Design and fabrication of buckled metal strain gauges using shape memory polymer and inkjet additive microfabrication

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 pre-compressed through a substrate size contraction of 2.5 for the first time.