Debashis Maji and Soumen Das
flexible sensors, microheaters, nichrome, PDMS, photolithography, buckling
Flexible MEMS sensor over biocompatible polymer substrates such as PDMS finds numerous biomedical applications. Present article deals with the fabrication challenges that are faced in the realization of metal thin film patterns over PDMS for development of flexible/implantable sensors. In future these miniature flexible sensors have potential applications such as flow sensor, pressure sensor in automated robotic surgery, wearable flexible drug delivery system, etc. Various issues starting from deposition of the thin metal film over the elastomer, development and controlled usage of film buckling in bending of elastomer, lithographically patterning of the film and final release of individual polymer sensor chips from the rigid substrate have been addressed in the present paper. Meanderline microheater patterns have been fabricated in the present study for possible usage in flow sensor. Fabricated structures showed excellent lithographic patterns over the elastomer. The resulting heater structures were easily released from the underlying substrate and showed good electrical continuity. Samples were used to measure temperature coefficient of resistance (TCR) of nichrome. Measured sheet resistance and TCR of the crack free deposited nichrome thin film over planar PDMS surface were 7.65 Ω/sq and 713 ppm/°C respectively.
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