Research

We aspire to build innovative microsystems that can detect and process all kinds of natural and electrical signals such as light, impedance, bio-potential, and so on, implemented by low-power low-noise analog integrated circuits and systems technology. We are currently focusing on two main subjects, integrated imaging and bio-medical interface systems. Please contact us if you want to know our work and capability in detail or consider collaboration to advance this field.

Integrated Imaging Systems

  • 2D/3D Image Sensor

Color and depth images taken by prototype sensor

Color and depth images taken by prototype sensor

Fabricated imager

Fabricated imager

We develop a 3D imaging system that can provide a depth image as well as a color image of arbitrary objects. We propose a split and binning pixel structure with a time-multiplexing architecture, acquiring both 2D and 3D images in a single imager. It employs the conventional pinned photodiode (PPD) for capturing 2D image and the time-of-flight (TOF) principle detecting the time delay between the emitted and reflected infrared light pulses to extract depth information. A fabricated prototype sensor successfully captures 480×270 depth images with inaccuracy of 38mm at 4.5m and provides full-HD color images of the same scene.

- Seong-Jin Kim, Byongmin Kang, James D. K. Kim, Keechang Lee, Chang-Yeong Kim, and Kinam Kim, “A 1920×1080 3.65μm-Pixel 2D/3D Image Sensor with Split and Binning Pixel Structure in 0.11μm Standard CMOS,” in IEEE Int. Solid-State Circuits Conf. (ISSCC) Dig. Tech. Papers, Feb. 2012, pp. 396- 397.
– Seong-Jin Kim, “Performance Evaluation of Pinning Potential Adjustment in Two-Dimensional/Three-Dimensional Image Sensor,” IEEE Electron Device Lett., vol. 33, no. 10, pp. 1426-1428, Oct. 2012.

  • Fingerprint SoC

Fingerprint images before and after on-chip processing

Fingerprint images before and after on-chip processing

Fabricated SoC

Fabricated SoC

A different type of imaging system based on capacitive sensing scheme is proposed and implemented for a fingerprint biometric application. Direct contact of the fingertip onto the sensor allows a thumb-size authentication system, which is desirable feature for potable consumer devices. We integrate a single-slop ADC and two 8-bit memories into a analog pixel structure to convert and store digitized fingerprint images. In order to extract feature points of the fingerprint image, column-parallel image processors are embedded as well. A prototype sensor demonstrates acquiring and recognizing the fingerprint image clearly.

- Seong-Jin Kim, Sang-Wook Han, Kwang-Hyun Lee and Euisik Yoon, “A CMOS Fingerprint System-on-a-Chip with Adaptable Pixel Networks and Column-Parallel Processors for Image Enhancement and Recognition,” IEEE J. Solid-State Circuits, vol. 43, no. 11, pp. 2558-2567, Nov. 2008.


Bio-medical interface system

  • Implantable Neural Spike Detector

Extracted spike signals from normal neural signal

Extracted spike signals from normal neural signal

Fabricated recording device

Fabricated recording device

In this project, a target system includes a neural signal recording IC, a power/data transmitter and receiver. Because the neural recording IC should be implanted in a brain, it has very strict constrain in dissipating electrical power. To minimize power consumption, we propose a delta-modulation based spike detection scheme. The spike signal in neural activities is an essential event but is fired rarely so that the spike detection can compress large amount of data efficiently. The delta-modulation doesn’t only compress the signal dynamic range, but also enable to extract the amplitude and frequency component of the neural signal, recognizing the spike in the analog domain. Proposed device achieves sub-µW power consumption in 0.5V power supply and much large power can be saved in a system level.

- Seong-Jin Kim, Lei Liu, Lei Yao, Wang Ling Goh, Yuan Gao, and Minkyu Je, “A 0.5-V Sub-μW/Channel Neural Recording IC with Delta-Modulation-Based Spike Detection,” in Proc. of IEEE Asian Solid-State Circuits Conf. (A-SSCC), Nov. 2014, pp. 189-192.

  • High-Throughput Coulter Counter Device

Size distribution of cancer cells spiked in diluted blood

Size distribution of cancer cells spiked in diluted blood

Conceptual structure of Coulter counter device

Conceptual structure of Coulter counter device

We report a cell counting device based on Coulter principle, which measures the concentration and size distribution of cell suspension in a single cell resolution. The device incorporates vertical through-hole array and electrically decoupled potentiometric sensing method with three electrode configuration to enhance its throughput up to 20,000 cells/s. The prototype device demonstrate the ability of counting and sizing when flowing a mixture of microbeads (6, 10, 15 µm) at 200 nL/sec for each channel, and even cells spiked in diluted blood, MCF-7 for biomedical applications. We expect to expand 1-D vertical through-hole structure into high-density of 2-D arrays in a small footprint easily for point-of-care diagnostic applications with extremely high-throughput.

- Yu Chen, Seong-Jin Kim, Jinhong Guo, Yuejun Kang, Jaya P. Kausalyac, Alicia Ghia Min Ongc, Walter Hunzikerc, and Jaehoon Chung, “Portable Coulter counter with vertical through-holes for high-throughput applications,” Sensor Actuat. B-Chem., vol. 213, pp. 375-381, Jul. 2015.

  • ISFET-based DNA Quantification Chip

Sequential monitoring of DNA molecules with different concentrations

Sequential monitoring of DNA molecules with different concentrations

Fabricated DNA chip

Fabricated DNA chip

We implement miniaturized lab-on-a-chip devices (LOC) for the quantification of biomolecules. To realize a real-time DNA quantification system, it is proposed an ion-sensitive field-effect (ISFET) sensing array integrated with CMOS readout circuitry to detect the surface potential determined by the negative charge in DNA molecules. The proposed biosensor incorporates new sensing pixel architecture and a correlated double sampling scheme for reducing offset fixed pattern noise and 1/f noise of the ISFET. In addition, we introduce a non-surface binding detection technique which is the measurements of DNA molecules without immobilizing them on the sensing surface for the real-time continuous monitoring of their concentrations. A prototype device can discriminate diverse concentrations of 19-bp oligonucleotides solution.

- Seong-Jin Kim and Euisik Yoon, “Label-free CMOS Bio Sensor with On-chip Noise Reduction Scheme for Real-time Quantitative Monitoring of Biomolecules,” IEEE Trans. Biomed. Circuits Syst., vol. 6, no.3, pp. 189-196, Jun. 2012.