Miniaturized and high‐power‐density 3D electronic devices pose new challenges on thermal management. Indeed, prompt heat dissipation in electrically insulating packaging is currently limited by the thermal conductivity achieved by thermal interface materials (TIMs) and by their capability to direct the heat toward heat sinks. Here, high thermal conductivity boron nitride (BN)‐based composites that are able to conduct heat intentionally toward specific areas by locally orienting magnetically functionalized BN microplatelets are created using magnetically assisted slip casting. The obtained thermal conductivity along the direction of alignment is unusually high, up to 12.1 W m−1 K−1, thanks to the high concentration of 62.6 vol% of BN in the composite, the low concentration in polymeric binder, and the high degree of alignment. The BN composites have a low density of 1.3 g cm−3, a high stiffness of 442.3 MPa, and are electrically insulating. Uniquely, the approach is demonstrated with proof‐of‐concept composites having locally graded orientations of BN microplatelets to direct the heat away from two vertically stacked heat sources. Rationally designing the microstructure of TIMs to direct heat strategically provides a promising solution for efficient thermal management in 3D integrated electronics.

Mycelium, as the root of fungi, is composed of filamentous strands of fine hyphae that bind discrete substrate particles into a block material. With advanced processing, dense mycelium-bound composites (DMCs) resembling commercial particleboards can be formed. However, their mechanical properties and performance under the working conditions of particleboards are unknown. Here, we show how weathering conditions affect the DMC stress and elastic modulus. DMC was made using Ganoderma lucidum mycelium grown on a substrate of sawdust and empty fruit bunch. The DMC was then subjected to weathering under tropical conditions over 35 days and tested under flexural, tensile, and compressive loading with reference to international standards. After exposure to specified weathering conditions, the maximum stress in flexure, tension, and compression decreased substantially. The addition of a protective coating improved the resistance of DMC to weathering conditions; however, the difference between coated and uncoated samples was only found to be statistically significant in tensile strength.

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Heat Transfer In article number 2205120, Hortense Le Ferrand and co‐workers present a high‐thermal‐conductivity BN‐based composite with locally oriented microstructures that can conduct heat intentionally toward specific areas. The customizable heat‐transfer paths highlight a solution for thermal management of future 3D integrated electronics.

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