• Korean Chemical Engineering Research
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• v.46 no.6
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• pp.1100-1106
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• 2008

In this study, we presented rapid and simple fabrication method of functionalized surface on various substrates as a universal platform for the selective immobilization of cells. The functionalized surface was achieved by using deposition of polyelectrolyte such as poly(allyamine hydrochloride) (PAH), poly(diallyldimethyl ammonium chloride) (PDAC), poly(4-ammonium styrene sulfonic acid) (PSS), poly(acrylic acid) (PAA) and fabrication of poly(ethylene glycol) (PEG) microstructure through micro-molding in capillaries (MIMIC) technique on each glass, poly(methyl methacrylate) (PMMA), polystyrene (PS) and poly(dimethyl siloxane) (PDMS) substrate. The polyelectrolyte multilayer provides adhesion force via strong electrostatic attraction between cell and surface. On the other hand, PEG microstructures also lead to prevent non-specific binding of cells because of physical and biological barrier. The characteristic of each modified surface was examined by using static contact angle measurement. The modified surface onto several substrates provides appropriate environment for cellular adhesion, which is essential technology for cell patterning with high yield and viability in the micropatterning technology. The proposed method is reproducible, convenient and rapid. In addition, the fabrication process is environmentally friendly process due to the no use of harsh solvent. It can be applied to the fabrication of biological sensor, biomolecules patterning, microelectronics devices, screening system, and study of cell-surface interaction.

• Journal of Industrial Convergence
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• v.20 no.12
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• pp.79-85
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• 2022

Recently, a smartphone manufactured on a flexible substrate has been released as an electronic device, and research on a stretchable electronic device is in progress. In this paper, a silicon-based stretchable material is made and used as a substrate to implement and evaluate an optical sensor device using oxide semiconductor. To this end, a substrate that stretches well at room temperature was made using a silicone-based solution rubber, and the elongation of 350% of the material was confirmed, and optical properties such as reflectivity, transmittance, and absorbance were measured. Next, since the surface of these materials is hydrophobic, oxygen-based plasma surface treatment was performed to clean the surface and change the surface to hydrophilicity. After depositing an AZO-based oxide film with vacuum equipment, an Ag electrode was formed using a cotton swab or a metal mast to complete the photosensor. The optoelectronic device analyzed the change in current according to the voltage when light was irradiated and when it was not, and the photocurrent caused by light was observed. In addition, the effect of the optical sensor according to the folding was additionally tested using a bending machine. In the future, we plan to intensively study folding (bending) and stretching optical devices by forming stretchable semiconductor materials and electrodes on stretchable substrates.

• Applied Chemistry for Engineering
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• v.34 no.3
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• pp.258-263
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• 2023

In this study, conductive polymers and the enzyme tyrosinase (Tyr) were deposited on the surface of a screen printed carbon electrode (SPCE), which can be fabricated as a disposable sensor chip, and applied to the detection of bisphenol F (BPF), an endocrine disruptor with proven links to male diseases and thyroid disorders, using electrochemical methods. On the surface of the SPCE working electrode, which was negatively charged by oxygen plasma treatment, a positively charged conductive polymer, poly(diallyldimethyl ammonium chloride) (PDDA), a negatively charged polymer compound, poly(sodium 4-styrenesulfonate) (PSS), and another layer of PDDA were layered by electrostatic attraction in the order of PDDA, PSS, and finally PDDA. Then, a layer of Tyr, which was negatively charged due to pH adjustment to 7.0, was added to create a PDDA-PSS-PDDA-Tyr sensor for BPF. When the electrode sensor is exposed to a BPF solution, which is the substrate and target analyte, 4,4'-methylenebis(cyclohexa-3,5-diene-1,2-dione) is generated by an oxidation reaction with the Tyr enzyme on the electrode surface. The reduction process of the product at 0.1 V (vs. Ag/AgCl) generating 4,4'-methylenebis(benzene-1,2-diol) was measured using cyclic and differential pulse voltammetries, resulting in a change in the peak current with respect to the concentration of BPF. In addition, we compared the detection performance of BPF using an ionic liquid electrolyte as an alternative to phosphate-buffered saline, which has been used in many previous sensing studies. Furthermore, the selectivity of bisphenol S, which acts as an interfering substance with a similar structure to BPF, was investigated. Finally, we demonstrated the practical applicability of the sensor by applying it to analyze the concentration of BPF in real samples prepared in the laboratory.