Shear-force sensors on flexible substrates using inkjet printing

Printing techniques are a promising way of fabricating low-cost electronics without the need for masking and etching. In recent years, additive printing techniques, such as inkjet and screen printing, have been adopted to fabricate low-cost and large-area electronics on flexible substrates. In this work, a three-axial normal and shear force sensor was designed and printed that consists of four miniaturized, printed capacitors. The partially overlapping electrodes are arranged in a manner, so that force sensitivity in orthogonal directions is achieved. A silicone rubber is used as an elastic dielectric and spacer between the two electrodes. The base unit of this sensor has been fabricated using inkjet printing and characterized for normal and shear forces. The force response was investigated in a force range from 0.1 N to 8 N, the normal-force sensitivity was determined to be Sz = 5 2 f F/N, and the shear-force sensitivity was Sy = 13 1 f F/N. Due to its sensing range, this sensor could be applicable in tactile sensing systems like wearables and artificial electronic skins.