Thermo-Wetting and Friction Reduction Characterization of Microtextured Superhydrophobic Surfaces

2011 ◽  
Author(s):  
Tae Jin Kim ◽  
Phillip Glass ◽  
Carlos H. Hidrovo
Keyword(s):  
Thermal Management ◽  
Channel Flow ◽  
Liquid Layer ◽  
Microfluidic Channel ◽  
Friction Reduction ◽  
Superhydrophobic Surfaces ◽  
Microfluidic Channels ◽  
Textured Surface ◽  
Flow Measurements ◽  
Gas Layer

Microtextured superhydrophobic surfaces have become ubiquitous in a myriad of engineering applications. These surfaces have shown potential in friction reduction applications and could be poised to make a big impact in thermal management applications. For instance higher heat transfer rate with less pumping power might be achievable through the aid of superhydrophobic surfaces. However, past and current research on superhydrophobic surface has focused mainly on modifying either the chemical component or the roughness factors of such surfaces. The purpose of this paper is to account for the thermal effects of the heated fluid flowing in superhydrophobic microfluidic channels. Herein we characterize the wetting behavior as a function of temperature of microtextured superhydrophobic surfaces, for both active and passive thermal management applications. A series of PDMS microtextured samples were fabricated using micromachining and soft lithography techniques. Flow measurements were performed using the superhydrophobic microfluidic channel. The channel surface roughness was large enough to induce the Cassie-Baxter state, a phenomenon in which a liquid rests on top of a textured surface with a gas layer trapped underneath the liquid layer. This gas layer induces a two-phase flow, and friction reduction can be achieved for the liquid channel flow. With this channel, flow rates were measured by varying the equilibrium temperature of the substrate. The temperature in the constant pressure source was controlled by circulating the water through a water-bath. As the heating reached a certain threshold the curvature of the liquid-gas interface was reversed and dewetting of the penetrated liquid layer was observed. This result suggests that the Cassie state in fluid flow can be prolonged even under increased pressure drops by increasing the temperature in the gas layer.

Stability Analysis of Cassie-Baxter State Under Pressure Driven Flow

2010 ◽  
Author(s):  
Tae Jin Kim ◽  
Carlos H. Hidrovo
Keyword(s):  
Liquid Layer ◽  
Friction Reduction ◽  
Wetting Transition ◽  
Textured Surface ◽  
Microchannel Flow ◽  
Flow Conditions ◽  
Cassie State ◽  
The Stability ◽  
Gas Layer ◽  
Micro Cavity

The Cassie-Baxter state is a phenomenon in which a liquid rests on top of a textured surface with a gas layer trapped underneath the liquid layer. This gas layer introduces an effective shear free boundary that induces slip at the liquid-gas interface, allowing for friction reduction in liquid channel flows. Multiple studies have shown that different surface configurations result in different friction reduction characteristics, and most work is aimed at controlling the roughness factor and its shape in order to achieve an increased slip flow. This paper investigates the effects that different texturing geometries have on the stability of the Cassie state under pressurized microchannel flow conditions. To test the stability effects associated with the pressurized microchannel flow conditions, microfluidic channels with microstructures on the side walls were designed and fabricated. The microstructures were designed to induce the Cassie state with a liquid-air interface forming between the texturing trenches. The air trapped within the microstructure is treated as an ideal gas, with the compressibility induced pressure rise acting as a restrictive force against the Wenzel wetting transition. The model was validated against experimental flow data obtained using microchannel samples with microtextured boundaries. The microchannels were fabricated in PDMS (poly-dimethylsiloxane) using soft lithography and were baked on a hot plate to ensure the hydrophobicity of the microtexture. Pressure versus flow rate data was obtained using a constant gravitational pressure head setup and a flow meter. The liquid-gas interface layer in the microchannel was visualized using bright field microscopy that allowed measurement of the liquid penetration depth into the microtexturing throughout the microhannel. The experimental results indicate that air trapped in the pockets created by micro-cavity structures prevented the liquid layer from completely filling the void. As expected, the pressure drop in the micro-cavity textured channel showed a considerable decrease compared to that in the flat surfaced channel. These results also suggest that micro-cavities can maintain the Cassie state of a liquid meniscus, resting on top of the surface, in larger pressure ranges than open spaced micro-pillars arrays.

Thermo-Wetting and Friction Reduction Characterization of Microtextured Superhydrophobic Surfaces

2012 ◽  
Vol 134 (11) ◽  
Author(s):  
Tae Jin Kim ◽  
Ravitej Kanapuram ◽  
Arnav Chhabra ◽  
Carlos Hidrovo
Keyword(s):  
Thermal Effects ◽  
Elevated Pressure ◽  
Friction Reduction ◽  
Superhydrophobic Surfaces ◽  
Microfluidic Channels ◽  
Pressure Drops ◽  
Cassie State ◽  
Heated Fluid ◽  
Gas Layer

Microtextured superhydrophobic surfaces have shown potential in friction reduction applications and could be poised to make a significant impact in thermal management applications. The purpose of this paper is to account for the thermal effects of the heated fluid flowing in superhydrophobic microfluidic channels. Through microscopic observation and flow rate measurements it was observed that (1) heating may prolong the Cassie state even under elevated pressure drops by increasing the temperature in the gas layer and that (2) excessive heating may pinch the microchannel flow due to the air layer invading into the liquid layer.

scholarly journals Design Methodology of Passive In-Line Relays for Molecular Communication in Flow-Induced Microfluidic Channel

Biosensors ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 65
Author(s):  
Puneet Manocha ◽  
Gitanjali Chandwani
Keyword(s):  
Communication System ◽  
Communication Systems ◽  
Microfluidic Channel ◽  
Microfluidic Channels ◽  
Molecular Communication ◽  
External Energy ◽  
Lab On Chip ◽  
Molecular Communication Systems ◽  
Macro Scale ◽  
On Chip

Molecular communication is a bioinspired communication that enables macro-scale, micro-scale and nano-scale devices to communicate with each other. The molecular communication system is prone to severe signal attenuation, dispersion and delay, which leads to performance degradation as the distance between two communicating devices increases. To mitigate these challenges, relays are used to establish reliable communication in microfluidic channels. Relay assisted molecular communication systems can also enable interconnection among various entities of the lab-on-chip for sharing information. Various relaying schemes have been proposed for reliable molecular communication systems, most of which lack practical feasibility. Thus, it is essential to design and develop relays that can be practically incorporated into the microfluidic channel. This paper presents a novel design of passive in-line relay for molecular communication system that can be easily embedded in the microfluidic channel and operate without external energy. Results show that geometric modification in the microfluidic channel can act as a relay and restore the degraded signal up-to 28%.

scholarly journals Three-dimensional particle tracking in microfluidic channel flow using in and out of focus diffraction

2015 ◽  
Vol 45 ◽  
pp. 218-224 ◽  
Author(s):  
Bushra Tasadduq ◽  
Gonghao Wang ◽  
Mohamed El Banani ◽  
Wenbin Mao ◽  
Wilbur Lam ◽  
...  
Keyword(s):  
Channel Flow ◽  
Particle Tracking ◽  
Three Dimensional ◽  
Microfluidic Channel

Skin friction reduction by large air bubbles in a horizontal channel flow

2007 ◽  
Vol 33 (2) ◽  
pp. 147-163 ◽  
Author(s):  
Yuichi Murai ◽  
Hiroshi Fukuda ◽  
Yoshihiko Oishi ◽  
Yoshiaki Kodama ◽  
Fujio Yamamoto
Keyword(s):  
Skin Friction ◽  
Channel Flow ◽  
Friction Reduction ◽  
Horizontal Channel ◽  
Air Bubbles ◽  
Skin Friction Reduction

Implementation of Wafer Level Packaging KOZ using SU-8 as Dielectric for the Merging of WL Fan Out to Microfluidic and Biomedical Applications

2017 ◽  
Vol 2017 (1) ◽  
pp. 000569-000575 ◽  
Author(s):  
André Cardoso ◽  
Raquel Pinto ◽  
Elisabete Fernandes ◽  
Steffen Kroehnert
Keyword(s):  
Biomedical Applications ◽  
Microfluidic Channel ◽  
Cost Effective ◽  
Curing Temperature ◽  
Microfluidic Channels ◽  
Wafer Level ◽  
Thermal Budget ◽  
Chip Area ◽  
Wide Range ◽  
Low Thermal Budget

Abstract Due to its versatility for high density, heterogeneous integration, Wafer Level Fan Out (WLFO) packaging has recently seen a tremendous growth in a broad array of applications, from telecommunications and automotive, to optical and environmental sensing, while addressing the challenges of the next big wave of the Internet of Things (IoT). In this context, WLFO is continuously being challenged to include new families of MEMS/NEMS/MOEMS sensors, low thermal budget devices and biochips with microfluidics for biomedical applications. Recent developments in WLFO technology by NANIUM [1] demonstrated the implementation of a keep-out-zone (KOZ) mechanism intended to 1st) protect sensitive sensor areas during the backend processing of WLFO wafers and 2nd) create open zones on the Re-Distribution Layers (RDL). This way, the KOZ mechanism provides a physical, direct path from the embedded device to the environment. This is a necessary feature for environment sensing (e.g., pressure) or to create optical paths free of dielectric and protected from the harsh chemistry steps of the WLFO process. This paper describes new developments on KOZ, implemented with SU-8 photoresist as a WLFO dielectric, whose application is a novelty in the WLFO platform. The use of SU-8 and the KOZ with it, addresses some gaps of the current WLFO technology towards the integration of chips with bio-sensitive areas and sensors with low thermal budget. Due to its well-known bio-compatibility and inert behavior, SU-8 can be used as a neutral dielectric to be in direct contact to target fluids (e.g., sera, blood). Also, due to its low curing temperature, SU-8 allows a very low temperature WLFO process and thus the embedding of temperature-limited devices that have been outside the WLFO realm, for example, magneto-resistive or magnetic-spin sensor chips, which degrades its performance above 160°C. More interestingly, SU-8 exhibits a particular non-conformal behavior, which creates very smooth surfaces even over the mildly rough mold compound area of a fan-out package. Adding to this, SU-8 is readily available in the market in a wide range of thicknesses, spanning from 0.5 μm to >100 μm, and further allowing multiple spin coatings to build thick layers. Thus, SU-8 can provide smooth and deep enough channels for microfluidic flow over the chip sensing areas and, at the same time, provide the necessary layer thickness discrimination for the KOZ mechanism. Combining these features, the SU-8 layers in WLFO can play the triple role of 1) RDL dielectric insulation, 2) KOZ mechanism and 3) embedded microfluidic channels as part of the RDL. In summary, besides the unprecedented use of SU-8 in WLFO packaging, KOZ implementation on SU-8 provides a true, attainable bridge between WLFO and integrated microfluidic applications, for biosensing and biomedical applications in general. Outlooking the potentialities of such a merge, a Fan-Out package can embed several chips interconnected by RDL lines, as it currently allows, and also connected by microfluidic channel for multi-point, multi-function biosensing, constituting a true Lab-on-Package, cost-effective solution. Instead of building all sensing areas and microfluidic channels over a large silicon (Si) chip, this solution builds the feed-in, feed-out areas of the microfluidic channel over the inexpensive fan-out area, minimizing the sensing chip area, with the consequent front-end cost reduction.

Detection of Directivity of Fluorescence From a Mixed Specimen Which Consists of Micro Particles Attached Different Fluorescent Substances Using a Light Waveguide Incorporated Optical TAS

2018 ◽  
Author(s):  
Toshifumi Ohkubo ◽  
Nobuyuki Terada ◽  
Yoshikazu Yoshida
Keyword(s):  
Microfluidic Channel ◽  
Laser Source ◽  
Microfluidic Channels ◽  
Fluorescent Substance ◽  
Total Analysis System ◽  
Micro Particles ◽  
Total Analysis ◽  
Light Waveguide ◽  
Analysis System ◽  
Near Future

A resin-based optical total analysis system (O-TAS) which consists both of microfluidic channels and light waveguides [1] is thought to be one of the most promising components in developing a “ubiquitous human healthcare system” in the near future. Along with this technology trend, we have already developed a transparent epoxy-resin-based optical TAS chip which has a specially prepared light waveguide structure of radially arranged configuration at an intersection portion with a microfluidic channel, in order to detect directivity of fluorescence from fluorescent substance attached micro particles [2],[3]. Schematic diagram of the optical TAS is shown in Figure 1. In the latest research, utilizing an AC modulated laser source and time-series averaging function on detected signal waveforms, we could have successfully obtained directivities of fluorescence from 5-μm-diameter particles with higher signal to noise (S/N) ratio [3].

scholarly journals Integration of Paper Based Electro-Osmotic Pumps to Continuous Microfluidic Channels

Proceedings ◽  
2018 ◽  
Vol 2 (13) ◽  
pp. 870
Author(s):  
Kerem Kaya ◽  
Ahmet Yasin Celik ◽  
Senol Mutlu
Keyword(s):  
Membrane Filter ◽  
Average Pore Size ◽  
Microfluidic Channel ◽  
Volumetric Flow Rate ◽  
Integrated System ◽  
Microfluidic Channels ◽  
Average Pore ◽  
Adhesive Film ◽  
Osmotic Pumps ◽  
Paper Fabrication

This work reports for the first-time integration of continuous microfluidic channels to the paper-based electro-osmotic pumps (EOPs) with liquid bridges. In addition, 0.2 μm pore sized cellulose acetate (CA) membrane filter is used to eliminate pressure-driven flow instead of filter paper which is common in paper microfluidics and has an average pore size of 10 μm. A factor of 57 increase in hydraulic resistance is achieved with the new paper. Fabrication of the pumps and microfluidic channels using paper, wax, adhesive film and PMMA plates is explained. Volumetric flow rate of 19 nL/min is achieved in the microfluidic system with 61 V/cm electrical field magnitude applied to DI water. The capability of the integrated system is shown with precise liquid motion in a Y-shaped microfluidic channel integrated with two EOPs.

Sign in / Sign up

Export Citation Format

Share Document