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3-1. Low-Power Sensors and Control Modules for IoT Applications
We have made significant progress in developing low-power gas sensors using micro-heaters and micro-LEDs. The micro-heaters are suspended to minimize heat loss through conduction, reducing energy consumption to under 10 mW, ideal for long-term battery operation [1, 2, 3, 4, 5]. Additionally, our monolithic micro-LED based gas sensor enables efficient light energy transfer for ultra-low power gas detection at around 0.1 mW [6]. To support these sensors, we designed a control module with multi-channel transmission, and individual micro-heater and micro-LED control, ensuring precise sensor singal measurements [7]. The module integrates multiple variable resistors and high-speed multiplexed switching to accurately measure the wide resistance range of semiconductor metal oxide (SMO) in response to target gases, enhancing detection accuracy and reliability. Furthermore, the MEMS sensors developed by our lab exhibit excellent sensor-to-sensor uniformity, are scalable for mass production, and operate at low power. These characteristics ensure stable and reliable long-term operation in various environments, making them highly suitable for integration with IoT technologies. This opens up significant potential for widespread use in a variety of applications, regardless of location or conditions.
- [1] D. Yang, D.H. Kim, S.H. Ko, A.P. Pisano, Z. Li and I. Park*, “Focused energy field (FEF) method for the localized synthesis and direct integration of 1D nanomaterials on microelectronic devices “, Advanced Materials, Vol.27, No.7, 1207-1215, Feb 2015, Front Cover Paper
- [2] K. Kang, D. Yang, J. Park, S. Kim, I. Cho, H. Yang, M. Cho, S. Mousavi, K. Choi, and I. Park*, “Micropatterning of metal oxide nanofibers by electrohydrodynamic (EHD) printing towards highly integrated and multiplexed gas sensor applications”, Sensors and Actuators B: Chemical, Vol.250, 574-583, Apr 2017
- [3] I. Cho, K. Kang, D. Yang, J. Yun, and I. Park*, “Localized Liquid-Phase Synthesis of Porous SnO2 Nanotubes on MEMS Platform for Low Power, High Performance Gas Sensors”, ACS Applied Materials & Interfaces, 9(32), 27111-27119, July 2017
- [4] D. Yang†, I. Cho†, D. Kim, M. A. Lim, Z. Li, J. Ok, M. Lee, and I. Park*, “Gas Sensor by Direct Growth and Functionalization of Metal-Oxide/Metal-Sulfide Core-Shell Nanowires on Flexible Substrates”, ACS Applied Materials and Interfaces, 11(27), 24298-24307, June 2019
- [5] D.D. Orbe, I.Cho, H.Yang, J.Choi, M.Kang, K.Chang, C.Jeong, S.Han, I.Park* “Pt Nanostructures Fabricated by Local Hydrothermal Synthesis for Low-Power Catalytic-Combustion Hydrogen Sensors”, ACS Applied Nano Materials, 4, 7-12, Dec, 2020
- [6] I. Cho, Y. C. Sim, M. Cho, Y.-H. Cho*, and I. Park*, “Monolithic Micro Light-Emitting Diode/Metal Oxide Nanowire Gas Sensor with Microwatt-Level Power Consumption”, ACS Sensors, 5(2), 563-570, Feb 2020
- [7] J. Suh, I. Cho, K. Kang, S. Kweon, M. Lee, H. Yoo, and I. Park*, “Fully integrated and portable semiconductor-type multi-gas sensing module for IoT applications”, Sensors and Actuators B: Chemical, Vol265. 660-667, July 2018.
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Figure 1. Low-power sensors and control modules for IoT applications: (1) A ZnO nanowire gas sensor that is locally synthesized and directly integrated onto a suspended micro-heater using a hydrothermal synthesis method. (I. Park, et al., Adv. Mat. 2015), (2) Microrod-like Pt nanostructures, locally synthesized on a small suspended microheater platform, acting as the catalytic layer for a low-power hydrogen combustion sensor (I. Park, et al., ACS Appl. Nano Mater., 2021). (3) Micro-LED embedded, ultra-low power, monolithic photoactivated gas sensor (I. Park, et al., ACS Sens. 2020). (4) Portable SMO-type multi-gas sensing module for IoT applications (I. Park, et al., Sens Actuators B Chem. 2018).
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3-2. Deep Learning-Enhanced E-Nose and High-Resolution Pressure Sensors
We have integrated deep learning techniques with gas and physical sensor technologies to overcome sensor limitations and expand into various applications. By applying deep learning algorithm, we developed an electronic nose (e-nose) system that recognizes patterns in signals from different gas sensor arrays, allowing it to distinguish between different gases and accurately predict their concentrations, providing more valuable information [8, 9, 10]. Additionally, we applied deep learning to improve the spatial resolution of pressure sensors, enabling precise detection of force location and intensity, which opens up applications in VR/AR and wearable sensors [11].
- [8] M. Kang†, I. Cho, J. Park, J. Jeong, K. Lee, B. Lee, D. D. Orbe, K. Yoon*, I. Park*, “High Accuracy Real-time Multi-Gas Identification by Batch-Uniform Gas Sensor Array and Deep Learning Algorithm”, ACS Sensors, 7, 430-440, Jan, 2022.
- [9] 2. K. Lee, I. Cho, M. Kang, J. Jeong, M. Choi, K. Y. Woo, K. Yoon*, Y. H. Cho*, I. Park*, “Ultra-low Power E-nose System based on Multi Micro-LED-Integrated, Nanostructured Gas Sensors and Deep Learning”, ACS Nano, 17, 539-551, Jan, 2023.
- [10] I. Cho†, K. Lee†, Y. C. Sim, J. Jeong, M. Cho, H. Jung, M. Kang, Y. H. Cho, S. C. Ha, K. Yoon*, Inkyu Park*, “Deep-learning-based gas identification by time-variant illumination of a single micro-LED-embedded gas sensor”, Light: Science & Applications, 12, 95, Apr. 2023.
- [11] O. Gul, J. Kim, K. Kim, H. J. Kim*, and I. Park*, Liquid-Metal-Based Soft Pressure Sensor and Multidirectional Detection by Machine Learning, Adv. Mater. Technol., 2302134, Apr. 2024 (중견과제, 문화기술과제, ETRI과제).
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Figure 2. Deep learning-enhanced e-Nose and high-resolution pressure sensors: (1) Micro-heater-based gas sensor array and deep learning-based e-nose system. (I. Park, et al., ACS. Sens. 2022), (2) Micro-LED-based gas sensor array and deep learning-based e-nose system (I. Park, et al., ACS Nano 2022). (3) Liquid-Metal-Based Soft Pressure Sensor and Multidirectional Detection by Machine Learning (I. Park, et al., Adv. Mater. Tech. 2024).
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3-3. Neuromorphic In-Sensor Computing and Extended Applications
To address the high computational demands of deep learning, we have developed a bio-inspired artificial olfactory neuron module that mimics the spiking behavior of human olfactory neurons [12]. This neuromorphic approach allows for in-sensor computing, significantly reducing the power required for processing CNN algorithms. By integrating this technology with our gas sensors, we have created a more efficient e-nose system with dramatically lower power consumption. Beyond gas sensing, we are extending this neuromorphic computing technology to tactile sensors, exploring its potential in augmented reality (AR) and virtual reality (VR) applications. By incorporating AI-driven tactile feedback, we are working towards enhancing the interactivity and realism of AR/VR systems, making them more responsive and immersive.
- [12] J. K. Han†, M. Kang†, J. Jeong, I. Cho, J. M. Yu, K. J. Yoon, I. Park*, Y. K. Choi*, “Artificial olfactory neuron for an in-sensor neuromorphic nose”, Advanced Science, 9, 2106017, Apr, 2022.
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Figure 3. Artificial olfactory neuron for an in-sensor neuromorphic nose (I. Park, Y. K. Choi, et al., Adv. Sci. 2022).
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