Strategies for tuning sensitivity to strain in sensors for flexible electronics

  • Yangyang Xin

Student thesis: Doctoral Thesis

Abstract

Significant developments in flexible/stretchable electronics are needed due to the increasing demand for stretchable sensors in soft robotics, prostheses, and human-machine interfaces. Stretchable strain sensors must be extremely sensitive to the applied strain in order to be used in monitoring human movement, tracking pulses, and identifying sounds. Percolated networks based on nanomaterials with intrinsic stretchability are primarily used to create large stretchable strain sensors with high sensitivity and stretchability. However, sensitivity and stretchability are two opposite faces of a coin, and these sensors face limited sensitivity both in tension and compression.The aforementioned drawbacks limit application such as large-scale deformable surface monitoring and effective e-skins for monitoring complex strain states. Pollution from strain, on the other hand, is a problem that must be avoided for other types of stretchable sensors. Strain-insensitive sensors are mostly based on the geometrical design with a complicated fabrication. New methods for developing strain-insensitive sensors based on percolated networks are urgently needed to simplify the fabrication process. Four objectives are listed to solve the problems as mentioned above: to develop a method to balance the stretchability and sensitivity; to design a stretchable strain sensor with whole range working ability; to create a strain insensitivity sensor different from the geometry design; to investigate the physical mechanism of the new method. In Chapter 2, a laser engraving method was used to increase the crack density in CNT paper, which successfully improved the stretchability while maintaining the high sensitivity. Then, in Chapter 3, a pre-stretching/releasing method was used to partially open the cracks in CNT paper in order to achieve sensitivity in both positive and negative strain. The Seebeck effect of percolated networks was then used to develop a strain-insensitive temperature sensor in Chapter 4. Finally, in Chapter 5, we performed a theoretical analysis to reveal the physical mechanism of the Seebeck coefficient’s stability in percolated networks.
Date of AwardSep 2021
Original languageEnglish (US)
Awarding Institution
  • Physical Science and Engineering
SupervisorGilles Lubineau (Supervisor)

Keywords

  • stretchable electronics
  • strain-sensitivity
  • strain-intensitivity
  • crack density
  • seebeck effect
  • percolted networks

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