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Kim, Pilnam,Kim, Ho-Young,Kim, Jae Kwan,Reiter, Gü,nter,Suh, Kahp Y. The Royal Society of Chemistry 2009 Lab on a chip Vol.9 No.22
<P>We examined the formation of a multiply curved meniscus inside rectangular nanochannels, whose width ranges from 50 to 800 nm at a constant height of 200 nm. When the channel width is smaller than approximately 400 nm under partial wetting conditions, a distinct multi-curvature meniscus was observed at the advancing front with an edge disjoined from the wall. In contrast, a typical pre-wetting film was observed at the front regardless of the channel size for complete wetting conditions. Our theoretical analysis demonstrated that the multi-curvature meniscus is generated from the increased contribution of an extra pressure due to intermolecular interactions near the wall. In particular, a plug-like meniscus profile was observed at the advancing liquid front for the 50 nm wide channel owing to an overlap between convex curvatures at the channel walls. Finally, we showed that the filling velocity of liquid can be decreased by decreasing the channel size due to the reduced wettability.</P>
Artificial Slanted Nanocilia Array as a Mechanotransducer for Controlling Cell Polarity
Kim, Hong Nam,Jang, Kyung-Jin,Shin, Jung-Youn,Kang, Daeshik,Kim, Sang Moon,Koh, Ilkyoo,Hong, Yoonmi,Jang, Segeun,Kim, Min Sung,Kim, Byung-Soo,Jeong, Hoon Eui,Jeon, Noo Li,Kim, Pilnam,Suh, Kahp-Yang American Chemical Society 2017 ACS NANO Vol.11 No.1
<P>We present a method to induce cell directional behavior using slanted nanocilia arrays. NIH-3T3 fibroblasts demonstrated bidirectional polarization in a rectangular arrangement on vertical nanocilia arrays and exhibited a transition from a bidirectional to a unidirectional polarization pattern when the angle of the nanocilia was decreased from 90 degrees to 30 degrees. The slanted nanocilia guided and facilitated spreading by allowing the cells to contact the sidewalls of the nanocilia, and the directional migration of the cells opposed the direction of the slant due to the anisotropic bending stiffness of the slanted nanocilia. Although the cells recognized the underlying anisotropic geometry when the nanocilia were coated with fibronectin, collagen type I, and Matrigel, the cells lost their directionality when the nanocilia were coated with poly-D-lysine and poly-L-lysine. Furthermore, although the cells recognized geometrical anisotropy on fibronectin coatings, pharmacological perturbation of PI3K-Rac signaling hindered the directional elongation of the cells on both the slanted and vertical nanocilia. Furthermore, myosin light chain II was required for the cells to obtain polarized morphologies. These results indicated that the slanted nanocilia array provided anisotropic contact guidance cues to the interacting cells. The polarization of cells was controlled through two steps: the recognition of underlying geometrical anisotropy and the subsequent directional spreading according to the guidance cues.</P>
김필남(Pilnam Kim),김덕호(Deok-Ho Kim),김병규(Byungkyu Kim),최성규(Seung Kyu Choi),이상호(Sang Ho Lee),Ali Khademhossei,Robert Lang,서갑양(Kahp Y. Suh) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
We developed a method for fabricating poly(ethylene glycol) (PEG) nanostructures using capillary lithography mediated UV exposure. A PEG dimethacrylate (PEG-DMA) was used for crosslinking, which could be applied to other PEG polymers having a crosslinking group. In comparison to unstructured, planar PEG films, the hydrophobicity was significantly enhanced on PEG nanostructures presumably due to embedded air in the nanostructures, as confirmed by contact angle measurements of water. A number of proteins and cells were tested to examine the effects of the modification of surface properties on protein adsorption and cell adhesion. It was found that proteins and cells adhered on a nanostructured PEG surface slightly higher than on a bare PEG film, but much less than on glass control, which could be attributed to the increased surface area and hydrophobicity.
Kwak, Jiyong,Shim, Jin-Kyoung,Kim, Dong Seok,Lee, Ji-Hyun,Choi, Junjeong,Park, Junseong,Shin, Kyoung-Jin,Kim, Se-Hoon,Kim, Pilnam,Huh, Yong-Min,Kim, Eui Hyun,Chang, Jong Hee,Kim, Sun Ho,Kang, Seok-Gu Spandidos Publications 2016 International journal of oncology Vol.49 No.2
<P>The existence of tumorspheres (TSs) might confer treatment resistance to pineoblastoma (PB). The existence of PB TSs with cellular immortalization potential has not yet been reported. We developed a procedure for isolating TSs from recurrent PB (rPB) and tested whether their properties made them suitable for use as a patient-derived xenograft (PDX). Immunocytochemical staining, RT-PCR and quantitative real-time PCR showed that, among stemness proteins, CD133, musashi and podoplanin were expressed at elevated levels in rPB TSs, but nestin was not. rPB TSs cultured under neuro-glial differentiation conditions expressed TUBB3, but not GFAP, MBP or NeuN. Unlike glioblastoma TSs, rPB TSs showed no clear evidence of invasion in 3D invasion assay or increased expression of genes associated with epithelial-mesenchymal transition. An orthotopic xenograft showed that tumor xenografts replicated the histopathological features of the patient tumor and expressed similar genome profiles, as determined by short tandem repeat genotyping. These data demonstrate the isolation and the characterization of rPB TSs for the first time. Using an orthotopic xenograft, we showed that rPB TSs could replicate the patient tumor, demonstrating their potential as a PDX for precision medicine.</P>
Hierarchical folding of elastic membranes under biaxial compressive stress
Kim, Pilnam,Abkarian, Manouk,Stone, Howard A. Nature Publishing Group, a division of Macmillan P 2011 Nature materials Vol.10 No.12
Mechanical instabilities that cause periodic wrinkling during compression of layered materials find applications in stretchable electronics and microfabrication, but can also limit an application??s performance owing to delamination or cracking under loading and surface inhomogeneities during swelling. In particular, because of curvature localization, finite deformations can cause wrinkles to evolve into folds. The wrinkle-to-fold transition has been documented in several systems, mostly under uniaxial stress. However, the nucleation, the spatial structure and the dynamics of the invasion of folds in two-dimensional stress configurations remain elusive. Here, using a two-layer polymeric system under biaxial compressive stress, we show that a repetitive wrinkle-to-fold transition generates a hierarchical network of folds during reorganization of the stress field. The folds delineate individual domains, and each domain subdivides into smaller ones over multiple generations. By modifying the boundary conditions and geometry, we demonstrate control over the final network morphology. The ideas introduced here should find application in the many situations where stress impacts two-dimensional pattern formation.
Solvent-Assisted Decal Transfer Lithography by Oxygen-Plasma Bonding and Anisotropic Swelling
Kim, Pilnam,Kwak, Rhokyun,Lee, Sung Hoon,Suh, Kahp Y. WILEY-VCH Verlag 2010 Advanced Materials Vol.22 No.22
<B>Graphic Abstract</B> <P>Solvent-assisted decal transfer lithography (DTL) enables the formation of well-defined micro-/nanostructures over a large area (∼4 in. wafer) by combining irreversible oxygen bonding and anisotropic swelling of poly(dimethoxylsiloxane) (PDMS). Such swelling-induced stress gradient allows for cohesion failure of the skin layer upon removal of the stamp, leaving behind a highly uniform layer (∼100 nm). <img src='wiley_img_2010/09359648-2010-22-22-ADMA200903440-content.gif' alt='wiley_img_2010/09359648-2010-22-22-ADMA200903440-content'> </P>
Stabilization of Ion Concentration Polarization Using a Heterogeneous Nanoporous Junction
Kim, Pilnam,Kim, Sung Jae,Han, Jongyoon,Suh, Kahp Y. American Chemical Society 2010 NANO LETTERS Vol.10 No.1
<P>We demonstrate a recycled ion-flux through heterogeneous nanoporous junctions, which induce stable ion concentration polarization with an electric field. The nanoporous junctions are based on integration of ionic hydrogels whose surfaces are negatively or positively charged for cationic or anionic selectivity, respectively. Such heterogeneous junctions can be matched up in a way to achieve continuous ion-flux operation for stable concentration gradient or ionic conductance. Furthermore, the combined junctions can be used to accumulate ions on a specific region of the device.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2010/nalefd.2010.10.issue-1/nl9023319/production/images/medium/nl-2009-023319_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl9023319'>ACS Electronic Supporting Info</A></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl9023319'>ACS Electronic Supporting Info</A></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl9023319'>ACS Electronic Supporting Info</A></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl9023319'>ACS Electronic Supporting Info</A></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl9023319'>ACS Electronic Supporting Info</A></P>