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Graphical Abstract:

Despite recent advances, high performance single-shot 3D microscopy remains an elusive task. By introducing designed diffractive optical elements (DOEs), one is capable of converting a microscope into a 3D “kaleidoscope,” in which case the snapshot image consists of an array of tiles and each tile focuses on different depths. However, the acquired multifocal microscopic (MFM) image suffers from multiple sources of degradation, which prevents MFM from further applications. We propose a unifying computational framework which simplifies the imaging system and achieves 3D reconstruction via computation. Our optical configuration omits optical elements for correcting chromatic aberrations and redesigns the multifocal grating to enlarge the tracking area. Our proposed setup features only one single grating in addition to a regular microscope. The aberration correction, along with Poisson and background denoising, are incorporated in our deconvolution-based fully-automated algorithm, which requires no empirical parameter-tuning. In experiments, we achieve spatial resolutions of 0.35um (lateral) and 0.5um (axial), which are comparable to the resolution that can be achieved with confocal deconvolution microscopy. We demonstrate a 3D video of moving bacteria recorded at 25 frames per second using our proposed computational multifocal microscopy technique.

In this study, we fabricated a membrane-type vibrational energy harvester by using a conventional micro-electro-mechanical (MEMS) method. The membrane-type vibrational energy harvester consists of a multi-layered diaphragm for stable and flexible vibration, a piezoelectric ZnO film for responding to the vibrational energy and for generating electric power, and a vibrator connected to the bottom of multi-layered diaphragm for enhancing the vibrational displacement of the diaphragm. First, we characterized the quality of a ZnO film through scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray diffraction (XRD), which showed a preferred c-axis orientation, a hexagonal rod shape and a quite smooth surface. After the membrane-type vibrational energy harvester had been fabricated, we integrated it into a printing circuit board to realize piezoelectric generation and confirm its performance. Finally, under vibrational motion, we obtained a useful output voltage of 400 mV, and we estimated that the energy harvester generated an actual output voltage of about 200 uV.

We report the direct patterning of diffractive optical elements (DOEs) on a flat conventional lateral-type light-emitting diode (LED) surface. Silicon dioxide, used as a diffractive optical element, was deposited on the flat surface of an LED by using plasma-enhanced chemical vapor deposition and was patterned by using nano-imprint lithography and ion-coupled plasma etching to produce nanometer-scale DOEs. This method suggests a new approach for the mass production of DOEs by minimizing the size of the optical device through direct patterning on the LED surface. The resulting DOEs also act as focal Fresnel lenses, leading to an enhancement of the external light-extraction efficiency of lateral-type LEDs based on the scattering effect and the concentration of the emitted light.

In this article, we introduce a simple fabrication method for SiO_2-based thin diffractive optical elements (DOEs) that uses the conventional processes widely used in the semiconductor industry. Photolithography and an inductively coupled plasma etching technique are easy and cost-effective methods for fabricating subnanometer-scale and thin DOEs with a refractive index of 1.45, based on SiO_2. After fabricating DOEs, we confirmed the shape of the output light emitted from the laser diode light source and applied to a light-emitting diode (LED) module. The results represent a new approach to mass-produce DOEs and realize a high-brightness LED module.

With growing environmental pollution caused in part by increase in particulate matter (PM), indoor air quality is becoming an important issue in modern society particularly as health and environment consciousness rises. In addition, as the need for a mask has emerged to prevent the spread of viruses such as the SARS-CoV-2 virus that causes the dreaded COVID-19, filter technology has become the focus of considerable research attention. In this study, we introduce a functional fiber that can improve the energy-efficiency for PM adhesion while lowering the pressure drop in an existing commercial high-efficiency particulate absorbing (HEPA) filter. Nanofibers made of polymer and metal nanoparticles were produced by electrospinning; the triboelectricity generated by friction between fibers and air was used to capture the PM. The PM adhesion performance and pressure loss of the developed filter (PVDF/Au) and the commercial HEPA filter were compared, and the charging effect of the filters was analyzed by comparing the power generation performance of the triboelectric nanogenerator. Compared to HEPA filter, PVDF/Au filter reduced pressure drop by about 25%, but, the PM adhesion-energy efficiency of PVDF/Au was superior to that of HEPA by 28.6% based on 90% PM2.5 removal. As a filter that increases the PM adhesion effect while lowering the energy consumption and the pressure drop of the filter, PVDF/Au is expected to be effectively utilized in the existing filtration type filter system.

As a result of industrialization and urbanization, several harmful factors such as the presence of particulate matter (PM) and yellow sand in the atmosphere, have become an issue. As the interest in improving the air quality has increased, the market for high performance air cleaning products able to filter even exceedingly small dust particles is rapidly expanding. In this study, we present a flexible dielectric film that can adsorb PM using triboelectricity. Without the problem of pressure loss or generation of hazardous substances that occurred in previous filters, this polydimethylsiloxane (PDMS)-based flexible dielectric film could be attached to an electric fan and PM can be removed. Triboelectricity is induced by the friction between PDMS and metal nanoparticles when vibration resulting from an external energy source occurs. It was experimentally confirmed that the PM removal efficiency of the PDMS-based flexible dielectric film was 20% higher than that of the control group, based on the standard 95% removal of PM. We expect that the proposed electrostatic film could be used as a highly efficient, flexible, and washable filter in PM removal systems.