PDMS Flow Sensors With Graphene Piezoresistors Using 3D Printing and Soft Lithography

This paper reports the fabrication and characterization of a flexible piezoresistive flow sensor comprising a polydimethylsiloxane (PDMS) cantilever with a serpentine graphene nanoplatelets (GNP) strain gauge embedded at the cantilever base. A facile and cleanroom-free processing work flow involving a combination of high-resolution powder bed fusion and soft lithography was used to fabricate PDMS cantilevers (aspect ratio 20) with 150 μm × 150 μm microchannels on its surface. A high gauge factor of 55 (up to 5 times higher than reported in comparable piezoresistive flow sensors) was achieved using drop- casted GNP ink as the piezoresistive sensing element in the aforementioned microchannels. Finally, the use of the PDMS- graphene cantilever as an airflow sensor with enhanced sensitivity (20 times more than comparable piezoresistive cantilever sensors), low hysteresis, good repeatability, and bidirectional sensing capability was demonstrated.