Jun Zhao,Ziliang Rui,Zhiwei Hu,Zhen Shangguan,Shuai Yin,Hao Peng
In battery thermal management (BTM), flexible phase change materials (FPCMs) emerge as highly promising substances, owing to their simple installment and low contact thermal resistance. However, FPCMs based on high thermal conductivity fillers and polymers always suffer from the enduring challenges of poor high-temperature resistance and poor filler-matrix compatibility. To solve these problems, a novel strategy is reported in this work, wherein FPCMs with excellent filler-matrix compatibility and satisfactory high-temperature resistance are synthesized by two steps: functionalizing the hexagonal boron nitride (hBN) surface and inducing the inter crosslinking between Styrene-Butadiene-Styrene(SBS) and Low-density polyethylene(LDPE). Vinyltrimethoxysilane (VTMS) molecules were introduced on the surface of raw hBN by hydroxylation and silanization surface modification to improve the compatibility of hBN with the matrix. Concluding from the results, the addition of 6.7 wt% LDPE doubled the high-temperature resistance of FPCMs, enabling them to maintain their structural integrity even at 200 °C for 1 h. The prepared FPCMs also exhibited higher thermal conductivity (increased by 20.5 %), low leakage rate (<0.6 wt% after 70 heating–cooling cycles), high enthalpy (122 J g −1 ), and strong adhesion (>0.1 MPa), etc. In terms of BTM performance, the FPCMs-based passive cooling BTM presents remarkable temperature control capabilities (maximum temperature reduction by 16.3 ℃) and uniform temperature performance (maximum temperature difference < 2.5 ℃). Collectively, this work will provide a promising approach for the fabrication of high-performance FPCMs in BTM and other thermal management applications for electronic devices.
Recently, wearable piezoresistive tactile sensors have attracted considerable attention owing to their potential applications, ranging from electronic skin to human-machine interaction. However, it is still difficult to mitigate the trade-off between sensitivity and linearity. Inspired by the hierarchical and gradient structures in natural systems, a versatile resistive pressure-sensing platform with controllable stress transfer and contact areas was fabricated by designing gradient styrene-butadiene-styrene triblock copolymer (SBS) sponges followed by the deposition of silver nanoparticles (Ag NPs) and polypyrrole (PPy). The gradient porous structures accompanied by gradient stiffness and conductivity enabled the external force to be efficiently transferred and localized to the sensing areas. Furthermore, the structures enabled a controllable response to the external stress via the gradual activation of electron pathways . These synergistic effects enabled the bioinspired tactile sensors to possess excellent sensing performance, which is demonstrated by large sensing range (∼80%), large linear range (∼72%), high sensitivity (∼1.07), low hysteresis behavior (7.66%), fast response time (177 ms), and excellent durability (more than 1100 cycles). Important applications of tactile sensors, including wrist-pulse-signal detection, speech recognition, finger bending, and tactile interfaces, have been successfully demonstrated. This conceptually simple but powerful approach can be applied to other nanomaterial systems to develop next-generation electronics.
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