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Choi, Dongwhi,Kim, Dong Sung American Chemical Society 2014 Langmuir Vol.30 No.23
<P>We report that the zeta potential of a pipet tip’s inner surface is one of the crucial parameters for controlling the electrical charge of the dispensed droplet. Since the charge is unexpected and undesirable for most experiments in various fields of science and, thereby, they can cause unsuspected problems, reducing the charge on a dispensed droplet is important for the results of pipetting-based experiments. We fabricate a graphene-based nanocomposite-coated pipet tip, which we called a zeta-pipet tip, as a proof-of-concept example to reduce the zeta potential of the pipet tip’s inner surface. The fabricated zeta-pipet tip can successfully mitigate the undesired droplet separation in the droplet merging experiments in an oil bath, which is one of the unexpected effects caused by the electrification. The findings of this study provide helpful guidelines for researchers in many fields of science and technology, who utilize a pipet tip in their respective experiments.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/langd5/2014/langd5.2014.30.issue-23/la5018196/production/images/medium/la-2014-018196_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/la5018196'>ACS Electronic Supporting Info</A></P>
Choi, Dongwhi,Tsao, Yu-Hsiang,Chiu, Che-Min,Yoo, Donghyeon,Lin, Zong-Hong,Kim, Dong Sung unknown 2017 Nano energy Vol.38 No.-
<P><B>Abstract</B></P> <P>Pipet tips are commonly utilized laboratory tools to transfer adjustable volume of liquid in various fields of chemistry, biology and physics. Recently, we have reported that the ordinary pipetting procedure always involves spontaneous liquid-solid contact electrification, resulting in generation of net electrical charges on the dispensed solution and the inner surface of the polymeric pipet tip. In this study, a concept of a smart pipet tip is proposed to evaluate the electrolyte concentration of the dispensed solution by use of spontaneously generated electric signals during the ordinary pipetting procedure. The smart pipet tip possessing triboelectricity and thermoelectricity detecting modules is advantageous as it performs <I>in situ</I> evaluation of solution characteristics without any subsidiary solution handling process. The spontaneously generated electric signals are intensively investigated with the theoretical analyses. The proof-of-concept demonstration of the present smart pipet tip is shown for <I>in situ</I> prediction of morphology of nanoparticles during their synthetic reaction, which critically determines their catalytic activity.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The present smart pipet tip enables <I>in situ</I> evaluation of solution characteristics. </LI> <LI> Firstly, the electrical charges inside the pipet tip is advantageously utilized. </LI> <LI> Multi-parametric effect on liquid-solid triboelectricity is effectively separated. </LI> <LI> The morphology of nanoparticles can be <I>in situ</I> predicted by using the smart pipet tip. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>We demonstrate that the developed smart pipet tip composed of triboelectricity and thermoelectricity detecting modules is useful for the evaluation of solution characteristics and chemical reactions.</P> <P>[DISPLAY OMISSION]</P>
Choi, Dongwhi,Kim, Do Wan,Yoo, Donghyeon,Cha, Kyoung Je,La, Moonwoo,Kim, Dong Sung Elsevier 2017 Nano energy Vol.36 No.-
<P><B>Abstract</B></P> <P>The successive process of contact and detachment of aqueous liquid from the solid surface with its resultant net electrical charge generation is termed as “discrete liquid-solid contact electrification”, which is unobtrusively ubiquitous in our daily life. So far, the natural occurrence of discrete liquid-solid contact electrification on surfaces in nature has not been investigated and reported despite the beneficial characteristics of such surfaces. This study firstly reveals the existence of the discrete liquid-solid contact electrification phenomenon and concomitant net electrical charge generation on the natural lotus leaf surface. To advantageously utilize the generated net electrical charges, for the first time, the naturally occurring surface is directly employed to fabricate the natural lotus leaf-TENG, called the LL-TENG. The further investigation about the electricity generation is continued by altering contact material of the LL-TENG to fluoropolymer while maintaining the lotus leaf's superior surface characteristics, in a simple and cost-effective manner via thermal nanoimprinting. The artificially modified TENG not only significantly increases the amount of the generated electricity, but also shows sustained electrical output performance even after 1 month of exposure in the external dusty environment with the help of the outstanding “lotus effect”.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The existence of discrete liquid-solid contact electrification on the lotus leaf surface is discovered. </LI> <LI> For the first time, the natural leaf surface is directly employed to fabricate the triboelectric nanogenerator (TENG). </LI> <LI> .The nature-inspired approach to fabricate the TENG is demonstrated in a cost-effective and mass-producible manner. </LI> <LI> The TENG shows the sustained electrical output performance with the help of the outstanding “lotus effect”. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Lee, Horim,Choi, Dongwhi,Kim, Dong Sung,Lim, Geunbae Springer Berlin Heidelberg 2015 Nano-micro letters Vol.7 No.4
<P>The spontaneously generated electrical charge of a droplet dispensed from conventional pipetting is undesirable and unpredictable for most experiments that use pipetting. Hence, a method for controlling and removing the electrical charge needs to be developed. In this study, by using the electrode-deposited pipet tip (E-pipet tip), the charge-controlling system is newly developed and the electrical charge of a droplet is precisely controlled. The effect of electrolyte concentration and volume of the transferred solution to the electrical charge of a dispensed droplet is theoretically and experimentally investigated by using the equivalent capacitor model. Furthermore, a proof-of-concept example of the self-alignment and self-assembly of sequentially dispensed multiple droplets is demonstrated as one of the potential applications. Given that the electrical charge of the various aqueous droplets can be precisely and simply controlled, the fabricated E-pipet tip can be broadly utilized not only as a general charge-controlling platform of aqueous droplets but also as a powerful tool to explore fundamental scientific research regarding electrical charge of a droplet, such as the surface oscillation and evaporation of charged droplets.</P><P><B>Electronic supplementary material</B></P><P>The online version of this article (doi:10.1007/s40820-015-0048-2) contains supplementary material, which is available to authorized users.</P>
표면-줄기세포 증식 관계 확인을 위한 마이크로 구조표면을 포함한 멀티웰 플랫폼 제작
안성아(Seonga An),최동휘(Dongwhi Choi),임지원(Jiwon Lim),김동성(Dong Sung Kim) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.11
Micro-scale topography fabrication have attracted much attention in biomedical engineering because of their potential for stem cell proliferation enhancement effect. In recent years, adult stem cells (ASCs) are proved as versatile troubleshooter in biomedical and pharmaceutical field. However, ASCs take up only a small proportion of somatic cells in human body and the study of enhancing the proliferation rate of ASCs became essential in modern society. Researchers suggested the use of topographic stimuli as solution for this problem. Numerous researches were executed to clarify the relationship of topography and ASCs proliferation but there are still difficulties in defining tendency to clearly deduce an optimal topography for enhancing proliferation rate due to an intervention of other factors. To overcome this weakness we propose a multi-well cell culture platform that allows simple way of screening effects of various kinds of topography on ASCs. In this study we fabricated multi-well cell culture platform containing micro-scale topography and carried out experiments of human Adipose derived Stem Cells (hASCs) proliferation. Through this experiment we verify the multi-well cell culture platform’s functionality then we expect that this multi-well cell culture platform system would contribute to finding optimal topography for enhancing ASCs proliferation rate.