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KAIST Team Develops Surface-Lighting MicroLED Patch with Significant Melanogenesis Inhibition Effect
A KAIST research team led by Ph.d candidate Jae Hee Lee and Professor Keon Jae Lee from the Department of Materials Science and Engineering has developed a surface-lighting microLED patch for UV-induced melanogenesis inhibition. Melanin is brown or dark pigments existing in the skin, which can be abnormally synthesized by external UV or stress. Since the excessive melanin leads to skin diseases such as spots and freckles, proper treatment is required to return normal skin condition. Recently, LED-based photo-stimulators have been released for skin care, however, their therapeutic effect is still controversial. Since conventional LED stimulators cannot conformally attach to the human skin, distance-induced side effects are caused by light loss and high heat transfer. To achieve effective phototreatment, the LED stimulator needs to be irradiated in contact with the human skin surface, enabling proper and uniform light deliver to the dermis with minimal optical loss. In this work, the research team fabricated skin-attachable surface-lighting microLED (SµLED, 4 × 4 cm2) patch by utilizing a thousand of microLED chips and silica-embedded light diffusion layer. 100 µm-sized LED chips are vertically-interconnected for high flexibility and low heat generation, allowing its long-term operation on the human skin. < Image 1. The overall concept of SµLED patch. a) SµLED patch operated on the human skin. b) Schematic illustration of SµLED patch structure. c) 4 × 4 cm2-sized SµLED patch. d) Schematic illustration of the advantages of SµLED patch such as efficient light delivery, low heat generation, and surface-lighting irradiation. > The research team confirmed melanogenesis inhibition by irradiating the SµLED patch and the conventional LED (CLED) on the artificial human skin and mice dorsal skin. The SµLED-treated groups of human cells and mouse tissues showed minimal epidermal photo-toxicity and consistently effective reduction in synthesized melanin, compared to CLED-treated groups. In addition, significant suppression of proteins/catalysts expression involved in melanin synthesis such as MITF (microphthalmia-associated transcription factor), Melan-A and tyrosinase was verified. < Image 2. The efficacy of melanogenesis inhibition on 3D human skin cells. a). Different irradiation conditions for a-MSH (major factor to stimulate melanin synthesis) treated cells. b) The ratio of pigmented area to total epidermis area. c) Relative variance of melanin level in 1 cm2-sized skin cells. A low variance means that melanin is evenly distributed, and a high variance means that the melanin is irregularly distributed. d) Optical images after in vitro experiments for 12 days. Scale bar, 1cm. e) Histological analysis of 3D skin, showing the greatest reduction in melanin after SµLED irradiation. Scale bar, 20 µm. > < Image 3. The efficacy of melanogenesis inhibition on mouse dorsal skin. a) Optical images of mice dorsal skin after photo-treatment for 20 days. b) Histological analysis of mice dorsal skin. Less brown color means less expression of protein/catalysis involved in melanin synthesis. Scale bar, 50 µm. > Prof. Keon Jae Lee said, “Our inorganic-based SµLED patch has outstanding characteristics in light efficiency, reliability, and durability. The SµLED patch is expected to give a great impact on the cosmetic field by reducing side effects and maximizing phototherapeutic effects.” The core technology of cosmetic SµLED has been transferred to Fronics co., Ltd, founded by Prof. Lee. Fronics is building foundry and equipment for mass production of SµLED masks for whole face cover and plans to release the products in March next year. This paper entitled “Wearable Surface-Lighting Micro-Light-Emitting Diode Patch for Melanogenesis Inhibition” was published in the November 2022 issue of Advanced Healthcare Materials.
Wearable Device to Monitor Sweat in Real Time
An on-skin platform for the wireless monitoring of flow rate, cumulative loss, and temperature of sweat in real time An electronic patch can monitor your sweating and check your health status. Even more, the soft microfluidic device that adheres to the surface of the skin, captures, stores, and performs biomarker analysis of sweat as it is released through the eccrine glands. This wearable and wireless electronic device developed by Professor Kyeongha Kwon and her collaborators is a digital and wireless platform that could help track the so-called ‘filling process’ of sweat without having to visually examine the device. The platform was integrated with microfluidic systems to analyze the sweat’s components. To monitor the sweat release rate in real time, the researchers created a ‘thermal flow sensing module.’ They designed a sophisticated microfluidic channel to allow the collected sweat to flow through a narrow passage and a heat source was placed on the outer surface of the channel to induce a heat exchange between the sweat and the heated channel. As a result, the researchers could develop a wireless electronic patch that can measure the temperature difference in a specific location upstream and downstream of the heat source with an electronic circuit and convert it into a digital signal to measure the sweat release rate in real time. The patch accurately measured the perspiration rate in the range of 0-5 microliters/minute (μl/min), which was considered physiologically significant. The sensor can measure the flow of sweat directly and then use the information it collected to quantify total sweat loss. Moreover, the device features advanced microfluidic systems and colorimetric chemical reagents to gather pH measurements and determine the concentration of chloride, creatinine, and glucose in a user's sweat. Professor Kwon said that these indicators could be used to diagnose various diseases related with sweating such as cystic fibrosis, diabetes, kidney dysfunction, and metabolic alkalosis. “As the sweat flowing in the microfluidic channel is completely separated from the electronic circuit, the new patch overcame the shortcomings of existing flow rate measuring devices, which were vulnerable to corrosion and aging,” she explained. The patch can be easily attached to the skin with flexible circuit board printing technology and silicone sealing technology. It has an additional sensor that detects changes in skin temperature. Using a smartphone app, a user can check the data measured by the wearable patch in real time. Professor Kwon added, “This patch can be widely used for personal hydration strategies, the detection of dehydration symptoms, and other health management purposes. It can also be used in a systematic drug delivery system, such as for measuring the blood flow rate in blood vessels near the skin’s surface or measuring a drug’s release rate in real time to calculate the exact dosage.” -PublicationKyeongha Kwon, Jong Uk Kim, John A. Rogers, et al. “An on-skin platform for wireless monitoring of flow rate, cumulative loss and temperature of sweat in real time.” Nature Electronics (doi.org/10.1038/s41928-021-00556-2) -ProfileProfessor Kyeongha KwonSchool of Electrical EngineeringKAIST
A Breakthrough for Cardiac Monitoring: Portable Smart Patch Makes It Possible for Real-time Observation of Heart Movement
Newly invented device makes the monitoring easier and convenient. Professor Hoi-Jun Yoo of KAIST, Department of Electrical Engineering, said that his research team has invented a smart patch for cardiac monitoring, the first of its kind in the world. Adhesive and can be applied directly to chest in human body, the patch is embedded with a built-in high performance semiconductor integrated circuit (IC), called Healthcare IC, and with twenty five electrodes formed on the patch’s surface. The 25-electrodes, with a capability of creating various configurations, can detect cardiac contractions and relaxations and collect electrocardiogram (ECG) signals. The Healthcare IC monitors ECG signals and sends the information to a portable data terminal like mobile phones, making it possible for a convenient, easy check up on cardiac observations. The key technologies used for the patch are the Healthcare IC that measures cardiovascular impedance and ECG signals, and the electronic circuit board made of four layers of fabric, between which electrodes, wireless antenna, circuit board, and flexible battery are installed. With the P-FCB (Planar Fashionable Circuit Board) technology, the research team explained, electrodes and a circuit board are directly stacked into the fabric. Additionally, the Healthcare IC (size: 5mm x 5mm), which has components of electrode control unit, ECG and cardiovascular resistance detection unit, data compression unit, Static Random Access Memory (SRAM), and wireless transmitter receiver, is attached on the fabric. The Healthcare IC is operated by an ultra-low electrical power. Like a medicated patch commonly used to relieve arthritis pains, the surface of smart patch is adhesive so that people can carry it around without much hassle. A finished product will be 15cm x 15 cm in size and 1mm high in thickness. The Healthcare IC can measure cardiovascular impedance variances with less than 0.81% distortion in 16 different configurations through differential current injectors and reconfigurable high sensitivity detection circuitry. “The patch will be ideal for patients who suffer a chronic heart disease and need to receive a continuous care for their condition. Once commercialized, the patch will allow the patients to conduct a self-diagnosis at anytime and anywhere,” said Yan Long, a member of the research team. There has been a continuously growing demand worldwide since 2000 for the development of technology that provides a suitable healthcare management to patients with a chronic heart disease (e.g., cardiovascular problems), but most of the technology developed today are only limited to monitoring electrical signals of heart activity. Cardiovascular monitors, commonly used at many of healthcare places nowadays, are too bulky to use and give uncomfortable feelings to patients when applied. Besides, the current monitors are connected to an electrical line for power supply, and they are unable to have a low power communication with an outdoor communication gadget, thus unavailable for wide use. Professor Yoo gave his presentation on this new invention at an international conference, International Solid-State Circuits Conference, held on February 8-10 in San Francisco. The subject of his presentation was “A 3.9mW 25-electorde Reconfigurable Thoracic Impedance/ECG SoC with Body-Channel Transponder.” (Picture 1) Structure of Smart Patch (Picture 2) Smart patch when applied onto human body (Picture 3) Data received from smart patch (Picture 4) Healthcare IC
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