Internal Modification of Poly(dimethylsiloxane) Microchannels with a Borosilicate Glass Coating

Abstract

We report on an original technique for the in situ coating of poly(dimethylsiloxane) (PDMS) microchannels with borosilicate glass, starting from an active nonaqueous and alkali-free precursor solution. By chemical reaction of this active solution inside the microchannel and subsequent thermal annealing, a protective and chemically inert glass borosilicate coating is bonded to the PDMS. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and nuclear magnetic resonance spectroscopy of the active solution show that it is composed of a silicon oxide network with boron connectivity. Thermal gravimetric analysis demonstrates the absence of organic content when curing is done above 150 degrees C. The borosilicate nature of the glass coating covalently bonded to the PDMS is demonstrated using ATR-FTIR spectroscopy and X-ray photoelectron spectroscopy. Atomic force microscopy and scanning electron microscopy show a smooth and crack-free coating. The latter is used as an efficient protective barrier against diffusion in PDMS of fluorescent rhodamine B dye that is dissolved either in water or in toluene. Moreover, the coating prevents swelling and consequent structural damage of the PDMS when the latter is exposed to harsh chemicals such as toluene.

Surface molecular property modifications for poly(dimethylsiloxane) (PDMS) based microfluidic devices

“…On the other hand, it was pointed out that the glasslike layer formed using Roman’s method (Roman et al 2005) was not covalently bonded to PDMS and was still in the gel form due to relatively low annealing temperature. To further improve the coating for prevention of diffusion and swelling, Orhan et al (2008) coated the PDMS channel with a borosilicate glass layer using an active solution of alkali-free precursors, TEOS and trimethoxyboroxine (TMB). This active solution was flushed into tetrabutylammonium fluoride (TBAF) oxidized PDMS channel and cured thermally at 160°C.…”

A rapid, inexpensive surface treatment for enhanced functionality of polydimethylsiloxane microfluidic channels

“…16,17 A number of groups have used alkoxysilanes as silica precursors in order to deposit glasslike surfaces within a PDMS microchannel. These methods have frequently involved elevated reaction temperatures, 11,12,[18][19][20][21] plasma pre-treatment of the PDMS, 12,[21][22][23] or have resulted in significant alteration in the dimensions of the treated microchannel (up to 60% reduction in cross section in a 35 Â 50 lm channel). 12 However, with appropriate reaction conditions, the decomposition of alkoxysilanes can be achieved at room temperature by using either acid-or base-catalyzed hydrolysis.…”

Polyvinylsilazane layer coating and its application in poly(dimethylsiloxane) microchip electrophoresis

“…However, this modification generally has a short lifetime with hydrophobicity recovery within hours, due to migration of short uncrosslinked PDMS chains to the surface [4]. Moreover, silicate surfaces on PDMS were prepared via sol-gel chemistry with different precursors of alkoxysilanes [5][6][7][8]. But the intrinsic contraction during its gelation and aging process caused serious cracking problem even with little mechanical stress [8].…”

“…Moreover, silicate surfaces on PDMS were prepared via sol-gel chemistry with different precursors of alkoxysilanes [5][6][7][8]. But the intrinsic contraction during its gelation and aging process caused serious cracking problem even with little mechanical stress [8]. Besides of this, transition metal sol-gel precursors (alkoxy metals) were also employed to deposit TiO 2 , ZrO 2 , and vanadia coating inside PDMS with similar sol-gel technique [9].…”