Poly(dimethylsiloxane) electrospray devices fabricated with diamond-like carbon–poly(dimethylsiloxane) coated SU-8 masters

Abstract

This study presents coupling of a poly(dimethylsiloxane) (PDMS) micro-chip with electrospray ionization-mass spectrometry (ESI-MS). Stable electrospray is generated directly from a PDMS micro-channel without pressure assistance. Hydrophobic PDMS aids the formation of a small Taylor cone in the ESI process and facilitates straightforward and low-cost batch production of the ESI-MS chips. PDMS chips were replicated with masters fabricated from SU-8 negative photoresist. A novel coating, an amorphous diamond-like carbon-poly(dimethylsiloxane) hybrid, deposited on the masters by the filtered pulsed plasma arc discharge technique, improved significantly the lifetime of the masters in PDMS replications. PDMS chip fabrication conditions were observed to affect the amount of background peaks in the MS spectra. With an optimized fabrication process (PDMS curing agent/silicone elastomer base ratio of 1/8 (w/w), curing at 70 degree C for 48 h) low background spectra were recorded for the analytes. The performance of PDMS devices was examined in the ESI-MS analysis of some pharmaceutical compounds and amino acids.

Thin chip microsprayer system coupled to quadrupole time-of-flight mass spectrometer for glycoconjugate analysis

“…The potential of these modern systems is considerably broadening the area of MS applicability in life sciences. The option of miniaturized devices for sample infusion into MS is driven by several technical, analytical and economical advantages such as: (1) simplification of the laborious chemical and biochemical strategies required currently for MS research; (2) high throughput nanoanalysis/identification of biomolecules; (3) elimination of the time-consuming optimization procedures; (4) an increase in the sensitivity by drastic reduction of the sample and reagent consumption, sample handling and potential sample loss; (5) high reproducibility of the experiments; (6) the potential to discover novel biologically-relevant structures due to increased ionization efficiency; (7) high signal-to-noise ratio; (8) reduced in-source fragmentation leading to a significant increase of the precision in the identification of unknown analytes in biological matrices; (9) flexibility and a broad area of applicability; (10) low cost of analysis and chip production; (11) the possibility for unattended high-throughput experiments reducing man power and intervention; (12) elimination of possible crosscontamination and carry-overs; (13) flexibility for different configurations and analyses, upgrading and modifications; (14) minimal infrastructure requirements for optimal functioning; (15) reduction of the ion source size facilitating manipulation and efficient ion transfer by precise positioning towards the MS sampling orifice.…”

“…[13][14][15] Different MS configurations [16][17][18][19] such as single and triple quadrupole MS ion trap and ultra high resolution Fourier-transform ion cyclotron resonance mass spectrometry (FTICR MS) were adapted to polymer-based chip ESI interfacing and optimized mostly for proteomic surveys.…”

Microfluidic Device for Rapid (<15 min) Automated Microarray Hybridization

“…A wide variation of PDMS structures can be molded by use of microfabricated SU-8 micromolds (17)(18)(19)(20)(21). Two types of photoresist (i.e., SU-8 25 and SU-8 100) available from Microchem Inc. were used.…”

Direct hot embossing of microelements by means of photostructurable polyimide

“…By means of nanoindentation experiments at room temperature, we have obtained a young's modulus of 4.19 GPa and a surface nanohardness of 415.06 MPa for the polyimide material used in this work that is maintained up to glass transition of the polyimide (300°C). In comparison, SU-8 photoresists that were used for direct hot embossing, 7,8 have a lower glass transition temperature (200°C) and young's modulus (2.0 GPa) as reported by the SU-8 suppliers. Compared to SU-8, polyimide possesses longer polymer chains, which explains its higher thermomechanical stability and compromises, however, the quality of patterning (straightness and smoothness of side walls of patterns) with photolithography.…”

“…On the other hand, further processing after photoresist patterning adds to the complexity of the manufacturing process in large-scale productions. There have been few, if any, thriving attempts to directly emboss polymers by means of bare photoresists, 7,8 and in particular polyimidebased photoresists. Here, we completely eliminate the silicone replications, and reinvent the use of photostructurable polyimide for direct hot embossing.…”