Processing Natural Wood into a High-Performance Flexible Pressure Sensor

Abstract

Flexible pressure sensors have received wide attention because of their potential applications in wearable electronics and electronic skins (e-skins). However, the high performance of the pressure sensors relies principally on the introduction of complex surface microstructures, which often involves either complicated procedures or costly microfabrication methods. Moreover, these devices predominantly use synthetic polymers as flexible substrates, which are generally nonbiodegradable or not ecofriendly. Here, we report a facile and scalable processing strategy to convert naturally rigid wood into reduced graphene oxide (rGO)-modified flexible wood (FW/rGO) via saw cutting, chemical treatment, and rGO coating, resulting in high-performance wood-based flexible piezoresistive pressure sensors. Benefiting from the largely deformable ribbon-like surface microstructures, the obtained wood-based pressure sensor displayed a high sensitivity of 1.85 kPa −1 over a broad linear range up to 60 kPa and showed high stability over 10 000 cyclic pressings. The favorable sensing performance of the pressure sensor allows for accurate recognition of finger movements, acoustic vibrations, and real-time pulse waves. Moreover, a large-area pressure sensor array has been successfully assembled on one piece of flexible wood for spatial pressure mapping. The proposed strategy of directly using natural wood for high-performance flexible pressure sensors is simple, low-cost, sustainable, and scalable, opening up a new avenue for the development of next-generation wearable electronics and e-skins.

Recent Application of Cellulose Gel in Flexible Sensing-A Review

“…Examples include identifying complex arterial pulse signals, thus highlighting its potential applications in real-time healthcare and medical diagnostics. [145] Reprinted with permission from Ref. 144 Adapted with permissions from Carbohydrate Polymers.…”

“…Fig.11(a)Various flexible, skin-mountable, and wearable strain sensors made of functional nanomaterials-polymer composites. Reprinted with permission from Ref 145. Adapted with permissions from ACS Applied Materials & Interfaces.…”

Transforming wood as next‐generation structural and functional materials for a sustainable future

“…Guan et al turned natural saw-cut wood into a flexible pressure sensor by chemical treatment and rGO coating. 180 This flexible wood-based wearable device can precisely detect finger movement, acoustic vibration, and arterial pulse signal. It has a fast response time of 150 ms, high sensitivity of 1.85 k Pa À1 over a wide linear range of 0-60 k Pa À1 , and very long stability of 1000 cycles.…”

Hive‐Inspired Multifunctional Wood‐Nanotechnology‐Derived Membranes with a Double‐Layer Conductive Network Structure for Flexible Electronics

“…Balsa wood was chosen as the starting material because of its low density, a unique 3D porous structure with multiple channels and a thin cell wall (Figure S1, S2, Supporting Information), which make it easier to partially destroy the cell walls. [27,28] The wood cell wall was a robust assembly of stiff cellulose fibrils intertwined with the matrix polymers of hemicelluloses and lignin, [29] hence it was rigid and was easily broken upon bending (Figure S3; Video S1, Supporting Information). The NW was made flexible by partially removing the lignin and the hemicellulose from the cell walls via the NaOH/Na 2 SO 3 chemical treatment.…”

“…The hemicellulose and the partial cellulose can be dissolved in an alkaline solution containing sulfite. [28] The Fourier Transform infrared spectroscopy (FTIR) (Figure 2b) showed that the peaks at 1736 and 1235 cm −1 for the carbonyl and C-O stretching were significantly reduced, reflecting a remarkable hemicellulose removal. Meanwhile, the decline of the peaks at 1593 and 1505 cm −1 yielded an aromatic skeleton, showing lignin partial removal during the NaOH/Na 2 SO 3 treatment.…”