Biomedical subjects

Ki-Hun Jeong

Publications and source records attributed to Ki-Hun Jeong.

4 recordsLinked to original sources

PubMed2006

Biologically inspired artificial compound eyes.

This work presents the fabrication of biologically inspired artificial compound eyes. The artificial ommatidium, like that of an insect's compound eyes, consists of a refractive polymer microlens, a light-guiding polymer cone, and a self-aligned waveguide to collect light with a small angular acceptance. The ommatidia are omnidirectionally arranged along a hemispherical polymer dome such that they provide a wide field of view similar to that of a natural compound eye. The spherical configuration of the microlenses is accomplished by reconfigurable microtemplating, that is, polymer replication using the deformed elastomer membrane with microlens patterns. The formation of polymer waveguides self-aligned with microlenses is also realized by a self-writing process in a photosensitive polymer resin. The angular acceptance is directly measured by three-dimensional optical sectioning with a confocal microscope, and the detailed optical characteristics are studied in comparison with a natural compound eye.

Animals↗

PubMed2005

Theoretical and experimental study towards a nanogap dielectric biosensor.

Theoretical and experimental studies of nanogap capacitors as potential label free biosensors are presented. The nanogap device is capable of detecting the existence of single stranded DNA (ssDNA) oligonucleotides (20-mer) in 100 nM aqueous solutions using a 20 nm gap of 1.2 pl in volume. While the dielectric properties of DNA solution have been widely investigated, early approaches are limited at low frequency by the parasitic noise due to the electrical double layer (EDL) impedance. Nanogap electrodes have the potential to serve as biomolecular junctions because their size (5-100 nm) minimizes electrode polarization effects regardless of frequency. In this paper, we modeled the effects of the EDL interaction between two parallel nanogap electrodes by solving the Poisson-Boltzmann (PB) equation for equilibrium state. When the gap size is smaller than the EDL thickness, the dependence of the nanogap capacitance on the ionic strength is insignificant. This is critical in using the capacitance change as an indicator of the existence of target molecules. The predicted capacitance of nanogaps filled with various ionic strength electrolytes was in quantitative agreement with the experimental measurements. The various concentrations of the target molecules in nanogap sensor were characterized. A capacitance change of a 20 nm x (10)1.5 microm x 4mm gap from 3.5 to 4.1 nF at 200 Hz was recorded between deionized water (DI) and 100 nM ssDNA solution (about 70,000 molecules inside the gap for equilibrium state).

Biosensing Techniques↗

PubMed2005

Artificial ommatidia by self-aligned microlenses and waveguides.

We report the fabrication of artificial ommatidia, the imaging units of insects' compound eyes, by use of polymer integrated optics. These biomimetic structures are obtained by configuring microlenses to play dual roles for self-writing of waveguides (during the fabrication) and collection of light (during the operation). The artificial ommatidium, consisting of a microlens, a spacer, and a waveguide, directly resembles the structure of its biological counterpart. Optical characterizations reveal single-peak angular sensitivity with a +/- 0.75 degrees acceptance angle that is comparable to those found in nature. Using geometric and physical optics, we also investigate the relationship between angular sensitivity and the geometry of artificial ommatidia.

Animals↗

PubMed2003

Reagentless mechanical cell lysis by nanoscale barbs in microchannels for sample preparation.

A highly effective, reagentless, mechanical cell lysis device integrated in microfluidic channels is reported. Sample preparation, specifically cell lysis, is a critical element in 'lab-on-chip' applications. However, traditional methods of cell lysis require purification steps or complicated fabrication steps that a simple mechanical method of lysis may avoid. A simple and effective mechanical cell lysis system is designed, microfabricated, and characterized to quantify the efficiency of cell lysis and biomolecule accessibility. The device functionality is based on a microfluidic filter region with nanostructured barbs created using a modified deep reactive ion etching process. Mechanical lysis is characterized by using a membrane impermeable dye. Three main mechanisms of micro-mechanical lysis are described. Quantitative measurements of accessible protein as compared to a chemically lysed sample are acquired with optical absorption measurements at 280 and 414 nm. At a flow rate of 300 microL min(-1) within the filter region total protein and hemoglobin accessibilities of 4.8% and 7.5% are observed respectively as compared to 1.9% and 3.2% for a filter without nanostructured barbs.

Animals↗