In this work, we developed a photoalignment and photopatterning method to fabricate polymer-stabilized-liquid-crystals (PSLCs) for optical data encryption and anti-counterfeiting purposes. The PSLCs possess both implicit optical patterns as well as explicit geometries, could serve with improved environmental robustness and thermal stability after a post-extraction process, and can be directly bonded onto various substrates. Based on this, we prototyped proof-of-concept optical data encryption and anti-counterfeiting demonstrations using either one single photoaligned and photopatterned PSLC, or a pair of cascade, spatially programmed PSLCs.
Neodymium-doped yttrium aluminum garnet (Nd: YAG) ceramics are extensively used as lasing media. However, limitations in traditional fabrication methods, such as long timescale and difficult structural customization, restrict its potential for advanced applications. Herein, we successfully fabricate Nd: YAG ceramics with customized 3D structures by micro-continuous liquid interface printing at a speed of 10 μm·s–1 and a resolution of 5.8 μm·pixel–1 followed by post-sintering. For the optical properties, photoluminescent spectra and emission images show that the sintered parts photoluminesce at 1064 nm. In summary, this new approach provided a potential solution for faster prototyping of customized lasing media.
Conductive self-healing (SH) hydrogels have been receiving significant attention benefiting from the behavior of living tissue to improve the design of health monitoring systems and soft robotics with the ability of repairing damages autonomously. Herein, we propose a novel approach of high-resolution 3D printing of ion-conductive SH hydrogel realized by high-speed continuous printing of interpenetrating polymer network (IPN) hydrogel based on physical crosslinking of poly(vinyl alcohol) combined with chemical/ionic crosslinking of acrylic acid and ferric chloride. The 3D printed hydrogel can fully recover the mechanical properties after 12 h without any external stimulus, and the ionic conductivity enables strain and pressure sensing capabilities.
In this work, we report rapid, high-resolution three-dimensional (3D) printing of piezoelectric composite structures via micro continuous liquid interface production (μCLIP). We formulated chemically functionalized, photo-curable resins using piezoelectric nanoparticles (PiezoNPs) such as barium titanate (BTO) and achieved 3D printings of high-resolution composite structures with piezoelectric performance comparable to other vat-polymerization-based works but come at drastically boosted speeds. Proof-of-concept demonstrations utilizing the composite further validate its capability in a variety of flexible and wearable sensing applications.
Magnetic-driven micro-robotic devices have shown promising potential in enabling applications in micromanipulation, biosensing, targeted drug delivery, and minimally invasive surgery. However, the fabrication of miniaturized magnetic structures with complex geometries has remained the major technical obstacle. In this study, we report the development of a new magnetically-active photopolymerizable resin comprises poly (ethylene glycol) diacrylate monomer, Fe3O4 magnetic nanoparticles, photoinitiator, and other functional additives. Micro-continuous liquid interface production (micro-CLIP) 3D printing process was employed to realize high-resolution and high-speed fabrication of complex structures. The key characteristic properties of resin along with the matching process conditions were investigated experimentally, which allows for establishing the set of optimal fabrication conditions in fabricating magnetic microactuators towards potential applications.
High-resolution optical longitudinal cortical imaging usually uses cranial window, which involves removing a skull portion and sealing the exposed brain area with a transparent cover glass, allowing ballistic photons to reach the cortex with minimal disturbance of the brain function. It enables obtaining high-resolution brain images in extended periods of time for long-term neuronal activity studies using confocal and two-photon microscopies. Photoacoustic microscopy (PAM), as the only imaging method that directly measure absorption contrast, is a complementary functional imaging method to provide absorption related brain information, such as total concentration of hemoglobin and oxygen saturation of hemoglobin. However, the use of traditional piezoelectric transducers (PZT) to collect ultrasound signal greatly limits the versatility of PAM. Though highly sensitive, PZT transducers are usually bulky and optically opaque. It blocks the light and is hard to be inserted into the limited distance between the optical objective and imaging sample, which are normally less than one millimeter when using a high- numerical aperture (NA) objective to achieve submicron resolution.
Here, we developed a simple and cost-efficient soft nanoimprint lithography (NIL) process to fabricate fully embedded micro-ring resonator ultrasound detectors on optically transparent substrates, and integrated the detector onto a cranial window, making cranial window itself an ultrasonic detector. We implanted this functional cranial window on mouse head and achieved longitudinal monitoring of cortex vasculature using PAM. Our low-cost, disposable, and optically transparent detector may potentially reshape the longitudinal functional brain imaging using PAM in small animals.
The spectroscopic information and the corresponding polarization states of a single-molecule emission possess wealth molecule-specific signatures that can be used to reveal the unique molecular electronic state, conformation, and its interactions with the host media. However, existing spectroscopic methods and advanced image analysis techniques, which can potentially provide quantitative analytical tools for the study of cellular dynamics, are yet limited by the diffraction limit. Therefore, developing a nanoscopic imaging platform for simultaneous acquisition of multiple molecular specific properties is highly desirable. Here we report a three-dimensional (3D), polarization-sensitive, spectroscopic photon localization microscopy (3D-Polar-SPLM) that simultaneously captures nanoscopic location of individual fluorescent emitters and their corresponding optical spectra and polarization states. To evaluate the capability of the imaging system, we imaged model system consisting quantum rods (QRs). Using 3D-Polar-SPLM, we spatially localized individual QRs with a lateral localization precision of 8 nm and an axial localization precision of 35 nm. In addition, we achieved a spectral resolution of 2 nm and a polarization angle measuring precision of 8 degrees. The spectral profile of the fluorescence emission provided a particle-specific signature for identifying individual QRs among the heterogeneous population, which significantly improved the fidelity in parallel 3D tracking of multiple QRs at a temporal resolution of 10 ms. Except its versatility, 3D-Polar-SPLM further provides advantageous in practical applications since it only employs a single light-path and therefore, is compatible with existing PALM/STORM, potentially bringing immediate impact to the broader research community, across physics, chemistry, material science and biology.
Recently, 3D printing has gone beyond being an industrial prototyping process and has gradually evolved as the tool to manufacture production-quality parts that are otherwise challenging by using traditional methods. Especially, translating 3D printing technique into the optical realm would dramatically improve the time- and cost-efficiency of customized optical elements, while conventional methods such as multiaxial lathes polishing, magnetorheological finishing, molding techniques are relatively expensive and time consuming. However, 3D printing also suffers from the inherent drawback: the reduced surface quality associated with the stair-stepping effect as a direct result of the layered deposition of the material. In this paper, we have demonstrated a time- and cost-effective single photon micro-stereolithography based 3D printing method to eliminate the layer stair-stepping effect. This method supports not only sub-voxel accuracy (~ 2 μm) of the surface in the range of 2 mm diameter, but also features deep sub-wavelength roughness (< 10 nm) of the surfaces and extremely good reproducibility. Furthermore, we designed and rapidly prototyped the aspherical lenses which not only feature low distortion, but also show remarkable optical quality in a broadband wavelength range from 400 nm to 800 nm.
KEYWORDS: Absorption, Solar cells, Solar energy, Scattering, Nanophotonics, Thin film solar cells, Finite-difference time-domain method, Silica, Thin films, Photonic crystals
Recent designs in nanophotonic light-trapping technologies offer promising potential to develop high-efficiency thin-film solar cell at dramatically reduced cost. However, the lack of a cost effective scalable nanomanufacturing technique remains the main road-block. In nature, diatoms exhibit high solar energy harvesting efficiency due to their frustules (i.e., hard porous cell wall made of silica) possessing remarkable hierarchical nano-features optimized for the photosynthetic process through millions of years evolution. To explore this unique light trapping effect, different species of diatoms (Coscinodiscus sp. and Coscinodiscus wailesii) are cultured and characterized by Scanning electron microscope (SEM). Rigorous Coupled Wave Analysis (RCWA) and Finite-difference time-domain (FDTD) method are employed to numerically study the nanophotonic light-trapping effect. The absorption efficiency is significantly enhanced over the spectrum region centered on 450nm and 700nm where the electric fields are found strongly confined within the active layer. The transmission and reflection spectra are also measured by optical spectroscopy and the experimental results are in good agreement with numerical simulations.
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