Dahye Baek

Hydrogel‐based photonic systems integrating luminescent emitters offer promise as soft, reconfigurable optical platforms, yet most designs lack internal optical engineering to control light propagation and confinement. Here, we present a lithographically programmable soft‐photonic platform in which upconversion nanocrystals (UCNs) encapsulated within fluorocarbon nanoemulsion droplets are embedded in a poly(ethylene glycol) diacrylate (PEGDA) hydrogel microdome. Upon drying, strong refractive index contrast between the PEGDA matrix and fluorocarbon droplets creates a cooperative optical microenvironment that structures the near‐infrared (NIR) excitation beam into a speckle‐like field with localized hot spots while extending the photon dwell time within the microdome via internal reflection‐based waveguiding. These effects yield a fully reversible, greater than sevenfold enhancement of upconversion luminescence—well beyond simple concentration or mechanical densification. This optical gain originates from multiple‐scattering‐assisted speckle excitation activated only in the contracted microdome state. Because UCNs are pumped by invisible NIR speckle illumination that rapidly varies in 3D across the microdome height, the incoherent sum of the photoluminescence manifests as a homogeneous filter‐free visible brightness increase. The hydrogel microdomes, fabricated via a customized digital micromirror device (DMD)‐based microlithography, enable high‐resolution patterning of moisture‐responsive displays, multicolor emission motifs, and reversible QR‐code encryption, establishing a scalable route toward speckle‐engineered soft photonic systems.

Colorimetric sensors for organophosphorus nerve agents often couple detection and degradation in a single inseparable process, limiting control over reaction rates and compromising selectivity. Here, we decouple these functions so that rapid neutralization precedes and enables VX- and GD-specific sensing. Highly nucleophilic 3-hydroxypyridyl amidoxime (HPAO) first accelerates the degradation of GD and VX agents. The resulting products─fluoride from GD and thiols from VX─then trigger orthogonal optical responses. 2-Allyl-5-nitrobenzo[d]isothiazol-3(2H)-one (ITZ) undergoes ring-opening isomerization only with thiols, yielding a subsecond colorless-to-yellow transition; fluoride does not elicit this response. In parallel, a polydiacetylene-oxime (PDA-Ox) matrix provides a blue-to-red transition in the presence of organophosphates. Combining these channels yields red for GD and orange for VX, enabling rapid, intuitive visual discrimination, while decontamination proceeds. Because neutralization and signaling are physically and chemically separated, the kinetics and readout can be optimized independently while maintaining orthogonality. We demonstrate operation in four formats: (i) solution-phase degradation with concurrent sensing, (ii) liquid mapping of contamination, (iii) wearable patch-based detection, and (iv) PDA-Ox-embedded patches for GD/VX visual differentiation. The patches further exhibited environmental durability and chemical robustness under deployment-relevant evaluations─including diurnal temperature cycling, low-temperature exposure, high-humidity conditioning, photostability, and accelerated aging─as well as interference challenges, using V- and G-series simulants, maintaining clear series discrimination upon simulant exposure with minimal background color change. We present a transformative technology that fundamentally challenges the traditional "detect-then-decontaminate" paradigm, offering potential for military and civilian chemical defense strategies.

Digital micromirror device (DMD) lithography has emerged as a powerful and reconfigurable platform for high‐resolution optical patterning across multiple length scales. Through microsecond mirror actuation and maskless spatial light modulation, DMD systems project user‐defined light patterns that enable real‐time fabrication of complex microstructures with high spatial precision. However, broader deployment remains limited by performance constraints, including resolution and throughput tradeoffs, narrow material compatibility, and the absence of robust strategies for volumetric structuring and functional integration. Recent progress in system‐level design has substantially improved pattern fidelity and adaptability. The development of organic–inorganic hybrid material platforms from photoreactive materials to all‐inorganic platforms has broadened the material design space and enabled new functional complexity. Beyond 2D planar fabrication based on binary DMD projection, recent dimensional lithography strategies integrate microfluidics and grayscale mask techniques, enabling the fabrication of 2.5D and 3D microstructures. Together, these support the fabrication of hierarchical, multi‐material microstructures with enhanced resolution, material complexity, and geometric freedom. This review presents a programmable framework that links optical design and computational patterning with material platforms and technical strategies. Collectively, these developments establish DMD lithography as a digitally controlled microfabrication platform for fabricating functional microarchitectures for applications in encryption, actuation, sensing, and bio integration.

Decoupling dynamic touch signals in the optical tactile sensors is highly desired for behavioral tactile applications yet challenging because typical optical sensors mostly measure only static normal force and use imprecise multi-image averaging for dynamic force sensing. Here, we report a highly sensitive upconversion nanocrystals-based behavioral biometric optical tactile sensor that instantaneously and quantitatively decomposes dynamic touch signals into individual components of vertical normal and lateral shear force from a single image in real-time. By mimicking the sensory architecture of human skin, the unique luminescence signal obtained is axisymmetric for static normal forces and non-axisymmetric for dynamic shear forces. Our sensor demonstrates high spatio-temporal screening of small objects and recognizes fingerprints for authentication with high spatial-temporal resolution. Using a dynamic force discrimination machine learning framework, we realized a Braille-to-Speech translation system and a next-generation dynamic biometric recognition system for handwriting.

In the field of surface‐enhanced Raman scattering (SERS), advances in nanotechnology and surface chemistry have contributed to fabricating the metal substrates with highly sophisticated architectures and strong binding affinity to target molecules which enhanced the sensitivity to target molecules. However, the elaborate yet complicated steps for the synthesis, patterning, and surface modification of metal substrates have often resulted in compromising the reliability, reproducibility, and reusability as SERS substrates. Here, a fully programmable and automated digital maskless flow microlithography process that spatiotemporally controls the fluid flow, UV irradiation, and the shape and location of SERS polymer matrix is provided to fabricate a reliable, reproducible, and reusable hydrogel‐based 3D SERS substrate. The SERS substrates are located inside the microfluidic device in the form of disk‐shaped hydrogels. By rationally designing the functional group chemistry of the hydrogel microposts, Ag nanoparticles are homogeneously synthesized in situ, a target molecule is amplified by 25‐fold inside the microposts, and an enhancement factor as high as 2.4 × 10⁸ is observed. Furthermore, a highly reusable multitarget sensing capability is demonstrated by a sequential analysis of multiple analytes without the trace of former analytes via the intermittent washing step.

Although the unique optical signaling properties of polydiacetylene (PDA) have been exploited in diverse bio-chemosensors, the practical application of most PDA sensor systems is limited by their instability in harsh environments and fluorescence signal weakness. Herein, a universal design principle for a highly stable PDA sensor system with a practical dual signaling capability is developed to detect cyanide (CN) ions, which are commonly found in drinking water. Effective metal intercalation and enhanced hydrophobic intermolecular interactions between PDA-metal supramolecules are used to construct highly stacked PDA-metal nanoplates that feature unusual optical stability upon exposure to strong acids, bases, organic solvents, and thermal/mechanical stresses, and can selectively detect CN anions, concomitantly undergoing a specific supramolecular structure change. To realize the practical dual signaling capability of the PDA sensor system, upconverting nanocrystals (UCNs) are incorporated into highly stacked PDA-metal nanoplates, and practical dual signaling (orthogonal changes in luminescence and visible color) is demonstrated using a portable detection system. The presented universal design principle is expected to be suitable for the development of other highly stable and selective PDA sensor systems with practical dual signaling capability.