Seung-Beom Ku

Han-Sol Lee

Kyeongho Eom

Minseong Um

Hyun-Su Lee

Hongseok Kim

Hanjun Cho

Woojoong Jung

Junyeol An

Junho Song

Minju Park

Jisan Ahn

Jungmin Kim

Chaehyun Kim

Sangil Lee

Minjae Kim

Duckhoon Ro

Kyungsoo Jeong

Our research spans a broad range of advanced systems from analog / mixed-signal integrated circuit (IC) design to emerging microsystem applications. We especially focus on biomedical / sensor / power / display / neuromorphic systems that need miniaturized low-power high-performance IC solutions for efficient and effective sensing, processing, interfacing, and powering.

본 연구는 아날로그/혼합 신호 집적 회로(IC) 설계에서부터 새로운 마이크로시스템 응용 분야에 이르기까지 광범위한 고급 시스템을 다룹니다. 특히 효율적이고 효과적인 감지, 처리, 인터페이스 및 전력 공급을 위해 소형화된 저전력 고성능 IC 솔루션이 필요한 생물 의학/센서/전력/디스플레이/뉴로모픽 시스템에 중점을 둡니다.

Energy-Management Integrated Circuit Design for Wireless Power and Data Transfer Applications

Wireless Applications: Biomedical Signals Telemetry System

Energy Management Integrated Circuits for Wireless Power Transmission

An Area and Power Efficient Fully Nonlinear 10-bit Column Driver with Time-Shared Multi-Gamma-Slope DAC and Time-Interleaved Sampling Buffer for Mobile AMOLED Displays

A Fully Integrated Portable Microplastic Detection System-on-Chip with High-Sensitivity RF MEMS Sensors and Narrow-Band Notch-Tracking Dielectric Discrimination Algorithms

Data-Driven Machine Learning Models for Predicting Engineering Properties in Deep-Sea Sediments

A Three-dimensional Bipolar Microneedle Electrode Array with Local Ground Integrated at Each Sidewall for Enhanced Focal Electric Stimulation

A Compact and Power Efficient 10 Bit Source Driver IC with Low Voltage Gamma Slope DAC for Mobile OLED Displays

A Hybrid Bidirectional Converter with Always-Half-Inductor Current Using Adaptive Target Current Tracking for USB-to-2-Cell Applications

A 96.5% Efficiency Hybrid Step-Up Converter with Low Input-Level Voltage Stress and Duty-Independent Constant Inductor Current

Spike-Based Q-learning in a Non-von Neumann Architecture

CMOS LIF Neurons with Local Membrane Dynamic Biasing Based on Reciprocal Inhibition for Self-Oscillatory Neural Networks

A Real-Time Error-Compensated Multisensor Acquisition System for Marine Geotechnical Investigation

An Analog Neuromorphic On-Chip Training System with IGZO TFT-Based 6T1C Synaptic Memory

An Area and Power Efficient Source Driver IC with Multi-Line Sensing Real-Time Pixel Compensation for OLED Displays

A Reconfigurable 3-Level Buck Converter with Supply Voltage Dynamic Split for Loop-Free Rapid VCF-Balancing and Dead-Zone Seamless Transition

Emerging Neuromorphic Devices-Compatible SNN Hardware with Adaptive STDP and Validation Using Novel CMOS Neuron-Synapse Circuits

A 10-V-Tolerant Dual-Mode Neural Stimulation System with Self-Sustaining Dynamic Supply and Error-Resilient Digital Stimulus Odometer

A Single-Input Multi-Output Resonant Regulating Rectifier Generating Three Outputs in a Half Cycle for Wirelessly Powered Biomedical Devices

Design Strategies of Capacitor-Based Synaptic Cell for High-Efficiency Analog Neural Network Training

A Multi-bit ECRAM-Based Analog Neuromorphic System with High-Precision Current Readout Achieving 97.3% Inference Accuracy

A 13.56-MHz 93.5%-Efficiency Optimal On/Off Timing Tracking Active Rectifier with Digital Feedback-Based Adaptive Delay Control

Enhanced Optogenetic Stimulation of Retinal Ganglion Cells with Assistive Electric Stimulation for Low Optical Power Artificial Vision

An RF MEMS Sensor Driver/Readout SoC with Resonant Frequency Shift and Closed-Loop Envelope Regulation for Portable Microplastic Detection

A Power-Efficient Envelope-Detector-Less Amplitude-Shift-Keying Forward Telemetry for Wirelessly Powered Biomedical Devices

A Scalable Distributed Linear Regulator with 99.5%-Accuracy Replica-based Current Sharing Calibration for Automotive Applications

An Energy-Efficient Real-Time Wearable ECG Acquisition System with Near-Data Prediagnosis for Mobile Applications

Development of Ocular Muscle Stimulation Systems and Optimization of Electrical Stimulus Parameters for Paralytic Strabismus Treatment

Verification of Neuromorphic Processing Accuracy against Non-Ideal Errors in Synapse-based Neural Network Systems

Quantitative Analyses of How Optimally Heterogeneous Neural Codes Maximize Neural Information in Jittery Transmission Environments

An Average Amplitude Regulation Scheme for Ambient Illuminance Adaptation in Retinal Prosthesis

A 92.7%-Efficiency 6.78-MHz Energy-Resuscitating Resonant Regulating Rectifier with Dual Outputs for Wirelessly Powered Devices

Retention-Aware Zero-Shifting Technique for Tiki-Taka Algorithm-Based Analog Deep Learning Accelerator

A 94.9% Efficiency Always-Power-Delivered SIDO Buck Converter with Continuous Current Balancing and Complementary Adaptive-Switching Regulation

A 96.3%-Efficiency Wide-Voltage-Range Three-Level Boost Converter with Loop-Free Self-Balancing and Dead-Zone PWM Control for Backlight LED Drivers

A 92%-Efficiency Inductor-Charging Switched-Capacitor Stimulation System with Level-Adaptive Duty Modulation and Offset Charge Balancing

Localization of hyperpolarization-activated cyclic nucleotide-gated channels in the vertebrate retinas across species and their physiological roles

A 9-V-Tolerant Stacked-Switched-Capacitor Stimulation System with Level-Adaptive Switch Control and Rapid Stimulus-Synchronized Charge Balancing for Implantable Devices

A 95.4% Hybrid Always-Dual-Path Recursive Step-Down Converter Using Adaptive Switching Level Control with 288mΩ Large-DCR Inductor

Rowhammer Attacks in Dynamic Random-Access Memory and Defense Methods

A Low-Stimulus-Scattering Pixel-Sharing Sub-Retinal Prosthesis SoC with Time-Based Photodiode Sensing and Per-Pixel Dynamic Voltage Scaling

Security Problems of Latest FPGAs and Reverse Engineering Methods of Xilinx 7-series FPGAs

Device-Algorithm Co-Optimization for an On-Chip Trainable Capacitor-Based Synaptic Device with IGZO TFT and Retention-Centric Tiki-Taka Algorithm

A Wide-Load-Range and High-Slew Capacitor-Less NMOS LDO with Adaptive-Gain Nested Miller Compensation and Pre-Emphasis Inverse Biasing

Complementary Multisplit Ring Resonant MEMS Sensor With Microfilter for Microplastics Concentration Measurement

A High-Efficiency High-Voltage-Tolerant Buck Converter with Inductor Current Emulator for Battery-Powered IoT Devices

A Multi-channel Neural Recording System with Neural Spike Scan and Adaptive Electrode Selection for High-density Neural Interface

A Fault-Tolerant Current-Starved Ring Oscillator with Signal-Flip Protection Delay Cells against Radiation Effects

A 13.56-MHz Wireless Power and Data Transfer System with Current-Modulated Energy-Reuse Back Telemetry and Energy-Adaptive Voltage Regulation

A 0.3V-V IN, 0.015ps-FoM Fully Integrated Analog-Assisted Digital LDO with Dual-Negative Gate Control and Adaptive Transient Recovery Path

A Load-Insensitive Hybrid LSK Back Telemetry System with Slope-Based Demodulation for Inductively Powered Biomedical Devices

High-Density Neural Recording System Design

A 80x60 Microbolometer CMOS Thermal Imager Integrated With a Low-Noise 12-B DAC

A Power-Efficient Resonant Current Mode Receiver with Wide Input Range over Breakdown Voltages Using Automated Maximum Efficiency Control

A Soft-Error-Tolerant SAR ADC with Dual-Capacitor Sample-and-Hold Control for Sensor Systems

Multi Look-up Table FPGA Reverse Engineering with Bitstream Extraction and Multiple PIP/PLP Matching

Dual-Path Three-Level Buck Converter with Loop-Free Auto-Calibration for Flying Capacitor Self-Balancing

Triple-Mode Switched-Inductor-Capacitor DC-DC Buck Converter with Reusable Flying Capacitor and Bang-Bang Zero-Current Detector for Wide Load Current Range

High Efficiency Hybrid Dual-Path Step-Up DC-DC Converter with Continuous Output Delivery Current for Low Output Ripple

A Time-Interleaved Resonant Voltage Mode Wireless Power Receiver with Delay-Based Tracking Loops for Implantable Medical Devices

On-Chip Compensated Type-III Buck Converter Using an Inner Feedback Loop with a Seamless CCM/DCM Transition Technique

A Radiation-Hardened SAR ADC with Delay-Based Dual Feedback Flip-Flops for Sensor Systems

A 90.7%-Efficiency Hybrid Optogenetic Stimulation System with Sub-Threshold Electrical Stimuli Achieving 70.6% Optical Energy Saving

An 80×80μm2/Pixel 55.48dB-Wide-DR 400-Pixel Subretinal Prosthesis SoC with Power-Aware Light Adaptation and Charge-Recycling Local Dynamic Supply

A 96.6% Single-Mode Hybrid Dual-Path Buck-Boost Converter with Conduction Loss Reduction through Conversion-Ratio-Based Adaptive 3-Phase Control

Wireless biphasic silicon solar cell retinal prosthesis with a push-pull mechanism for enhanced focal stimulation and charge balance

First M3D-Integrated 4K ECRAM Chip with Sub-100 nm Channels Achieving 100% Yield and Highly Uniform Performance for Analog AI Computing

A 97% Peak-Efficiency Dual-Channel 3-Fine-Level Buck-Boost Converter with Capacitive Inrush Current Reduction and Seamless Mode Transition Using a Slim 0.65-Thickness Inductor

A Reconfigurable Multi-Level AC-DC/DC-DC Ocean Energy Harvester IC Achieving 77.7% End-to-End Power Efficiency for Triboelectric Nanogenerators

A Hybrid Touch Sensing AFE with Common-CVQ (Currents, Voltages, and Charges) Subtraction to Improve Display Noise Immunity for Large Sensing Load up to 820pF

An Inductor-First Hybrid Buck-Boost Converter Featuring Seamless Single-Mode Operation, 97.2% Peak Efficiency, and 565mA/mm3 Current Density with Ultra-Compact 1mm3-Volume Inductor

A 97.4%-Peak-Efficiency Always-Half-Inductor-Current Hybrid Bidirectional Converter with Adaptive Target Current Tracking for USB-to-2-Cell Bidirectional Power Transfer

A Real-Time Pixel-Compensated Source Driver IC with Dual Slope Error Detection and Multi-Channel Time-Multiplexing Compensator for Compact OLED Displays

A Compact 10b Source Driver IC with Sigma-Delta Pulse Width Modulation for Low-Voltage Digital Interpolation Achieving 1884µm²/Channel

Efficiency of Combined Optogenetic and Electric Stimulation Depending on Amplitude and Waveform of Electric Stimulation in Mouse Retina

Adaptive SNN Neuromorphic Hardware for Interfacing between Emerging Neuron and Synaptic Devices

A Novel Invasive Biosensor Sensor Module Integrating Multi-Sensors and Readout IC for Enhanced Convenience in Daily Life Biomonitoring

A Fully Integrated Microplastic Detection SoC with 0.1–3 GHz Bandwidth and 35 dB Dynamic Range for Narrow-Band Notch RF MEMS Sensor System

An Analog Neuromorphic On-Chip Training System with IGZO TFT-Based 6T1C 367-State Synaptic Memory Achieving 0.99-R2 Linearity and 104-Times Enhanced Retention Time

A 90.8%-Efficiency SIMO Resonant Regulating Rectifier Generating 3 Outputs in a Half Cycle with Distributed Multi-Phase Control for Wirelessly-Powered Implantable Devices

A 96.5% Peak Efficiency Duty-Independent DC-DC Step-Up Converter with Low Input-Level Voltage Stress and Mode-Adaptive Inductor Current Reduction

A Fully Nonlinear Compact 10b Source Driver with Low-Voltage Gamma Slope DAC and Data/Phase Dependent Current Modulation Achieving 2411µm²/Channel for Mobile OLED Displays

Noise Immunity in Capacitive Sensing: Single-Ended AFE Design with Common-Current Subtraction for Mutual- and Self-Capacitance Sensing in 390pF Load

An Area and Power Efficient Fully Nonlinear 10-bit Column Driver with Time-Shared Multi-Gamma-Slope DAC and Time-Interleaved Sampling Buffer for Mobile AMOLEDs

A 92.7%-Efficiency 6.78-MHz Dual-Output Energy-Resuscitating Resonant Regulating Rectifier for Wirelessly Powered Systems

An ECRAM-Based Analog Compute-in-Memory Neuromorphic System with High-Precision Current Readout for Deep Learning

CMOS Leaky Integrate-and-Fire Neurons with Local Dynamic Biasing and Inhibitory Self-Oscillation

An RF MEMS Sensor Driver/Readout SoC with Resonant Frequency Shift and Closed-Loop Envelope Regulation for Microplastic Detection

A 93.5%-Efficiency 13.56-MHz-Bandwidth Optimal On/Off Tracking Active Rectifier with Fully Digital Feedback-Based Delay Control for Adaptive Efficiency Compensation

A 9V-Tolerant 71.4%-Efficiency Stacked-Switched-Capacitor Stimulation System with Level-Adaptive Switching Control and Rapid Stimulus-Synchronized Charge Balancing

A Stimulus-Scattering-Free Pixel-Sharing Sub-Retinal Prosthesis SoC with 35.8dB Dynamic Range Time-Based Photodiode Sensing and Per-Pixel Dynamic Voltage Scaling

A Fast-Transient and Wide-Range Output Capacitor-Less NMOS LDO Regulator with Adaptive-Gain Nested Miller Compensation and Pre-Emphasis Inverse Biasing

A Circuit Modeling Method of OLED On-Cell Touch Panels Including the Touch Objects for Full-Frame Touch Simulation

Implementation of Full-Panel Circuit Models for Interference Estimation Between Touch and Display Operation in On-Cell Touch AMOLED

A Hybrid Always-Dual-Path Recursive Step-Down Converter Using Adaptive Switching Level Control Achieving 95.4% Efficiency with 288mΩ Large-DCR Inductor

A 92%-Efficiency Inductor-Charging Switched-Capacitor Stimulation System with Level-Adaptive Duty Modulation and Offset Charge Balancing for Muscular Stimulation

Carbon Black based Resistive Strain Gauge Sensor for Penile Measurement

A Load-Insensitive Hybrid Back Telemetry System for Wirelessly-Powered Implantable Devices

A 2.45-GHz RF Energy Harvester with On-Chip 8-VCR SC Booster for IoT Devices

Hyung-Min Lee

A 95.2% Efficiency Dual-Path DC-DC Step-Up Converter with Continuous Output Current Delivery and Low Voltage Ripple

Analog CMOS-Based Resistive Processing Unit for Deep Neural Network Training

A Wireless Slanted Optrode Array with Integrated Micro LEDs for Optogenetics

We present an inductively powered 32-channel wireless integrated neural recording (WINeR) system-on-a-chip (SoC) to be ultimately used for one or more small freely behaving animals. The inductive powering is intended to relieve the animals from carrying bulky batteries used in other wireless systems, and enables long recording sessions. The WINeR system uses time-division multiplexing along with a novel power scheduling method that reduces the current in unused low-noise amplifiers (LNAs) to cut the total SoC power consumption. In addition, an on-chip high-efficiency active rectifier with optimized coils help improve the overall system power efficiency, which is controlled in a closed loop to supply stable power to the WINeR regardless of the coil displacements. The WINeR SoC has been implemented in a 0.5-μ m standard complementary metal-oxide semiconductor process, measuring 4.9×3.3 mm 2 and …

An inductively powered scalable 32-channel wireless neural recording system-on-a-chip for neuroscience applications

We present an active full-wave rectifier with offset-controlled high speed comparators in standard CMOS that provides high power conversion efficiency (PCE) in high frequency (HF) range for inductively powered devices. This rectifier provides much lower dropout voltage and far better PCE compared to the passive on-chip or off-chip rectifiers. The built-in offset-control functions in the comparators compensate for both turn-on and turn-off delays in the main rectifying switches, thus maximizing the forward current delivered to the load and minimizing the back current to improve the PCE. We have fabricated this active rectifier in a 0.5-μm 3M2P standard CMOS process, occupying 0.18 mm 2 of chip area. With 3.8 V peak ac input at 13.56 MHz, the rectifier provides 3.12 V dc output to a 500 Ω load, resulting in the PCE of 80.2%, which is the highest measured at this frequency. In addition, overvoltage protection (OVP) as …

An integrated power-efficient active rectifier with offset-controlled high speed comparators for inductively powered applications

A power-efficient wireless stimulating system for a head-mounted deep brain stimulator (DBS) is presented. A new adaptive rectifier generates a variable DC supply voltage from a constant AC power carrier utilizing phase control feedback, while achieving high AC-DC power conversion efficiency (PCE) through active synchronous switching. A current-controlled stimulator adopts closed-loop supply control to automatically adjust the stimulation compliance voltage by detecting stimulation site potentials through a voltage readout channel, and improve the stimulation efficiency. The stimulator also utilizes closed-loop active charge balancing to maintain the residual charge at each site within a safe limit, while receiving the stimulation parameters wirelessly from the amplitude-shift-keyed power carrier. A 4-ch wireless stimulating system prototype was fabricated in a 0.5-μm 3M2P standard CMOS process, occupying 2 …

A power-efficient wireless system with adaptive supply control for deep brain stimulation

A power-efficient wireless switched-capacitor based stimulating (SCS) system for electrical/optical deep brain stimulation (DBS) is presented. The SCS system efficiently charges storage capacitors directly from an inductive link and delivers accurately balanced charge to the tissue, improving the overall stimulator efficiency. In addition, the decaying exponential stimulus pulses generated by SCS can be more effective than conventional rectangular and ramp stimuli in activating neural tissue when consuming the same amount of energy, leading to higher stimulus efficacy. A 4-channel wireless SCS system in 0.35 μm CMOS process achieves stimulator efficiency of 80.4% with capacitor pairs charged to ±2V, while the decaying exponential stimulus requires equal or less stimulus energy and injected charge than other stimuli depending on pulse width to activate the same tissue area. The SCS system has also been …

A Power-Efficient Switched-Capacitor Stimulating System for Electrical/Optical Deep Brain Stimulation

We present an adaptive reconfigurable active voltage doubler (VD)/rectifier (REC) (VD/REC) in standard CMOS, which can adaptively change its topology to either a VD or a REC by sensing the output voltage, leading to more robust inductive power transmission over an extended range. Both active VD and REC modes provide much lower dropout voltage and far better power conversion efficiency (PCE) compared to their passive counterparts by adopting offset-controlled high-speed comparators that drive the rectifying switches at proper times in the high-frequency band. We have fabricated the active VD/REC in a 0.5- 3-metal 2-poly CMOS process, occupying 0.585 of chip area. In an exemplar setup, VD/REC extended the power transmission range by 33 (from 6 to 8 cm) in relative coil distance and 41.5 (from 53 to 75 ) in relative coil orientation compared to using the REC alone. While providing 3.1-V dc output …

16.7 An adaptive reconfigurable active voltage doubler/rectifier for extended-range inductive power transmission

Tongue drive system (TDS) is a tongue-operated, minimally invasive, unobtrusive, and wireless assistive technology (AT) that infers users' intentions by detecting their voluntary tongue motion and translating them into user-defined commands. Here we present the new intraoral version of the TDS (iTDS), which has been implemented in the form of a dental retainer. The iTDS system-on-a-chip (SoC) features a configurable analog front-end (AFE) that reads the magnetic field variations inside the mouth from four 3-axial magnetoresistive sensors located at four corners of the iTDS printed circuit board (PCB). A dual-band transmitter (Tx) on the same chip operates at 27 and 432 MHz in the Industrial/Scientific/Medical (ISM) band to allow users to switch in the presence of external interference. The Tx streams the digitized samples to a custom-designed TDS universal interface, built from commercial off-the-shelf (COTS …

A wireless magnetoresistive sensing system for an intraoral tongue-computer interface

The recent development of optogenetics has created an increased demand for advancing engineering tools for optical modulation of neural circuitry. This paper details the design, fabrication, integration, and packaging procedures of a wirelessly-powered, light emitting diode (LED) coupled optrode neural interface for optogenetic studies. The LED-coupled optrode array employs microscale LED (μLED) chips and polymer-based microwaveguides to deliver light into multi-level cortical networks, coupled with microelectrodes to record spontaneous changes in neural activity. An integrated, implantable, switched-capacitor based stimulator (SCS) system provides high instantaneous power to the μLEDs through an inductive link to emit sufficient light and evoke neural activities. The presented system is mechanically flexible, biocompatible, miniaturized, and lightweight, suitable for chronic implantation in small freely behaving animals. The design of this system is scalable and its manufacturing is cost effective through batch fabrication using microelectromechanical systems (MEMS) technology. It can be adopted by other groups and customized for specific needs of individual experiments.

Design, fabrication, and packaging of an integrated, wirelessly-powered optrode array for optogenetics application

Recently we have shown that an architecture based on resistive processing unit (RPU) devices has potential to achieve significant acceleration in deep neural network (DNN) training compared to today's software-based DNN implementations running on CPU/GPU. However, currently available device candidates based on non-volatile memory technologies do not satisfy all the requirements to realize the RPU concept. Here, we propose an analog CMOS-based RPU design (CMOS RPU) which can store and process data locally and can be operated in a massively parallel manner. We analyze various properties of the CMOS RPU to evaluate the functionality and feasibility for acceleration of DNN training.

Analog CMOS-based resistive processing unit for deep neural network training

In this paper, we present a fully integrated active voltage doubler in CMOS technology using offset-controlled high speed comparators for extending the range of inductive power transmission to implantable microelectronic devices (IMD) and radio-frequency identification (RFID) tags. This active voltage doubler provides considerably higher power conversion efficiency (PCE) and lower dropout voltage compared to its passive counterpart and requires lower input voltage than active rectifiers, leading to reliable and efficient operation with weakly coupled inductive links. The offset-controlled functions in the comparators compensate for turn-on and turn-off delays to not only maximize the forward charging current to the load but also minimize the back current, optimizing PCE in the high frequency (HF) band. We fabricated the active voltage doubler in a 0.5- 3M2P std . CMOS process, occupying 0.144 of chip area. With 1 …

A high frequency active voltage doubler in standard CMOS using offset-controlled comparators for inductive power transmission

This article proposes a new boost converter topology called dual-path step-up dc-dc converter (DPUC). Unlike the conventional boost converter (CBC), the DPUC has a hybrid structure using one inductor and one flying capacitor to make dual current delivery paths. This allows continuous current delivering to the output, reducing both the dc level of the inductor current and the output voltage ripple. Therefore, the DPUC has higher efficiency and smaller output voltage ripple than those of the CBC. In addition, the feedforward characteristic of the flying capacitor can alleviate the effect of right-half-plane zero that degrades the transient response. Even with the inductor dc resistance of 200 mΩ, the DPUC achieves a high efficiency of 95.2% and a small ripple of up to 15 mV.

High-efficiency hybrid dual-path step-up DC–DC converter with continuous output-current delivery for low output voltage ripple

In this paper, we review recent advances in reverse engineering with an emphasis on FPGA devices and experimentally verified advantages and limitations of reverse engineering tools. The paper first introduces essential components for programming Xilinx FPGAs (Xilinx, San Jose, CA, USA), such as Xilinx Design Language (XDL), XDL Report (XDLRC), and bitstream. Then, reverse engineering tools (Debit, BIL, and Bit2ncd), which extract the bitstream from the external memory to the FPGA and utilize it to recover the netlist, are reviewed, and their limitations are discussed. This paper also covers supplementary tools (Rapidsmith) that can adjust the FPGA design flow to support reverse engineering. Finally, reverse engineering projects for non-Xilinx products, such as Lattice FPGAs (Icestorm) and Altera FPGAs (QUIP), are introduced to compare the reverse engineering capabilities by various commercial FPGA products.

Recent advances in FPGA reverse engineering

This paper presents a wireless-enabled, flexible optrode array with multichannel micro light-emitting diodes (μ-LEDs) for bi-directional wireless neural interface. The array integrates wirelessly addressable μ-LED chips with a slanted polymer optrode array for precise light delivery and neural recording at multiple cortical layers simultaneously. A droplet backside exposure (DBE) method was developed to monolithically fabricate varying-length optrodes on a single polymer platform. In vivo tests in rat brains demonstrated that the μ-LEDs were inductively powered and controlled using a wireless switched-capacitor stimulator (SCS), and light-induced neural activity was recorded with the optrode array concurrently.

A wireless slanted optrode array with integrated micro leds for optogenetics

A power-efficient wireless capacitor charging system for inductively powered applications has been presented. A bank of capacitors can be directly charged from an ac source by generating a current through a series charge injection capacitor and a capacitor charger circuit. The fixed charging current reduces energy loss in switches, while maximizing the charging efficiency. An adaptive capacitor tuner compensates for the resonant capacitance variations during charging to keep the amplitude of the ac input voltage at its peak. We have fabricated the capacitor charging system prototype in a 0.35-μm 4-metal 2-poly standard CMOS process in 2.1 mm 2 of chip area. It can charge four pairs of capacitors sequentially. While receiving 2.7-V peak ac input through a 2-MHz inductive link, the capacitor charging system can charge each pair of 1 μF capacitors up to ±2 V in 420 μs, achieving a high measured charging …

A Power-Efficient Wireless Capacitor Charging System Through an Inductive Link

DC-DC boost converters are widely used to increase the supply voltage in various applications, including LED drivers, energy harvesting, etc. [1-5]. The conventional boost converter (CBC) is shown in Fig. 27.5.1, where the switches S 1 and S 2 are turned on and off alternately at φ 1 and φ 2 , respectively, and the inductor current (I L ) is built up and delivered to the output. There are some critical issues in CBC because the output delivery current (I S ) is not continuous. As a result, the I L can be much larger than the load current (I LOAD ) as φ 1 becomes longer. Since a bulky-size inductor having a low parasitic DC resistance (R dcr ) is not usable for mobile applications with a strictly limited space, this large I L results in significant conduction loss in the large R DCR of a small-size inductor. Another issue is that the discontinuous I S in φ 2 causes large voltage ripple (AV OUT ) at the output. Moreover, switching spike voltages …

A 95.2% efficiency dual-path DC-DC step-up converter with continuous output current delivery and low voltage ripple

This letter proposes a loop-free autocalibration technique for self-balancing of flying capacitors in a three-level dc–dc buck converter. The proposed converter utilizes a dual-path power stage with balancing switches that adaptively short flying capacitors at de-energizing phases. Thus, the dual-path three-level converter ensures that flying capacitor voltages are self-balanced at half the input voltage without using additional feedback calibration loops, leading to robust operation and competitive efficiencies. The prototype was fabricated in the 0.13- μ m CMOS BCD process and adopted two flying capacitors of 4.7 μ F each and an inductor of 10 μ H with a dc resistance of 128 mΩ. When an 8-V input was converted to a 3-V output voltage with a load current of 400 mA, the measured efficiency was 88.6% at 800 kHz switching while flying capacitors are automatically balanced.

Dual-path three-level buck converter with loop-free autocalibration for flying capacitor self-balancing

In this letter, a noninverting buck-boost converter with state-based current control is proposed for Li-ion battery management. Unlike conventional multimode control in buck-boost converters, our control scheme utilizes a state controller with a single-level error current and a state checking clock to define the operation mode at every cycle. The state-based buck-boost converter enables seamless mode transition and stable output regulation with fixed interleaving patterns even when input and output voltages are similar, ensuring robust mode change with inherent hysteresis. The prototype IC was fabricated in a 0.18-μm BCD process and achieved 90.9% efficiency with 1.1-A maximum load current capability at 1-MHz switching frequency.

A Noninverting Buck–Boost Converter With State-Based Current Control for Li-ion Battery Management in Mobile Applications

Lithium-ion batteries are generally used in mobile devices, but the voltage range of the battery varies from 2.7 to 4.2V. To provide a mid-3V-range output from the battery, a converter capable of step-up/down-conversion is necessary. For this purpose, non-inverting buck-boost topologies with multimode control [1-3] have been widely used. However, they have limited efficiency slightly higher than 90%, which comes from the fact that a main current path always encompasses two switches. To increase the efficiency in the buck mode where the converter operates for most of the usage time, a flying capacitor buck-boost (FCBB) was proposed in [4]. Despite its high power efficiency, it requires large-size LDMOS to endure a large voltage range up to 8V at switching node, resulting in cost inefficiency. Since all these topologies have a common controller that covers both buck and boost modes of operation, compensator …

A 97% high-efficiency 6μs fast-recovery-time buck-based step-up/down converter with embedded 1/2 and 3/2 charge-pumps for li-lon battery management

ABSTRACT A resistive processing unit (RPU) includes a circuit includ ing at least two current mirrors connected in series, and a capacitor connected with the at least two current mirrors, the capacitor providing a weight based on a charge level of the capacitor. The capacitor is charged or discharged by one of the at least two current mirrors.

Circuit methodology for highly linear and symmetric resistive processing unit

A piecewise linear 10 bit DAC for LCD data driver with robust interpolation method of drain current modulation is presented. It has higher effective bit resolution than the linear 10 bit switched-capacitor DAC when applied to nonlinear liquid crystal characteristics. By adopting a simultaneous design flow based on the estimations for the mismatch and nonlinearity effects on channel driver performance, the proposed DAC accomplishes good DNL of 0.37 LSB and excellent channel uniformity such that the mean and the standard deviation of the maximum output voltage deviations are 6.35 mV and 0.54 mV, respectively. The data driver with the new interpolation shows 8.2% shrinkage of chip area in comparison with the conventional 8 bit data driver with R-DAC.

A Piecewise Linear 10 Bit DAC Architecture With Drain Current Modulation for Compact LCD Driver ICs

Ph.D. in Electrical and Computer Engineering

Professor, School of Electrical Engineering

Obesity increases the risks of diabetes, hypertension, and cardiovascular diseases, ultimately contributing to mortality. Korean Society for the Study of Obesity (KSSO) was established to improve the management of obesity through research and education; to that end, the Committee of Clinical Practice Guidelines of KSSO reviews systemic evidence using expert panels to develop clinical guidelines. The clinical practice guidelines for obesity were revised in 2018 using National Health Insurance Service Health checkup data from 2006 to 2015. Following these guidelines, we added a category, class III obesity, which includes individuals with body mass index (BMI) ≥35 kg/m2. Agreeing with the International Federation for the Surgery of Obesity and Metabolic Disorders, Asian Pacific Chapter consensus, we determined that bariatric surgery is indicated for Korean patients with BMI ≥35 kg/m2 and for Korean patients …

2018 Korean society for the study of obesity guideline for the management of obesity in Korea

Photoluminescent graphene quantum dots (GQDs) have fascinating optical and electronic properties with numerous promising applications in biomedical engineering. In this work, we first studied the in vivo biodistribution and the potential toxicity of carboxylated photoluminescent GQDs. KB, MDA-MB231, A549 cancer cells, and MDCK normal cell line were chosen as in vitro cell culture models to examine the possible adverse effects of the carboxylated photoluminescent GQDs. The carboxylated GQDs are desirable for increased aqueous solubility. All cancer cells efficiently took up the carboxylated GQDs. No acute toxicity or morphological changes were noted in either system at the tested exposure levels. A long-term in vivo study revealed that the GQDs mainly accumulated in liver, spleen, lung, kidney, and tumor sites after intravenous injection. To reveal any potential toxic effect of the GQDs on treated mice …

In Vivo Biodistribution and Toxicology of Carboxylated Graphene Quantum Dots

Exosomes are endosome-derived nanovesicles involved in cellular communication. They are natural nanocarriers secreted by various cells, making them suitable candidates for diverse drug delivery and therapeutic applications from a material standpoint. They have a phospholipid bilayer decorated with functional molecules and an enclosed parental matrix, which has attracted interest in developing designer/hybrid engineered exosome nanocarriers. The structural versatility of exosomes allows the modification of their original configuration using various methods, including genetic engineering, chemical procedures, physical techniques, and microfluidic technology, to load exosomes with additional cargo for expanded biomedical applications. Exosomes show enormous potential for overcoming the limitations of conventional nanoparticle-based techniques in targeted therapy. This review highlights the exosome …

Hybrid exosomes, exosome-like nanovesicles and engineered exosomes for therapeutic applications

The dramatic increase in the prevalence of obesity and its accompanying comorbidities are major health concerns in Korea. Obesity is defined as a body mass index≥ 25 kg/m2 in Korea. Current estimates are that 32.8% of adults are obese: 36.1% of men and 29.7% of women. The prevalence of being overweight and obese in national surveys is increasing steadily. Early detection and the proper management of obesity are urgently needed. Weight loss of 5% to 10% is the standard goal. In obese patients, control of cardiovascular risk factors deserves the same emphasis as weight-loss therapy. Since obesity is multifactorial, proper care of obesity requires a coordinated multidisciplinary treatment team, as a single intervention is unlikely to modify the incidence or natural history of obesity.

2014 clinical practice guidelines for overweight and obesity in Korea

The limitations of conventional therapeutic drugs necessitate the importance of developing novel therapeutics to treat diverse diseases. Conventional drugs have poor blood circulation time and are not stable or compatible with the biological system. Nanomaterials, with their exceptional structural properties, have gained significance as promising materials for the development of novel therapeutics. Nanofibers with unique physiochemical and biological properties have gained significant attention in the field of health care and biomedical research. The choice of a wide variety of materials for nanofiber fabrication, along with the release of therapeutic payload in sustained and controlled release patterns, make nanofibers an ideal material for drug delivery research. Electrospinning is the conventional method for fabricating nanofibers with different morphologies and is often used for the mass production of nanofibers. This review highlights the recent advancements in the use of nanofibers for the delivery of therapeutic drugs, nucleic acids and growth factors. A detailed mechanism for fabricating different types of nanofiber produced from electrospinning, and factors influencing nanofiber generation, are discussed. The insights from this review can provide a thorough understanding of the precise selection of materials used for fabricating nanofibers for specific therapeutic applications and also the importance of nanofibers for drug delivery applications.

Electrospinning nanofibers for therapeutics delivery

METHODS—This study was based on the 1998 Korea National Health and Nutrition Examination Survey. Selection methods for a nationwide representative sample of Koreans and other survey methods were detailed elsewhere (2). Complete data were obtained for 9,771 of 10,876 individuals (89.8%) who participated in the Health Examination Study. We restricted our analyses to men because the proportion of Korean women who smoked was too small (8.3%) to allow detailed analyses (2). Finally, data from 3,452 men 20 years of age formed the basis of this analysis. The surveys included questions about age, education level, occupation, income, marital status, smoking habits, alcohol consumption, exercise, previous and current diseases, and family disease history, among others. The nutrition survey employed in this study assessed daily energy and nutrient intakes by using 24-h recall and a food-intake frequency method. Past smokers were defined as those who had abstained from smoking for 3 months at the time of examination. Information on the daily smoking habits of current smokers was obtained from questions about the average number of cigarettes smoked daily during the month before the interview. Because participants often reported their current smoking amounts by the unit of pack (20 cigarettes), five categories were established: 10, 10–19, 20–29, 30–39, and 40 cigarettes/day. The total number of packyears of cigarettes smoked was also calculated from the total number of years spent smoking multiplied by the number of packs smoked daily. Total pack-years were divided into quartiles for the analyses. The 2001 definition of …

Association between cigarette smoking and metabolic syndrome: the Korea National Health and Nutrition Examination Survey

Blood compatible graphene/heparin conjugate is simply formulated through noncovalent interaction between chemically reduced graphene and heparin. Charge repulsion of negatively charged heparin on graphene plates renders hydrophobic graphene to be solublized in aqueous media without any precipitation or aggregation even after 6 months. Unfractioned heparin (UFH) with higher molecular weight was effective for graphene solubilization while low molecular weight heparin (LMWH) was not. Noncovalently interacting heparin chains on graphene plates preserve their anticoagulant activity after conjugation with graphene. Graphene/UFH conjugate shows much enhanced anti factor Xa (FXa) activity of 29.6 IU/mL compared with pristine graphene oxide (GO; 1.03 IU/mL).

Blood compatible graphene/heparin conjugate through noncovalent chemistry

Biosensors research is a fast growing field in which tens of thousands of papers have been published over the years, and the industry is now worth billions of dollars. The biosensor products have found their applications in numerous industries including food and beverages, agricultural, environmental, medical diagnostics, and pharmaceutical industries and many more. Even though numerous biosensors have been developed for detection of proteins, peptides, enzymes, and numerous other biomolecules for diverse applications, their applications in tissue engineering have remained limited. In recent years, there has been a growing interest in application of novel biosensors in cell culture and tissue engineering, for example, real‐time detection of small molecules such as glucose, lactose, and H 2 O 2 as well as serum proteins of large molecular size, such as albumin and alpha‐fetoprotein, and inflammatory …

Recent advances in application of biosensors in tissue engineering

Cannon, PC (57) ABSTRACT Polysaccharides, which are widely used as an anticoagula tion drugs, especially heparin, are clinically administered only by intravenous or Subcutaneous injection because of their strong hydrophilicity and high negative charge. Amphiphilic heparin derivatives were Synthesized by con jugate to bile acids, Sterols, and alkanoic acids, respectively. The hydrophobicity of the heparin derivatives depended on the feed mole ratio of heparin to hydrophobic agent. The heparin derivatives were slightly hydrophobic and exhibited good Solubility in a water-acetone Solvent, as well as water. The heparin derivatives have a high anticoagulant activity. These slightly hydrophobic heparin derivatives can be absorbed in gastric intestinal tract and can be used as oral dosage form. Also, the heparin derivatives can be used for the Surface modification to prevent anticoagulation for medi cal devices …

Amphiphilic polysaccharide derivatives

Due to the wide range and various applications of graphene in multidisciplinary fields, such as electronics, solar cells, biomedicine, bioengineering, drug delivery, gene delivery and semiconductors, graphene and its derivatives have attracted most significant interest of diverse group of scientists in the last decades. Besides numerous applications in electrical and mechanical fields, their non-invasive biomedical imaging properties allow their wide-spread biological applications. Optical imaging probes play a pivotal role in early cancer detection, image based surgery, disease diagnosis and cellular imaging. Graphene has been widely studied in drug delivery systems due to its unique features and comparatively less/non-toxic properties in biological systems, thus promoting graphene quantum dots as potential organic optical imaging agents to substitute toxic cadmium or tellurium quantum dots. Many groups have …

Bioapplication of graphene oxide derivatives: drug/gene delivery, imaging, polymeric modification, toxicology, therapeutics and challenges

Because of the superiority of GQDs (graphene quantum dots) in biomedical imaging, in terms of biocompatibility and toxicity of semiconductor quantum dots, GQDs bring new opportunities for the diagnosis and detection of diseases. In this study, we synthesized photoluminescent (PL) graphene quantum dots (GQDs) through a simple exfoliation and oxidation process, and then coated them with polydopamine (pDA) for enhanced stability in water and low toxicity in vivo. From the results, the GQDs coated with pDA showed an excellent stability of PL intensity. It showed that the PL intensity of noncoated GQDs in PBS solution rapidly decreased with time, resulting in a 45% reduction of the PL intensity for 14 days of incubation in PBS solution. After coating with polydopamine, PL intensities of polydopamine-coated GQDs was maintained more stably for 14 days compared with uncoated GQDs. We have observed the in …

Surface coating of graphene quantum dots using mussel-inspired polydopamine for biomedical optical imaging

Background : The incidence of transfusion transmission of human T‐ lymphotropic virus type I (HTLV‐I) and HTLV type II (HTLV‐II) has not been compared directly or to that of human immunodeficiency virus type 1 (HIV‐1). The effects of refrigerator storage of the blood component on infectivity of the viruses needs definition. Study Design and Methods : The circumstances influencing the transmission of HTLV‐I, HTLV‐ II, and HIV‐1 via blood of donors whose sera were stored in a repository and who were retrospectively documented as having been infected at blood donation were examined. Confirmation and typing of anti‐HTLV positivity in donors and recipients used polymerase chain reaction, supplemented by specific peptide testing. Results : Overall, 27 percent (26/95) of the recipients of blood components from anti‐HTLV‐ I‐ and ‐II‐positive donors became infected (9 with HTLV‐I and 17 with HTLV‐II). No …

Transfusion transmission of retroviruses: human T‐lymphotropic virus types I and II compared with human immunodeficiency virus type 1

The use of water-soluble, functionalized quantum dots (QDs) that are highly stable against oxidation for biological and biomedical applications is currently one of the fastest growing fields of nanotechnology. Polymer-based nanoparticles are now widely used for drug delivery and targeted therapy. We modified the surface of near Infrared QDs by the solid dispersion method using PEG–PCDA and PCDA–Herceptin conjugates to demonstrate water-solubility and target-specific properties. Upon UV irradiation, QD cores located within nanoprobes were further stabilized by intramicellar cross-linking between neighboring PCDA–Herceptin moieties. These cross-linked nanoprobes showed higher stability and less toxicity. Near-IR QDs-loaded micelles were spherical with diameters of around 130–150nm. The anti-tumor effect of near-IR QDs-loaded micelles against MDA-MB-231 tumors was remarkably better than that of …

Targeted near-IR QDs-loaded micelles for cancer therapy and imaging

Graphene-based nanomaterials are of great interest in a wide range of applications in electronics, the environment, and energy as well as in biomedical and bioengineering. Their unique properties make them generally applicable as prognostic, diagnostic, and therapeutic agents in cancer. In this work, we focused on photodynamic and photothermal therapeutic properties of our previously synthesized carboxylated photoluminescent graphene nanodots (cGdots). The cGdots are ∼5 nm in diameter and excited at 655 nm. Our findings reveal that, upon laser irradiation by near-infrared (wavelength 670 nm) sensitizer, electrons of the cGdots starts to vibrate and form electron clouds, thereby generating sufficient heat (>50 °C) to kill the cancer cells by thermal ablation. The generation of singlet oxygen also occurs due to irradiation, thus acting similarly to pheophorbide-A, a well-known photodynamic therapeutic agent …

Photoluminescent graphene nanoparticles for cancer phototherapy and imaging

We designed a cancer-cell specific photosensitizer nano-carrier by synthesizing pheophorbide a (PheoA) conjugated glycol chitosan (GC) with reducible disulfide bonds (PheoA-ss-GC). The amphiphilic PheoA-ss-GC conjugates self-assembled in aqueous condition to form core–shell structured nanoparticles (PheoA-ss-CNPs) with good colloidal stability and switchable photoactivity. The photoactivity of PheoA-ss-CNPs in an aqueous environment was greatly suppressed by the self-quenching effect, which enabled the PheoA-ss-CNPs to remain photo-inactive and in a quenched state. However, after the cancer cell-specific uptake, the nanoparticular structure instantaneously dissociated by reductive cleavage of the disulfide linkers, followed by an efficient dequenching process. Compared to non-reducible PheoA-conjugated GC-NPs with stable amide linkages (PheoA–CNPs), PheoA-ss-CNPs rapidly restored …

Cancer cell-specific photoactivity of pheophorbide a–glycol chitosan nanoparticles for photodynamic therapy in tumor-bearing mice

The combined delivery of photo- and chemo-therapeutic agents is an emerging strategy to overcome drug resistance in treating cancer, and controlled light-responsive drug release is a proven tactic to produce a continuous therapeutic effect for a prolonged duration. Here, a combination of light-responsive graphene, chemo-agent doxorubicin and pH-sensitive disulfide-bond linked hyaluronic acid form a nanogel (called a graphene–doxorubicin conjugate in a hyaluronic acid nanogel) that exerts an activity with multiple effects: thermo and chemotherapeutic, real-time noninvasive imaging, and light-glutathione-responsive controlled drug release. The nanogel is mono-dispersed with an average diameter of 120 nm as observed by using TEM and a hydrodynamic size analyzer. It has excellent photo-luminescence properties and good stability in buffer and serum solutions. Graphene itself, being photoluminescent …

A hyaluronic acid nanogel for photo–chemo theranostics of lung cancer with simultaneous light-responsive controlled release of doxorubicin

Background — Heparin administration is usually limited to intravenous or subcutaneous injection. Oral delivery of heparin is an alternative to this and has been in great demand for treating patients who are at a high risk of deep vein thrombosis or pulmonary embolism. In this study, new heparin derivatives were synthesized to enhance the oral absorption of heparin in the gastrointestinal tract. Methods and Results — By using heparin of 3000 Da [LMWH(3 kDa)], heparin of 6000 Da [LMWH(6 kDa)], and unfractionated heparin (UFH), we synthesized 3 kinds of conjugates of heparin and deoxycholic acid (DOCA): LMWH(3 kDa)-DOCA, LMWH(6 kDa)-DOCA, and UFH-DOCA. After oral administration of 100 mg/kg of heparin-DOCA, the maximum activated partial thromboplastin times of the LMWH(3 kDa)-DOCA, LMWH(6 kDa)-DOCA, and UFH-DOCA were 31.0±6.0, 87.8±11.1, and 51.0±8.7 seconds, respectively …

Conjugation of low-molecular-weight heparin and deoxycholic acid for the development of a new oral anticoagulant agent

A simple reaction process is developed to synthesize blue, green, yellow and red colour graphene nanoparticles (GNPs) from carbon fibers. Here, we have focused on synthesis of near infra-red GNPs and their biological application for optical imaging of deep tissues and organs.

Near infra-red photoluminescent graphene nanoparticles greatly expand their use in noninvasive biomedical imaging

Age differences among risk groups may account for rate differences in progression of human immunodeficiency virus type 1 (HIV-1) infection to AIDS. Institutions in 6 US cities used a common protocol to study infected homosexual blood donors, recipients of blood components, and factor VIII-treated hemophiliacs. Follow-up was every 6 months. Actuarial risk for AIDS 8 years after infection was 51% among blood recipients, 36% among homosexual donors, and 24% among hemophiliacs. Significant risk group differences were explained by age differences among cohorts (medians of 61, 29, and 22 years, respectively). When age was adjusted for and both CD4 cell value and zidovudine treatment were used as time-dependent covariates, homosexual donors had more rapid progression than the other groups. Omitting Kaposi's sarcoma as an IDS-defining condition removed any significant differences among risk …

Broad Advanced System & Integrated Circuit (BASIC Lab)

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An Area and Power Efficient Fully Nonlinear 10-bit Column Driver with Time-Shared Multi-Gamma-Slope DAC and Time-Interleaved Sampling Buffer for Mobile AMOLED Displays

A Fully Integrated Portable Microplastic Detection System-on-Chip with High-Sensitivity RF MEMS Sensors and Narrow-Band Notch-Tracking Dielectric Discrimination Algorithms

Data-Driven Machine Learning Models for Predicting Engineering Properties in Deep-Sea Sediments

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교수님 소개

이형민

연구실 키워드

알럼나이가 간 회사

연구실 지원 방법

대우 조건

연도별 논문 인용수

저널 & 학회 논문 출판 수

연구실 논문 목록

An Area and Power Efficient Fully Nonlinear 10-bit Column Driver with Time-Shared Multi-Gamma-Slope DAC and Time-Interleaved Sampling Buffer for Mobile AMOLED Displays

A Fully Integrated Portable Microplastic Detection System-on-Chip with High-Sensitivity RF MEMS Sensors and Narrow-Band Notch-Tracking Dielectric Discrimination Algorithms

Data-Driven Machine Learning Models for Predicting Engineering Properties in Deep-Sea Sediments

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