Microfabricated photoplastic cantilever with integrated photoplastic/carbon based piezoresistive strain sensor

Abstract

We present an SU-8 micrometer sized cantilever strain sensor with an integrated piezoresistor made of a conductive composite of SU-8 polymer and carbon black particles. The composite has been developed using ultrasonic mixing. Cleanroom processing of the polymer composite has been investigated and it has been shown that it is possible to pattern the composite by standard UV photolithography. The composite material has been integrated into an SU-8 microcantilever and the polymer composite has been demonstrated to be piezoresistive with gauge factors around 15–20. Since SU-8 is much softer than silicon and the gauge factor of the composite material is relatively high, this polymer based strain sensor is more sensitive than a similar silicon based cantilever sensor.

Epoxy based photoresist/carbon nanoparticle composites

“…We therefore started to investigate SU-8/carbon NP strain gauges. In our initial work we reported on the realization of an all polymer cantilever with integrated SU-8/carbon NP piezoresistive readout [11]. In this work only one type of carbon particle was tested and the focus was on the possibility of fabricating a complete micromechanical device with an SU-8 based strain gauge.…”

Microelectromechanical strain and pressure sensors based on electric field aligned carbon cone and carbon black particles in a silicone elastomer matrix

“…% loading used in piezoresistive cantilevers containing, for instance, carbon black in SU-8 polymer. 10 The mixtures of CNC and CB particles in Dow Corning 734 are grayish and semitransparent after curing, as demonstrated by the free standing films shown in Figs. 3(a) and 3(b).…”

“…6 Electrically conductive polymer composites have been demonstrated as inexpensive and efficient materials sensitive to pressure variation, deformation, and temperature. 7,8 These materials can be made by dispersing high concentrations of electrically conductive particles, for instance, carbon black (CB) particles [9][10][11][12][13][14][15] or metal particles, [16][17][18] in dielectric polymer matrices. The dispersed particles will form electrically conductive pathways in the polymer matrix if the particle concentration is sufficiently high, above the percolation threshold.…”

Polymer MEMS Sensors

“…Hence, SU-8 microcantilevers with integrated piezoresistor made of nanocomposite of SU-8 and Carbon Black have been developed. [23,[25][26][27]. In such a device, the strain in the microcantilever is measured by the change in resistance of the embedded piezoresistive layer containing conducting nanoparticles.…”

“…Th e performance of SU-8 based polymer nanomechanical sensors could be enhanced by incorporating ultra-sensitive electrical transduction schemes that are compatible with SU-8 processing [23][24][25][26][27][28][29][30][31][32]. Design and development of SU-8 microcantilever sensors with four novel electrical transduction schemes namely (1) polymer nanocomposite piezoresistive microcantilever sensors [25][26][27] (2) Organic CantiFET [28] (3) AZO CantiFET [29] and (4) polymer nanocomposite piezoelectric microcantilever sensors [30][31][32] are discussed here.…”