Micro-Pattern of Graphene Oxide Films Using Metal Bonding

Abstract

Recently, graphene has been explored in several research areas according to its outstanding combination of mechanical and electrical features. The ability to fabricate micro-patterns of graphene facilitates its integration in emerging technologies such as flexible electronics. This work reports a novel micro-pattern approach of graphene oxide (GO) film on a polymer substrate using metal bonding. It is shown that adding ethanol to the GO aqueous dispersion enhances substantially the uniformity of GO thin film deposition, which is a great asset for mass production. On the other hand, the presence of ethanol in the GO solution hinders the fabrication of patterned GO films using the standard lift-off process. To overcome this, the fabrication process provided in this work takes advantage of the chemical adhesion between the GO or reduced GO (rGO) and metal films. It is proved that the adhesion between the metal layer and GO or rGO is stronger than the adhesion between the latter and the polymer substrate (i.e., cyclic olefin copolymer used in this work). This causes the removal of the GO layer underneath the metal film during the lift-off process, leaving behind the desired GO or rGO micro-patterns. The feasibility and suitability of the proposed pattern technique is confirmed by fabricating the patterned electrodes inside a microfluidic device to manipulate living cells using dielectrophoresis. This work adds great value to micro-pattern GO and rGO thin films and has immense potential to achieve high yield production in emerging applications.

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

“…A decrease in water contact angle with an increase in the concentration of GO dispersion was observed. This behavior can be explained by the fact that graphene oxide is rich in oxygen-containing functional groups (see Figure 6 a), which can form hydrogen bonds when in contact with water [ 33 ]. Higher concentrations of GO result in the deposition of a larger amount of GO flakes and an increase in the surface concentration of oxygen-containing functional groups, thereby increasing the hydrophilicity of the coated COC.…”

A Review of Cyclic Olefin Copolymer Applications in Microfluidics and Microdevices

“…A COC-PDMS bonding was demonstrated by Sunkara et al [170] at room temperature by oxygen plasma exposure of both surfaces followed by APTES solution treatment of the PDMS. Using a different silane, Abunahla et al [185] bonded COC to PDMS. After plasma treatment, the PDMS microchannel is placed in a silane solution composed of 6 wt% TMSPMA and 95 vol% ethanol for 1 h. The substrate was then bonded with a reduced GO patterned COC substrate.…”

“…Following exposure, the microchannel swells and its features are defined where it is then bonded with a blank COC and washed in water to remove the ink. [194] Schelcher et al [70] combined thermal and solvent bonding by applying cyclohexane and hexadecane to a COC substrate before bonding it with another COC in a heated Thermal/plasma bonding High Medium Long High [ 153] Solvent bonding High Low Low Low [ 192,194] Solvent/thermal bonding High Low Medium Low-medium [ 70,193] Solvent/plasma bonding High Medium Medium Medium-high [ 106] PDMS-COC bonding method Bonding strength Process complexity Time Cost References Plasma bonding Low Medium Low Medium-high [ 184,186] Plasma/silane bonding Medium-high High Long Medium-high [ 170,177,183,[185][186][187] Solvent/thermal bonding Medium-high Low Medium Low-medium [90] hydraulic press at 110 °C and 600 kPa for 3 min. Table 5 compares the different bonding methods for COC-COC and PDMS-COC devices, and Table 6 summarizes the process for the bonding techniques in this review.…”

“…Various fabrication techniques for thin films on top of flexible COC films have been reported. [185,[217][218][219][220] Alazzam et al [160,[218][219][220] established a method for fabricating thin films of reduced GO (rGO) using plasma-enhanced lift-off, which was then utilized in LOC applications. According to the results, GO adheres effectively to the surface of the COC.…”

“…On-chip Raman detection Nanoimprinting [26] Laser chips Nanoimprinting [ 25,207] Fiber probes Rolling and thermal annealing [ 209,210] Sensing Thermoplastic binders [211][212][213][214] Lab on chip Plasma-enhanced lift-off and metal bonding thermal bonding [ 160,185,[218][219][220]224] Memristors Plasma-enhanced lift-off [221][222][223] Tunable RF filter Plasma-enhanced lift-off [ 217] Porous gold Film Deposition/etching [ 220] Tuning the wettability of COC Plasma-enhanced lift-off [ 161] DNA analysis Print, cut, and laminate (PCL) [ 225] gations focused on the applications of COCs in thermal systems, such as in renewable energy or thermal insulation. Cui et al [226] investigated the performance of solar concentrators made of COC (TOPAS 5013) and compared it with optical silicone MS-1002 and reported that COC and silicone are good choices in replacing the conventional glass material in solar collectors.…”