Abstract As demand for customized wearable electronics grows, free‐form Li‐ion batteries (LIBs) are attracting significant attention. Although substantial advancements have been made in printed LIBs for shape‐versatile electronics, the development of printable solid‐state electrolytes remains challenging due to the difficulty of simultaneously achieving desirable rheological properties and ionic conductivity. In this study, a solvent‐free, non‐flammable solid polymer electrolyte (SPE) is designed as a novel three‐dimensional (3D) printable electrolyte via direct ink writing (DIW) for all‐solid‐state batteries (ASSBs). The solvent‐free nature of this SPE eliminates post‐annealing steps, enhancing safety by mitigating risks of leakage, short‐circuiting, and fire. Additionally, precise control over polymer molecular weight and electrolyte composition enables high printing resolution (~100 μm), high ionic conductivity (0.705 mS cm −1 at 25°C), and intrinsic non‐flammability. A 3D‐printed ASSB, featuring a LiFePO 4 cathode and Li 4 Ti 5 O 12 anode with a mass loading of 7 mg cm −2 , achieves a high areal capacity of 1.14 mAh cm −2 , surpassing all previously reported directly printed ASSBs. This SPE facilitates scalable production of fully DIW‐printed ASSBs with superior design flexibility and space efficiency, enabling printing onto customized targets such as flexible substrates and advancing the development of next‐generation wearable electronics. image

Soft electronic components are essential building blocks for realizing form-factor-free applications; however, most designs are confined to 2D or 2.5D structures due to challenges in maintaining 3D structural integrity. This limitation is particularly critical for electromagnetic devices, such as resonators, where dielectric losses from elastomeric substrates severely hinder high-performance functionality. Here, directly printed 3D electromagnetic soft plasmonic enhanced-quality(Q) factor resonators are proposed, using highly conductive composites. By incorporating an immiscible solvent into an elastomer matrix, emulsion phases are formed that significantly enhance the storage modulus, enabling the fabrication of 3D-printed structures while improving their electrical conductivity. 3D microwave plasmonic resonators with a high degree of design freedom, such as pillars and hooks are demonstrated. These structures exhibit improved resistance to dielectric interference by leveraging the resonance in lossless air. Moreover, integrating a coplanar ground plane further decouples the resonators from lossy substrates, resulting in a 3.4-fold enhancement in the Q-factor (octupole mode) compared to 2D resonators. This improvement enables stable operation on high-permittivity surfaces, such as human skin. Additionally, a single 3D resonator demonstrates wireless deformation-sensing capabilities, facilitating the simultaneous detection of strain amplitude and orientation. This result can pave the way for advanced sensing applications in soft electronics.