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Open Access Publications from the University of California

Wearable Microfluidic Diaphragm Pressure Sensor for Health and Tactile Touch Monitoring.

  • Author(s): Gao, Yuji;
  • Ota, Hiroki;
  • Schaler, Ethan W;
  • Chen, Kevin;
  • Zhao, Allan;
  • Gao, Wei;
  • Fahad, Hossain M;
  • Leng, Yonggang;
  • Zheng, Anzong;
  • Xiong, Furui;
  • Zhang, Chuchu;
  • Tai, Li-Chia;
  • Zhao, Peida;
  • Fearing, Ronald S;
  • Javey, Ali
  • et al.

Flexible pressure sensors have many potential applications in wearable electronics, robotics, health monitoring, and more. In particular, liquid-metal-based sensors are especially promising as they can undergo strains of over 200% without failure. However, current liquid-metal-based strain sensors are incapable of resolving small pressure changes in the few kPa range, making them unsuitable for applications such as heart-rate monitoring, which require a much lower pressure detection resolution. In this paper, a microfluidic tactile diaphragm pressure sensor based on embedded Galinstan microchannels (70 µm width × 70 µm height) capable of resolving sub-50 Pa changes in pressure with sub-100 Pa detection limits and a response time of 90 ms is demonstrated. An embedded equivalent Wheatstone bridge circuit makes the most of tangential and radial strain fields, leading to high sensitivities of a 0.0835 kPa-1 change in output voltage. The Wheatstone bridge also provides temperature self-compensation, allowing for operation in the range of 20-50 °C. As examples of potential applications, a polydimethylsiloxane (PDMS) wristband with an embedded microfluidic diaphragm pressure sensor capable of real-time pulse monitoring and a PDMS glove with multiple embedded sensors to provide comprehensive tactile feedback of a human hand when touching or holding objects are demonstrated.

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