Fabrication of anti-protein-fouling poly(ethylene glycol) microfluidic chip electrophoresis by sandwich photolithography

Concepts and recent advances in microchip electrophoresis coupled to mass spectrometry: Technologies and applications

The online coupling of microchip electrophoresis (ME) as a fast, highly efficient, and low-cost miniaturized separation technique to mass spectrometry (MS) as an information-rich and sensitive characterization technique results in ME-MS an attractive tool for various applications. In this paper, we review the basic concepts and latest advances in technology for ME coupled to MS during the period of 2016-2021, covering microchip materials, structures, fabrication techniques, and interfacing to electrospray ionization (ESI)-MS and matrix-assisted laser desorption/ionization-MS. Two critical issues in coupling ME and ESI-MS include the electrical connection used to define the electrophoretic field strength along the separation channel and the generation of the electrospray for MS detection, as well as, a miniaturized ESI-tip. The recent commercialization of ME-MS in zone electrophoresis and isoelectric focusing modes has led to the widespread application of these techniques in academia and industry. Here we summarize recent applications of ME-MS for the separation and detection of antibodies, proteins, peptides, carbohydrates, metabolites, and so on. Throughout the paper these applications are discussed in the context of benefits and limitations of ME-MS in comparison to alternative techniques.

Patterning Wettability for Open-Surface Fluidic Manipulation: Fundamentals and Applications

Effective manipulation of liquids on open surfaces without external energy input is indispensable for the advancement of point-of-care diagnostic devices. Open-surface microfluidics has the potential to benefit health care, especially in the developing world. This review highlights the prospects for harnessing capillary forces on surface-microfluidic platforms, chiefly by inducing smooth gradients or sharp steps of wettability on substrates, to elicit passive liquid transport and higher-order fluidic manipulations without off-the-chip energy sources. A broad spectrum of the recent progress in the emerging field of passive surface microfluidics is highlighted, and its promise for developing facile, low-cost, easy-to-operate microfluidic devices is discussed in light of recent applications, not only in the domain of biomedical microfluidics but also in the general areas of energy and water conservation.

User-Friendly Microfabrication Method for Complex Topological Structure and Three-Dimensional Microchannel with the Application Prospect in Polymerase Chain Reaction (PCR)

One of the most important challenges in the field of microfluidics is the rapid fabrication of microchips with complex topologies. Although the processing method of microfluidic chips has made brilliant achievements in the past 20 years, almost all traditional processing methods still face huge obstacles in the production of complex topologies and three-dimensional microchannel. Nowadays, the main methods of manufacturing microfluidic chips such as numerical control microprocessing, laser ablation, inkjet printing, photolithography, dry etching, and lithography, galvanoformung and abformung (LIGA) technology are not only inapplicable to the complex topological structure and the rapid processing of three-dimensional microfluidic chips but also rely on expensive processing equipment, complex manufacturing process, and low yield. To solve the problems of these traditional processing methods, we propose a low-cost methodology to obtain a microfluidic chip by sewing the chip pipe to the substrate with an embroidery machine as low as $6. Compared with the above-mentioned traditional microprocessing technologies, the new chip processing technology proposed by us does not involve professional microprocessing equipment and professional skills. Therefore, this new chip processing technology can significantly improve the efficiency of microprocessing.

Blood-typing and irregular antibody screening through multi-channel microfluidic discs with surface antifouling modification

A novel surface modification technology for microfluidic disks was developed for multichannel blood-typing detection and irregular antibody screening. The antifouling material, poly(ethylene glycol) methacrylate (PEGMA), was used to modify the surface of the microfluidic disk for improving its hydrophilicity and blood compatibility. With the modification of PEGMA, the hydrophilicity was sufficiently improved with a 44.5% reduction of water contact angle. The modified microfluidic disk also showed good biocompatibility with a reduction of hemolytic index (from 3.4% to 1.2%) and platelet adhesion (from 4.6 × 10⁴/cm² to 1.9 × 10⁴/cm²). Furthermore, the PEGMA modification technique conducted on the microfluidic disk achieved successful adjustment of burst frequency for each chamber in the microchannel, allowing a sequential addiction of reagents in the test protocol of manual polybrene (MP) blood typing. Clinical studies showed that the proposed MP microfluidic disk method not only performed at extremely high consistency with the traditional tube method in the identification of ABO/RhD blood types, but also accomplished an effective screening method for detecting irregular antibodies. In conclusion, this study demonstrated that the easily mass-produced MP microfluidic disk exhibited good blood-typing sensitivity and was suitable for clinical applications.

Scaling Laws in Directional Spreading of Droplets on Wettability-Confined Diverging Tracks

Spontaneous pumpless transport of droplets on wettability-confined tracks is important for various applications, such as rapid transport and mixing of fluid droplets, enhanced dropwise condensation, biomedical devices, and so forth. Recent studies have shown that on an open surface, a superhydrophilic track of diverging width, laid on a superhydrophobic background, facilitates the transport of water from the narrower end to the wider end at unprecedented rates (up to 40 cm/s) without external actuation. The spreading behavior on such surfaces, however, has only been characterized for water. Keeping in mind that such designs play a key role for a diverse range of applications, such as handling organic liquids and in point-of-care devices, the importance of characterizing the spreading behavior of viscous liquids on such surfaces cannot be overemphasized. In the present work, the spreading behavior on the aforementioned wettability-patterned diverging tracks was observed for fluids of different viscosities. Two dimensionless variables were identified, and a comprehensive relationship was obtained. Three distinct temporal regimes of droplet spreading were established: I), a Washburn-type slow spreading, II) a much faster Laplace pressure-driven spreading, and III), a sluggish density-augmented Tanner-type film spreading. The results offer design guidance for tracks that can pumplessly manage fluids of various viscosities and surface tensions.

Impact of Anti-Biofouling Surface Coatings on the Properties of Nanomaterials and Their Biomedical Applications

Understanding and subsequently controlling non-specific interactions between engineered nanomaterials and biological environment have become increasingly important for further developing and advancing nanotechnology for biomedical applications. Such non-specific interactions, also known as the biofouling effect, mainly associate with the adsorption of biomolecules (such as proteins, DNAs, RNAs, and peptides) onto the surface of nanomaterials and the adhesion or uptake of nanomaterials by various cells. By altering the surface properties of nanomaterials the biofouling effect can lead to in situ changes of physicochemical properties, pharmacokinetics, functions, and toxicity of nanomaterials. This review provides discussions on the current understanding of the biofouling effect, the factors that affect the non-specific interactions associated with biofouling, and the impact of the biofouling effect on the performances and functions of nanomaterials. An overview of the development and applications of various anti-biofouling coating materials to preserve and improve the properties and functions of engineered nanomaterials for intended biomedical applications is also provided.

Recent advances in protein analysis by capillary and microchip electrophoresis

This review article describes the significant recent advances in the analysis of proteins by capillary and microchip electrophoresis during the period from mid-2014 to early 2017. This review highlights the progressions, new methodologies, innovative instrumental modifications, and challenges for efficient protein analysis in human specimens, animal tissues, and plant samples. The protein analysis fields covered in this review include analysis of native, reduced, and denatured proteins in addition to Western blotting, protein therapeutics and proteomics.