In this study, we report on the fabrication and characterization of an ECL polymer-based ethanol gas sensor designed for environmental monitoring. The sensor was fabricated through MEMS processes involving the formation of reservoirs, the integration of IDE electrodes, and the drop-casting of polymer coatings. To evaluate the stability of the conductive polymer sensor, the baseline resistance was monitored, and gas sensing characteristics were assessed at ethanol concentrations ranging from 800 ppm to 20,000 ppm. Experimental results demonstrated that the ECL polymer sensor exhibited a sensitivity of 0.0009%/ppm and a rapid response time of 10 seconds. These findings validate the feasibility of developing scalable, high-performance ethanol sensors by integrating functional ECL polymers with microfabrication processes. This work provides a foundation for future advancements in flexible, wearable, and real-time environmental sensing technologies targeting industrial safety, biomedical applications, and indoor air quality monitoring.

Conventional door locks using physical keys pose risks such as loss, theft, and unauthorized duplication. Recent advancements have introduced electronic smart locks leveraging biometric, RFID, and wireless technologies. In the post-COVID-19 era, there is increasing demand for contactless systems to reduce surface transmission of pathogens. This paper presents the development of a keyless, touchless smart door lock system based on Internet of Things (IoT) architecture using infrared (IR) technology for password input. The system replaces physical keypads with IR transmitter-receiver pairs, enabling users to enter passcodes without direct contact. The prototype was developed with custom hardware schematics and a control program, supporting hygienic and convenient access. Performance evaluations include repeatability and robustness tests under varying lighting conditions. Results show high reliability and low standard deviation in input registration times, though minor delays were observed under direct sunlight due to IR signal interference. This system offers strong commercial potential for residential, healthcare, and public access applications, particularly for hygiene-sensitive users.

A vision sensor for simultaneous imaging and distance sensing is proposed herein. This vision sensor uses two images with a depth of field by two different aperture sizes to extract distance data. The aperture was fabricated through the microelectromechanical systems process. The optical parameter related to making a blur was precisely selected to reduce the active voltage and response time. The aperture measurement result showed that the maximum displacement of 1170 mu m was obtained when 12 V was applied which enlarge aperture size from 2.75 mm to 3.92 mm. The response time was 16.6 ms with a rising and falling time of 6.2 and 10.4 ms, respectively. The distance data was obtained using the depth from defocus method, which compares the blurriness of two images using the aperture size. Through deep learning, the image and distance information were simultaneously obtained in a single camera. The result of a three-dimensional depth map showed an average accuracy of 98.7% when sensing the maximum distance of 10 m. To examine the accuracy of the device, experiments were conducted for different colors, and the result showed that maximum and minimum error rates of 3.46% and 1.83% were achieved, respectively. In addition, the error rate according to brightness was investigated, and the average error rate was maintained at 2.64% between 10 000 and 200 lx. The proposed sensor can be installed in self-driving robots, drones, and various smart devices.

Electrostatic energy harvester for two axis vibration is developed.It was fabricated by using silicon-glass anodic bonding and deep silicon etching.The device which generates energy from only one directional vibration has much different resonant frequency for each direction.To gain energy from two or more directional vibration the structure was designed to have equal resonant frequency along the x, y-axis by symmetric spring-mass structure.When the direction of ambient vibration is changed from x-axis to y-axis, the device still generates equal amount of energy.Resonant frequency of the structure is 191 Hz along the x-axis vibration direction.The device size is 9.0 mm×9.0 mm×0.6 mm.Vibration of which the acceleration is 1.2 m/s 2 and the frequency is 191 Hz generates 0.73 µW/cm 3 .Although vibration direction is not matched, power is generated more than 0.2 µW/cm 3 at resonant frequency.

A Thermally Actuating multi-layered tunable aperture for distance sensing is proposed to measure distance to the obstacle. This tunable aperture uses metal of high thermal expansion to make different aperture size by Joule’s heating which operates when the voltage is applied to two copper metal structure. This aperture consists of eight thermal actuators that can obtain 3D image and distance information in a single camera simultaneously. The distance data can be obtained by Depth from Defocus method which compares blurriness of two images from each aperture size. The proposed thermal actuator is chevron type that has two beams that are slightly bent from each other to amplify the displacement of aperture perpendicularly. To find the exact displacement, COMSOL MULTIPHYSICS simulation tool was used. The device was fabricated with MEMS technology with two masks, and aperture was formed by bonding four identical layers with 45 degrees to each other to create octagonal shape. The dimension of thermally actuating part is 10mm by 100um by 40um and overall dimension is 10mm by 10mm by 2.2mm. The measurement result shows that the average displacement of 462um was obtained when 7.2V was applied which makes the aperture size from 546um to 1008um.

To measure the distance of an object, we propose a distance sensor that combines a tunable aperture operated by the thermal expansion of silicon chevron beams with a commercial camera similar to the automotive black box. The distance sensor is composed of a tunable aperture, a lens with an 8 mm focal length, and a 1/4-inch full high definition image sensor, where a tunable aperture is attached to the camera lens. To estimate the distance to the object, the blur difference is expressed in the form of a depth map using the depth from defocus algorithm. The mean error of distance estimation was 0.29 m. The area of the tunable aperture in the distance sensor is 1.18 mm(2) at OFF state and 2.79 mm(2) when the voltage is applied. The distance sensor can display an image and a distance simultaneously and can be applied to autonomous vehicles, drones, and robots.

In this paper, we estimate depth information using two defocused images from dual aperture camera. Recent advances in deep learning techniques have increased the accuracy of depth estimation. Besides, methods of using a defocused image in which an object is blurred according to a distance from a camera have been widely studied. We further improve the accuracy of the depth estimation by training the network using two images with different degrees of depth-of-field. Using images taken with different apertures for the same scene, we can determine the degree of blur in an image more accurately. In this work, we propose a novel deep convolutional network that estimates depth map using dual aperture images based on boundary cue. Our proposed method achieves state-of-the-art performance on a synthetically modified NYU-v2 dataset. In addition, we built a new camera using fast variable apertures to build a test environment in the real world. In particular, we collected a new dataset which consists of real world vehicle driving scenes. Our proposed work shows excellent performance in the new dataset.

A tunable aperture and lens are monolithically fabricated in wafer-level. The tunable aperture inserted in a camera can estimate distance as comparing blur of images by two different size apertures. We design optical system and integrate tunable aperture and first lens of camera. The plano-concave lens is fabricated by anodic bonding and thermal reflow under atmospheric pressure with one mask. The silicon substrate is used as spacer between tunable aperture and lens. Another glass substrate is attached to the silicon substrate by triple anodic bonding for tunable aperture operated by liquid crystal. The lens has diameter of 4.5 mm and sag height of 566 um and the tunable aperture has f-numbers of 1.8 and 4.0. This fabrication can control parameter of lens easily. Also, it can reduce error by alignment and gap among apertures and lenses. This distance sensor can be applied to the Advanced Driver Assistance System (ADAS).

The number of infertile couples considering using assisted reproductive technologies (ARTs) is growing. Several key indices, such as sperm concentration and motility, are considered when determining an appropriate technique among the existing ARTs. While microscopy is the only way to observe sperms, this method tends to overlook the actual swimming ability of sperms because sperms can be observed only within a very narrow field of view (FOV). In this paper, we propose a microfluidic chip capable of measuring the motility of sperms by inducing the actual swimming ability of sperms in microchannels. To determine whether sperms swim by themselves and reach the target point, 5–10 min is required in an incubator at 37 °C, which inevitably causes the evaporation of the fluid at the microfluidic chip inlet or outlet. A unique structure has been added to the microfluidic chip to prevent unwanted fluid flow due to evaporation, and counting and sorting capabilities of the fabricated device have been experimentally demonstrated. The microfluidic chip is shown to have a good agreement with commercial chips in total sperm counting. Another feature of sorting motile and progressive sperm to 95% on one chip is also verified. This feature differentiates our solution from the existing commercial chips and can help increase the success rate of ARTs. The developed MFC can provide a way to determine the actual swimming motility of sperms using a microscope in small clinics or a portable kit which is publicly available without the expensive sperm analysis equipment.

A real-time distance sensing system based on single vision is necessary to obtain distance information and the image at the same time for Advanced Driver Assistance System (ADAS). The sensor system developed in my laboratory uses barrel with three lenses. By simulation of CodeV software for the lens barrel, combination of two plano-convex lenses and one concave-convex lens was optimized for converging to CIS with 90.6% at 17lp/mm and 37.6% at 51lp/mm for f/14 in Modulation Transfer Function (MTF). This paper reports the fabrication of plano-convex lens using only one mask by microfabrication. Diameter and plane surface of lens was determined by using cavity on silicon substrate. The height of glass cylinder depends on Chemical-Mechanical Polishing (CMP) and the glass cylinder transforms to lens with spherical surface in thermal reflow process at 850°C. Whole system including lens barrel has a few cubic centimeter size favorably compared with Lidar and stereo vision.

For distance detection, a tunable aperture using liquid crystal is proposed, achieving high resolution images in real-time. The tunable aperture inserted into a camera has been designed to two sizes, which can create different Depth of Field images. By analyzing these two images, distance to object can be extracted. Initially, the aperture has large size with zero voltage. When the driving voltage is applied, the aperture transfers itself to smaller size by realignment of liquid crystal molecules in the device. The diameter of aperture is 4.4 mm with f/1.8 and 2.0 mm with f/4.0. The proposed device has low driving voltage of 2.8 V and fast response time of 9.84 ms. Compact size aperture of $10\times {10}\times 1.8$ mm(3) is assembled in a camera with focal length of 8 mm which contains 5 glass lenses and 1/2.7- inch full high definition (FHD) image sensor. The tunable aperture has high stability due to no mechanically moving parts. This distance sensor can be applied to the various field of depth map application which is the self-driving car, drones and manufacturing machine.

As the problem of male infertility becomes more and more serious around the world, Home-Kit has been proposed to make it easier for the general public to carry out sperm tests at home. The applied technology is lensless imaging and microfluidic chip technology, and despite its many advantages, it has a fatal disadvantage of evaporation due to heat generation. As a solution to this problem, a microfluidic chip with a unique structure was proposed, and the sperm counting and motile sperm sorting characteristics were also verified experimentally. As a result, combining this microfluidic chip with the developed KIT showed the possibility of developing a sufficiently reliable home male infertility diagnostic KIT.

Globally, couples suffering from infertility are increasing every year. Assisted reproductive technologies (ARTs) have been performed to overcome infertility and it is important to sort healthy sperms to increase the success rate. In this paper, we propose a microfluidic sperm sorting chip (MSSC) with a feedback channel and vertical orientation. The feedback channel minimizes unintentional fluid flow due to evaporation that interferes with sperm sorting, and a vertically oriented sorting chip inspired by the female uterus improves sperm sorting efficiency by three times. As a result of the experiments with fabricated microfluidic chips, progressive motile sperm was sorted by the rate of 94%.

This paper presents a modeling of trenched coplanar waveguide (TCPW) for redistribution layer (RDL) and RF MEMS switch which is flip-chip bonded to RDL. RF MEMS switch have been developed for its excellent characteristics and is integrated with ICs for mobile phone applications, which requires new modeling of heterogeneous multi-chip integration. An RLC lumped element model of the RF MEMS switch was extracted from the measurement results of commercially available switch from DC to 10GHz. Then the modeling of the TCPW were carried out and both modeling of MEMS switches and TCPW were combined. We studied different substrates with different geometry to get comparable characteristic from silicon substrate which has high dielectric constant to currently used substrate such as Duroid. We found that 50um trenched CPW on a 1um thick silicon dioxide on a HRS substrate of RDL showed the highest performance.

A tunable aperture with single layer blades actuated by thermal expansion of silicon beams is developed. The tunable aperture that consists of blade including misaligned silicon chevron beam can achieve high displacement of the blade. To design the desired tunable aperture, COMSOL MULTIPHYSICS simulator and MEMS fabrication process are used. The dimension of the tunable aperture is 10.2mm X 10.2mm X 0.365mm. In the results, diameter of the fabricated tunable aperture is achieved 1.6mm under no applied voltage and 1.25mm under applied voltage of 3V. Also it has analog state compared to other type of tunable aperture. Using the tunable aperture could obtain 3D image and distance information in a single camera system simultaneously.

A tunable aperture using a metal expansion by Joule's heating which operates when the voltage is applied to two copper metal structures having high thermal resistance is proposed. This aperture has four thermal actuators that can obtain 3D image and distance information in a single camera. The proposed thermal actuator is based on two slightly bent beams that can actuated in directed direction and this bent structure can amplify the displacement. To find the exact displacement for desired F/#, simulation was done by COMSOL MULTIPHYSICS 5.5. The device was fabricated by MEMS process. The silicon wafer is etched for 40um with DRIE process to form the copper beam structures. The copper beam structures are formed by electroplating process and the unnecessary copper layer was removed by CMP process. This beams were released with backside silicon DRIE. after silicon backside DRIE, two identical wafer is perpendicularly bonded to create tunable aperture. Proposed tunable aperture can be implemented into distance sensor for the Advanced Driver Assistance System (ADAS) in automotive.

This is a historical description about how Korea was transformed from the fringe to the global forefront in mobile telecommunications. It was an audacious challenge to develop a commercial CDMA(Code Division Multiple Access) cellular system which is technically more advanced, but not field proven hence risky, than TDMA cellular system that was the main trend of the times and opted by established majors. ETRI with Samsung, LG, Hyundai and Maxon pursed a co-development path to the national project supported by the Ministry of Information and Communication, Korea, at that time, in along with the joint development with Qualcomm, the original proponent of CDMA. After the successful commercialization first in Korea, CDMA turned into the major trend of the times, and Korean manufacturers became innovative leaders in the world.