Jiseok Lee

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.

Silver nanoparticles (AgNPs) are known for their unique plasmonic colors and interaction with light, making them ideal for color printing and data encoding. Traditional methods like electron beam lithography (EBL) and focused ion beam (FIB) milling, however, suffer from low throughput and high costs. In this paper, a scalable and cost‐efficient method is introduced for producing multiplexed plasmonic colors by in situ photoreducing AgNPs within microgel architectures with controlled porosity. Utilizing a digital micro‐mirror device (DMD)‐based flow microlithography system combined with a programmable dithering‐mask technique, the high‐throughput synthesis of shape or barcoded microparticles is facilitated, along with large‐scale, high‐resolution images embedded with hidden multiplexed plasmonic colors. This approach allows for a hidden multiplexed plasmonic color code library, significant enhancing the encoding capacity of barcode microparticles from 3³ to 30³ (a 1000‐fold increase). Additionally, quantitative agreement is achieved between chemically encrypted and optically decrypted plasmonic colors using a deep learning classifier. Moreover, the method also supports the production of large scale (>5.6 × 5.6 cm²), high‐resolution (>300 dpi) microgel arrays encrypted with multiple plasmonic colors in under 30 min. The multiplexed plasmonic coloration strategy in microgel architectures paves a new way for hidden data storage, secure optical labeling, and anti‐counterfeiting technologies.

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.

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.

Direct optical printing of functional inorganics shows tremendous potential as it enables the creation of intricate two-dimensional (2D) patterns and affordable design and production of various devices. Although there have been recent advancements in printing processes using short-wavelength light or pulsed lasers, the precise control of the vertical thickness in printed 3D structures has received little attention. This control is vital to the diverse functionalities of inorganic thin films and their devices, as they rely heavily on their thicknesses. This lack of research is attributed to the technical intricacy and complexity involved in the lithographic processes. Herein, we present a generalized optical 3D printing process for inorganic nanoparticles using maskless digital light processing. We develop a range of photocurable inorganic nanoparticle inks encompassing metals, semiconductors, and oxides, combined with photolinkable ligands and photoacid generators, enabling the direct solidification of nanoparticles in the ink medium. Our process creates complex and large-area patterns with a vertical resolution of ∼50 nm, producing 50-nm-thick 2D films and several micrometer-thick 3D architectures with no layer height difference via layer-by-layer deposition. Through fabrication and operation of multilayered switching devices with Au electrodes and Ag-organic resistive layers, the feasibility of our process for cost-effective manufacturing of multilayered devices is demonstrated.

Optical three-dimensional (3D) printing techniques have attracted tremendous attention owing to their applicability to mask-less additive manufacturing, which enables the cost-effective and straightforward creation of patterned architectures. However, despite their potential use as alternatives to traditional lithography, the printable materials obtained from these methods are strictly limited to photocurable resins, thereby restricting the functionality of the printed objects and their application areas. Herein, we report a generalised direct optical printing technique to obtain functional metal chalcogenides via digital light processing. We developed universally applicable photocurable chalcogenidometallate inks that could be directly used to create 2D patterns or micrometre-thick 2.5D architectures of various sizes and shapes. Our process is applicable to a diverse range of functional metal chalcogenides for compound semiconductors and 2D transition-metal dichalcogenides. We then demonstrated the feasibility of our technique by fabricating and evaluating a micro-scale thermoelectric generator bearing tens of patterned semiconductors. Our approach shows potential for simple and cost-effective architecturing of functional inorganic materials.

Optical three-dimensional (3D) printing techniques have attracted tremendous attention owing to their applicability to mask-less additive manufacturing, which enables the cost-effective and straightforward creation of patterned architectures. However, despite their potential use as alternatives to traditional lithography, the printable materials obtained from these methods are strictly limited to photocurable resins, thereby restricting the functionality of the printed objects and their application areas. Herein, we report a generalised direct optical printing technique to obtain functional metal chalcogenides via digital light processing. We developed universally applicable photocurable chalcogenidometallate inks that could be directly used to create 2D patterns or 3D architectures of various sizes and shapes. Our process is applicable to a diverse range of functional metal chalcogenides for compound semiconductors and 2D transition-metal dichalcogenides. We then demonstrated the feasibility of our technique by fabricating and evaluating a micro-scale thermoelectric generator bearing tens of patterned semiconductors. Our approach shows potential for simple and cost-effective architecturing of functional inorganic materials.

Microfluidic systems with large surface‐to‐volume ratios and superior light transmission are used to efficiently transfer mass and convert energy, and to enhance photocatalytic reactions. Utilizing the entire solar spectrum for promoting photocatalytic reactions is highly desirable and near‐infrared (NIR) radiation, in particular, has a high transmission efficiency through common polymers and materials used to construct microfluidic devices. Herein, a reliable microfluidic system using bimodal light‐harvesting technique is reported to improve the photocatalytic efficiency of C(sp3)‐H functionalization reactions using coumarin dye (C153) and lanthanide‐doped upconversion nanocrystals (UCNs). Using two light‐harvesting components (C153 and UCNs) in polycarbosilane polymer matrix, a bimodal light‐harvesting microfluidic reactor is realized in which the inner surface of the microfluidic channel is reliably coated with a transparent composite of C153/UCNs to simultaneously downshift visible light and upconvert NIR light. A double‐stacked microfluidic system that successfully enhanced the photocatalytic conversion efficiency of Rose Bengal‐based aza‐Henry photocatalytic reactions by twofold (≈93% conversion). The study provides a design principle of next‐generation microfluidic reactor for a robust photocatalytic organic synthesis.