Laser-Induced Graphene Electrodes on Poly(ether–ether–ketone)/PDMS Composite Films for Flexible Strain and Humidity Sensors

Abstract

Laser-induced graphene prepared on polymer substrates with a high modulus is a widely applied method to fabricate varied flexible electronics; however, the resulting relatively poor stretchability considerably limits its applicability. In this paper, an elastic composite consisting of poly(ether−ether−ketone) powder and poly(dimethylsiloxane) (PDMS) is reported to fabricate stretchable electrodes using direct laser-induced graphitization without transferring. The liquid composites before curing can be cast into various shapes for different applications. To balance the conductivity and stretchability of stretchable electrodes, we optimized the composite mass ratios and laser parameters and performed a series of morphological and performance characterizations on the composites; furthermore, we analyzed the elemental composition and functional groups of the laser-induced products. With the proper encapsulating method, strain sensors were prepared, exhibiting high sensitivity (a gauge factor of 78) and a stable resistance response over 50% operating range with the ability to monitor both fine pulse beats and larger strains such as human joint movement. Furthermore, a humidity sensor composited with laser-patterned interdigital electrode and graphene oxide on the elastic composite substrate had characteristics of high sensitivity (14.18 pF/%RH) and fast recovery time (9 s), which could be used for breathing monitoring and noncontact sensing. In conclusion, laser-induced graphene prepared in one step on a stretchable composite film of polymers with a high modulus and low modulus is a promising method to fabricate wearable electronics.

Linear Capacitive Pressure Sensor with Gradient Architecture through Laser Ablation on MWCNT/Ecoflex Film

“…Therefore, we considered that SiO 2 and SiC were produced during laser ablation. These analyses above were similar to the findings of previous studies [15,39]. In addition, Figure 4b shows the Raman spectra of the Ecoflex film, MWCNT film, and the MWCNT/Ecoflex film, as well as the MWCNT/Ecoflex film after laser ablation.…”

“…The wide use of flexible sensors, including use in applications such as electronic skins [1][2][3][4], human-computer interaction [5,6], cardiovascular monitoring [7], body joint detection [8][9][10], breathing tests [11][12][13], and information communication [14,15], has attracted academic attention. According to the working principles, flexible pressure sensors can be classified as piezoresistive [16,17], capacitive [18], triboelectric [19], and piezoelectric [20], which can effectively convert mechanical deformation into quantifiable electrical signals.…”

A Highly Sensitive Strain Sensor with Wide Linear Sensing Range Prepared on a Hybrid-Structured CNT/Ecoflex Film via Local Regulation of Strain Distribution

“…The peak detected at 1079 cm –1 indicates the vibrations caused by Si–O–Si and observed at 1010 cm –1 indicates the alkane C–H skeleton vibrations. The peak at 859 cm –1 indicates aromatic C–H stretching vibrations and at 786 cm –1 indicates the olefin C–H deformation vibration. − Compared to Ecoflex’s FTIR spectrum, the FTIR spectrum of CNT/Ecoflex and laser-engraved CNT/Ecoflex do not generate any new absorption peaks. The numerous hydrogen bonds in CNT/Ecoflex indicate a strong interaction between CNT and Ecoflex, consequently causing a slight increase in the average square resistance of the film (Figure S3) and is consistent with the former research …”

In Situ Electrical Contacts to Graphene by Laser Scribing

“…Pristine LIG-based devices have found applications in flexible systems such as energy storage devices, electrothermal heaters, and chemical sensors, enduring up to 10,000 bending cycles. − However, the top layer of LIG, which is exposed to air, exhibits weak adhesion due to its porous and fibrous network structure. This makes it susceptible to detachment compared to the LIG adjacent to the substrate, leading to easy lamination or the transfer of LIG patterns , to other substrates.…”