Development of PDMS-based Drag Force-type Flowmeter with Graphite-CNT Composite as Piezoresistive Material

In this study, a polydimethylsiloxane (PDMS)-based drag force-type flowmeter was fabricated using a graphite-carbon nanotube (CNT) composite as a piezoresistive material and evaluated. The device was in the form of a cantilever, which was composed of the soft material, PDMS, and fabricated using a mold manufactured by a three-dimensional printer. The cost-effective graphite was mixed with CNTs to serve as a piezoresistive material. The optimal mixing ratio was investigated, and the piezoresistive material formed using a graphite:PDMS:CNT ratio of 1.5:1:0.01 was adopted, which showed a stable output and a high sensitivity. Various forward and backward air flows in the range of 0-10 m/s were measured using the fabricated flowmeter, and both tensile and compression characteristics were evaluated. The measured results showed a stable output, with the resistance change gradually increasing with the air flow rate. Repeatability characteristics were also tested at a repeated air flow of 10 m/s, and the flowmeter responded to the applied air flow well. Consequently, the fabricated device has a high sensitivity and can be used as a flowmeter.