, 171-174, 2003

9. Complex Mixtures Difficult to distinguish components Signal of one component can swamp others Difficult to standardize

10. A Possible Solution Fractionate the analyte stream Differentiate molecules based on size, shape or charge On-chip family of membranes

11. On-chip Family of Membranes uControlled filtration characteristics  Pattern membrane characteristics  Biocompatible  Use with or without electrophoresis

12. Two Membrane Types Under Evaluation  Cellulose Acetate Spin cast uAlumina Nanofabricated

13. Filtration Characteristics vs Preparation

14. Purification: DNA from Heme Membrane + electrophoresis Mohamed, et al., Chromatography A, 2005

15. Proposed Selective Gas Sensor On-chip membrane & ionization

16. An Antibody Based Cell Sensor Binding agent - immobilized antibody Electrical measurement - impedance

19. Number of captured CD4+ cells vs Impedance Mishra, et al., Biosensors & Bioelcectronics, 2005.

20. Amperometric biosensor using ion channel proteins 4 LAYERS 4. Protein: sensing component 3. Lipid membrane: provides the proper environment for the sensor proteins 2. Hydrogel: structural (localization and stability) 1. Electrode: Detection 4 3 2 1 I analyte