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Chad I. Rogers

Bio: Chad I. Rogers is an academic researcher from Brigham Young University. The author has contributed to research in topics: Peristaltic pump & Polydimethylsiloxane. The author has an hindex of 6, co-authored 7 publications receiving 942 citations.

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Journal ArticleDOI
TL;DR: The successful demonstration of electrophoresis and electroosmotic pumping in a microfluidic device provided a nonmechanical method for both fluid control and separation, and integration of multiple processes can be highly enabling for many applications.
Abstract: Microfluidics consist of microfabricated structures for liquid handling, with cross-sections in the 1–500 μm range, and small volume capacity (fL-nL) Capillary tubes connected with fittings,1 although utilizing small volumes, are not considered microfluidics for the purposes of this paper since they are not microfabricated Likewise, millifluidic systems, made by conventional machining tools, are excluded due to their larger feature sizes (>500 μm) Though micromachined systems for gas chromatography were introduced in the 1970’s,2 the field of microfluidics did not gain much traction until the 1990’s3 Silicon and glass were the original materials used, but then the focus shifted to include polymer substrates, and in particular, polydimethylsiloxane (PDMS) Since then the field has grown to encompass a wide variety of materials and applications The successful demonstration of electrophoresis and electroosmotic pumping in a microfluidic device provided a nonmechanical method for both fluid control and separation4 Laser induced fluorescence (LIF) enabled sensitive detection of fluorophores or fluorescently labeled molecules The expanded availability of low-cost printing allowed for cheaper and quicker mask fabrication for use in soft lithography5 Commercial microfluidic systems are now available from Abbott, Agilent, Caliper, Dolomite, Micralyne, Microfluidic Chip Shop, Micrux Technologies and Waters, as a few prominent examples For a more thorough description of the history of microfluidics, we refer the reader to a number of comprehensive, specialized reviews,3, 6–11 as well as a more general 2006 review12 The field of microfluidics offers many advantages compared to carrying out processes through bulk solution chemistry, the first of which relates to a lesson taught to every first-year chemistry student Simply stated, diffusion is slow! Thus, the smaller the distance required for interaction, the faster it will be Smaller channel dimensions also lead to smaller sample volumes (fL-nL), which can reduce the amount of sample or reagents required for testing and analysis Reduced dimensions can also lead to portable devices to enable on-site testing (provided the associated hardware is similarly portable) Finally, integration of multiple processes (like labeling, purification, separation and detection) in a microfluidic device can be highly enabling for many applications Microelectromechanical systems (MEMS) contain integrated electrical and mechanical parts that create a sensor or system Applications of MEMS are ubiquitous, including automobiles, phones, video games and medical and biological sensors13 Micro-total analysis systems, also known as labs-on-a-chip, are the chemical analogue of MEMS, as integrated microfluidic devices that are capable of automating multiple processes relevant to laboratory sciences For example, a typical lab-on-a-chip system might selectively purify a complex mixture (through filtering, antibody capture, etc), then separate target components and detect them Microfluidic devices consist of a core of common components Areas defined by empty space, such as reservoirs (wells), chambers and microchannels, are central to microfluidic systems Positive features, created by areas of solid material, add increased functionality to a chip and can consist of membranes, monoliths, pneumatic controls, beams and pillars Given the ubiquitous nature of negative components, and microchannels in particular, we focus here on a few of their properties Microfluidic channels have small overall volumes, laminar flow and a large surface-to-volume ratio Dimensions of a typical separation channel in microchip electrophoresis (μCE) are: 50 μm width, 15 μm height and 5 cm length for a volume of 375 nL Flow in these devices is normally nonturbulent due to low Reynolds numbers For example, water flowing at 20°C in the above channel at 1 μL/min (222 cm/s) results in a Reynolds number of ~05, where <2000 is laminar flow Since flow is nonturbulent, mixing is normally diffusion-limited Small channel sizes also have a high surface-to-volume ratio, leading to different characteristics from what are commonly found in bulk volumes The material surface can be used to manipulate fluid movement (such as by electroosmotic flow, EOF) and surface interactions For a solution in contact with a charged surface, a double layer of charge is created as oppositely charged ions are attracted to the surface charges This electrical double layer consists of an inner rigid or Stern Layer and an outer diffuse layer An electrostatic potential known as the zeta potential is formed, with the magnitude of the potential decreasing as distance from the surface increases The electrical double layer is the basis for EOF, wherein an applied voltage causes the loosely bound diffuse layer to move towards an electrode, dragging the bulk solution along Charges on the exposed surface also exert a greater influence on the fluid in a channel as its size decreases Larger surface-to-volume ratios are more prone to nonspecific adsorption and surface fouling In particular, non-charged and hydrophobic microdevice surfaces can cause proteins in solution to denature and stick We focus our review on advances in microfluidic systems since 2008 In doing this, we occasionally must cover foundational work in microfluidics that is considerably less recent We do not focus on chemical synthesis applications of microfluidics although it is an expanding area, nor do we delve into lithography, device fabrication or production costs Our specific emphasis herein is on four areas within microfluidics: properties and applications of commonly used materials, basic functions, integration, and selected applications For each of these four topics we provide a concluding section on opportunities for future development, and at the end of this review, we offer general conclusions and prospective for future work in the field Due to the considerable scope of the field of microfluidics, we limit our discussion to selected examples from each area, but cite in-depth reviews for the reader to turn to for further information about specific topics We also refer the reader to recent comprehensive reviews on advances in lab-on-a-chip systems by Arora et al10 and Kovarik et al14

736 citations

Journal ArticleDOI
TL;DR: 3D printed valves are successfully demonstrated for up to 800 actuations and use a custom resin formulation tailored for low non-specific protein adsorption.
Abstract: We report the successful fabrication and testing of 3D printed microfluidic devices with integrated membrane-based valves. Fabrication is performed with a low-cost commercially available stereolithographic 3D printer. Horizontal microfluidic channels with designed rectangular cross sectional dimensions as small as 350 μm wide and 250 μm tall are printed with 100% yield, as are cylindrical vertical microfluidic channels with 350 μm designed (210 μm actual) diameters. Based on our previous work [Rogers et al., Anal. Chem. 83, 6418 (2011)], we use a custom resin formulation tailored for low non-specific protein adsorption. Valves are fabricated with a membrane consisting of a single build layer. The fluid pressure required to open a closed valve is the same as the control pressure holding the valve closed. 3D printed valves are successfully demonstrated for up to 800 actuations.

220 citations

Journal ArticleDOI
TL;DR: Poly-PEGDA, which displays resistance to nonspecific adsorption, could have broad use in small volume analysis and biomedical research, and has greater resistance to permeation by small hydrophobic molecules than PDMS.
Abstract: Nonspecific adsorption in microfluidic systems can deplete target molecules in solution and prevent analytes, especially those at low concentrations, from reaching the detector Polydimethylsiloxane (PDMS) is a widely used material for microfluidics, but it is prone to nonspecific adsorption, necessitating complex chemical modification processes to address this issue An alternative material to PDMS that does not require subsequent chemical modification is presented here Poly(ethylene glycol) diacrylate (PEGDA) mixed with photoinitiator forms on exposure to ultraviolet (UV) radiation a polymer with inherent resistance to nonspecific adsorption Optimization of the polymerized PEGDA (poly-PEGDA) formula imbues this material with some of the same properties, including optical clarity, water stability, and low background fluorescence, that make PDMS so popular Poly-PEGDA demonstrates less nonspecific adsorption than PDMS over a range of concentrations of flowing fluorescently tagged bovine serum albumin so

63 citations

Journal ArticleDOI
TL;DR: Comparison of circular and rectangular valve geometries indicates that the surface area for membrane interaction in the valve region is important for valve performance.
Abstract: Pneumatically actuated, non-elastomeric membrane valves fabricated from polymerized polyethylene glycol diacrylate (poly-PEGDA) have been characterized for temporal response, valve closure, and long-term durability. A ∼100 ms valve opening time and a ∼20 ms closure time offer valve operation as fast as 8 Hz with potential for further improvement. Comparison of circular and rectangular valve geometries indicates that the surface area for membrane interaction in the valve region is important for valve performance. After initial fabrication, the fluid pressure required to open a closed circular valve is ∼50 kPa higher than the control pressure holding the valve closed. However, after ∼1000 actuations to reconfigure polymer chains and increase elasticity in the membrane, the fluid pressure required to open a valve becomes the same as the control pressure holding the valve closed. After these initial conditioning actuations, poly-PEGDA valves show considerable robustness with no change in effective operation after 115,000 actuations. Such valves constructed from non-adsorptive poly-PEGDA could also find use as pumps, for application in small volume assays interfaced with biosensors or impedance detection, for example.

37 citations

Journal ArticleDOI
TL;DR: These microfluidic devices with pressure-driven injection for electrophoretic analysis of amino acids, peptides, and proteins have strong potential to be integrated within more complex systems.
Abstract: We have developed microfluidic devices with pressure-driven injection for electrophoretic analysis of amino acids, peptides, and proteins. The novelty of our approach lies in the use of an externally actuated on-chip peristaltic pump and closely spaced pneumatic valves that allow well-defined, small-volume sample plugs to be injected and separated by microchip electrophoresis. We fabricated three-layer poly(dimethylsiloxane) (PDMS) microfluidic devices. The fluidic layer had injection and separation channels, and the control layer had an externally actuated on-chip peristaltic pump and four pneumatic valves around the T-intersection to carry out sample injection. An unpatterned PDMS membrane layer was sandwiched between the fluidic and control layers as the actuated component in pumps and valves. Devices with the same peristaltic pump design but different valve spacings (100, 200, 300, and 400 μm) from the injection intersection were fabricated using soft lithographic techniques. Devices were characterized through fluorescent imaging of captured plugs of a fluorescein-labeled amino acid mixture and through microchip electrophoresis separations. A suitable combination of peak height, separation efficiency, and analysis time was obtained with a peristaltic pump actuation rate of 50 ms, an injection time of 30 s, and a 200-μm valve spacing. We demonstrated the injection of samples in different solutions and were able to achieve a 2.4-fold improvement in peak height and a 2.8-fold increase in separation efficiency though sample stacking. A comparison of pressure-driven injection and electrokinetic injection with the same injection time and separation voltage showed a 3.9-fold increase in peak height in pressure-based injection with comparable separation efficiency. Finally, the microchip systems were used to separate biomarkers implicated in pre-term birth. Although these devices have initially been demonstrated as a stand-alone microfluidic separation tool, they have strong potential to be integrated within more complex systems.

28 citations


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TL;DR: This review introduces readers to the basic principles and fundamentals of flow chemistry and critically discusses recent flow chemistry accounts.
Abstract: Flow chemistry involves the use of channels or tubing to conduct a reaction in a continuous stream rather than in a flask Flow equipment provides chemists with unique control over reaction parameters enhancing reactivity or in some cases enabling new reactions This relatively young technology has received a remarkable amount of attention in the past decade with many reports on what can be done in flow Until recently, however, the question, “Should we do this in flow?” has merely been an afterthought This review introduces readers to the basic principles and fundamentals of flow chemistry and critically discusses recent flow chemistry accounts

1,192 citations

Journal ArticleDOI
TL;DR: This review provides a comprehensive overview of the isothermal amplification of nucleic acids encompassing work published in the past two decades including applications in bioanalysis, diagnostics, nanotechnology, materials science, and device integration.
Abstract: Isothermal amplification of nucleic acids is a simple process that rapidly and efficiently accumulates nucleic acid sequences at constant temperature. Since the early 1990s, various isothermal amplification techniques have been developed as alternatives to polymerase chain reaction (PCR). These isothermal amplification methods have been used for biosensing targets such as DNA, RNA, cells, proteins, small molecules, and ions. The applications of these techniques for in situ or intracellular bioimaging and sequencing have been amply demonstrated. Amplicons produced by isothermal amplification methods have also been utilized to construct versatile nucleic acid nanomaterials for promising applications in biomedicine, bioimaging, and biosensing. The integration of isothermal amplification into microsystems or portable devices improves nucleic acid-based on-site assays and confers high sensitivity. Single-cell and single-molecule analyses have also been implemented based on integrated microfluidic systems. In this review, we provide a comprehensive overview of the isothermal amplification of nucleic acids encompassing work published in the past two decades. First, different isothermal amplification techniques are classified into three types based on reaction kinetics. Then, we summarize the applications of isothermal amplification in bioanalysis, diagnostics, nanotechnology, materials science, and device integration. Finally, several challenges and perspectives in the field are discussed.

1,144 citations

Journal ArticleDOI
TL;DR: The purpose of this review is to convey the fundamentals of droplet microfluidics, a critical analysis on its current status and challenges, and opinions on its future development.
Abstract: Droplet microfluidics generates and manipulates discrete droplets through immiscible multiphase flows inside microchannels Due to its remarkable advantages, droplet microfluidics bears significant value in an extremely wide range of area In this review, we provide a comprehensive and in-depth insight into droplet microfluidics, covering fundamental research from microfluidic chip fabrication and droplet generation to the applications of droplets in bio(chemical) analysis and materials generation The purpose of this review is to convey the fundamentals of droplet microfluidics, a critical analysis on its current status and challenges, and opinions on its future development We believe this review will promote communications among biology, chemistry, physics, and materials science

990 citations

Journal ArticleDOI
TL;DR: The salient features of PDMS molding with those of 3D-printing are compared and an overview of the critical barriers that have prevented the adoption of3D-printed systems by microfluidic developers are given, namely resolution, throughput, and resin biocompatibility.
Abstract: In the last two decades, the vast majority of microfluidic systems have been built in poly(dimethylsiloxane) (PDMS) by soft lithography, a technique based on PDMS micromolding. A long list of key PDMS properties have contributed to the success of soft lithography: PDMS is biocompatible, elastomeric, transparent, gas-permeable, water-impermeable, fairly inexpensive, copyright-free, and rapidly prototyped with high precision using simple procedures. However, the fabrication process typically involves substantial human labor, which tends to make PDMS devices difficult to disseminate outside of research labs, and the layered molding limits the 3D complexity of the devices that can be produced. 3D-printing has recently attracted attention as a way to fabricate microfluidic systems due to its automated, assembly-free 3D fabrication, rapidly decreasing costs, and fast-improving resolution and throughput. Resins with properties approaching those of PDMS are being developed. Here we review past and recent efforts in 3D-printing of microfluidic systems. We compare the salient features of PDMS molding with those of 3D-printing and we give an overview of the critical barriers that have prevented the adoption of 3D-printing by microfluidic developers, namely resolution, throughput, and resin biocompatibility. We also evaluate the various forces that are persuading researchers to abandon PDMS molding in favor of 3D-printing in growing numbers.

787 citations

Journal ArticleDOI
TL;DR: This critical review covers the current state of 3D printing for microfluidics, focusing on the four most frequently used printing approaches: inkjet, stereolithography (SLA), two photon polymerisation (2PP) and extrusion printing (focusing on fused deposition modeling).
Abstract: 3D printing has the potential to significantly change the field of microfluidics. The ability to fabricate a complete microfluidic device in a single step from a computer model has obvious attractions, but it is the ability to create truly three dimensional structures that will provide new microfluidic capability that is challenging, if not impossible to make with existing approaches. This critical review covers the current state of 3D printing for microfluidics, focusing on the four most frequently used printing approaches: inkjet (i3DP), stereolithography (SLA), two photon polymerisation (2PP) and extrusion printing (focusing on fused deposition modeling). It discusses current achievements and limitations, and opportunities for advancement to reach 3D printing's full potential.

764 citations