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A Stretchable And Strain-Insensitive Pressure Sensor

Published:
Lead Inventor: Sihong Wang
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SUMMARY

  • Pressure sensors are essential to a vast array of applications, where they sense and measure pressure, and transmit information, which help ascertain the performance of a given device. In fact, the size for the global pressure sensor market was estimated to be $11.38 billion in 2019, and is expected to reach $24.84 billion by 2027 at the CAGR of 10.3% from 2020 to 2027.

  • For the emerging field of soft electronics that has been rapidly developed for conformably interfacing with soft and dynamic human or robotic bodies, pressure sensing is a core function for a wide range of desired applications ranging from wearable health monitoring and prosthetic e-skins, to human-machine/robot interactions.

  • To provide stable, high-fidelity and irritation-free functions on these soft, curvilinear and deforming surfaces, pressure sensors are desired to have skin-like stretchability, which needs to be combined with the most important requirement for sensors—highly accurate and perturbation-free signal detection.

  • However, despite several reports of stretchable pressure sensors, their quantitative sensing performances to pressures are all significantly altered by the applied stretching. This has been a major impediment for realizing a wide range of sophisticated functions that need highly quantitative and real-time measurement and/or control of on-skin pressures.

  • This technology overcomes this challenge, and is a novel, stretchable pressure sensor, which can seamlessly adhere to soft/dynamic surfaces and maintain conformability under surface deformation. More importantly, the sensing performance is unaltered at up to 50% strain, which is necessary to quantitatively measure on-skin pressure.

FIGURE

Fig. 1. Structure and strain-unperturbed performance of the stretchable pressure sensor. (A) Three-dimensional structure of the sensor and its equivalent circuit.  Ces is the electrostatic capacitance between the top and bottom electrodes, and Ctop and Cbottom are the electrical double layer (EDL) capacitances of the top interface and the bottom interface between the ionic dielectric and the electrode, respectively. The height of spacers is 350 µm, which is the same as that of the pyramids. (B) Schematic illustrations of the pressure sensor operating under unstretched (left) and stretched (right) states. (C) Capacitance responses as the sensing signal to three repeated pressure values when the sensor is unstretched (0% strain, left) and stretched (50% strain, right). (D) Scanning electron microscopy (SEM) images of the micropyramid structures with stiffening microelectrodes (at the backside) at 0 and 50% strains. Scale bars, 500 µm. (E) Photographs of the sensor attached to a hand wrist without and with outward bending. The inset picture is the enlarged view showing the maintained conformability of the sensor under skin deformation. 

 

ADVANTAGES

ADVANTAGES

  • Stretchable and strain-insensitive pressure sensor that performs extremely well under strain compared to currently available stretchable pressure sensors.
  • Provides unaltered sensing performance under stretching in that it exhibits 98% strain-insensitivity up to 50% strain.
  • Flexibility allows it to adhere to soft/dynamic surfaces for a variety of applications, all while maintaining accuracy.

 

APPLICATIONS

  • Wearable electronics, including wearable health monitoring
  • Prosthetic e-skins and quantitative measurement of on-skin pressure
  • Soft robotics
  • ICOS devices to measure trace gases in the upper atmosphere
  • Sensors built and tested

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