Micro-Pattern of Graphene Oxide Films Using Metal Bonding

Enhanced Graphene Oxide Electrical Properties for Thin-Film Electronics Using an Active/Shrinkable Substrate

The advances in material science along with the development of fabrication techniques have enabled the realization of thin-film-based electronics on active substrates. This has substantially enhanced and supported the deployment of electronic devices in several emerging applications with flexible functionality. In this work, we report a novel fabrication of graphene oxide (GO)-based memristor devices on an active/shrinkable substrate. The standard lithography process is used to fabricate planar Au-rGO-Au devices on a polymer substrate that has the ability to shrink at a certain temperature (i.e., 170 °C). Upon heating, the devices are shrunk to 50% of their original size. A detailed electrical characterization has been carried out to study the switching behavior of the fabricated devices before and after shrinking. The results prove that upon shrinking, the device preserves its switching ability with enhanced electrical parameters (i.e., switching voltage). Also, material characterization performed for the deposited GO on the active substrate shows improved properties of the GO film due to the enhanced arrangement of GO flakes after shrinking. The novel approach proposed in this work provides new insights into and offers the ability to scale thin-film electronics postfabrication and thus overcome some of the device scaling challenges due to manufacturing limitations. It also unfolds a new path for the realization of GO-based electronic devices with improved electrical properties, which is a crucial aspect of the development of highly flexible and lightweight green electronics.

Micropatterning of cells via adjusting surface wettability using plasma treatment and graphene oxide deposition

The wettability of a polymer surface plays a critical role in cell-cell interaction and behavior. The degree to which a surface is hydrophobic or hydrophilic affects the adhesion and behavior of cells. Two distinct techniques for patterning the surface wettability of a Cyclic Olefin Copolymer (COC) substrate were developed and investigated in this article for the purpose of patterning cell growth. These include oxygen plasma treatment and graphene oxide (GO) coating to alter the wettability of the COC substrate and create hydrophilic patterned regions on a hydrophobic surface. When the two techniques are compared, patterning the surface of COC using GO film results in a more stable wettability over time and increases the roughness of the patterned area. Interestingly, both developed techniques were effective at patterning the COC surface’s wettability, which modulated cell adhesion and resulted in micropatterning of cell growth. The novel methods described herein can be used in the fields of cell and tissue culture as well as in the development of new biological assays.

Tuning the Surface Wettability of Cyclic Olefin Copolymer by Plasma Treatment and Graphene Oxide Deposition and Reduction

Selective altering of surface wettability in microfluidic channels provides a suitable platform for a large range of processes, such as the phase separation of multiphase systems, synthesis of reaction controlled, nanoliter sized droplet reactors, and catalyst impregnation. Herein we study the feasibility to tune the wettability of a flexible cyclic olefin copolymer (COC). Two methods were considered for enhancing the surface hydrophilicity. The first is argon/oxygen plasma treatment, where the effect of treatment duration on water contact angle and COC surface morphology and chemistry were investigated, and the second is coating COC with GO dispersions of different concentrations. For enhancing the hydrophobicity of GO-coated COC surfaces, three reduction methods were considered: chemical reduction by Hydroiodic acid (HI), thermal reduction, and photo reduction by exposure of GO-coated COC to UV light. The results show that as the GO concentration and plasma treatment duration increased, a significant decrease in contact angle was observed, which confirmed the ability to enhance the wettability of the COC surface. The increase in hydrophilicity during plasma treatment was associated with the increase in surface roughness on the treated surfaces, while the increase during GO coating was associated with introducing oxygen-containing groups on the GO-coated COC surfaces. The results also show that the different reduction methods considered can increase the contact angle and improve the hydrophobicity of a GO-coated COC surface. It was found that the significant improvement in hydrophobicity was related to the reduction of oxygen-containing groups on the GO-coated COC modified surface.

Dielectrophoresis-field flow fractionation for separation of particles: A critical review

Dielectrophoresis-field flow fractionation (DEP-FFF) has emerged as an efficient in-vitro, non-invasive, and label-free mechanism to manipulate a variety of nano- and micro-scaled particles in a continuous-flow manner. The technique is mainly used to fractionate particles/cells based on differences in their sizes and/or dielectric properties by employing dielectrophoretic force as an external force field applied perpendicular to the flow direction. The dielectrophoretic force is the result of a spatially non-uniform electric field in the microchannel that can be generated either by exploiting microchannel geometry or using special arrangements of microelectrode arrays. Several two-dimensional (e.g., coplanar interdigitated, castellated) and three-dimensional (e.g., top-bottom, side-wall) microelectrode designs have been successfully utilized to perform fractionation of heterogeneous samples. Although originally introduced as a separation technique, DEP-FFF has attracted increasing interest in performing other important operations such as switching, focusing, dipping, and surface functionalization of target particles. Nonetheless, the technique still suffers from limitations such as low throughput and joule heating. By comparatively analyzing recent developments that address these shortcomings, this work is a step forward towards realizing the full potential of DEP-FFF as an ideal candidate for point-of-care (POC) devices with diverse applications in the fields of biomedical, chemical, and environmental engineering.