Significant strain-rate dependence of sensing behavior in TiO2@carbon fibre/PDMS composites for flexible strain sensors

Carbon fibre (CF) embedded into elastomeric media has been attracting incredible interest as flexible strain sensors in the application of skin electronics owing to their high sensitivity in a very small strain gauge. To further improve the sensitivity of CF/PDMS composite strain sensor, the relatively low temperature prepared TiO2 nanowire via hydrothermal route was employed herein to functionalize CF. The results showed a significant increase in the sensitivity of the TiO2@CF/PDMS composite strain sensors which was reflected by the calculated gauge factor. As the prepared TiO2 nanowire vertically embraced the surroundings of the CF, the introduced TiO2 nanowire contributed to a highly porous structure which played a predominant role in improving the sensitivity of strain sensors. Moreover, the significant strain rate dependent behavior of TiO2@CF/PDMS strain sensor was revealed when performing monotonic tests at varied strain rate. Therefore, introducing TiO2 nanowire on CF offers a new technique for fabricating flexible strain sensors with improved sensitivity for the application of flexible electronics.

Piezoresistive Characteristics of Nanocarbon Composite Strain Sensor by Its Longitudinal Pattern Design

For an engineering feasibility study, we studied a simple design to improve NCSS (nanocarbon composite strain sensor) sensitivity by using its geometric pattern at a macro scale. We fabricated bulk- and grid-type sensors with different filler content weights (wt.%) and different sensor lengths and investigated their sensitivity characteristics. We also proposed a unit gauge factor model of NCSS to find a correlation between sensor length and its sensitivity. NCSS sensitivity was improved proportional to its length incremental ratio and we were able to achieve better linear and consistent data from the grid type than the bulk type one. We conclude that the longer sensor length results in a larger change of resistance due to its piezoresistive unit summation and that sensor geometric pattern design is one of the important issues for axial load and deformation measurement.

3D-Printed Load Cell Using Nanocarbon Composite Strain Sensor

The development of a 3D-Printed Load Cell (PLC) was studied using a nanocarbon composite strain sensor (NCSS) and a 3D printing process. The miniature load cell was fabricated using a low-cost LCD-based 3D printer with UV resin. The NCSS composed of 0.5 wt% MWCNT/epoxy was used to create the flexure of PLC. PLC performance was evaluated under a rated load range; its output was equal to the common value of 2 mV/V. The performance was also evaluated after a calibration in terms of non-linearity, repeatability, and hysteresis, with final results of 2.12%, 1.60%, and 4.42%, respectively. Creep and creep recovery were found to be 1.68 (%FS) and 4.16 (%FS). The relative inferiorities of PLC seem to originate from the inherent hyper-elastic characteristics of polymer sensors. The 3D PLC developed may be a promising solution for the OEM/design-in load cell market and may also result in the development of a novel 3D-printed sensor.