Acoustofluidics-Assisted Coating of Microparticles.

Microparticles have been applied in many areas, ranging from drug delivery, diagnostics, cosmetics, personal care, and the food industry to chemical and catalytic reactions, sensing, and environmental remediation. Coating further provides additional functionality to the microparticles, such as controlled release, surface modification, bio-fouling resistance, stability, protection, etc. In this study, the conformal coating of microparticles with a positively charged polyelectrolyte (polyallylamine hydrochloride, PAH) by utilizing an acoustofluidic microchip was proposed and demonstrated.

Polymer Micro/Nanofabrication and Manufacturing.

Polymer microfabrication/nanofabrication and manufacturing are processes that involve the creation of small-scale structures using various polymeric materials [...

Fabrication of Polymer Microfluidics: An Overview.

Microfluidic platform technology has presented a new strategy to detect and analyze analytes and biological entities thanks to its reduced dimensions, which results in lower reagent consumption, fast reaction, multiplex, simplified procedure, and high portability. In addition, various forces, such as hydrodynamic force, electrokinetic force, and acoustic force, become available to manipulate particles to be focused and aligned, sorted, trapped, patterned, etc. To fabricate microfluidic chips, silicon was the first to be used as a substrate material because its processing is highly correlated to semiconductor fabrication techniques.

One-Step Hot Microembossing for Fabrication of Paper-Based Microfluidic Chips in 10 Seconds.

In recent years, microfluidic paper-based analytical devices (µPADs) have been developed because they are simple, inexpensive and power-free for low-cost chemical, biological and environmental detection. Moreover, paper is lightweight; easy to stack, store and transport; biodegradable; biocompatible; good for colorimetric tests; flammable for easy disposal of used paper-based diagnostic devices by incineration; and can be chemically modified. Different methods have been demonstrated to fabricate µPADs such as solid wax printing, craft cutting, photolithography, etc.

Membrane filtration: An unconventional route for fabrication of the flexible and dissolvable, polymer microneedle patches.

Utilization of dissolvable, polymer microneedles (MNs) for transdermal drug delivery offers many advantages such as being painless to patients, biocompatibility, biodegradability, and active and controlled drug release. There are many different approaches for fabrication of such MNs; however, most of them still suffer from tedious procedures, stringent fabrication conditions, expensive equipment, or substantially long processing time. In this work, we applied membrane filtration to fabricate dissolvable, polymer MNs.

Applications of microfluidics in microalgae biotechnology: A review.

Microalgae have been one of the important sources for biofuel production owing to their competitive advantages such as no need to tap into the global food supply chain, higher energy density, and absorbing carbon dioxide to mitigate global warming. One of the key factors to ensure successful biofuel production is that it requires not only bioprospecting of the microalgae with high lipid content, high growth rate and tolerance to environmental parameters but also on-site monitoring of the cultivation process and optimization of the culturing conditions. However, as the conventional techniques usually involve in complicated procedures, or are time-consuming or labor intensive, microfluidics technology offers an attractive alternative to resolve these issues.

Development of flow through dielectrophoresis microfluidic chips for biofuel production: Sorting and detection of microalgae with different lipid contents.

In this study, a continuous flow dielectrophoresis (DEP) microfluidic chip was fabricated and utilized to sort out the microalgae (C. vulgaris) with different lipid contents. The proposed separation scheme is to allow that the microalgae with different lipid contents experience different negative or no DEP force at the separation electrode pair under the pressure-driven flow.

Polydimethyl siloxane wet etching for three dimensional fabrication of microneedle array and high-aspect-ratio micropillars.

Among various transdermal drug delivery (TDD) approaches, utilizing the microneedles (MNs) not only can penetrate the skin but also deliver the drug with reduced tissue damage, reduced pain, and no bleeding. However, the MNs with larger height are required to overcome the skin barrier for effective TDD. Unlike 2D patterning, etching polydimethyl siloxane (PDMS) micropillars for fabrication of 3D microstructures is presented.

Electrokinetic trapping and surface enhanced Raman scattering detection of biomolecules using optofluidic device integrated with a microneedles array.

In this study, microneedles which possess sharp tips were utilized to trap and detect the biomolecules. Owing to the large curvature, the tips of the microneedles created a substantially high gradient of electric field under the non-uniform electric field which served as not only the trapping sites but also the substrate for surface enhanced Raman scattering (SERS). Separation of polystyrene microparticles with different sizes and two kinds of biomolecules (Staphylococcus aureus (S.

Black silicon SERS substrate: effect of surface morphology on SERS detection and application of single algal cell analysis.

In this study, we have investigated the effect of the surface morphology of the black silicon substrate on surface enhanced Raman spectroscopy (SERS) and explored its application of single algal cell detection. By adjusting the O2 and SF6 flow rates in the cryogenic plasma etching process, different surface morphologies of the black silicon substrate was produced without performing the lithographic process. It was found the Raman signals were better enhanced as the tip density of the black silicon substrate increased.

Fabrication of long poly(dimethyl siloxane) nanochannels by replicating protein deposit from confined solution evaporation.

A relatively simple, inexpensive and reliable technique was developed to fabricate an array of nanochannels. Moreover, the nanochannels are directly integrated to microchannels as a whole, which facilitates solution loading from the millimeter-scaled loading reservoirs into the nanochannels. It is found that continuous bovine serum albumin (BSA) line structures with triangle-like cross section at nanoscale can be obtained by evaporation of BSA solution with concentration between 0.

Separation of microalgae with different lipid contents by dielectrophoresis.

In this study, the effect of the solution conductivity on the behavior of microalgal cells (Chlorella) with different lipid contents under a non-uniform electric field was investigated. It was found that, for the algal cells with 11 wt% lipid content, the crossover frequency is between 2 and 10 MHz when the solution conductivity is within 1.4 and 2.

Constructing a superhydrophobic surface on polydimethylsiloxane via spin coating and vapor-liquid sol-gel process.

In this study, a superhydrophobic surface on polydimethylsiloxane (PDMS) substrate was constructed via the proposed vapor-liquid sol-gel process in conjunction with spin coating of dodecyltrichlorosilane (DTS). Unlike the conventional sol-gel process where the reaction takes place in the liquid phase, layers of silica (SiO(2)) particles were formed through the reaction between the reactant spin-coated on the PDMS surface and vapor of the acid solution. This led to the SiO(2) particles inlaid on the PDMS surface.

Packaging of microfluidic chips via interstitial bonding technique.

In this paper, we describe an interstitial bonding technique for packaging of microfluidic chips. The cover plate is first placed on top of the microfluidic chip, followed by dispensing the UV-curable resin into the resin-loading reservoirs. With the interstitial space between the cover plate and the microfluidic chip connecting to the loading reservoirs, the UV-curable resin wicks through capillary force action and hydrostatic pressure generated by the liquid level in the resin-loading reservoirs.

Long-range and superfast trapping of DNA molecules in an ac electrokinetic funnel.

In this work we report a microfluidic platform capable of trapping and concentrating a trace amount of DNA molecules efficiently. Our strategy invokes nonlinear electro-osmotic flow induced by charge polarization under high-frequency ac fields. With the asymmetric quadrupole electrode design, a unique converging flow structure can be created for generating focusing effects on DNA molecules.

New valve and bonding designs for microfluidic biochips containing proteins.

Two major concerns in the design and fabrication of microfluidic biochips are protein binding on the channel surface and protein denaturing during device assembly. In this paper, we describe new methods to solve these problems. A "fishbone" microvalve design based on the concept of superhydrophobicity was developed to replace the capillary valve in applications where the chip surface requires protein blocking to prevent nonspecific binding.

Microfluidic enzyme-linked immunosorbent assay technology.

In this chapter, we have presented an overview of microfluidic enzyme-linked immunosorbent assay (ELISA) by first introducing the principle of immunoassay, ELISA, and microfabricated devices, followed by a discussion of microfabrication technology and the characterization of microfluidic components. Significant advances in laboratory technology are contributing to the further understanding of microfluidic function, surface modification and immobilization, which lead to the development of improved biomolecule detection methods and prospective applications. For the future, the exploitation of more robust-manufacturing processes and integrated assay systems in an automatic fashion with much reduced assay time and reagent consumption will allow for the effective detection and quantification of biological agents that are of interest in medical diagnostics, food safety surveillance, and environmental monitoring.

Surface modification for enhancing antibody binding on polymer-based microfluidic device for enzyme-linked immunosorbent assay.

A novel surface treatment method using poly(ethyleneimine) (PEI), an amine-bearing polymer, was developed to enhance antibody binding on the poly(methyl methacrylate) (PMMA) microfluidic immunoassay device. By treating the PMMA surface of the microchannel on the microfluidic device with PEI, 10 times more active antibodies can be bound to the microchannel surface as compared to those without treatment or treated with the small amine-bearing molecule, hexamethylenediamine (HMD). Consequently, PEI surface modification greatly improved the immunoassay performance of the microfluidic device, making it more sensitive and reliable in the detection of IgG.