Biomanufacturing of Hierarchical Biocomposites for High-Performance Thermal Interface Materials

This topic addresses the thermal management challenge to dissipate the large amount of heat generated by today’s high-density microelectronics and power storage systems to ensure and maintain performance, reliability, and safety [3, 4, 6] Thermal interface materials (TIMs) are a critical component in this thermal management. TIMs are designed to fill microgaps and surface irregularities between the otherwise bare surfaces between device and cooling system. Without a TIM, if two nominally flat and smooth solid surfaces are joined to form a bare contact, surface microroughness can limit the actual area of contact between the two solids to about 1–2% of the apparent contact area [11]. The solid-to-solid conduction through the contact points and conduction through the air trapped between the area of noncontact are poor thermal conductors and they limit the heat transfer from one surface to another. This thermal contact resistance needs to be reduced by inserting a TIM in the contact interface to eliminate air voids by filling the air gap at the device/cooling system interface.The general requirements for a good TIM include low interfacial thermal resistance, high thermal conductivity, low elastic modulus, good adhesion, good conformability, long-term stability, and appropriate thermal expansion [7]. This is particularly challenging for mechanically flexible applications because the soft, polymeric materials commonly used as a matrix for TIMs generally have low thermal conductivity (TC) [7, 1], leading to difficulty in handling the thermal management demands. Drones and electric vehicles represent another application classic thermal management challenge arising from high C-rate battery pack discharge/charge cycles during operation. The drone case may be particularly difficult since payload and flight time constraints often dictate passive thermal management approaches such as heat sinks and air cooling [5], with TIMs a critical component for thermal coupling between the heat sink and battery packaging. In addition to thermal conductivity demands, power and high-frequency systems also often require TIMs that pair high heat conduction with electrical insulation, breakdown resistance, low leakage, and geometric conformity [1, 2]. While traditional thermal pastes and greases perform well under certain conditions, they still face challenges such as insufficient thermal conductivity (TC), aging, and poor reliability when applied in high-frequency, high-power density applications. In recent years, significant progress has been made in the material design and synthesis of high-performance TIMs. However, balancing various aspects such as interfacial thermal resistance, TC, and mechanical properties in TIMs continues to pose a significant challenge. Biomanufactured and biocomposite filler-type TIMs with simultaneous high TC and electrical insulation [8, 9] may be ideal materials to address these thermal and electrical requirements, while also offering a lower cost, supply chain sustainable solution compared to cutting-edge fillers such as boron-based semiconductors and carbon nanotubes.