[Show abstract][Hide abstract] ABSTRACT: Surface modification of materials with microscale features through plasma treatment or deposition is of high value, and is considered one of the great challenges in plasma-based materials processing. This article reports a versatile method for the fabrication of microcavity plasma array devices. A 7?X?7 microcavity plasma array device (each cavity was 250?mu m in diameter and separated by 500?mu m) was used in this study to demonstrate the capability of these devices for localised, non-contact surface treatment/polymer deposition. The device can be reused multiple times for plasma treatment and polymerisation. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) imaging and region of interest (ROI) analysis, in addition to surface hydration, were employed to characterise the micropatterns on microplasma-treated PS. The results showed that microplasma treatment/deposition could be spatially confined to regions exposed to the individual ignited microcavities. However, the results also demonstrated that the size of the treated spots tended to increase with increasing treatment time until they eventually overlapped resulting in a homogeneous surface treatment confined to the size of the array. Similarly, the concentration of oxygen quantified on the treated spots reached saturation after 75?s of treatment. The versatility of the device was demonstrated by depositing an array of octadiene plasma polymer (ODpp) onto a silicon substrate as confirmed by XPS imaging and ROI analysis. A key advantage of these microcavity array devices is that they can be easily integrated into manufacturing and do not require contact with the substrate surface to impart well-defined chemical modifications on materials surfaces.
Plasma Processes and Polymers 07/2012; DOI:10.1002/ppap.201100166 · 2.96 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In this paper we describe the spatial surface chemical modification of
bonded microchannels through the integration of microplasmas into a
microfluidic chip (MMC). The composite MMC comprises an array of
precisely aligned electrodes surrounding the gas/fluid microchannel.
Pairs of electrodes are used to locally ignite microplasmas inside the
microchannel. Microplasmas, comprising geometrically confined
microscopic electrically-driven gas discharges, are used to spatially
functionalise the walls of the microchannels with proteins and enzymes
down to scale lengths of 300 μm inside 50 μm-wide microchannels.
Microchannels in poly(dimethylsiloxane) (PDMS) or glass were used in
this study. Protein specifically adsorbed on to the regions inside the
PDMS microchannel that were directly exposed to the microplasma. Glass
microchannels required pre-functionalisation to enable the spatial
patterning of protein. Firstly, the microchannel wall was functionalised
with a protein adhesion layer, 3-aminopropyl-triethoxysilane (APTES),
and secondly, a protein blocking agent (bovine serum albumin, BSA) was
adsorbed onto APTES. The functionalised microchannel wall was then
treated with an array of spatially localised microplasmas that reduced
the blocking capability of the BSA in the region that had been exposed
to the plasma. This enabled the functionalisation of the microchannel
with an array of spatially separated protein. As an alternative we
demonstrated the feasibility of depositing functional thin films inside
the MMC by spatially plasma depositing acrylic acid and 1,7-octadiene
within the microchannel. This new MMC technology enables the surface
chemistry of microchannels to be engineered with precision, which is
expected to broaden the scope of lab-on-a-chip type applications.
Proceedings of SPIE - The International Society for Optical Engineering 12/2011; DOI:10.1117/12.903293 · 0.20 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A rapid, high-precision method for localised plasma-treatment of bonded PDMS microchannels is demonstrated. Patterned electrodes were prepared by injection of molten gallium into preformed microchannel guides. The electrode guides were prepared without any additional fabrication steps compared to conventional microchannel fabrication. Alignment of the "injected" electrodes is precisely controlled by the photomask design, rather than positioning accuracy of alignment tools. Surface modification is detected using a fluorescent dye (Rhodamine B), revealing a well-defined micropattern with regions less than 100 µm along the length of the microchannel.
Lab on a Chip 10/2010; 11(3):541-4. DOI:10.1039/c0lc00339e · 5.75 Impact Factor