CNTs as Ultra-Low-Powered Aqueous Flow Sensors in PDMS Microfluidic Systems

We have developed ultra-low-powered CNT aqueous flow sensors integrated in microfluidic channels using MEMS-compatible fabrication technology. The sensors are first built on a glass substrate with microelectrode array. Electronic-Grade CNTs (EG-CNTs) are then aligned between the microelectrodes using AC dielectrophoretic (DEP) technique, which are utilized as sensing elements. The EG-CNTs exhibit very stable adhesion to the electrodes, therefore greatly increase the repeatability of the sensors. The CNT sensors are enclosed in a microfluidic chamber by bonding a polydimethylsiloxane (PDMS) microchannel to the glass substrate with the CNT sensor array. We demonstrated the response of the CNT flow sensor to different aqueous flow rates at room temperature. The sensors only needed ultra-low-power (~1μW) to detect the DI-water flow rate ranging from 0.8ms-1 to 2.1ms-1. Preliminary experiments show that there is a linear relation between the resistance changing ratio of the sensor and the flow rate. Our sensors show hysteresis of ~ 10% before temperature compensation. Based on our results, we proved the feasibility of utilizing CNTs as aqueous flow sensors with ultra-low-power consumption. Meanwhile, our results show great potentials of CNTs-based flow sensor for microfluidic, biomedical and bio-molecular applications