Microcontact Printing Using Poly(dimethylsiloxane) Stamps Hydrophilized by Poly(ethylene oxide) Silanes

Abstract

The patterning of a surface using microcontact printing (μCP) generally employs a hydrophobic micropatterned stamp made from poly(dimethylsiloxane) (PDMS) to place ink molecules on a surface with spatial control. We present a simple procedure to hydrophilize PDMS stamps based on the O2 plasma oxidation of PDMS (referred to as PDMSox) and the grafting of poly(ethylene oxide) silanes (PEO−Si) to the oxidized surface. The wetting properties of a PDMSox surface derivatized with PEO having none, one, or two silanes and having chains with 7−70 EO units are inspected. All PDMSox surfaces treated with PEO−Si are hydrophilic and have advancing and receding contact angles of ∼40° and ∼30°, respectively. These surfaces remain hydrophilic for periods longer than 7 days, which saves having to hydrophilize stamps freshly prior to their usage. In particular, grafting a PEO having two triethoxysilane end groups and a molecular weight (MW) of 3400 g mol-1 enables inking and microcontact printing a polar Pd/Sn catalyst for electroless deposition (ELD) from a stamp to an amino-functionalized glass surface. The printed pattern of colloids has high accuracy and contrast, as reflected by the selective ELD of NiB in the printed regions of the glass. The same stamp can be reused for many cycles of inking and printing without degradation of the quality of the final NiB patterns. The hydrophilic layer provided by the grafted PEO molecules is, in some cases, not sufficiently thick to incorporate and print enough polar ink to form a complete monolayer of cysteamine, for example, onto printed Au substrates. Oxidizing a planar PDMS surface through a mask permits the patterning of PEO onto PDMSox. It then becomes possible to ink the stamp with proteins either by depositing proteins from solution onto the areas left underivatized with PEO or by printing proteins in the PEO-derivatized areas only. The proteins on the planar PDMS/PDMSox-PEO surface in turn are microcontact printed with high accuracy onto glass. This work may help expand μCP to applications in which it is desirable to use polar inks or proteins.

Arrangement of PC12 Cells on a Silicon Chip via Extracellular Matrix (ECM) Layer Patterning by Atmospheric Pressure Plasmas

“…Ayumi ANDO, Hidetaka UNO 1) , Toshifumi ASANO 2) , Tsuneo URISU 1) and Satoshi HAMAGUCHI It is shown that neuronal model cells PC12 (rat adrenal pheochromocytoma cell line) can be cultured on a silicon (Si) substrate with the use of extracellular matrix (ECM) patterned by atmospheric-pressure plasmas (APPs). Arrangement of neuron cells in a desired pattern on a Si chip is an important step for the development of neuron cell chips.…”

Hydrophilic Surface Modification of PDMS Microchannel for O/W and W/O/W Emulsions

“…Layer by layer methods [21,22] result in long term stable hydrophilic coatings but involve carefully controlled multiple steps. Polyethylene oxide (PEO)-modified PDMS chips have been prepared to confer good water wettability to the microfluidic walls, but localization of these "in-bulk" treatments is not possible (and finalization of devices by sealing, i.e., with plasma, is also difficult) [23,24]. Photoinitiated grafting [25][26][27] strategies increase operational costs and become cumbersome in bonded microchannels due to non-uniformity of coatings.…”

Topographically Flat, Chemically Patterned PDMS Stamps Made by Dip‐Pen Nanolithography

“…The mechanically stable flat stamp is prepared without a photomask (since the structure may be directly written onto the surface by DPN), and the pattern drawn by DPN combined with subsequent chemical modification of the exposed areas of the stamp, allows one to create a surface with well-defined chemical regions that can be used to confine ink transport to sub-100 nm dimensions and prevent the lateral diffusion of the ink (Scheme 1). Others have used contact inking, [29,30] metal contact masks, [31,32] and template-mediated selfassembly approaches[33] to fabricate (sub)micron-sized chemical patterns on PDMS, but the approach described herein is remarkably simple and straightforward to implement and does not require complex and expensive photo-or e-beam lithography. More importantly, the high registration and resolution of DPN allow one to create stamps using this approach that ** C.A.M.…”

“…For these experiments, either a perfluorinated silane was used to render those areas ambiphobic [32] or a PEG silane was used to make them resist the adsorption of biomolecules. [31] As an initial proof-of-concept, we prepared a flat stamp with a pattern consisting of 7×5 arrays of 1μm dots defined initially by the DPN-generated PEG features with the surrounding areas passivated with 1H,1H,2H,2H-perfluorooctadecyltrichlorosilane (PFODTS). This stamp was immersed in a 2 mM ethanolic solution of octadecanethiol (ODT), rinsed with ethanol, and then blown dry with N 2 .…”

“…Proteins often exhibit strong interactions with hydrophobic surfaces such as PDMS, but modification with PEG silane can significantly inhibit protein adsorption. [31] In a typical experiment, we immersed our PEG-silanepassivated flat stamp into a 1 mg/ml tetramethylrhodamine 5-(and-6)-isothiocyanate (TRITC) conjugated anti-mouse IgG solution for 10 min. The stamp was subsequently rinsed with PBS buffer and Mili-Q water to remove protein residue on the PEG passivated areas of the stamp.…”