Nanoparticle-Structured Highly Sensitive and Anisotropic Gauge Sensors

Abstract

The ability to tune gauge factors in terms of magnitude and orientation is important for wearable and conformal electronics. Herein, a sensor device is described which is fabricated by assembling and printing molecularly linked thin films of gold nanoparticles on flexible microelectrodes with unusually high and anisotropic gauge factors. A sharp difference in gauge factors up to two to three orders of magnitude between bending perpendicular (B(⊥)) and parallel (B(||)) to the current flow directions is observed. The origin of the unusual high and anisotropic gauge factors is analyzed in terms of nanoparticle size, interparticle spacing, interparticle structure, and other parameters, and by considering the theoretical aspects of electron conduction mechanism and percolation pathway. A critical range of resistivity where a very small change in strain and the strain orientation is identified to impact the percolation pathway in a significant way, leading to the high and anisotropic gauge factors. The gauge anisotropy stems from molecular and nanoscale fine tuning of interparticle properties of molecularly linked nanoparticle assembly on flexible microelectrodes, which has important implication for the design of gauge sensors for highly sensitive detection of deformation in complex sensing environment or on complex curved surfaces such as wearable electronics and skin sensors.

Surface‐Mediated Interconnections of Nanoparticles in Cellulosic Fibrous Materials toward 3D Sensors

“…[ 35 ] The devices were housed in a Teflon chamber with tubing connections to vapor, gas, and N 2 sources (at 22 ± 1 °C). The electrical conductivity (σ) of the NP thin film can be described by a thermally activated conduction path [ 36 ] where r is the particle core radius, ε is the dielectric constant of interparticle medium, d is the interparticle distance, and other parameters e = 1.6 × 10 −19 C, ε 0 = 8.854 × 10 −12 F m −1 , R = 1.38 × 10 −23 J K −1 , T = 300 K, and β (4–10 nm −1 ) is the electron coupling term dependent on particle size and relatively independent of distance of the interparticle linkages, respectively. The resistance ( R ), reciprocal to electric conductivity (σ) is reported as relative differential resistance change, i.e., ∆ R / R i , where ∆ R represents the resistance response and R i represents the initial resistance.…”

Designing Metallic and Insulating Nanocrystal Heterostructures to Fabricate Highly Sensitive and Solution Processed Strain Gauges for Wearable Sensors

“…Upon applied strain, the increased interparticle distance would increase the resistance of NC thin films, perfectly matching the resistive strain gauge system. With these advantages, NCs have been used to construct strain gauge sensors . While NC‐based strain gauge sensors allow low‐cost and easy fabrication methods with higher sensitivity than bulk materials, the performance of NC based strain gauges still needs to be improved; these sensors show disadvantages such as mediocre sensitivity, low durability and stability, asymmetric hysteresis, and slow response time despite the fact that many efforts have been made to enhance their performance.…”

Vectorial strain gauge method using single flexible orthogonal polydimethylsiloxane gratings

“…Yang 7 reported a self-powered wind vector sensor system for wind speed and direction detection using four same triboelectric nanogenerators arranged along four different directions to sense the magnitude and direction of wind signals. Zhao 8 fabricated a high sensitivity vectorial strain gauge by assembling two same flexible microelectrodes in cross direction, which can be tuned to detect the magnitude and orientation and were appropriate for wearable and conformal electronics. However, the above approach was prone to errors which were related to the assembly of two or more of sensitive elements and the complexity of the fabrication process being at the same time of relatively large size.…”