Sungkyu Seo

Lensfree cell holography on a chip: From holographic cell signatures to microscopic reconstruction

We present a lensfree on-chip imaging platform that can record 2D holographic diffraction signatures of various cells for cytometry applications. We also illustrate that these lensfree cell holograms permit reconstruction of microscopic images of the same cells enabling a powerful diagnostic tool for especially global health related problems such as malaria, HIV or TB.

A CMOS sensor array IC of nanowell devices for molecular sensing

The paper demonstrates a CMOS integrated sensor IC for an array of novel nanowell devices used for molecular sensing. The size of the nanowell (10-100 nm) enables high-fidelity detection and analysis through broadband dielectric spectroscopy (BDS) of the parallel-plate capacitor formed by the nanowell and the trapped molecule. The signal transduction is done by a novel, continuous-time detector circuit followed by a low-noise lock-in architecture which measures the admittance of the sensor as a function of frequency for BDS. The CMOS IC has a capacitance resolution of 14 aF (frequency /spl sim/1 Hz to 1 GHz) and power consumption of only 30 /spl mu/W/channel. The CMOS front-end is implemented in TSMC 018 /spl mu/ technology.

“Fatal Scream” Of Bacteria Infected By Phages: Nanoscale Detection Of Bacteriophage Triggered Ion Cascade

A rapid, inexpensive and specific identification of arbitrary bacteria under field conditions is urgently needed. To this end, we have introduced and tested a new technology, called SEPTIC, SEnsing of Phage‐Triggered Ion Cascade. In its prototype form based on a nanowell chip, SEPTIC has already been shown to be capable of unambiguous identification of live bacteria on a time scale of seconds to minutes, many times faster than any other system. The technology is based on using noise analysis to detect the massive ionic fluxes associated with the initial step of bacteriophage infection, the injection of the phage DNA into the cell. Here we show the results and pose a number of unsolved problems of noise. Ultimately, sensors based on this new technology would be able to save many lifes.

Multi-angle LUCAS for high-throughput on-chip cytometry

We illustrate that by recording under-sampled diffraction patterns of cells at different illumination angles, we can achieve high-throughput on-chip characterization of a heterogeneous cell solution over an ultra large volume of ∼5 ml. This platform, termed multi-angle LUCAS, is especially promising for cost-effective point-of-care cell counting applications.

Smartphone based automated microparticle analysis system

Cell and microparticle analysis is one of the major task in all pathological labs. The concentration profile, such as red blood cell (RBC), white blood cell (WBC), platelet concentration are the key parameters for early diagnosis of many diseases. However in most laboratories, especially in resource limited settings, this diagnosis are done manually using conventional optical microscope. This manual process is slow and prone to subjective error. In this paper we demonstrate a smartphone based automated cell detection and counting system. The system is based on the lens-free imaging method, which is a compact facility made up of inexpensive components. We evaluated the performance of the system as well as smartphone algorithm by evaluating the concentration of the micro particles of different sizes. This results were then compared with the conventional optical microscope result. The correlation coefficients of this comparisons shows a great agreement between the two modalities. This kind of compact system along with the wireless facility would be a good point of care facility in resource limited settings.

A flexible strain-gauge sensor for flexible input devices

This study demonstrates a novel polymer-based flexible strain-gauge sensor for flexible input devices in flexible displays. Proposed novel strain-gauge sensor for user interfaces (UIs) in flexible display measures the deformation of an object by using its electrical resistance change. This strain-gauge sensor was fabricated by the double-sided fabrication method with polymer and metal, i.e., polyimide and Nickel-Chrome. Experimental results show that this sensor linearly detects the forces more than 500gf, i.e., 5N, with the force resolution of less than 10gf, i.e., 0.1N. Also it can linearly detect the bending radius from 5mm to 100mm. This flexible strain-gauge sensor array may be positioned on the bezel area of a flexible display device enabling various input methodology as well as UIs.

Comparison of two types of tactile sensing layer in touch screen panel for force sensitive detection

Here we present two types of Touch Screen Panels (TSPs) consisted of silicone gel and glycerin as the transparent Tactile Sensing Layer (TSL) measuring touch force(z axis) and touch position(x-y axis). The principle of the TSP is based on capacitive methods in which the distance between top and bottom substrates is varied by touch or interaction force leading the capacitance change between two substrates. Silicone gel as the TSL showed the force detection resolution of about 50gf and the dynamic range of 0-500gf. For the same test, Glycerin showed the detection resolution of 10gf and the dynamic range of 200gf. These relatively excellent results are caused from the permittivity and hardness of the new two TSL materials.

Lens-free automated cell detection system for telemedicine application

Cell and micro particle analysis is one of the major tasks in many clinical labs culturing cells. The functional profiles of cells such as concentration, size, morphology and viability are the key parameters for early diagnosis of many diseases. However in most labs, especially in the resource limited settings, these processes are done fully manually using conventional optical microscopes, which are slow and prone to subjective errors. Recently the lens-free shadow imaging system has been introduced as an alternative for the conventional optical microscopy. In this paper we demonstrate a dedicated algorithm for lens-free shadow imaging system, which was implemented as a smartphone application. This android application can wirelessly acquire the images from the lens-free system and process them automatically. The results can be obtained locally or sent to a remote expert for further analysis. The feasibility of this system was evaluated by comparing the results with the standard optical microscope.

Underwater multispectral imaging system for environmental monitoring

In this article, we present a novel underwater monitoring system based on the hyperspectral imager. This system consists of the commercial hyperspectral camera and white-colored LED lighting. We evaluated the performance of the proposed hyperspectral imaging system by conducting the small scale experiments to identify the difference of two different oil samples. For the classification between oil samples and seawater, we analyzed the spectrum profiles of oils and seawater. Though that, we can clearly not only distinguish the oil samples from seawater but also distinguish the bunker C oil from lubricating oil. This result shows the feasibility to application of our proposed setup for the underwater oil spill monitoring system.

An automated cell detection algorithm for lensfree shadow imaging platform

Here we propose an automated cell detection and counting algorithm for lens-free shadow imaging platform. This approach is based on the adaptive thresholding algorithm. The spatial variation of the threshold values is determined by the moving window technique. The shadow images of the Red Blood Cells(RBCs) are well detected and specified by the algorithm. The cell counting results from the algorithm for different concentration of blood cells are verified with the established cell counting results.