Significance Efficient thermal transport is critical for applications ranging from electronics and energy to advanced manufacturing and transportation; it is essential in emerging domains like wearable computing and soft robotics, which require thermally conductive materials that are also soft and stretchable. However, heat transport within soft materials is limited by the dynamics of phonon transport, which results in a trade-off between thermal conductivity and compliance. We overcome this by engineering an elastomer composite embedded with elongated inclusions of liquid metal (LM) that function as thermally conductive pathways. These composites exhibit an extraordinary combination of low stiffness (<100 kPa), high strain limit (>600%), and metal-like thermal conductivity (up to 9.8 W⋅m−1⋅K−1) that far exceeds any other soft materials. Soft dielectric materials typically exhibit poor heat transfer properties due to the dynamics of phonon transport, which constrain thermal conductivity (k) to decrease monotonically with decreasing elastic modulus (E). This thermal−mechanical trade-off is limiting for wearable computing, soft robotics, and other emerging applications that require materials with both high thermal conductivity and low mechanical stiffness. Here, we overcome this constraint with an electrically insulating composite that exhibits an unprecedented combination of metal-like thermal conductivity, an elastic compliance similar to soft biological tissue (Young’s modulus < 100 kPa), and the capability to undergo extreme deformations (>600% strain). By incorporating liquid metal (LM) microdroplets into a soft elastomer, we achieve a ∼25× increase in thermal conductivity (4.7 ± 0.2 W⋅m−1⋅K−1) over the base polymer (0.20 ± 0.01 W⋅m−1·K−1) under stress-free conditions and a ∼50× increase (9.8 ± 0.8 W⋅m−1·K−1) when strained. This exceptional combination of thermal and mechanical properties is enabled by a unique thermal−mechanical coupling that exploits the deformability of the LM inclusions to create thermally conductive pathways in situ. Moreover, these materials offer possibilities for passive heat exchange in stretchable electronics and bioinspired robotics, which we demonstrate through the rapid heat dissipation of an elastomer-mounted extreme high-power LED lamp and a swimming soft robot.

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High thermal conductivity in soft elastomers with elongated liquid metal inclusions.

Decoupling of inter-particle polarization and intra-particle polarization in core-shell structured nanocomposites towards improved dielectric performance

Ti3C2Tx MXene contained nanofluids with high thermal conductivity, super colloidal stability and low viscosity

Aluminum matrix composites loaded with various fractions of multi-walled, well-structured boron nitride nanotubes (BNNTs), up to 5 wt.% fractions, were fabricated using powder constituents by means of a high pressure torsion technique (HPT) at room temperature under 5 GPa pressurization. Transient ultrathin amorphous-like layers, with a thickness of 2–5 nm, composed of Al(BNO) phases, which formed under severe plastic deformation and developed under further heat treatments of the composites at 350 °C and 450 °C, were detected at the interfacial regions between Al grains and tightly embracing them BN layers. Room temperature hardness and tensile tests on fabricated composites before and after heat treatments were conducted. The highest value of room temperature tensile strength was obtained on Al-5 wt.% BNNT samples annealed at 450 °C, that reached up to ~ 420 MPa, thus exhibiting more than a doubled increase in strength compared to HPT-fabricated pure Al samples under identical compacting conditions.

Aluminum matrix composites reinforced with multi-walled boron nitride nanotubes fabricated by a high-pressure torsion technique

Combined effect of using porous media and nano-particle on melting performance of PCM filled enclosure with triangular double fins

Enhanced thermal conductivity of epoxy composites by introducing graphene@boron nitride nanosheets hybrid nanoparticles

Thermally conductive polymer composites (TCPCs) are highly desirable for thermal management in modern electrical systems and next-generation flexible electronic devices. However, the integration of superior thermal conductivity, good mechanical performance, and high thermostability in TCPCs remains a daunting challenge, due to the utilization of abundant rigid fillers (such as graphene, boron nitride and aluminum nitride) and the low thermal stability of polymer matrices. Herein, a highly thermally conductive film with excellent mechanical strength and toughness is developed based on soft liquid metal (LM) and rigid aramid nanofibers (ANFs), via a vacuum infiltration technique. The LM/ANF composite films possess superior in-plane and through-plane thermal conductivity (7.14 @ 1.68 W m−1 K−1) because of the formation of a tightly packed structure, in which LM droplets are randomly distributed among the well-ordered ANFs to construct efficient heat conduction networks. Meanwhile, an outstanding tensile strength of 108.5 MPa and a high toughness of 10.3 MJ m−3 are achieved in the LM/ANF composite films. Furthermore, the LM/ANF composite films also have remarkable thermostability, flexibility, and mechanical reliability, without an obvious change in the thermal conductivity even at an elevated temperature of 250 °C and after repeated folding for 1000 cycles, respectively. These admirable features shed light on the application of the LM/ANF composite films for thermal management of high-power integrated electronic devices.

Highly thermally conductive liquid metal-based composites with superior thermostability for thermal management

Herein, we report a new strategy to effectively enhance the thermal conductivity of epoxy composites by constructing a three-dimensional thermally conductive network with 2D boron nitride nanosheet...

Synergistic Enhanced Thermal Conductivity of Epoxy Composites with Boron Nitride Nanosheets and Microspheres

Thermally conductive polymer composites (TCPCs) are highly desirable for thermal management in electronic devices and modern electrical systems. However, it remains still a great challenge to reconciliate the conflict between thermal conductivity and mechanical properties of TCPCs. Herein, we realized the development of multilayer gradient boron nitride nanosheet/aramid nanofiber (BNNS/ANF) films with excellent thermal conductivity and improved tensile strength. The multilayer gradient BNNS/ANF films achieved a superior in-plane thermal conductivity of 19.13 W/(m K) and a high tensile strength of 59.3 MPa, with 23.6% and 61.6% increases compared to the single-layer BNNS/ANF film at the same BNNS content. Finite element analysis was used to clarify the enhanced mechanism of the multilayer gradient structure on thermal conductivity and tensile strength. These desirable properties demonstrate that the multilayer gradient structure is an efficient strategy to address the conflict between thermal conductivity and mechanical properties, and paves the way for the design and preparation of high-performance TCPC for thermal management applications.

Simultaneously improved thermal conductivity and mechanical properties of boron nitride nanosheets/aramid nanofiber films by constructing multilayer gradient structure

Two-dimensional boron nitride nanosheets (BNNSs) hold great promise as thermal management materials because of their ultrahigh thermal conductivity and wide band gap However, the scalable exfoliat

Lihua Zhao

Papers

Enhanced thermal conductivity of epoxy composites by introducing graphene@boron nitride nanosheets hybrid nanoparticles

Highly thermally conductive liquid metal-based composites with superior thermostability for thermal management

Synergistic Enhanced Thermal Conductivity of Epoxy Composites with Boron Nitride Nanosheets and Microspheres

Simultaneously improved thermal conductivity and mechanical properties of boron nitride nanosheets/aramid nanofiber films by constructing multilayer gradient structure

Aqueous-Phase Exfoliation and Functionalization of Boron Nitride Nanosheets Using Tannic Acid for Thermal Management Applications