Recent developments in PDMS surface modification for microfluidic devices
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.
Citations
More filters
TL;DR: It is found that continuous, directional water transport occurs on the surface of the ‘peristome’—the rim of the pitcher—because of its multiscale structure, which optimizes and enhances capillary rise in the transport direction, and prevents backflow by pinning in place any water front that is moving in the reverse direction.
Abstract: Numerous natural systems contain surfaces or threads that enable directional water transport. This behaviour is usually ascribed to hierarchical structural features at the microscale and nanoscale, with gradients in surface energy and gradients in Laplace pressure thought to be the main driving forces. Here we study the prey-trapping pitcher organs of the carnivorous plant Nepenthes alata. We find that continuous, directional water transport occurs on the surface of the 'peristome'--the rim of the pitcher--because of its multiscale structure, which optimizes and enhances capillary rise in the transport direction, and prevents backflow by pinning in place any water front that is moving in the reverse direction. This results not only in unidirectional flow despite the absence of any surface-energy gradient, but also in a transport speed that is much higher than previously thought. We anticipate that the basic 'design' principles underlying this behaviour could be used to develop artificial fluid-transport systems with practical applications.
737 citations
TL;DR: The evolution of chip materials reflects the two major trends of microfluidic technology: powerful microscale research platforms and low-cost portable analyses.
Abstract: Through manipulating fluids using microfabricated channeland chamber structures, microfluidics is a powerful tool to realize high sensitive, high speed, high throughput, and low cost analysis. In addition, the method can establish a well-controlled microenivroment for manipulating fluids and particles. It also has rapid growing implementations in both sophisticated chemical/biological analysis and low-cost point-of-care assays. Some unique phenomena emerge at the micrometer scale. For example, reactions are completed in a shorter amount of time as the travel distances of mass and heat are relatively small; the flows are usually laminar; and the capillary effect becomes dominant owing to large surface-to-volume ratios. In the meantime, the surface properties of the device material are greatly amplified, which can lead to either unique functions or problems that we would not encounter at the macroscale. Also, each material inherently corresponds with specific microfabrication strategies and certain native p...
652 citations
TL;DR: Zhao et al. as discussed by the authors proposed a simple yet versatile method to assemble hydrogels and elastomers into hybrids with extremely robust interfaces (interfacial toughness over 1,000 Jm−2) and functional microstructures such as microfluidic channels and electrical circuits.
Abstract: Inspired by mammalian skins, soft hybrids integrating the merits of elastomers and hydrogels have potential applications in diverse areas including stretchable and bio-integrated electronics, microfluidics, tissue engineering, soft robotics and biomedical devices. However, existing hydrogel–elastomer hybrids have limitations such as weak interfacial bonding, low robustness and difficulties in patterning microstructures. Here, we report a simple yet versatile method to assemble hydrogels and elastomers into hybrids with extremely robust interfaces (interfacial toughness over 1,000 Jm−2) and functional microstructures such as microfluidic channels and electrical circuits. The proposed method is generally applicable to various types of tough hydrogels and diverse commonly used elastomers including polydimethylsiloxane Sylgard 184, polyurethane, latex, VHB and Ecoflex. We further demonstrate applications enabled by the robust and microstructured hydrogel–elastomer hybrids including anti-dehydration hydrogel–elastomer hybrids, stretchable and reactive hydrogel–elastomer microfluidics, and stretchable hydrogel circuit boards patterned on elastomer. Soft hybrids that integrate hydrogels and elastomers can be used in applications, such as stretchable electronics and soft robotics, but usually have shortcomings. Here, Zhao and co-workers show a simple method of assembling hydrogel/elastomer hybrids with robust interfaces and functional microstructures.
595 citations
TL;DR: An overview of the current state of single-cell analysis involving droplet microfluidics is given and examples where dropletmicrofluidic can further biological understanding are offered.
Abstract: Droplet microfluidics allows the isolation of single cells and reagents in monodisperse picoliter liquid capsules and manipulations at a throughput of thousands of droplets per second. These qualities allow many of the challenges in single-cell analysis to be overcome. Monodispersity enables quantitative control of solute concentrations, while encapsulation in droplets provides an isolated compartment for the single cell and its immediate environment. The high throughput allows the processing and analysis of the tens of thousands to millions of cells that must be analyzed to accurately describe a heterogeneous cell population so as to find rare cell types or access sufficient biological space to find hits in a directed evolution experiment. The low volumes of the droplets make very large screens economically viable. This Review gives an overview of the current state of single-cell analysis involving droplet microfluidics and offers examples where droplet microfluidics can further biological understanding.
417 citations
TL;DR: A simple and easy protocol combining a second extended oxygen plasma treatments and proper storage to produce usable hydrophilic PDMS devices is reported.
Abstract: Rapid prototyping of polydimethylsiloxane (PDMS) is often used to build microfluidic devices. However, the inherent hydrophobic nature of the material limits the use of PDMS in many applications. While different methods have been developed to transform the hydrophobic PDMS surface to a hydrophilic surface, the actual implementation proved to be time consuming due to differences in equipment and the need for characterization. This paper reports a simple and easy protocol combining a second extended oxygen plasma treatments and proper storage to produce usable hydrophilic PDMS devices. The results show that at a plasma power of 70 W, an extended treatment of over 5 min would allow the PDMS surface to remain hydrophilic for more than 6 h. Storing the treated PDMS devices in de-ionized water would allow them to maintain their hydrophilicity for weeks. Atomic force microscopy analysis shows that a longer oxygen plasma time produces a smoother surface.
387 citations
References
More filters
Book•
01 Jan 1982
TL;DR: The results of typical analyses obtained in the laboratories of the authors occupy eleven pages, and will prove, useful to analysts and others for reference and guidance; the list of important works of reference provided will also be equally serviceable.
Abstract: The Analytical Process - Measurements - Tools of the Trade - Experimental Error - Statistics and Spreadsheets - Calibration Methods - Chemical Equilibrium - Let the Titrations Begin - Activity - Systematic Treatment of Equilibrium - Monoprotic Acid-Base Equilibria - Polyprotic Acid-Base Equilibria - Acid-Base Titrations - EDTA Titrations - Fundamentals of Electrochemistry - Electrodes and Potentiometry - Redox Titrations - Electroanalytical Techniques - Fundamentals of Spectrophotometry - Applications of Spectrophotometry - Spectrophotometers - Atomic Spectroscopy - Mass Spectrometry - Introduction to Analytical Separations - Gas Chromatography - High Performance Liquid Chromatography - Chromatographic Methods and Capillary Electrophoresis - Gravimetric and Combustion Analysis - Sample Preparation - Quality Assurance - Glossary - Appendices - Solutions to Exercises - Answers to Problems - Index
3,327 citations
TL;DR: This paper describes the compatibility of poly(dimethylsiloxane) (PDMS) with organic solvents; this compatibility is important in considering the potential of PDMS-based microfluidic devices in a number of applications, including that of microreactors for organic reactions.
Abstract: This paper describes the compatibility of poly(dimethylsiloxane) (PDMS) with organic solvents; this compatibility is important in considering the potential of PDMS-based microfluidic devices in a number of applications, including that of microreactors for organic reactions. We considered three aspects of compatibility: the swelling of PDMS in a solvent, the partitioning of solutes between a solvent and PDMS, and the dissolution of PDMS oligomers in a solvent. Of these three parameters that determine the compatibility of PDMS with a solvent, the swelling of PDMS had the greatest influence. Experimental measurements of swelling were correlated with the solubility parameter, δ (cal1/2 cm-3/2), which is based on the cohesive energy densities, c (cal/cm3), of the materials. Solvents that swelled PDMS the least included water, nitromethane, dimethyl sulfoxide, ethylene glycol, perfluorotributylamine, perfluorodecalin, acetonitrile, and propylene carbonate; solvents that swelled PDMS the most were diisopropylam...
2,370 citations
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
Book•
17 Dec 1993
TL;DR: This work presents a meta-analysis of Capillary Electrophoresis for the Analysis of Single Cells: Electrochemical, Mass Spectrometric, and Radiochemical Detection, and its applications for Drugs in Biological Fluids.
Abstract: ModesIntroduction to Capillary Electrophoresis, R.P. Oda and J.P. LandersMicellar Electrokinetic Chromatography, J.R. MazzeoCapillary Electrophoresis Separation of Enantiomers by Cyclodextrin Array Chiral Analysis, A. GuttmanCapillary Isoelectric Focusing, R. Rodr guez-D az, T. Wehr, M. Zhu, and V. LeviTheory and Practice of Capillary Electrochromatography, M.M. Dittmann and G.P. RozingAnalyteCapillary Ion Electrophoresis, W.R. JonesAnalysis of Small Organic Molecules by Capillary Electrophoresis, K.D. AltriaCapillary Electrophoresis of Peptides, T. van de Goor, A. Apffel, J. Chakel, and W. HancockCapillary Electrophoresis of Proteins, T. Pritchett and F.A. RobeyCarbohydrate Analysis by Capillary Electrophoresis, J.D. Olechno and J.A. NolanSeparation of DNA by Capillary Electrophoresis, K.J. Ulfelder and B.R. McCordEssential Aspects of Capillary ElectrophoresisOptical Detection Techniques for Capillary Electrophoresis, S.L. Pentoney, Jr. and J.V. SweedlerElectrochemical Detection in Capillary Electrophoresis, C. HaberData Analysis in Capillary Electrophoresis, B.J. WandersEffects of Sample Matrix on Capillary Electrophoretic Analysis, Z.K. ShihabiOn-Line Sample Preconcentration for Capillary Electrophoresis, D.S. Burgi and R.-L. ChienApplicationsCapillary Electrophoresis for the Analysis of Single Cells: Electrochemical, Mass Spectrometric, and Radiochemical Detection, F.D. Swanek, S.S. Ferris, and A.G. EwingCapillary Electrophoresis for the Analysis of Single Cells: Laser-Induced Fluorescence Detection, S.J. Lillard and E.S. YeungCapillary Gel Electrophoresis for Large Scale DNA Sequencing: Separation and Detection, N.J. DovichiCapillary Electrophoresis for the Analysis of Drugs in Biological Fluids, R.P. Oda, M.E. Roche, J.P. Landers, and Z.K. ShihabiUse of Capillary Electrophoresis for Binding Studies, F.A. RobeyImmunoassays and Enzyme Assays Using Capillary Electrophoresis, N.M. Schultz, L. Tao, D.J. Rose, Jr., and R.T. KennedyClinical Applications of Capillary Electrophoresis, R.P. Oda, V.J. Bush, and J.P. LandersSpecialized Aspects of Capillary ElectrophoresisCapillary Surface Modification in Capillary Electrophoresis, A.M. Dougherty, N. Cooke, and P. ShiehImproved Capillary Electrophoretic Separations Associated with Controlling Electroosmotic Flow, C.S. LeeContinuous Separations by Electrophoresis in Rectangular Channels, P.F. Gavin and A.G. EwingTwo-Dimensional Liquid Chromatography-Capillary Electrophoresis, D.J. Jeffery, T.F. Hooker, and J.W. JorgensonCapillary Electrophoresis-Mass Spectrometry, J.C. Severs and R.D. SmithMicrofabricated Devices for Performing Capillary Electrophoresis, S.C. Jacobson and J.M. RamseyFraction Collection with Micro-Preparative Capillary Electrophoresis, M.A. Strausbauch and P.J. WettsteinAppendix 1: Calculations for Practical UseAppendix 2: TroubleshootingAppendix 3: Seperation Conditions for Classes of AnalytesIndex
785 citations
"Recent developments in PDMS surface..." refers background in this paper
...The separation time and efficiencies are affected by separation parameters such as the length of separation channel, background electrolyte and separation field strength [107]....
[...]
TL;DR: In this paper, the authors provide an in-depth look at the state-of-the-art in integrated microfludic devices for a broad range of application areas from on-chip DNA analysis, immunoassays and cytometry to advances in integrated detection technologies for and miniaturized fuel processing devices.
738 citations