Out-of-plane high-density piezoresistive silicon microwire/p–n diode array for force- and temperature-sensitive artificial whisker sensors

Abstract

We propose an out-of-plane high-aspect-ratio 'whisker-like' microwire array sensor for use in multisite contact force and temperature detection with high spatial resolution. Although the wire element has two terminal electrodes, the device consists of force-sensitive wire arrays where one end of the wire is attached to the substrate and the other end is free to be touched. We fabricated a force-sensitive wire array based on p-type (p-) silicon with 3 µm diameter and 30 µm length (1 Ω cm) assembled over an n-type (n-) silicon substrate (3–6 Ω cm), which resulted in a p-silicon wire/p–n diode system array. Due to the piezoresistance effect of the p-silicon wire, the electrical conductance changes upon contact of an individual wire with an object. The shift in the rectifying current–voltage (I–V) curves of the embedded p–n diode depends on the temperature through the silicon wire. Thus, the same alignment can be used as a force sensor and a temperature sensor. Both force- and temperature-sensitive microwire sensor arrays with a small detection area (~20 µm2) and high spatial resolution (~100 µm in pitch) have potential in numerous applications, including artificial electronic fingertips in a robot hand/prosthetics, multisite sensing of contact force, shear force, surface roughness and slip, and local temperature sensing capabilities.