Surface coatings of silver nanowires lead to effective, high conductivity, high-strain, ultrathin sensors

Abstract

Abstract:Integrated sensors for bodily measurements require a sensing material that are highly conductive, flexible, thin and sensitive. It is important that these materials be non-invasive in application but robust in nature to allow for effective, continuous measurement. Herein, we report a comparative study of two simple, scalable methods to produce silver nanowire (AgNW) polyurethane (PU) composite materials: layer-by-layer (LBL) and mixed filtration.Both types of composites formed were ultrathin (~50 µm) and highly conductive (10 4 S/m), with the LBL method ultimately found to be superior due to its low percolation threshold.Electrical resistance of the LBL composites was found to vary with strain, making these materials suitable for strain sensing. LBL composites displayed a working strain up to ~250% and a high gauge factor (G), with values of G~70 reported. The sensors reported here were ~10 9 -times more conductive and ~10 4 -times thinner than their carbon-based composite sensor counterparts with similar gauge factor. This made the strain sensors presented here among one of the most flexible, highly sensitive, thinnest, conductive materials in literature.We demonstrated that with these properties, the LBL composites formed were ideal for bodily motion detection. Introduction:

Stumbling through the Research Wilderness, Standard Methods To Shine Light on Electrically Conductive Nanocomposites for Future Healthcare Monitoring

“…[57,58] Thus, dispersion factors can result in regions of high and low conductor density which have been reported to greatly affect the linearity of a composite system's electrical response to strain. [14,59] Poor dispersal of conductive material can lead to a scenario where network effects now dominate the linearity of the response rather than the matrix, which would lead to a less than optimum working range for a particular system. Or in other words, a working range that is lower than the maximum value set by the polymer and it's yield strain.…”

Strain Sensors with a High Sensitivity and a Wide Sensing Range Based on a Ti3C2Tx (MXene) Nanoparticle–Nanosheet Hybrid Network

“…Another strategy is to synthesize new conductive materials and tune their microstructures to enhance the sensing performance. Generally, a strain sensor made of a 1D material always exhibits a large working range but a poor sensitivity, since 1D materials with a high aspect ratio can maintain good interconnection while manifesting inconspicuous resistance changes under an extended strain range . Conversely, strain sensors based on 2D materials demonstrate good sensitivity but suffer from low stretchability and stability, which may be related with the low aspect ratio of 2D materials .…”

Ti3C2Tx MXene-graphene composite films for wearable strain sensors featured with high sensitivity and large range of linear response

“…carbon black, carbon nanotubes and graphene) [14][15][16][17][18][19][20][21], metal materials (e.g. Ag nanowires and Au nanoplates) and so on [22][23][24][25][26][27][28][29]. However, a sensing material with an unitary morphology is generally subject to its own structural characteristics and cannot simultaneously take both sensitivity and stretchability into account.…”