Conference Paper

Self-actuated polymeric valve for autonomous sensing and mixing

Dept. of Micro & Nanotechnology, Denmark Tech. Univ., Lyngby, Denmark
DOI: 10.1109/SENSOR.2005.1497385 Conference: Solid-State Sensors, Actuators and Microsystems, 2005. Digest of Technical Papers. TRANSDUCERS '05. The 13th International Conference on, Volume: 2
Source: IEEE Xplore


We present an autonomously operated microvalve array for chemical sensing and mixing, which gains the actuation energy from a chemical reaction on the valve structure. An 8-μm-thick flapper valve made in SU-8 is coated with stress-loaded Al on one side and Ti on the other side. The metal films keep the flapper in a flat, stress-balanced closed position. Upon contact with an analyte composed of a NaOH solution the Al film is etched from the valve surface unbalancing the surface stress and bending the flapper. A deflection of up to 45 μm is observed allowing for effective release of a green marker from a reservoir. Calculations reveal that valve operation with stress originating from biochemical processes will require considerable enhancement of the actuation efficiency.

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    • "To move our research towards real life devices we have also developed two integrated read-out modes for SU-8 cantilevers; an optical read-out scheme where the cantilever also acts as a waveguide [32] and a piezo-resistive read-out using Au strain gauges [33]. Moreover, proof-of-concept of an autonomous read-out method has been presented [34]. "
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    ABSTRACT: Here, we present the activities within our research group over the last five yearswith cantilevers fabricated in the polymer SU-8. We believe that SU-8 is an interestingpolymer for fabrication of cantilevers for bio/chemical sensing due to its simple processingand low Young’s modulus. We show examples of different integrated read-out methodsand their characterisation. We also show that SU-8 cantilevers have a reduced sensitivity tochanges in the environmental temperature and pH of the buffer solution. Moreover, weshow that the SU-8 cantilever surface can be functionalised directly with receptormolecules for analyte detection, thereby avoiding gold-thiol chemistry.
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    ABSTRACT: We present a polymer microvalve that allows the detection of biopolymer degradation without the need of external energy. The valve is based on a polymer container filled with a colored marker solution and closed by a thin lid. This structure is covered by a film of poly(L-lactide) and degradation of the biopolymer triggers the release of the color which is detected visually. The autonomous valve has potential for the fast testing of biopolymer degradation under various environmental conditions or by specific enzymes.
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