Design and Fabrication of Buckled Metal Strain Gauges Using Shape Memory Polymer and Inkjet Additive Microfabrication Robert C. Roberts, Sheng Zeng, and Norman C. Tien Additive Microfabrication Laboratory Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong Email:
[email protected] Abstract— This paper reports on the design and fabrication of buckled metal strain gauges formed using a thermally contracting shape memory polymer (SMP) via inkjet printed silver nanoparticles to create sensors realized in a large initial compressive stress state. Printed devices are placed into an oven to simultaneously sinter the nanoparticles and shrink the substrate into its final dimensions creating devices with feature sizes unobtainable by direct printing. An unconventional offset serpentine strain gauge geometry is presented which overcomes the local anisotropy of SMP contraction. A prototype process is then employed to realize and demonstrate functional strain gauges using printed silver on SMP. The simple fabrication process allows for the realization of metal strain gauges precompressed through a substrate size contraction of 2.5 for the first time. Keywords—Additive Microfabrication; Inkjet Printing; Silver Nanoparticles; Strain Gauge; Shape Memory Polymer
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INTRODUCTION
Recently, the field of stretchable electronics has been exploring the use of nanomaterials to develop strain gauges that overcome the deformation limits of conventional metal devices that are typically limited to
