Single-Nanowire strain sensors fabricated by nanoskiving

Abstract

This article describes the fabrication of single-nanowire strain sensors by thin sectioning of gold films with an ultramicrotome—i.e., “nanoskiving.” The nanowire sensors are transferred to various substrates from the water bath on which they float after sectioning. The electrical response of these single nanowires to mechanical strain is investigated, with the lowest detectable strain determined to be 1.6 × 10−5 with a repeatable response to strains as high as 7 × 10−4. The sensors are shown to have an enhanced sensitivity with a gauge factor of 3.1 on average, but as high as 9.5 in the low strain regime (ε ~ 1 × 10−5). Conventional thin films of gold of the same height as the nanowires are used as controls, and are unable to detect those same strains. The practicality of this sensor is investigated by transferring a single nanowire to polyimide tape, and placing the sensor on the wrist to monitor the pulse pressure waveform from the radial artery. The nanowires are fabricated with simple tools and require no lithography. Moreover, the sensors can be “manufactured” efficiently, as each consecutive section of the film is a quasi copy of the previous nanowire. The simple fabrication of these nanowires, along with the compatibility with flexible substrates, offers possibilities in developing new kinds of devices for biomedical applications and structural health monitoring.

Metal Mesh as a Transparent Omnidirectional Strain Sensor

“…The stretch sensitivity is evaluated by the gauge factor, which is the ratio of Δ R / R 0 to Δ L / L 0 , as shown in Figure a where L 0 is the initial length of the sensor, and Δ L is the length changes along the tensile strain. The linearly defined gauge factor in region of 0–15% strain is 14.3, which is higher than those of Ag film and Ag nanowires–based sensor . In the strain region of 15–35%, the average gauge factor is up to 99.5.…”

Engineering Colloidal Lithography and Nanoskiving to Fabricate Rows of Opposing Crescent Nanogaps

“…The structures of the CNWs retain its original shape in the process of transferring them onto a substrate for imaging and removing the sacrificial nanosphere template. [ 43,44 ] The large area SEM image of CNWs is shown in Figure S1a, Supporting Information, it demonstrates the long axis nanostructures can be obtained via the combination of colloidal lithography and nanoskiving technique.…”

“…The coupling between the nanogaps and tips leads to extreme electric field enhancement in the tipped‐nanogaps, resulting in potential applications in, for example, surface‐enhanced spectroscopy. [ 43 ] Here, we fabricated a crescent nanogaps dimer consisting of two crescent nanogaps with opposing tip, termed as OCNGs. The fabrication process is to successively deposit gold (110 nm)/aluminum (4 nm)/gold (110 nm) sandwich films on the close‐packed colloidal monolayer in the deposition step (Figure 3b,d).…”

“…[ 54 ] However, the SERS enhancement factor is less than the max enhancement (| E | 4 max ), because the Raman probe molecules can attach anywhere along the y ‐axis of the crescent nanostructures and also the Raman signal is a weighted average. [ 43 ]…”

“…Herein, we combined colloidal lithography and nanoskiving (CL‐nanoskiving) [ 41–43 ] to develop a novel low‐cost method for preparing different types of crescent‐shaped plasmonic nanostructures. In contrast to the previous periodic crescent nanogap arrays, [ 44 ] our crescent nanostructures were fabricated based on close‐packed nanospheres and vertical physical sectioning.…”