Self-powered pressure sensor based on microfluidic triboelectric principle for human-machine interface applications

In pace with the fourth industrial revolution, the human-machine interface (HMI) has prospered due to the need of information exchange between human and machines. Although tremendous effort has been devoted to the development of various sensors for HMI systems, those that are made using rigid electronics have constraints in wearability, comfortability, and power consumption. In this paper, a wearable and stretchable self-powered pressure sensor is proposed based on the microfluidic triboelectric principle. Triboelectric output is produced through the charge electrification when the pre-filled liquid in the reservoir flows into a polydimethylsiloxane-made microchannel at an applied pressure. The pressure sensor can generate a peak-to-peak output voltage of 4.2 mV-42.6 mV when an input pressure ranging from 50 kPa to 275 kPa was applied. We further characterize the dynamic response of the pressure sensor where the peak-to-peak output voltage is seen to have increased from 0.2 mV to 11.5 mV when the frequency of the compression pressure is raised from 1 Hz to 13 Hz. As a proof of principle in demonstrating the pressure sensor for wearable HMI application, the soft pressure sensor was attached on a human finger to function as a touch button. The touch button was then used to control a real-time light-emitting diode illumination and gaming interaction. Unlike the conventional touch button that only produces a binary output, this compact touch button can emulate a real-time impact event from the applied pressure. These remarkable features enrich the sensing dimension for HMI, which shows the potential of our work for advanced human-machine manipulation.