Flow and Heat Transfer in Micro and Millifluidic Devices

Dear Colleagues,

Small-scale fluidic devices are currently being applied in multiple fields. Their applications include lab-on-chips, microreactors, heat sinks, ink jet printing, microrheometers for fluids, cell and particle analysis, and organs-on-chips. These devices are portable, minimize reactant consumption and waste production and can be used in flexible, on-demand production of small batches.

Micro- and millidevices have high surface/volume ratio, which enables efficient heat and mass transport. However, the design of these devices still needs to account for heat and mass transport limitations, and solutions to optimize transport phenomena need to be developed. For example, mixing is a limiting factor in lab-on-chips, microreactors and crystallization. Interestingly, solutions, such as acoustic streaming promoted by piezoelectric actuators, have been proposed to enhance mixing and reduce heat and mass transport limitations. Heat transport limitations are a reason for concern in the microprocessor industry, and the development of heat sinks is a hot topic of research. In this context, new nanofluids have been proposed to improve the thermal conductivity of liquids. Boiling in microchannels is a common phenomenon in heat dissipation, and modified surfaces are usually used to improve bubble formation and release. In medicine, new nanoparticles have been proposed for application in cancer thermotherapies.

In a microfluidic device, heating elements, sensors, actuators, micropumps and other elements can be integrated to control, with a high spatial and temporal resolution, the heat and mass flow rates, temperature and solute concentrations. High-precision temperature control, temperature gradients and temperature cycles can be implemented. Reactions can be controlled with high precision, minimizing the production of secondary products and improving the purity of the desired products and selectivity of sensors.

Microdevices present new modeling challenges for the computational fluid dynamics community since phenomena usually negligible at the macroscale become relevant at the microscale level. At the microscale level, matter (particles and fluids) can be manipulated by sound waves, electrical interactions, light, temperature gradients, which opens up new possibilities for new separation processes and manufacturing processes. On the other hand, particles and cells comprise a significant fraction of the channels’ size, and the continuum hypothesis can no longer be applied; therefore, new methods need to be developed to incorporate electrical and acoustic interactions and surface tension effects into the conventional flow, heat and mass transport modeling and simulation. New nanoparticles and phase change materials can be applied in innovative ways to improve heat transport and storage. The complex dynamics of these materials, when suspended in liquids and subject to magnetic and electric fields, represent novel modelling and computational challenges.

In this Special Issue on “Flow and Heat Transfer in Micro and Millifluidic Devices”, we welcome review articles and original research, fundamental or applied, theoretical, numerical or experimental works on microscale flow and heat transport. Topics include, but are not limited to:

• Heat sinks;
• Heat dissipation enhancement of nanofluids;
• Methods to predict nanofluid properties;
• Numerical simulation of flow and heat transport in microdevices;
• Heat transport enhancement by microbubbles and microdroplets;
• Safe devices for reactions involving highly explosive, toxic or flammable reactants;
• Milliscale heat transport applications;
• Phase change materials;
• Thermal devices for biomedical applications;
• Nanoparticles and microparticles for cell level thermotherapies;
• Boiling numerical simulations;
• Thermophoretic transport;
• Thermoregulation modeling;
• Temperature control in PCR devices;
• 3D-printed devices;
• Mixing;
• Microreactors;
• Droplet reactors;
• Crystallization;
• Acoustic streaming;
• Electrowetting;
• Cell and particle transport in microfluidics;
• Inkjet printing;
• Jet 3D printing.

Dr. João Mário Miranda
Dr. Rui A. Lima
Dr. Reinaldo R. Souza
Dr. Soraia F. Neves
Guest Editors

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