Spin-Printing of Liquid Crystal Polymer into Recyclable and Strong All-Fiber Materials

Fiber-reinforced polymers are widely used as lightweight materials in aircraft, automobiles, wind turbine blades, and sports products. Despite the beneficial weight reduction achieved in such applications, these composites often suffer from poor recyclability and limited geometries. 3D printing of liquid crystal polymers into complex-shaped all-fiber materials is a promising approach to tackle these issues and thus increase the sustainability of current lightweight structures. Here, we report a spin-printing technology for the manufacturing of recyclable and strong all-fiber lightweight materials. All-fiber architectures are created by combining thick print lines and thin spun fibers as reinforcing elements in bespoke orientations. Through controlled extrusion experiments and theoretical analyses, we systematically study the spinning process and establish criteria for the generation of thin fibers and laminates with unprecedented mechanical properties. The potential of the technology is further illustrated by creating complex structures with unique all-fiber architectures and mechanical performance.     

Ultrastrong Hierarchical Porous Materials via Colloidal Assembly and Oxidation of Metal Particles

Porous materials are useful as lightweight structures, bone substitutes, and thermal insulators, but exhibit poor mechanical properties compared to their dense counterparts. Biological materials such as bone and bamboo are able to circumvent this trade‐off between porosity and mechanical performance by combining pores at multiple length scales. Inspired by these biological architectures, a manufacturing platform that allows for the fabrication of Al₂O₃ foams and Al₂O₃/Al composites with hierarchical porosity and enhanced mechanical properties is developed. Macroscale pores are formed through the assembly of aluminum particles around templating air bubbles in wet foams, whereas the thermal oxidation of the metal particles above 800 °C generates porosity at the micrometer scale. After elucidating the mechanism of pore formation under different sintering conditions at the microscale, the mechanical performance of the resulting hierarchical foams using compression experiments and finite element simulations is evaluated. Porous materials manufactured via this simple approach are found to reach unparalleled mechanical properties with near‐zero sintering shrinkage and minimum loss in mechanical strength. The ability to produce macroscopic objects with ultrahigh strength at porosities up to 95% makes this an attractive manufacturing technology for the fabrication of high‐performance lightweight structures or advanced thermal and acoustic insulators.     

Self-Templated Hierarchically Porous Carbon Nanorods Embedded with Atomic Fe-N4 Active Sites as Efficient Oxygen Reduction Electrocatalysts in Zn-Air Batteries

Iron-nitrogen-carbon materials are being intensively studied as the most promising substitutes for Pt-based electrocatalysts for the oxygen reduction reaction (ORR). A rational design of the morphology and porous structure can promote the accessibility of the active site and the reactants/products transportation, accelerating the reaction kinetics. Herein, 1D porous iron/nitrogen-doped carbon nanorods (Fe/N-CNRs) with a hierarchically micro/mesoporous structure are prepared by pyrolyzing the in situ polymerized pyrrole on the surface of Fe-MIL-88B-derived 1D Fe₂O₃ nanorods (MIL: Material Institut Lavoisier). The Fe₂O₃ nanorods not only partially dissolve to generate Fe³⁺ for initiating polymerization but serve as templates to form the 1D structure during polymerization. Furthermore, the pyrrole coated Fe₂O₃ nanorod architecture prevents the porous structure from collapsing and protects Fe from aggregation to yield atomic Fe-N₄ moieties during carbonization. The obtained Fe/N-CNRs display exceptional ORR activities (E_1/2 = 0.90 V) and satisfactory long-term durabilities, exceeding those for Pt/C. Furthermore, the unprecedented Fe/N-CNRs catalytic performance is demonstrated with Zn-air batteries, including a superior maximum power density (181.8 mW cm⁻²), specific capacity (998.67 W h kg⁻¹), and long-term durability over 100 h. The prominent performance stems from the unique 1D structure, hierarchical pore system, high surface area, and homogeneously dispersed single-atom Fe-N₄ moieties.     

Biomimetically Assembled Sponge-Like Hydrogels for Efficient Solar Water Purification

Hydrogel-based evaporators for interfacial solar vapor generation (SVG) have emerged as a promising and sustainable strategy for freshwater production. Nevertheless, developing a green and simple approach in the fabrication of porous hydrogel-based evaporators with tunable porous structures and superior mechanical properties continues to be a challenge. Herein, cryo-assembled templating and polymerization (CTP) is proposed as an ecological, simple yet effective approach to synthesizing sponge-like hydrogels (SPHs) with outstanding mechanical properties. Moreover, inspired by the structural geometry of conifer plants of radially aligned microchannels and vertical vessels granting impressive water transportation abilities, the polyzwitterionic SPH evaporators with biomimetically assembled structure (B-SPH) raise the water transport rate by up to nearly 2 orders of magnitude compared to bulk hydrogels. The B-SPH also enables an SVG rate up to ≈ 3.45 kg m⁻² h⁻¹ under one sun irradiation and an energy efficiency of ≈ 95%. In addition, the as-prepared materials feature stable mechanical properties and SVG performance even after being rolled, folded, and twisted over hundred times. It is anticipated that the B-SPH prepared by CTP method provides insights into scalable hydrogel-based evaporators with elaborate porous structures and durable mechanical properties in an energy-efficient manner.     

3D-Printed Electrostatic Microactuators for Flexible Microsystems

Developing small-scale, lightweight, and flexible devices with integrated microactuators is one of the critical challenges in wearable haptic devices, soft robotics, and microrobotics. In this study, a novel fabrication process that leverages the benefits of 3D printing with two-photon polymerization and flexible printed circuit boards (FPCBs) is presented. This method enables flexible microsystems with 3D-printed electrostatic microactuators, which are demonstrated in a flexible integrated micromirror array and a legged microrobot with a mass of 4 mg. 3D electrostatic actuators on FPCBs are robust enough to actuate the micromirrors while the device is deformed, and they are easily integrated with off-the-shelf electronics. The crawling robot is one of the lightest legged microrobots actuated without external fields, and the legs actuated with 3D electrostatic actuators enable a locomotion speed of 0.27 body length per second. The proposed fabrication framework opens up a pathway toward a variety of highly integrated flexible microsystems.     

Direct Laser Writing of Low‐Density Interdigitated Foams for Plasma Drive Shaping

Monolithic porous bulk materials have many promising applications ranging from energy storage and catalysis to high energy density physics. High resolution additive manufacturing techniques, such as direct laser writing via two photon polymerization (DLW‐TPP), now enable the fabrication of highly porous microlattices with deterministic morphology control. In this work, DLW‐TPP is used to print millimeter‐sized foam reservoirs (down to 0.06 g cm^?3) with tailored density‐gradient profiles, where density is varied by over an order of magnitude (for instance from 0.6 to 0.06 g cm^?3) along a length of <100 µm. Taking full advantage of this technology, however, is a multiscale materials design problem that requires detailed understanding of how the different length scales, from the molecular level to the macroscopic dimensions, affect each other. The design of these 3D‐printed foams is based on the brickwork arrangement of 100 × 100 × 16 µm³ log‐pile blocks constructed from sub‐micrometer scale features. A block‐to‐block interdigitated stitching strategy is introduced for obtaining high density uniformity at all length scales. Finally, these materials are used to shape plasma‐piston drives during ramp‐compression of targets under high energy density conditions created at the OMEGA Laser Facility.     

Rapid 2D Patterning of High-Performance Perovskites Using Large Area Flexography

Solution processing of metal halide perovskites offers the potential for efficient, high-speed roll-based manufacturing of emerging optoelectronic devices such as lightweight photovoltaics and light emitting diodes at lower cost than achievable with incumbent technologies (e.g., Silicon). However, current perovskite fabrication methods are limited in their speed, uniformity, and patterning resolution, relying on subtractive postdeposition scribing for integration of modules and device arrays. Here, a method for flexographic printing of MA_0.6FA_0.4PbI₃ at 60 m min⁻¹, the fastest reported perovskite absorber deposition and the first report of inline drying integrated with roll-based printing, is presented. This process delivers high-resolution patterning (< 3 µm line edge roughness) and precise thickness control through rheological design of precursor inks, allowing scalably printed 50 µm features over large areas (140 cm²), while obviating damaging scribing steps. 2D scanning photoluminescence (PL) is applied to resolve correlations between ink leveling dynamics and optoelectronic quality. Integrating these highly uniform printed perovskite absorbers into n-i-p planar perovskite solar cells, photovoltaic conversion efficiency up to 20.4% (0.134 cm²), the highest performance yet reported for any roll-printed perovskite cells is achieved. This study, thus, establishes flexography as a scalable approach to deposit precisely-patterned high-quality perovskites extensible to applications in emitter and detector arrays.     

Nanosecond Pulsed Laser-Assisted Deposition to Construct a 3D Quasi-Gradient Lithiophilic Skeleton for Stable Lithium Metal Anodes

The continuous growth of Li dendrites and volumetric deformation of Li severely impede the commercial application of Li metal anodes. To regulate Li stripping/plating, electrodeposition or magnetron sputtering is extensively utilized to fabricate lithiophilic-metal deposited 3D Li hosts. However, the binding force between lithiophilic-metal and host is weak, inevitably leading to numerous cracks/defects of lithiophilic-surface-layer during Li plating/stripping. Herein, a quasi-gradient (Cu-Cu₃Sn-Sn-SnO₂) 3D skeleton consisting of hierarchical Sn/SnO₂ composite metallurgically bonded to copper foam through Cu₃Sn alloy (LAD-SSC@CF) is designed, and prepared in one-step by a nanosecond-pulsed-laser-assisted deposition strategy. The homogeneous Li nucleation sites provided by Li₂₂Sn₅ formed by the reaction of Sn/SnO₂ with Li can inhibit Li dendrites growth. Meanwhile, the porous space and strong bonding of Cu₃Sn layer avoid structural deterioration of anodes. Consequently, a symmetric cell based on LAD-SSC@CF@Li exhibits an outstanding cycling stability of 1500 h at 1 mA cm⁻². In particular, a full cell with LiFePO₄ cathode provides good capacity retention of 81.3% at 5 C after 600 cycles. Moreover, the successful preparation of other composite materials (In, Zn, Sn-Bi, etc.) loading on various substrates (Kapton film, ceramic, copper foil, etc.) demonstrates the versatility of pulsed-laser-assisted deposition strategy for preparing battery materials.     

All-Dielectric Nanostructure Fabry–Pérot-Enhanced Mie Resonances Coupled with Photogain Modulation toward Ultrasensitive In2S3 Photodetector

As the fresh blood of 2D family, non-layered 2D materials (2DNLMs) have demonstrated great potential in the application of next-generation optoelectronic devices. However, stemming from the weak light absorption brought by atomically thin thickness and the interfacial recombination brought by surface dangling bonds, traditional 2DNLM photodetectors are always accompanied by limited performance. Herein, a structure that integrates Si nanopillar array and non-layered 2D In₂S₃ to construct an ultrasensitive photodetector is designed. In particular, periodically Si nanopillars can act as Fabry–Pérot-enhanced Mie resonators that can effectively control and enhance the light absorption of 2D In₂S₃. On the other hand, a vertical built-in electric field is introduced in the In₂S₃ channel to capture photogenerated holes and leave electrons recycling in In₂S₃, obtaining a high photogain. Benefiting from these two mechanisms, this proposed photodetector presents a high responsivity of 4812 A W⁻¹ and short rise/decay time of 5.2/4.0 ms at the wavelength of 405 nm. Especially, a high light on–off ratio greater than 10⁶ and a record-high detectivity of 5.4 × 10¹⁵ Jones are achieved, representing one of the most sensitive photodetectors based on 2D materials. This deliberate device design concept suggests an effective scheme to construct high-performance 2DNLM optoelectronic devices.     

Controllable Patterning of Porous MXene (Ti3C2) by Metal-Assisted Electro-Gelation Method

Since discovered in 2011, transition metal carbides or nitrides (MXenes) have attracted enormous attention due to their unique properties. Morphology regulation strategies assembling 2D MXene sheets into 3D architecture have endowed the as-formed porous MXene with a better performance in various fields. However, the direct patterning strategy for the porous MXene into integration with multifunctional and multichannel electronic devices still needs to be investigated. The metal-assisted electro-gelation method the authors propose can directly generate porous-structured MXene hydrogel with a tunable feature. By electrolyzing the sacrificial metal, the released metal cations initiate the electro-gelation process during which electrostatic interactions occur between cations and the MXene sheets. A high spatial resolution down to micro-meter level is achieved utilizing the method, enabling high-performance hydrogels with more complex architectures. Electronics prepared through this metal-assisted electro-gelation process have shown promising applications of the porous MXene in energy and biochemical sensing fields. Energy storage devices with a capacitance at 33.3 mF cm⁻² and biochemical sensors show prominent current responses towards metabolites (sensitivity of H₂O₂: 165.6  µ A mm ⁻¹ cm⁻²; sensitivity of DA: 212 nA  µ m ⁻¹ cm⁻²), suggesting that the metal-assisted electro-gelation method will become a prospective technique for advanced fabrication of MXene-based devices.     

Wood-Inspired Binder Enabled Vertical 3D Printing of g-C3N4/CNT Arrays for Highly Efficient Photoelectrochemical Hydrogen Evolution

2D nanomaterials are very attractive for photoelectrochemical applications due to their ultra-thin structure, excellent physicochemical properties of large surface-area-to-volume ratios, and the resulting abundant active sites and high charge transport capacity. However, the application of commonly used 2D nanomaterials with disordered-stacking is always limited by high photoelectrode tortuosity, few surface-active sites, and low mass transfer efficiency. Herein, inspired by wood structures, a vertical 3D printing strategy is developed to rapidly build vertically aligned and hierarchically porous graphitic carbon nitride/carbon nanotube (g-C₃N₄/CNT) arrays by using lignin as a binder for efficient photoelectrochemical hydrogen evolution. Arising from the directional electron transport and multiple light scattering in the out-of-plane aligned and porous architecture, the resulting g-C₃N₄/CNT arrays display an outstanding hydrogen evolution performance, with the hydrogen yield up to 4.36 µmol (cm⁻² h⁻¹) at a bias of −0.5 V versus RHE, 12.7 and 41.6 times higher than traditional thick g-C₃N₄/CNT and g-C₃N₄ films, respectively. Moreover, this 3D printed structure can overcome the agglomeration problem of the commonly used g-C₃N₄ with powder configuration and shows desirable recyclability and stability. This facile and scalable vertical 3D printing strategy will open a new avenue to highly enhance the photoelectrochemical performance of 2D nanomaterials for sustainably production of clean energy.     

Wood Robot with Magnetic Anisotropy for Programmable Locomotion

The development of environmentally-friendly stimuli-responsive materials is vital to green electronics, sensors, and biomedicine. However, fast responsiveness and precise locomotion control of biomass materials have not been accomplished. Herein, a magnetically responsive wood is reported that can achieve programmable locomotion in the rotating magnetic field. The magnetized wood is fabricated by removing lignin from the cell walls, which produces a porous microstructure, enabling facile and stable combination between NdFeB and wood. With the directional arrangement of magnetic moments after magnetization, the magnetized wood with obviously positive and negative magnetic poles is magnetic stability, and can complete various movements including spatial flipping, bypass obstacles, climb up, and down under the driven by magnetic torques. Meanwhile, the magnetized wood is lightweight (0.26 g cm⁻³), showing a fast walking speed of up to 11.3 mm s⁻¹ under magnetic actuation (10 mT and 0.6 Hz), which is greater than those of petroleum-based polymeric materials. Benefitting from the unique porous structure, the magnetized wood can be used as the drug-carrier to deliver and release nano-cargoes effectively. This approach expands the range of stimuli-responsive materials beyond hydrogel, elastomers, and synthetic polymer, inspiring the creation of next-generation intelligent robots based on biocompatible and sustainable biomass materials.     

3D HfO2 Thin Film MEMS Capacitor with Superior Energy Storage Properties

Capacitors are ubiquitous and crucial components in modern technologies. Future microelectronic devices require novel dielectric capacitors with higher energy storage density, higher efficiency, better frequency and temperature stabilities, and compatibility with integrated circuit (IC) processes. Here, in order to overcome these challenges, a novel 3D HfO₂ thin film capacitor is designed and fabricated by an integrated microelectromechanical system (MEMS) process. The energy storage density (ESD) of the capacitor reaches 28.94 J cm⁻³, and the energy storage efficiency of the capacitor is up to 91.3% under an applied electric field of 3.5 MV cm⁻¹. The ESD can be further improved by reducing the minimum period structure size of the 3D capacitor. Moreover, the 3D capacitor exhibits excellent temperature stability (up to 150 °C) and charge-discharge endurance (10⁷ cycles). The results indicate that the 3D HfO₂ thin film MEMS capacitor has enormous potential in energy storage applications in harsh environments, such as pulsed discharge and power conditioning electronics.     

A–D–A type organic donors employing coplanar heterocyclic cores for efficient small molecule organic solar cells

Two linear organic A–D–A molecules (DTPT and DTPTT) comprised of electron-donating (D) coplanar heteroacenes as core end-capping with electron-accepting (A) dicyanovinylene were investigated as electron donor materials in organic photovoltaic (OPV) applications. The photophysical and electrochemical properties of these two dyes were examined. The A–D–A configuration renders these two molecules to have intense and red-shifted absorption characteristics for better light-harvesting (higher photocurrent density), while retaining relatively low HOMO energy levels for keeping sufficiently high open circuit voltage (V_oc) in OPV. The optical constants and molecular orientation of thin films were acquired with variable-angle spectroscopic ellipsometry (VASE). Due to the anisotropic behavior observed in thin film, these two organic donors were firstly adopted to combine with electron acceptor C₆₀ in a vacuum-processed planar heterojunction (PHJ) solar cells. The optimized DTPT-based PHJ device yielded a PCE of 3.01%, whereas the PHJ device based on DTPTT, delivered an inferior PCE of 1.70%. The exciton diffusion length extracted from spectrum-response modeling of PHJ devices is ∼5 nm and ∼4 nm for DTPT and DTPTT, respectively. Replacement of C₆₀ with C₇₀ for a better spectral response in 400–500 nm, planar-mixed heterojunction (PMHJ) SMOSCs without a thin donor layer in between the active layer and MoO₃ was found to produce optimum device results. The optimized DTPTT-based device showed a PCE of 3.02%, while the shorter counterpart DTPT delivered a PCE up to 5.64%.     

Ordered 3D Thin‐Shell Nanolattice Materials with Near‐Unity Refractive Indices

The refractive indices of naturally occurring materials are limited, and there exists an index gap between indices of air and available solid materials. With many photonics and electronics applications, there has been considerable effort in creating artificial materials with optical and dielectric properties similar to air while simultaneously being mechanically stable to bear load. Here, a class of ordered nanolattice materials consisting of periodic thin‐shell structures with near‐unity refractive index and high stiffness is demonstrated. Using a combination of 3D nanolithography and atomic layer deposition, these ordered nanostructured materials have reduced optical scattering and improved mechanical stability compared to existing randomly porous materials. Using ZnO and Al₂O₃ as the building materials, refractive indices from 1.3 down to 1.025 are achieved. The experimental data can be accurately described by Maxwell Garnett effective media theory, which can provide a guide for index design. The demonstrated low‐index, low‐scattering, and high‐stiffness materials can serve as high‐quality optical films in multilayer photonic structures, waveguides, resonators, and ultra‐low‐k dielectrics.     

Lightweight Self-Forming Super-Elastic Mechanical Metamaterials with Adaptive Stiffness

Scarcity of stiff, yet compliant, materials is a major obstacle toward biological-like mechanical systems that perform precise manipulations while being resilient under excessive load. A macroscopic cellular structure comprising two pre-stressed elastic “phases” is introduced, which displays a load-sensitive stiffness that drops by 30 times upon a “pseudoductile transformation” and accommodates a fully recoverable compression of over 60%. This provides an exceptional 20 times more deformability beyond the linear-elastic regime, doubling the capability of previously reported super-elastic materials. In virtue of the pre-stressing process based on thermal-shrinkage, it simultaneously enables a heat-activated self-formation that transforms a flat laminate into the metamaterial with 50 times volumetric growth. The metamaterial is thereby inherently lightweight with a bulk density in the order of 0.01 g cm⁻³, which is one order of magnitude lower than existing super-elastic materials. Besides the highly programmable geometrical and mechanical characteristics, this paper is the first to present a method that generates single-crystal or poly-crystal-like 3D lattices with anisotropic or isotropic super-elasticity. This pre-stress-induced adaptive stiffness with high deformability could be a step toward in situ deployed ultra-lightweight mechanical systems with a diverse range of applications that benefit from being stiff and compliant.     

A General One‐Pot Synthesis Strategy of 3D Porous Hierarchical Networks Crosslinked by Monolayered Nanoparticles Interconnected Nanoplates for Lithium Ion Batteries

A structure of 3D porous hierarchical networks is highly desired for mass production of electrode materials for lithium‐ion batteries due to its unique role in promoting battery performance. Herein, a general strategy using expanded graphites as both a structure‐directed template and a solution container is proposed for the synthesis of various cathode materials with 3D porous hierarchical networks formed by the crosslinkage of monolayered primary nanoparticles interconnected nanoplates, which all show high capacity, superior cyclic performance, and rate capability. The LiNi_0.8Co_0.15Al_0.05O₂/Li half cell delivers a capacity of 118 mAh g^?1 at 20 C (5.6 A g^?1) and capacity retention of 71.6% after 1000 cycles at 1 C, while the LiNi_0.8Co_0.15Al_0.05O₂/graphite full cell shows 79.9% and 80.0% capacity retentions after 1400 cycles at 1 C and 3000 cycles at 5 C, respectively. The superior performance is attributed to the unique 3D porous hierarchical networks with a stable surface and structure, which is related to the sufficient oxidization of Ni²⁺ and the formation of little residual lithium at surface intrinsic to this strategy. The study opens a generalized new avenue for facile, cheap, green, and mass production of various oxide materials with 3D porous hierarchical networks.     

Homogeneous Li+ Flux Distribution Enables Highly Stable and Temperature-Tolerant Lithium Anode

3D carbon hosts can enable low-stress Li metal anodes (LMAs) with improved structural and interfacial stability. However, the uneven Li⁺ flux and large concentration polarization, resulting from intrinsically poor Li affinity and limited porosity of carbon scaffolds, make the precise control of Li plating/stripping still one the key challenges facing advanced LMAs. Here it is demonstrated that a lightweight carbon scaffold, featuring parallel-aligned porous fibers, can work well for homogeneous Li⁺ flux distribution and reduced concentration gradient to form a stable solid electrolyte interphase, and then synergistically guide smooth Li nucleation/growth even at low temperatures. As a result, the obtained LMAs delivers a high areal capacity up to 15 mAh cm⁻², ultralong lifespan (4800 cycles at 4 mA cm⁻²) with very low voltage hysteresis of ≈21 mV, a high practically available specific capacity of 863.9 mAh g⁻¹ after 1000 cycles, and a long-term stable behavior at low-temperature operation. As coupling with the commercial LiNi_1/3Co_1/3Mn_1/3O₂ cathodes and common carbonate-based electrolyte, the corresponding practical cells also possess an ultralong lifespan and outstanding low-temperature functionality. This study not only presents an advanced carbon host candidate but also sheds new light on crucial design principles of carbon scaffolds for practically feasible rechargeable metal batteries.     

Microporous,Crystalline, and Water-Processable Framework Materials of Organic Amphiphile Salts

Porous framework materials are of major importance for a wide range of technologies. Nevertheless, many of these materials lack processibility as they are typically synthesized under rather harsh conditions and obtained as microcrystalline powders that cannot easily be coated or deposited from solution. Herein, a new approach to water-processable metal–organic framework materials is presented. The materials are based on amphiphilic organic building blocks consisting of polar carboxylate groups and non-polar alkyl chains connected to a rigid aromatic core. The amphiphilic building blocks assemble to porous framework structures via bonding to kinetically labile sodium ions from concentrated aqueous solution. The obtained crystalline materials, termed amphiphile salt frameworks , are thermally and mechanically stable (some derivatives up to 365 °C and up to at least 4000 bar hydrostatic pressure), exhibit persistent microporous channels accessible to several gases (N₂, CO₂, propane, propylene, n-butane), and can be reversibly assembled/disassembled by crystallization from or dissolution in water. Systematic variation of the hydrophobic side chains of the amphiphile building blocks allows extracting structure-property relationships and first design rules for this new class of water-processable microporous framework materials.     

Lightweight,Superelastic Boron Nitride/Polydimethylsiloxane Foam as Air Dielectric Substitute for Multifunctional Capacitive Sensor Applications

Porous polymeric foams as dielectric layer for highly sensitive capacitive based pressure sensors have been extensively explored owing to their excellent flexibility and elasticity. Despite intensive efforts, most of previously reported porous polymer foams still suffer from difficulty in further lowering the attainable density limit of ≈0.1 g cm^?3 while retaining high sensitivity and compressibility due to the limitations on existing fabrication techniques and materials. Herein, utilizing 3D interconnected networks of few‐layer hexagonal boron nitride foams (h‐BNFs) as supporting frameworks, lightweight and highly porous BN/polydimethylsiloxane composite foams (BNF@PDMS) with densities reaching as low as 15 mg cm^?3 and permittivity close to that of air are fabricated. This is the lightest PDMS‐based foam reported to date. Owing to the synergistic effects between BN and PDMS, these lightweight composite foams possess excellent mechanical resilience, extremely high compressibility (up to 95% strain), good cyclic performance, and superelasticity. Being electrically nonconductive, the potential application of BNF@PDMS as a dielectric layer for capacitive sensors is further demonstrated. Remarkably, the as‐fabricated device can perform multiple sensing functions such as noncontact touch sensor, environmental monitoring sensor, and high sensitivity pressure sensor that can detect extremely low pressures of below 1 Pa.