Chain-like aligned boron nitride embedded in elastomer for thermal management in wearable electronics

With ongoing advances in integration density, power output and miniaturization of wearable electronics, efficient thermal management has become increasingly critical. To address heat accumulation, thermally conductive composites with aligned fillers have attracted growing attention. However, the random distribution and orientation of fillers in elastomers demands high filler loading in order to achieve desired thermal conductivity, inevitably sacrificing mechanical properties and limiting flexible applications. Herein, we develop a stretchable and thermally conductive composite by applying prolonged magnetic field to form chain-like aligned boron nitride (BN) sheets within an elastomer matrix (polydimethylsiloxane, PDMS) to effectively reduce the thermal percolation threshold. The resulting composite with only 20 wt% filler loading achieves a high through-plane thermal conductivity of 1.57 W·m⁻¹ ·K⁻¹ , more than 800 % higher than that of the pristine elastomer matrix. Meanwhile, it maintains an excellent mechanical compliance with up to 134 % elongation at break. When employed as encapsulation materials, the composite can not only effectively dissipate heat in LEDs by reducing temperature increase by approximately 37 %, but also can significantly accelerate the response of wearable temperature sensors by reducing the sensing time by 54 %. Our strategy presents a promising pathway for designing stretchable thermal management materials for next-generation wearable electronic devices. • A new thermally conductive and stretchable boron nitride/elastomer nanocomposite. • A two-stage magnetic-field-induced chain-like alignment mechanism. • Accelerating the response speed of wearable temperature sensor as an encapsulation material.