Hydrophobicity Recovery of Polydimethylsiloxane after Exposure to Corona Discharges
TL;DR: In this paper, contact angle measurements of a high-temperature-vulcanized polydimethylsiloxane (PDMS) elastomer have been obtained for different periods of time in dry air.
About: This article is published in Polymer.The article was published on 1998-05-01. It has received 406 citations till now. The article focuses on the topics: Polydimethylsiloxane & Contact angle.
Citations
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TL;DR: PDMS surface hydrophilicity and micro-textures were generally unaffected when exposed to the different chemicals, except for micro-texture changes after immersion in potassium hydroxide and buffered hydrofluoric, nitric, sulfuric, and hydrofluic acids.
Abstract: Polydimethylsiloxane (PDMS Sylgard® 184, Dow Corning Corporation) pre-polymer was combined with increasing amounts of cross-linker (5.7, 10.0, 14.3, 21.4, and 42.9 wt.%) and designated PDMS1, PDMS2, PDMS3, PDMS4, and PDMS5, respectively. These materials were processed by spin coating and subjected to common microfabrication, micromachining, and biomedical processes: chemical immersion, oxygen plasma treatment, sterilization, and exposure to tissue culture media. The PDMS formulations were analyzed by gravimetry, goniometry, tensile testing, nanoindentation, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). Spin coating of PDMS was formulation dependent with film thickness ranging from 308 μm on PDMS1 to 171 μm on PDMS5 at 200 revolutions per minute (rpm). Ultimate tensile stress (UTS) increased from 3.9 MPa (PDMS1) to 10.8 MPa (PDMS3), and then decreased down to 4.0 MPa (PDMS5). Autoclave sterilization (AS) increased the storage modulus (σ) and UTS in all formulations, with the highest increase in UTS exhibited by PDMS5 (218%). PDMS surface hydrophilicity and micro-textures were generally unaffected when exposed to the different chemicals, except for micro-texture changes after immersion in potassium hydroxide and buffered hydrofluoric, nitric, sulfuric, and hydrofluoric acids; and minimal changes in contact angle after immersion in hexane, hydrochloric acid, photoresist developer, and toluene. Oxygen plasma treatment decreased the contact angle of PDMS2 from 109∘ to 60∘. Exposure to tissue culture media resulted in increased PDMS surface element concentrations of nitrogen and oxygen.
1,127 citations
TL;DR: In this article, the authors explored the possibility of the existence of a common scale, which can be used to gauge bond strength between various surfaces and found that the changes in wettability of surfaces owing to various levels of plasma exposure can be a useful parameter to gauge the bond strength.
Abstract: An issue in microfabrication of the fluidic channels in glass/poly (dimethyl siloxane) (PDMS) is the absence of a well-defined study of the bonding strength between the surfaces making up these channels. Although most of the research papers mention the use of oxygen plasma for developing chemical (siloxane) bonds between the participating surfaces, yet they only define a certain set of parameters, tailored to a specific setup. An important requirement of all the microfluidics/biosensors industry is the development of a general regime, which defines a systematic method of gauging the bond strength between the participating surfaces in advance by correlation to a common parameter. This enhances the reliability of the devices and also gives a structured approach to its future large-scale manufacturing. In this paper, we explore the possibility of the existence of a common scale, which can be used to gauge bond strength between various surfaces. We find that the changes in wettability of surfaces owing to various levels of plasma exposure can be a useful parameter to gauge the bond strength. We obtained a good correlation between contact angle of deionized water (a direct measure of wettability) on the PDMS and glass surfaces based on various dosages or oxygen plasma treatment. The exposure was done first in an inductively coupled high-density (ICP) plasma system and then in plasma enhanced chemical vapor deposition (PECVD) system. This was followed by the measurement of bond strength by use or the standardized blister test.
825 citations
Cites background from "Hydrophobicity Recovery of Polydime..."
...[2]‐[4]. Most of this research indicates that PDMS material in general comprises of repeated units of— , which on exposure to oxygen plasma develops silanol groups ( OH) at the expense of methyl groups . As argued by Garbassi et al. [5], the oxidation of the surface layer increases the concentration of hydroxyl groups and this leads to the formation of strong intermolecular bonds [ 6 ], [7]....
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TL;DR: This review will present recent research on surface modifications of PDMS using techniques ranging from metal layer coatings and layer‐by‐layer depositions to dynamic surfactant treatments and the adsorption of amphipathic proteins.
Abstract: PDMS is enjoying continued and ever increasing popularity as the material of choice for microfluidic devices due to its low cost, ease of fabrication, oxygen permeability and optical transparency. However, PDMS's hydrophobicity and fast hydrophobic recovery after surface hydrophilization, attributed to its low glass transition temperature of less than -120 degrees C, negatively impacts on the performance of PDMS-based microfluidic device components. This issue has spawned a flurry of research to devise longer lasting surface modifications of PDMS, with particular emphasis on microfluidic applications. This review will present recent research on surface modifications of PDMS using techniques ranging from metal layer coatings and layer-by-layer depositions to dynamic surfactant treatments and the adsorption of amphipathic proteins. We will also discuss significant advances that have been made with a broad palette of gas-phase processing methods including plasma processing, sol-gel coatings and chemical vapor deposition. Finally, we will present examples of applications and future prospects of modified PDMS surfaces in microfluidics, in areas such as molecular separations, cell culture in microchannels and biomolecular detection via immunoassays.
749 citations
15 Oct 2002
TL;DR: The results reveal that when exposed to UV, the PDMS macromolecules in the surface region of Sylgard-184 undergo chain scission, involving both the main chain backbone and the side groups, and form a network whose wetting properties are similar to those of a UV-modified model PDMS.
Abstract: We report on the surface modification of Sylgard-184 poly(dimethyl siloxane) (PDMS) networks by ultraviolet (UV) radiation and ultraviolet/ozone (UVO) treatment. The effects of the UV light wavelength and ambient conditions on the surface properties of Sylgard-184 are probed using a battery of experimental probes, including static contact angle measurements, Fourier transform infrared spectroscopy, near-edge X-ray absorption fine structure, and X-ray reflectivity. Our results reveal that when exposed to UV, the PDMS macromolecules in the surface region of Sylgard-184 undergo chain scission, involving both the main chain backbone and the side groups. The radicals formed during this process recombine and form a network whose wetting properties are similar to those of a UV-modified model PDMS. In contrast to the UV radiation, the UVO treatment causes very significant changes in the surface and near-surface structure of Sylgard-184. Specifically, the molecular oxygen and ozone created during the UVO process interact with the UV-modified specimen. As a result of these interactions, the surface of the sample contains a large number of hydrophilic (mainly -OH) groups. In addition, the material density within the first approximately 5 nm reaches about 50% of that of pure silica. A major conclusion that can be drawn from the results and analysis described in this work is that the presence of the silica fillers in Sylgard-184 does not alter the surface properties of the UVO- and UV-modified Sylgard-184.
736 citations
TL;DR: Recent advances in nonbiofouling PDMS surface modification strategies applicable to microfluidic technology are summarized and two main categories are classified: physical approach including physisorption of charged or amphiphilic polymers and copolymers, as well as chemical approach including self assembled monolayer and thick polymer coating.
Abstract: Fast advancements of microfabrication processes in past two decades have reached to a fairly matured stage that we can manufacture a wide range of microfluidic devices. At present, the main challenge is the control of nanoscale properties on the surface of lab-on-a-chip to satisfy the need for biomedical applications. For example, poly(dimethylsiloxane) (PDMS) is a commonly used material for microfluidic circuitry, yet the hydrophobic nature of PDMS surface suffers serious nonspecific protein adsorption. Thus the current major efforts are focused on surface molecular property treatments for satisfying specific needs in handling macro functional molecules. Reviewing surface modifications of all types of materials used in microfluidics will be too broad. This review will only summarize recent advances in nonbiofouling PDMS surface modification strategies applicable to microfluidic technology and classify them into two main categories: (1) physical approach including physisorption of charged or amphiphilic polymers and copolymers, as well as (2) chemical approach including self assembled monolayer and thick polymer coating. Pros and cons of a collection of available yet fully exploited surface modification methods are briefly compared among subcategories.
495 citations
Cites background from "Hydrophobicity Recovery of Polydime..."
...Oxygen plasma (Duffy et al. 1998), UV/ozone (Efimenko et al. 2002; Hillborg et al. 2004), and corona discharges (Hillborg and Gedde 1998; Kim et al. 2000) are commonly used for surface activation purpose....
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...discharges (Hillborg and Gedde 1998; Kim et al. 2000) are commonly used for surface activation purpose....
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References
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01 Jan 1992
TL;DR: Theory of polymer characterization vibrational spectroscopy of polymers is discussed in this paper, where high-resolution NMR spectro-graphs are used for polymers in solution editing techniques.
Abstract: Theory of polymer characterization vibrational spectroscopy of polymers experimental IR spectroscopy of Polymers applications of IR spectroscopy to polymers Raman spectroscopy of polymers high-resolution NMR spectroscopy of polymers in solution special editing techniques for high-resolution NMR spectroscopy of polymers high-resolution NMR spectroscopy of solid polymers applications of high-resolution solid-state NMR spectroscopy of polymers NMR relaxation spectroscopy of polymers NMR imaging of polymeric materials.
460 citations
TL;DR: In this paper, the effect of plasma treatments on polydimethylsiloxane elastomer using four different plasma gases ( argon, helium, oxygen, and nitrogen) was investigated.
Abstract: Plasma treatment of silicone surfaces is a useful way of increasing wettability to improve adhesion and a first step in producing various organosilicon thin-film composites. Despite numerous earlier studies, there is no consensus on the effect of plasma treatment nor on the mechanism of the subsequent hydrophobic recovery. X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were used to study the effect of plasma treatments of polydimethylsiloxane elastomer using four different plasma gases: argon, helium, oxygen, and nitrogen. In each case, the surface was oxidized to produce a thin, wettable, brittle silica-like layer. These surfaces progressively recover their hydrophobicity by diffusion of untreated polymer chains through cracks in the treated layer. Angle-resolved XPS detected the untreated, diffused layer and SEM revealed the common occurrence of cracks in the treated layer, although conditions could be found for each gas where the surface becomes completely wettable by wat...
379 citations
TL;DR: In this article, a hypothesis for aging produced by dry band arcing in silicone rubber material used for outdoor insulation is presented and experimentally proven, and the analytical techniques used to study the permanent changes are Fourier transform infrared (FTIR) spectroscopy, energy dispersive X-ray (EDX) analysis, XRD, and surface roughness measurement.
Abstract: A hypothesis for aging produced by dry band arcing in silicone rubber material used for outdoor insulation is presented and experimentally proven. Aging is indicated by permanent changes. The analytical techniques used to study the permanent changes are Fourier transform infrared (FTIR) spectroscopy, energy dispersive X-ray (EDX) analysis, X-ray diffraction (XRD), and surface roughness measurement. The authors highlight the fact that there are permanent changes occurring in the material that lead to progressive degradation in the long run, even though there can be a complete recovery of surface hydrophobicity in a short time. >
177 citations
01 Jan 1988
TL;DR: This chapter discusses adsorption and wetting or contact angle processes purely from the point of view of the liquid phase, because one assumes that the solid phase does not in any way respond, reorient, or otherwise change in the different liquid environments.
Abstract: Classical surface chemistry assumes that solid surfaces are rigid, immobile, and at equilibrium. These assumptions allow one to probe adsorption and wetting or contact angle processes purely from the point of view of the liquid phase, because one assumes that the solid phase does not in any way respond, reorient, or otherwise change in the different liquid environments. Although such assumptions may be partially correct for truly rigid solids, they are generally inappropriate for polymers (see also Chapter 7).
176 citations
TL;DR: In this paper, a study on the loss and recovery of hydrophobicity of RTV (room-temperature vulcanizing) silicone-rubber insulator coatings in a salt-fog chamber is reported.
Abstract: The results of a study on the loss and recovery of hydrophobicity of RTV (room-temperature vulcanizing) silicone-rubber insulator coatings in a salt-fog chamber are reported. The results complement those previously reported on the ability of the coatings to suppress leakage current and insulator flashover. The temporary loss of hydrophobicity caused by dry-band arcing and the subsequent recovery are studied in depth. The gradual loss of hydrophobicity as determined from the leakage current and the contact-angle measurements is shown to be related to the physical changes to the coating brought about by dry-band arcing. >
150 citations