Highly Anisotropic, Thermally Conductive, and Stretchable Carbon Fiber/Nanotube Elastomer Composite Fabricated via a Multilayer Float Assembly Method

Flexible/stretchable small electronic devices require efficient thermal management to maintain optimal performance and prevent heat degradation. Thermally dissipating materials, such as filler-reinforced elastomer composites possessing high thermal conductivity and stretchability, have become promising solutions to address these issues. However, conventional methods of randomly blending fillers, along with the trade-off between high filler loading and mechanical properties, make these demands challenging. Herein, a carbon fibers (CFs)/carbon nanotubes (CNTs) elastomer composite was fabricated using the multilayer float assembly method (FAM). This method enables CFs to align in a specific direction, increasing the heat conduction pathway and leading to high anisotropic in-plane thermal conductivity. CNTs were used as bridges to enhance the interconnected surface areas between CFs, lowering the interfacial thermal resistance (ITR) between CFs. Furthermore, by using multilayer FAM, CFs were partially exposed in the elastomer, reducing local stress concentration and thus enabling the composite to maintain high stretchability at high loadings. As a result, a high in-plane thermal conductivity of 32.6 W/m·K at 60 wt % (16,000% enhancement over the raw elastomer), with a strain exceeding 45%, was achieved. In particular, the composite is notably ultrathin (200 μm) without requiring additional modifications, making it well suited to the ongoing trend toward miniaturization in electronic devices. This composite is anticipated to play a key role in thermal management applications for compact, flexible, and stretchable devices.