A tensorial shear stress sensor based on light-emitting GaN nanopillars

Abstract

A force sensor capable of detecting both the magnitude and direction of the shear stress is proposed and demonstrated. The structure is based on an array of gallium nitride (GaN) light-emitting nanostructures and an off-the-shelf imager. The directional sensitivity originates from symmetry breaking of the nanostructures. Only a common bias is required for all GaN elements, making two-dimensional mapping of the stress relatively simple. As the stress sensing relies only on differential measurements, no stringent uniformity requirement across the sensor array is necessary.

Ultrathin Tactile Sensors with Directional Sensitivity and a High Spatial Resolution

“…Recently, a method of measuring the shear force based on gallium nitride (GaN) nanostructures was reported . Instead of inducing a change of resistance or capacitance, the device used optically active piezoelectric nanostructures.…”

“…To apply the shear force, a stress applicator was fabricated by patterning a square of photoresist (SPR220; 2.2 μm) on a sapphire wafer using optical lithography. The photoresist was then exposed again to ultraviolet light to render it transparent to visible wavelengths …”

“…The photoresist was then exposed again to ultraviolet light to render it transparent to visible wavelengths. 40 To create sufficient clearance for the stress applicator, we opted to use an imaging optics configuration to project the image of the sensor array to the DSLR camera. During measurements, the sample was excited by a 405 nm laser diode at an angle.…”

“…Recently, a method of measuring the shear force based on gallium nitride (GaN) nanostructures was reported. 40 Instead of inducing a change of resistance or capacitance, the device used optically active piezoelectric nanostructures. The stressinduced change in the electronic band structure was monitored by measuring the light emission using a photodetector.…”

Nanoarchitectonics for Wide Bandgap Semiconductor Nanowires: Toward the Next Generation of Nanoelectromechanical Systems for Environmental Monitoring

“…[244,245] For mechanical sensing in extreme conditions, WBG semiconductor nanowires of SiC, group III-nitrides, and diamond are the material of choice due to their outstanding electrical properties, chemical inertness, mechanical durability and especially, a tunable giant piezoresistive effect. [246][247][248][249][250] For instance, Gao et al reported the piezoresistance behaviors of single p-type 6H-SiC nanowires under different compressive stresses using a conductive AFM as the test bed. [246] The authors observed the decrease of the nanowire resistance with increasing compressive strain.…”