Supporting Information: Short and long time drop dynamics on lubricated substrates

Supporting Information: Short and long time drop dynamics on lubricated substrate

Nanoarrays of tethered lipid bilayer rafts on poly(vinyl alcohol) hydrogels

Lipid rafts are cholesterol-and sphingolipid-rich domains that function as platforms for signal transduction and other cellular processes. Tethered lipid bilayers have been proposed as a promising model to describe the structure and function of cell membranes. We report a nano(submicro) array of tethered lipid bilayer raft membranes (tLBRMs) comprising a biosensing platform. Poly(vinyl alcohol) (PVA) hydrogel was directly patterned onto a solid substrate, using ultraviolet-nanoimprint lithography (UV-NIL), as an inert barrier to prevent biofouling. The robust structures of the nanopatterned PVA hydrogel were stable for up to three weeks in phosphate-buffered saline solution despite significant swelling (100% in height) by hydration. The PVA hydrogel strongly restricted the adhesion of vesicles, resulting in an array of highly selective hydrogel nanowells. tLBRMs were not formed by direct vesicle fusion, although raft vesicles containing poly(ethylene glycol) lipopolymer were selectively immobilized on gold substrates patterned with PVA hydrogel. The deposition of tLBRM nano(submicro) arrays was accomplished by a mixed, self-assembled monolayer-assisted vesicle fusion method. The monolayer was composed of a mixture of 2-mercaptoethanol and poly(ethylene glycol) lipopolymer, which promoted vesicle rupture. These results suggest that the fabrication of inert nanostructures and the site-selective modification of solid surfaces to induce vesicle rupture may be essential in the construction of tLBRM nano(submicro) arrays using stepwise self-assembly.This work was supported by Core Research for Evolutional Science and Technology (CREST) of Japan Science and Technology Agency (JST), and New Energy and Indstrial Technology Development Organization (NEDO)

Soft lithography for microfluidics: a review

Soft lithography has provided a low-expertise route toward micro/nanofabrication and is playing an important role in microfluidics, ranging from simple channel fabrication to the creation of micropatterns onto a surface or within a microfluidic channel. In this review, the materials, methods, and applications of soft lithography for microfluidics are briefly summarized with a particular emphasis on integrated microfluidic systems containing physical microstructures or a topographically patterned substrate. Relevant exemplary works based on the combination of various soft lithographic methods using microfluidics are introduced with some comments on their merits and weaknesses.This work was supported by Korea Science and Engineering Foundation (KOSEF) grant funded by the Korea government (MOST) (R01-2007-000- 20675-0) and the Grant-in-Aid for Next-Generation New Technology Development Programs from the Korea Ministry of Commerce, Industry and Energy (No.10030046). This work was also supported by the Korea Research Foundation Grant funded by the Korean Government (MOEHRD, Basic Research Promotion Fund)(KRF-2007-331-D00064) for Sun Min Kim

Soft lithographic patterning of supported lipid bilayers onto a surface and inside microfluidic channels

We present simple soft lithographic methods for patterning supported lipid bilayer (SLB) membranes onto a surface and inside microfluidic channels. Micropatterns of polyethylene glycol (PEG)-based polymers were fabricated on glass substrates by microcontact printing or capillary moulding. The patterned PEG surfaces have shown 97 +/- 0.5% reduction in lipid adsorption onto two dimensional surfaces and 95 +/- 1.2% reduction inside microfluidic channels in comparison to glass control. Atomic force microscopy measurements indicated that the deposition of lipid vesicles led to the formation of SLB membranes by vesicle fusion due to hydrophilic interactions with the exposed substrate. Furthermore, the functionality of the patterned SLBs was tested by measuring the binding interactions between biotin (ligand)-labeled lipid bilayer and streptavidin (receptor). SLB arrays were fabricated with spatial resolution down to similar to 500 nm on flat substrate and similar to 1 mu m inside microfluidic channels, respectively.This work was supported by the Micro Thermal System Research Center of Seoul National University and Core Research for Evolutional Science and Technology (CREST) of Japan Science and Technology Corporation

Biomimetic Strategies for the Glioblastoma Microenvironment

Glioblastoma multiforme (GBM) is a devastating type of tumor with high mortality, caused by extensive infiltration into adjacent tissue and rapid recurrence. Most therapies for GBM have focused on the cytotoxicity and have not targeted GBM spread. However, there have been numerous attempts to improve therapy by addressing GBM invasion, through understanding and mimicking its behavior using three-dimensional (3D) experimental models. Compared with two-dimensional models and in vivo animal models, 3D GBM models can capture the invasive motility of glioma cells within a 3D environment comprising many cellular and non-cellular components. Based on tissue engineering techniques, GBM invasion has been investigated within a biologically relevant environment, from biophysical and biochemical perspectives, to clarify the pro-invasive factors of GBM. This review discusses the recent progress in techniques for modeling the microenvironments of GBM tissue and suggests future directions with respect to recreating the GBM microenvironment and preclinical applications

Capillary kinetics of thin polymer films in permeable microcavities

We present a Poiseuille model that can explain the rate of capillary rise of thin polymer films in permeable microcavities. In comparison to the traditional Poiseuille formulation, two features of the system were considered: the permeable nature of the enclosure and the effect of thin polymer films that are confined to the substrate. The model predicts that the rate is inversely proportional to the channel width, contrary to what the original Poiseuille model predicts, and it is proportional to the initial film thickness, which the original model cannot account for. The modified model is in satisfactory agreement with experimental data.This work was supported by the Brain Korea 21 Project in 2004

Measurement of viscosity of confined polymer melt using capillary kinetics

We present a simple method to measure viscosity of thin polymer melt that is confined between a substrate and a permeable plate using a modified Poiseuille equation. When a patterned polydimethylsiloxane (PDMS) mold is placed on a styrene-butadiene-styrene (SBS) block copolymer film spin-coated onto a substrate and heated above the polymer's glass transition temperature, capillarity forces the polymer melt into the void of the channel. To calculate the viscosity of the confined polymer melt, the height of capillary rise was measured as a function of time for a number of film thicknesses (220, 350, 540, 1000, and 1300 nm) and at two different temperatures (70 and 100 degrees C). It was found that the viscosity increases with decreasing film thickness at 70 degrees C, whereas it decreases with decreasing film thickness at 100 degrees C. This discrepancy might be related to the confinement-induced solid-like behavior of the polymer melt and wall slip at the polymer/solid interface. Furthermore, the viscosity turned out to be nearly equal to the bulk value for relatively large film thickness (> similar to 500 nm) regardless of the temperature, which corresponds to earlier findingsclose2

Fabrication of non-biofouling polyethylene glycol micro- and nanochannels by ultraviolet-assisted irreversible sealing

We present a simple and widely applicable method to fabricate micro- and nanochannels comprised entirely of crosslinked polyethylene glycol ( PEG) by using UV- assisted irreversible sealing to bond partially crosslinked PEG surfaces. The method developed here can be used to form channels as small as similar to 50 nm in diameter without using a sophisticated experimental setup. The manufactured channel is a homogeneous conduit made completely from non-biofouling PEG, exhibits robust sealing with minimal swelling and can be used without additional surface modification chemistries, thus significantly enhancing reliability and durability of microfluidic devices. Furthermore, we demonstrate simple analytical assays using PEG microchannels combined with patterned arrays of supported lipid bilayers ( SLBs) to detect ligand ( biotin) receptor ( streptavidin) interactionsclose666

Inorganic polymer photoresist for direct ceramic patterning by photolithography

A novel negative, inorganic polymer photoresist was demonstrated to be suitable for simple and direct fabrication of tribological SiCN-based ceramic microstructures via UV photolithography and subsequent pyrolysis at 800 degrees C.The authors acknowledge the National Research Laboratory (M10400000367-06J0000-36710) for financial support. Especially, the authors want to thank KBSI and KAIST for SEM and TEM support. K. Y. Suh is grateful for financial support from theMicro Thermal System Research Center of Seoul National University