Droplet Coalescence by Selective Wettability Enhancement in Microfluidic Devices

Alamoodi, Nahla; Alazzam, Anas

doi:10.3390/nano10040737

Cited by 13 publications

(11 citation statements)

References 28 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Due to the presence of oxygen functional groups that form hydrogen bonds, GO is known to have hydrophilic characteristics, resulting in low contact angles [ 22 , 23 ]. By reducing GO to rGO form, the hydrophobicity of the material is increased, hence increasing the contact angle between water droplets and GO surfaces [ 24 ].…”

Section: Resultsmentioning

confidence: 99%

Tunable Switching Behavior of GO-Based Memristors Using Thermal Reduction

et al. 2022

Self Cite

View full text Add to dashboard Cite

This work reports on the fabrication of a novel planar reduced graphene oxide (rGO) memristor (MR) device. For the first time in the literature, the MR tunable resistive switching behavior is controlled by the GO reduction time at a constant temperature. The device is fabricated using standard microfabrication techniques on a flexible cyclic olefin copolymer substrate (COC). Thermal reduction of the GO layer at low temperatures (100 °C) avoids the drawbacks of chemical reduction methods such as toxicity and electrode metal damage during fabrication, while allowing for fine-tuning of the MR’s switching behavior. The device has analog switching characteristics, with a range of different resistance states. By taking advantage of the slow nature of GO thermal annealing, the switching properties of the rGO memristors can be precisely controlled by adjusting the reduction period. At short annealing times (i.e., T < 20 h), the devices switch from high to low resistance states, while at longer annealing times the switching behavior is reversed, with the device switching from low to high resistance states (LRS to HRS). Resistive switching occurs as a result of the diffusion and removal of the oxygen functional groups in the GO film caused by Joule heating induced by the electric current. Complete electrical characterization tests are presented along with wettability and X-ray diffraction (XRD) tests. This work opens a new vision for realizing rGO-based MR devices with tunable switching properties, broadening the application horizon of the device.

show abstract

Section: Resultsmentioning

confidence: 99%

Tunable Switching Behavior of GO-Based Memristors Using Thermal Reduction

et al. 2022

Self Cite

View full text Add to dashboard Cite

show abstract

“…In our recent work [ 3 , 4 , 19 ] we have shown that treating COC with O 2 /Ar plasma followed by spin coating with GO dispersions resulted in stable GO coatings. Here, we investigated whether there is an apparent effect of plasma treatment on the wettability of the COC after the GO deposition.…”

Section: Resultsmentioning

confidence: 99%

“…First, the COC substrate was cleaned using isopropanol and DI. Next, the substrate was treated with an argon/oxygen low pressure inductive plasma (HARRICK PLASMA, Model: Expanded plasma cleaner/PDC-002, Ithaca, NY, USA) for a fixed duration (5, 20, 60 and 120 min) to increase the surface energy of the substrate and enhance the bonding between GO and COC substrate [ 19 ]. Plasma treatment was performed at a pressure of 626 mtorr, gas flowrates of 1–2 scfh, and a maximum power of 29.6 W with radio frequency (RF) of 12 MHz.…”

Section: Methodsmentioning

confidence: 99%

“…Graphene oxide has a high concentration of oxygen-containing functional groups, which can form hydrogen bonds when in contact with water. Recently, Alazzam and Alamoodi [ 4 , 19 ] have proposed a new surface modification method, taking advantage of the hydrophilicity of GO to pattern water wet surfaces on COC. The COC substrates were patterned with graphene oxide by photolithography.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

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

et al. 2021

Self Cite

View full text Add to dashboard Cite

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.

show abstract

“…Scenarios of microscale and nanoscale droplet collision dynamics have been widely investigated by either experiments or numerical simulations. Nahla et al [ 10 ] demonstrated a new approach for droplet coalescence in microfluidic channels based on selective surface energy alteration, which focused on the coalescence process of the micro-nano droplet. Lian et al [ 11 ] experimentally investigated the bouncing dynamics of impact droplets on the superhydrophobic surfaces for shortening contact time, and established the relationship between Weber number and contact time to find the minimum Weber number that formed the pancake-like bouncing behavior.…”

Section: Introductionmentioning

confidence: 99%

A Numerical Investigation on the Collision Behavior of Unequal-Sized Micro-Nano Droplets

et al. 2020

View full text Add to dashboard Cite

Micro-nano droplet collisions are fundamental phenomena in the applications of nanocoating, nano spray, and microfluidics. Detailed investigations of the process of the droplet collisions under higher Weber are still lacking when compared with previous research studies under a low Weber number below 120. Collision dynamics of unequal-sized micro-nano droplets are simulated by a coupled level-set and volume of fluid (CLSVOF) method with adaptive mesh refinement (AMR). The effects of the size ratio (from 0.25 to 0.75) and different initial collision velocities on the head-on collision process of two unequal-sized droplets at We = 210 are studied. Complex droplets will form the filament structure and break up with satellite droplets under higher Weber. The filament structure is easier to disengage from the complex droplet as the size ratio increases. The surface energy converting from kinetic energy increases with the size ratio, which promotes a better spreading effect. When two droplets keep the constant relative velocity, the motion tendency of the droplets after the collision is mainly dominated by the large droplet. On one hand, compared with binary equal-sized droplet collisions, a hole-like structure can be observed more clearly since the initial velocity of a large droplet decreases in the deformation process of binary unequal-sized droplets. On the other hand, the rim spreads outward as the initial velocity of the larger droplet increases, which leads to its thickening.

show abstract

Droplet Coalescence by Selective Wettability Enhancement in Microfluidic Devices

Cited by 13 publications

References 28 publications

Tunable Switching Behavior of GO-Based Memristors Using Thermal Reduction

Tunable Switching Behavior of GO-Based Memristors Using Thermal Reduction

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

A Numerical Investigation on the Collision Behavior of Unequal-Sized Micro-Nano Droplets

Contact Info

Product

Resources

About