Design and Fabrication of an Aerosol Jet Printed Tactile Sensor on Flexible Substrate

Inkjet printing for fabricating microstructures has gained popularity during the last decade, making it possible to realize complex electronic circuits, components, and devices previously manufactured using 2-D lithographic processes. Aerosol jet printing enables the deposition of feature sizes in the micrometer-scale order. This work investigates a tactile sensor that features a strain gauge in a circular pattern and uses aerosol inkjet printing delivered from the NeXus, a custom-built microfabrication platform that can deposit silver ink on a flexible printed circuit (FPC) substrate. The finite-element analysis (FEA) to evaluate the performance of the tactile sensor is also presented, packaged in between cover and bedding created with elastomer to fit the tactile sensor. The elastomer covering and bedding contains a dimple and cavity complying with external deformation, which concentrates on the applied indented force. A simulation was used to optimize the configuration of the dimple size, cover, and bedding design required to improve the sensor performance. The fabrication method for creating 10-mm-diameter circular strain gauge tactile sensors includes an annealing process using the oven, developed by comparing different curing times. Finally, experimental indentation tests were carried out under varying curing schedules, evaluated by loading packaged sensors with increasing weight, and indented the force profile from 0.5 to 2.0 N. Results show a 67% decrease in resistance from 2 to 20 h of oven cure and about a 0.08% increase in sensitivity.