基礎講座 電気泳動(Electrophoresis)

A hydrogel-dielectric-elastomer system, polyacrylamide and poly(dimethylsiloxane) (PDMS), is adapted for extrusion printing for integrated device fabrication. A lithium-chloride-containing hydrogel printing ink is developed and printed onto treated PDMS with no visible signs of delamination and geometrically scaling resistance under moderate uniaxial tension and fatigue. A variety of designs are demonstrated, including a resistive strain gauge and an ionic cable.

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3D Printing of Transparent and Conductive Heterogeneous Hydrogel-Elastomer Systems.

Organs-on-chips (OoCs), also known as microphysiological systems or ‘tissue chips’ (the terms are synonymous), have attracted substantial interest in recent years owing to their potential to be informative at multiple stages of the drug discovery and development process. These innovative devices could provide insights into normal human organ function and disease pathophysiology, as well as more accurately predict the safety and efficacy of investigational drugs in humans. Therefore, they are likely to become useful additions to traditional preclinical cell culture methods and in vivo animal studies in the near term, and in some cases replacements for them in the longer term. In the past decade, the OoC field has seen dramatic advances in the sophistication of biology and engineering, in the demonstration of physiological relevance and in the range of applications. These advances have also revealed new challenges and opportunities, and expertise from multiple biomedical and engineering fields will be needed to fully realize the promise of OoCs for fundamental and translational applications. This Review provides a snapshot of this fast-evolving technology, discusses current applications and caveats for their implementation, and offers suggestions for directions in the next decade. Organs-on-chips (OoCs) could be useful at various stages of drug discovery and development, providing insight regarding human organ physiology in both normal and disease contexts, as well as accurately predicting developmental drug safety and efficacy. This Review discusses the advances that have enabled OoCs to demonstrate physiological relevance, and the challenges and opportunities that need to be tackled to tap the full potential of OoC utility for translational research.

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Organs-on-chips: into the next decade

Micro-magnetofluidics refers to the science and technology that combines magnetism with microfluidics to gain new functionalities. Magnetism has been used for actuation, manipulation and detection in microfluidics. In turn, microfluidic phenomena can be used for making tunable magnetic devices. This paper presents a systematic review on the interactions between magnetism and fluid flow on the microscale. The review rather focuses on physical and engineering aspects of micro-magnetofluidics, than on the biological applications which have been addressed in a number of previous excellent reviews. The field of micro-magnetofluidics can be categorized according to the type of the working fluids and the associated microscale phenomena of established research fields such as magnetohydrodynamics, ferrohydrodynamics, magnetorheology and magnetophoresis. Furthermore, similar to microfluidics the field can also be categorized as continuous and digital micro-magnetofluidics. Starting with the analysis of possible magnetic forces in microscale and the impact of miniaturization on these forces, the paper revisits the use of magnetism for controlling fluidic functions such as pumping, mixing, magnetowetting as well as magnetic manipulation of particles. Based on the observations made with the state of the art of the field micro-magnetofluidics, the paper presents some perspectives on the possible future development of this field. While the use of magnetism in microfluidics is relatively established, possible new phenomena and applications can be explored by utilizing flow of magnetic and electrically conducting fluids.

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Micro magnetofluidics : interactions between magnetism and fluid flow on the microscale

Here, we report the creation of highly adhesive transparent and stretchable coatings via spray-deposition of solution-based silver nanowires (AgNWs). The AgNW dispersion was spray-deposited on a polydopamine-modified stretchable elastomeric substrate to prepare thin, stretchable, transparent, highly conductive films. The polydopamine layer on the elastomeric substrate created a highly hydrophilic surface, which facilitated the subsequent spraying of the AgNW solution. Additionally, the spray-deposited AgNWs demonstrated excellent adhesion to the substrate, which allowed the fabrication of stretchable electrodes with high conductivity. The AgNW-coated elastomeric substrate exhibited ∼80% transmittance with an average sheet resistance of ∼35 Ω/□, making it suitable for transparent electrode applications. The conductivity of the transparent electrode was maintained up to ∼20% mechanical elongation, which demonstrated the stretchable characteristics of the AgNW-coated elastomeric substrate.

Reversibly stretchable transparent conductive coatings of spray-deposited silver nanowires.

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.

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Oxygen plasma treatment for reducing hydrophobicity of a sealed polydimethylsiloxane microchannel

Motion of a droplet on a planar surface has applications in droplet-based lab on a chip technology. This paper reports the experimental results of the shape, contact angles, and motion of ferrofluid droplets driven by a permanent magnet on a planar homogeneous surface. The water-based ferrofluid in use is a colloidal suspension of single-domain magnetic nanoparticles. The effect of the magnetic field on the apparent contact angle of the ferrofluid droplet was first investigated. The results show that an increasing magnetic flux decreases the apparent contact angle of a sessile ferrofluid droplet. Next, the dynamic contact angle was investigated by observing the shape and the motion of a sessile ferrofluid droplet. The advancing and receding contact angles of the moving ferrofluid were measured at different moving speeds and magnetic field strengths. The measured contact angles were used to estimate the magnitude of the forces involved in the sliding motion. Scaling analysis was carried out to derive the critical velocity, beyond which the droplet is not able to catch up with the moving magnet.

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Yong Chin Chua

Papers

Oxygen plasma treatment for reducing hydrophobicity of a sealed polydimethylsiloxane microchannel

Magnetowetting and Sliding Motion of a Sessile Ferrofluid Droplet in the Presence of a Permanent Magnet