PROJECT

Our research group is dedicated towards investigating the underlying physics of microfluidics and microscale transport processes at interfaces. The emphasis is put on fluid/solid interfaces, where we aim to determine the interfacial energy, or wettability.

 

As this energy depends on the microscale geometry of the interface as well as on the balance between adhesive and cohesive forces, it can be used to manipulate the physical regimes associated with micro-scale devices in order to achieve new functionality.

The transport processes under analysis include mass, momentum, energy or entropy and encompass the varied fields of biotechnology, biomedical engineering, chemical engineering, material handling and thermal management of electronic devices/systems.

 

Up to now, significant contributions have been made to the cooling technology of electronic devices/chips where microchannel two-phase flow and surface engineering have been used to control the microstructure and composition of the interface to optimize the rates of heat transfer.

Below, it follows a brief discription of our main activitivies. If any doubts should persist or if you wish to know more about our work, please be sure to contact us with your questions.

KEY ACTIVITIES

Surface Physics and Chemistry


Wettability is a key parameter which affects the processes occurring at fluid-surface interfaces, particularly in microfluidics and in the development of microelectromechanical systems. In this context, a fundamental part of the research activities performed at IN+μTP addresses the systematic modification of the physical and chemical properties of the surfaces to infer on their effect on the flows under investigation. The surfaces are fully characterized, combining optical microscopy, confocal microscopy and optical tensiometry.

Microfluidics and Bio(micro)fluidics

This research area addresses the detailed description of the microscale flow dynamics, with particular emphasis to the adhesion/cohesion phenomena occurring at the fluid/surface interface.  The assays cover different geometries, including the transport of microdroplets and flows in microchannels, both with Newtonian and non-Newtonian fluids. The flow morphology, pressure drop measurements, and velocity profiles are obtained combining various non-intrusive techniques, such as micro-PIV and high-speed visualization. An emergent application for this research area consists in the development of microfluidic devices for clinical diagnostics (lab-on-chip devices).

Heat transfer in phase-change flows

The heat transfer mechanisms in flows with phase change are also strictly dependent on the transport mechanisms occurring at the fluid/solid interfaces. These mechanisms are investigated in pool boiling and in flow boiling for configurations which are relevant for cooling applications at various scales, e.g. for the cooling of high power electronics. The boiling regimes are characterized based on high-speed visualization, being this information complemented with temperature measures obtained with thermocouples and with time-resolved thermography. This research also includes the characterization of spray impingement in confined environments. Optimization of the atomization characteristics, namely in terms of the size and velocity distribution of the droplets, is performed based on Phase-Doppler Interferometry measurements.

Thermodynamics of electromechanical systems

Even though MEMS are today a well-established research field, consisting in the miniaturization of a wide range of large-scale systems, there are substantial differences in the thermodynamic analysis of these systems, when compared to those operating at the macroscale, which are not adequately addressed yet. The significant increase of the surface-to-volume ratio leads to drastic differences on the energy transport and conversion processes occurring at the interfaces. The activities performed here also include other energy conversion micro-systems and cover several design issues, namely the effect of the micro-fabrication techniques on the thermal behavior of the materials and consequences to the MEMS functionality, feasibility and efficiency.

Interfacial plus Micro-scale Transport Phenomena

Center for Innovation, Technology and Policy Research

Instituto Superior Técnico

in3@tecnico.ulisboa.pt | +351 218 417 379