Electrical conduction of nanoparticle monolayer for accurate tracking of mechanical stimulus in finger touch sensing

Abstract

A flexible strain gauge is an essential component in advanced human-machine interfacing, especially when it comes to many important mobile and biomedical appliances that require the detection of finger touches. In this paper, we report one such strain gauge made from a strip of nanoparticle monolayer onto a flexible substrate. This proposed gauge operates on the observation that there is a linear relationship between electrical conduction and mechanical displacement in a compressive state. Due to its prompt temporal response, the gauge can accurately track various mechanical stimuli running at the frequencies of interest. Experiments have confirmed that the proposed strain gauge has a strain detection limit as low as 9.4 × 10(-5), and its gauge factor can be as large as 70, making this device particularly suitable for sensitive finger touch sensing. Furthermore, negligible degradation in the gauge's output electrical signal is observed even after 9000 loading/unloading cycles.

Nanoparticle monolayer-based flexible strain gauge with ultrafast dynamic response for acoustic vibration detection

“…In our previous investigation, convective assembly at the confined contact angle was developed to synthesize a uniform monolayer of Au NPs [13], and the operating principle of this technique is schematically illustrated in Fig. 1(a).…”

“…to assemble NP strip with a width of 2-3 m was described in our previous work [13]. Au NPs were dispersed onto an amorphous C film supported by a Cu grid for transmission electron microscopy (TEM) observations.…”

“…Monolayer MoS 2 was demonstrated to reproducibly sense mechanical strain as low as 0.53% [12]. Even more dramatically, a Au NP monolayer could convert mechanical strain as low as 0.0094% [13] into a reliable output signal based on electron tunneling events occurring within the nanoscale crevices. However, nanoarchitecture ensembles can simultaneously provide both desired reliability and a broad detection range beyond the elastic regime.…”

“…To a certain extent, these artificial nanoarchitectures, individually or collectively through their ensembles, mimic the functionalities of some natural organ counterparts, which helps the mechanical gauges to deliver the operating range of mechanical strain and signal reliability required by the applications. Individual VO 2 nanowires [11], monolayers of MoS 2 or graphene [12], and monolayers of NP [13] were observed to create a reversible electrical current or voltage signal due to piezoelectric or piezoresistive mechanisms, with superior detection limits. Monolayer MoS 2 was demonstrated to reproducibly sense mechanical strain as low as 0.53% [12].…”

Survey of plasmonic gaps tuned at sub-nanometer scale in self-assembled arrays

“…Tian et al claimed that a minimum gap size of 0.4 nm can be achieved; this is more sensitive than the tunable range in conventional stretching techniques. In our previous investigations, the gap within the NP monolayer can be tuned towards the sub-nm scale if the point of contact between the NPs and the polymer substrate is assumed [50,66]. The minimum gap sizes reported in several researches are listed in Fig.…”