MEMS RFInterrogated Biosensor MIB Sbastien Payen Advisor Prof
MEMS RF-Interrogated Biosensor (MIB) Sébastien Payen Advisor: Prof. Albert Pisano Department of Mechanical Engineering and BSAC, University of California at Berkeley Industrial Advisory Board, March 2005 © 2005 University of California Prepublication Data Spring 2005
Long Range Goals § A new interdisciplinary research program bridging the domains of biochemistry, radiofrequency I. D. tags, telecommunications, and intelligent network. § Microfabricated structure that comprises a microneedle, a functionalized gel, a tuned tank oscillator circuit and a miniature antenna. § The MIB utilizes volume changes in the functionalized polymer (hydrogel) in order to change mechanically the tuning of the simple tank oscillator circuit. The functionalized polymer changes in volume in response to changes in the biological organism in which the microneedle is inserted. § Changes in the tank oscillator circuit can be determined by remote RF interrogation, using a passive scheme in which the need for a local power source on the MIB is made unnecessary. © 2005 University of California Prepublication Data Spring 2005
Potential Application: Wine Industry Data collection RFInterrogation © 2005 University of California Prepublication Data Spring 2005
Potential Application: Healthcare Receiver Transmitter RF-Interrogation Patch § Hydrogel functionalized to react to antibodies. § Patch for diabetic patients: hydrogel functionalized to glucose § Monitoring of at-risk patients © 2005 University of California Prepublication Data Spring 2005
Signal Pathway Integrated circuit components Antenna Filter: Cellulose Acetate Capillary Tube Bio-organism fluid Capacitor plate Air Parylene coated with conductive layer Hydrogel © 2005 University of California Prepublication Data Spring 2005
Example: Acid Content of Grapes Sensitivity requirement for p. H meter: ± 0. 05 p. H range: 3. 1 to 3. 6 Sensitivity requirement for Brix meter: ± 0. 2 Brix range: 0 to 30% Brix Refractometer © 2005 University of California Prepublication Data Spring 2005
Example: Acid Content of Grapes Bio-organism: Grape, fruits, roots Interface: Crop – Needle Fluidic Delivery: Micro-Channel Need to puncture grape / skin Porous and Rigid Membrane Biosensor: Hydrogel Impermeable and flexible Membrane: Parylene Transduction mechanism: Capacitor Integrated Circuit Signal Transmission: Antenna Frequency: HF / UHF © 2005 University of California Prepublication Data Spring 2005
Hydrogels: Introduction Credit to Beebe et al. § Hydrogel: class of polymer with a high affinity for water. Swell upon diffusion of water through their polymer fiber matrix. § Swell in response to: Temperature, electric field, p. H, and other analytes. © 2005 University of California Prepublication Data Spring 2005
Functionalized MEMS Hydrogel Structure 1 in § Widely used hydrogel: § Acrylic acid and 2 -hydroxyethyl methacrylate (in a 1: 4 molar ratio) § Ethylene glycol dimethacrylate (1 wt%) § A photoinitiator (3 wt%) § Acrylic Acid gives the sensitivity to p. H § Swells for high p. H (>7) § Shrinks at low p. H (<4) 200 µm § UV light (wave length is 365 nm) through a photo-mask 400 µm § Wash the non-cured hydrogel © 2005 University of California Prepublication Data Spring 2005 using methanol and water
Properties of Hydrogel § Can be functionalized to react to different analytes § Compatible with microfabrication techniques § Good shell life: § Once mixed: 3 -6 Months § Once cured and dried: 1 Month § Can withstand several cycles. Limited by adhesion § Minimum size using UV light: 50 um © 2005 University of California Prepublication Data Spring 2005
Test structure Size of the pores: • 0. 4 µm • 3 µm • 5 µm • 8 µm • 12 µm Parylene Hydrogel Option 1 Nucleopore membrane Water diffusion Option 2 © 2005 University of California Prepublication Data Spring 2005
Future Work § Characterization of the hydrogel § Test of hydrogel swelling § Test of membrane deflection upon swelling of the hydrogel: flexible membrane is going to be parylene § Proof-of-concept device: integration of hydrogel, flexible membrane and outside electrical circuit to measure change in capacitance and change of the resonance frequency © 2005 University of California Prepublication Data Spring 2005
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