Two orders of magnitude increase in metal piezoresistor sensitivity through nanoscale inhomogenization

Abstract

Metal-based piezoresistive sensing devices could find a much wider applicability if their sensitivity to mechanical strain could be substantially improved. Here, we report a simple method to enhance the strain sensitivity of metal films by over two orders of magnitude and demonstrate it on specially designed microcantilevers. By locally inhomogenizing thin gold films using controlled electromigration, we have achieved a logarithmic divergence in the strain sensitivity with progressive microstructural modification. The enhancement in strain sensitivity could be explained using non-universal tunneling-percolation transport. We find that the Johnson noise limited signal-to-noise ratio is an order of magnitude better than silicon piezoresistors. This method creates a robust platform for engineering low resistance, high gauge factor metallic piezoresistors that may have profound impact on micro and nanoscale self-sensing technology.

Cracking effects in squashable and stretchable thin metal films on PDMS for flexible microsystems and electronics

“…In the former case, the geometric effect will dominate and the gauge factor will naturally be low 86 , 87 . In the latter case, a discontinuous metal film can be evaporated onto a rigid support using a very thin film—this results in an enhanced gauge factor 86 , 88 , 89 . A discontinuous film can also be formed on a flexible support via various forms of film cracking 90 – 94 , both process and strain-induced—this also results in a higher gauge factor.…”

“… 88 Au (50 nm) Silicon L 460 not given Inhomogenized film Mohanasundaram et al . 89 Cu (188 nm) Mylar L/T 2.2/−0.6 <0.1% Geometric Rajanna and Mohan 90 Au (200 nm) PDMS/Kapton L 40–75 0–0.6% None suggested Wen et al . 91 Au (nanowires) paper/PDMS L 7.4 0–12.5% Cross conduction Gong et al .…”

A Route toward Ultrasensitive Layered Carbon Based Piezoresistive Sensors through Hierarchical Contact Design

“…This approach relies on the stress/strain induced breakage/formation of the physical contacts between BSUs and/or the related electron tunneling resistance variation to achieve high GFs. The BSUs being explored include different types of metallic nanoparticles, − nanographenes, − and metal–carbon nanotube hybrid particles, − which respectively impart GFs in the range of 100–460, 110–507, and 155–220. Because of the availability of a wide range of BSUs in terms of composition, size, and shape, the approach of creating heterogeneously structured granular matter and composite materials is more versatile and potentially has general applicability for developing ultrasensitive piezoresistive sensors at small deformations.…”

“…Highlights of the ultrasensitive piezoresistive sensors reported in the literature (open symbols) and this work (filled symbols) categorized according to material composition. M1–M8: − aggregation/assembly of metallic nanoparticles; S1–S4: − individual carbon nanotube sensors; G1–G6: − aggregation/assembly of nanographene; SM1 and SM2: , aggregation/assembly of metal–carbon nanotube hybrid particles; C1 and C2: , carbon material sensors other than carbon nanotubes and graphene; nSC1–nSC3: nanosized various semiconductor sensors; − CCAS1–3, LLAS1–2, and DDLS1: layered carbon sensors with designed hierarchical contact structures respectively representing circle–circle contact area sensor (CCAS), line–line contact area sensor (LLAS), and dot–dot contact line sensor (DDLS). The symbols listed on the top of Figure (right triangle, upper right triangle (filled and unfilled), and square) respectively represent ∂GF/∂ε > 0, ∂GF/∂ε < 0, and ∂GF/∂ε = 0 of the strain dependence behavior of GFs.…”

Direct Laser Writing of Functional Strain Sensors in Polyimide Tubes

“…This approach apparently lacks efficiency and creates huge difficulties in robustly developing a highly sophisticated, specialized, and, in particular, customized force/strain sensing system. Such a conventional gap existing between the design/fabrication of the sensitive component and the sensing elements could potentially be overcome by the various novel sensing materials emerged in recent years, such as metal nanomaterials, − carbon nanomaterials, − and composite/hybrid materials ,− as well as the associated flexible and easy-to-apply processing methods, e.g., deposition, ,,,, spraying, ,,, blending, , and 3D printing. − Among the different methods/techniques that have recently emerged, the direct laser writing carbonization (DLWc) technique is considered to have a great potential in filling the gap mentioned above. Similar to most of the currently available direct writing techniques, − DLWc also possesses the ability to create sophisticated and refined patterns.…”