Flexible, scalable, and efficient thermoelectric touch detector based on PDMS and graphite flakes

Abstract

This paper presents freestanding thermoelectric touch detectors consisting of graphite conductive flakes into a polydimethylsiloxane matrix. An optimal concentration of graphite flakes (45 wt%) lead to robust and homogeneous detectors that exhibited signal-noise ratio values up to 170 with rise and falling times below 1 s and 7 s, respectively. The detectors performance was stable over continuous operation and did not reveal significant degradation while bended under different curvature radii (45, 25 and 15 mm) and consecutive bending cycles. Moreover, the twist of the thermal gradient direction between the electrodes of the detector enables a Yes or No response which opens new usage possibilities. Therefore, this work provides an efficient way to develop robust, low-cost, and scalable thermal detectors with potential use in wearable technologies.

Screen-printed, flexible, and eco-friendly thermoelectric touch sensors based on ethyl cellulose and graphite flakes inks

“…To complement the characterization of the samples printed on OP and Cot, S measurements were performed (S3). As expected [4,7], all values were positive (G is reported as a p-type material) and around 20 µV/ • C, regardless of the substrate and printing conditions (Figure 6), meaning that the TE behaviour for this specific application will show similar responses notwithstanding the differences in R Sheet . The V OC of the samples was measured over time, in order to study the gloved finger touches response of the TE elements.…”

“…Graphite (G) among other carbon-based materials is known to have TE response but with relatively small S, when compared with more established TE materials [4]. However, there are reports showing that some of these materials can perform better than common organic conducting counterparts such as PEDOT:PSS, since the S is sometimes larger and they are able to sustain higher processing T if needed [6][7][8][9][10][11].…”

“…In terms of geometry, TE devices can assume vertical or planar structures, depending on how the heat flows and on the layout of the TE elements during fabrication [29], and can be made of thermocouples (p-n pairs) which is the common configuration or can be made with just one single TE type [4,20,30,31]. The formulation of TE inks for screen-printing allows great freedom for different geometries and large area applications, without the need for complex cleanroom processes.…”

MXene Nanosheet/Organics Superlattice for Flexible Thermoelectrics

“…Developing composite materials, specifically nano- composites based on organic/inorganic compositing, has been proven to be an effective strategy to achieve the best of both worlds, namely, good electrical transport properties of inorganics and excellent flexibility/low thermal conductivities of organics. For example, Figueira et al 11 fabricated a flexible, scalable, and efficient TE touch detector based on a poly(dimethylsiloxane)/graphite flakes composite. Compared with 3D materials, two-dimensional (2D) materials, such as atomically thin graphene, black phosphorus, and transition-metal dichalcogenide, are rigid against bending because of strong in-plane covalent bonding but intrinsically flexible because of the lack of out-of-plane constraint 12,13 and exhibit excellent electronic transport properties.…”

“…Developing composite materials, specifically nanocomposites based on organic/inorganic compositing, has been proven to be an effective strategy to achieve the best of both worlds, namely, good electrical transport properties of inorganics and excellent flexibility/low thermal conductivities of organics. For example, Figueira et al fabricated a flexible, scalable, and efficient TE touch detector based on a poly­(dimethylsiloxane)/graphite flakes composite.…”