Seungjun Chung

Conventional anti‐counterfeiting technologies that utilize optical devices often rely on visible or near‐infrared features; however, directly exposed optical signatures can be vulnerable to duplication or environmental degradation in simple tag‐based systems. In this study, we demonstrate a flexible terahertz (THz) encryption platform based on visibly concealed metasurface patterns, called the THz‐encoded metasurface pattern (TEMP), enabling robust physical anti‐counterfeiting authentication. The TEMP is fabricated by integrating a flexible double‐split ring resonator metasurface with a metallic composite layer that is opaque in the visible region but transparent and tunable in the THz region. The metasurface exhibits polarization‐dependent LC resonances, providing polarization‐selective spectral responses. Meanwhile, the refractive index of the composite layer is tailored by adjusting the composition of the conductive fillers; when the layer is integrated with the metasurface, an intrinsic physical key is generated for authentication. The resulting THz transmittance spectra are further encrypted through affine transformation and stored in quick response (QR) codes, achieving stable and reversible spectral reconstruction with even after 1000 bending cycles. By combining optical concealment, spectral uniqueness, and mechanical robustness, the flexible TEMP platform offers a practical THz‐based pathway for nondestructive and physically encrypted authentication.

3D photovoltaics (3DPVs) are highly promising for next‐generation energy systems, as they maximize space utilization and power output. However, most reported 3DPVs remain unsuitable for deformable applications. When 3DPVs are integrated with mechanically deformable platforms, a fundamental trade‐off emerges: achieving large mechanical stretchability typically leads to a reduction in areal coverage. Here, we present a single‐material, mechanically origami‐coded 3D kirigami platform that enables programmable 3DPVs with unprecedented stretchability and areal coverage. Origami, which transforms 2D geometries into 3D forms, provides an effective structural strategy to overcome the long‐standing trade‐off between stretchability and areal coverage. Leveraging this concept, we introduce an origami‐inspired mechanical coding scheme that embeds programmable folding behavior into the structure. A simple extension–release cycle drives unit folding initiation and full origami activation, achieving ultrahigh stretchability (500%) and initial effective areal coverage (225%), while maintaining stable photovoltaic output under extreme deformation and repeated cycling. To ensure reliable electrical integration, an intrinsically integrable nano‐root anchored AgNWs–In–Ga multiphasic alloy conductor was co‐fabricated with the structure, providing stable conductivity and enabling reversible stack‐and‐connect operation. This approach highlights geometric programmability as a key enabler for freeform photovoltaics, establishing a pathway toward multifunctional 3D energy systems for adaptive devices, and urban energy harvesting.

Atomically thin two‐dimensional transition metal dichalcogenides (2D TMDCs), especially monolayer MoS ₂ , have garnered considerable attention as promising materials for next‐generation transistors. However, their large surface‐to‐volume ratio renders them highly sensitive to defects, underscoring the need for selective, localized, and precise control of their defect profiles. Here, we introduce a laser‐assisted microlens array processing (LAMP) technique that enables highly localized n‐type optical doping of monolayer MoS ₂ by utilizing self‐assembled polystyrene microspheres as microlenses to focus a 532 nm continuous‐wave laser below the diffraction limit. Under low laser powers (40–60 mW), sulfur vacancies are selectively generated without inducing global thermal damage, allowing systematic control of the vacancy concentration. Spectroscopic analyses reveal electron‐donor‐like defects and tunable vacancy density. MoS ₂ transistors treated by LAMP exhibit finely tunable doping, yielding up to a 51‐fold increase in field‐effect mobility and a 37‐fold increase in carrier density, with the enhanced n‐type characteristics remaining stable for several weeks. Unlike direct laser irradiation, LAMP offers high spatial resolution, low energy consumption, and reproducible vacancy engineering while minimizing thermal damage. This complementary metal–oxide–semiconductor‐compatible strategy provides a robust post‐fabrication approach for precise electronic property tuning in two‐dimensional transition metal dichalcogenide devices.

The exquisite spatiotemporal regulation of drug biodistribution is paramount for optimal targeted cancer theranostics. Robotic ingestible devices promise to reinvent the way drugs interact with gastrointestinal (GI) tissues and malignant tumors. However, no study has yet demonstrated theranostic functions beyond merely conveying synthetic drugs. Here, we present an orally administrable, functionally integrated soft microrobot capable of localized therapeutic regulation of copper (Cu)–dependent cell death mechanism, termed “cuproptosis” within GI tumors. By leveraging the interplay of mechanical, electrical, and biochemical functions, the robot actively targets and grasps the tumor and generates anticancer Cu-rich electrochemical interfacing with the targeted tumor microenvironment. This tumor-robot interface, characterized by in situ generated electric multipole fields and on-demand burst Cu ²⁺ ion release, induces ~10 ⁴ -fold increase in local concentration of Cu ²⁺ ions, and drives their dense accumulation and directed infiltration for effective cuproptotic cancer treatment, with tumor penetration capabilities far beyond those of passive diffusion. Demonstrations of minimally invasive, long-range tumor targeting in porcine organs and mouse tumor eradication in vivo demonstrate the translational potential of our approach as microrobotic theranostic platforms for targeting GI cancer.

Flexible thermoelectric sensors convert temperature gradients into electrical energy, allowing rapid, real-time responses to subtle temperature changes without relying on external power sources or mechanical vibrations. These features allow seamless integration into wearable electronics and humanoid robotic systems, where mechanical flexibility, environmental stability, and customizable design are essential. In this study, a skin-mountable free-form thermoelectric sensor was fabricated through direct ink writing using a printable Ag@Ag₂Te/Ag composite ink. The ink was optimized by engineering the morphology and Ag/Te stoichiometry of the hybrid thermoelectric material, along with the rheological properties of the composite ink, to ensure a high thermoelectric response and print fidelity simultaneously. The resulting thermoelectric films exhibited a stable output under high-humidity conditions and repeated mechanical deformations. Leveraging the geometric freedom provided by direct ink writing, a fan-shaped thermoelectric sensor was fabricated to detect localized thermal stimuli and maintain a reliable temperature-dependent response when it was seamlessly mounted on a fingertip. This research provides a promising approach toward customizable, self-powered thermoelectric sensors for wearable electronics and soft robotics.

Photothermal neural stimulation enables optical excitation or inhibition of neural activity depending on the dynamics of localized temperature changes, offering high spatial resolution without genetic modification. However, quantitative analysis of these temperature dynamics remains limited due to the lack of suitable direct sensing technologies, posing a challenge to the safe and controlled application of photothermal neural stimulation techniques. This challenge is addressed by developing transparent thermoelectric temperature sensor arrays with high spatiotemporal resolution, integrated with electrical and optical recording capabilities. These microscale sensors stably and accurately capture rapid temperature increases and decreases, and thermal equilibrium induced by thermo‐plasmonic effects at the neural interface, regardless of the environment. The multifunctional platform allows simultaneous electrical and optical monitoring of neural responses during the photothermal stimulation, enabling detailed analysis of the correlation between localized temperature changes and neural activities. a reversible neural inhibition window (1.4–4.5 °C) and thresholds for irreversible damage (>6.1 °C) are identifyed. Using high temporal‐resolution sensing, localized thermo‐plasmonic temperature dynamics over tens of milliseconds, and associated neural signal suppression and reactivation are captured. This approach provides unprecedented insight into the interplay between photothermal effects and neural activity, establishing a foundation for precise, temperature‐guided neuromodulation therapies and advanced neural circuit research.