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Chladni patterns based on nanomechanics in the microfluidic environment are presented. In contrast with the macroscopic observations in the gaseous environment, nanoparticles are found to move to the nodes, whereas micron-sized particles move to the antinodes of the vibrating interface. This opens the door to size-based sorting of particles in microfluidic systems, and to highly parallel and controlled assembly of biosensors and nanoelectronic circuits.

Piezoelectric fans have emerged as a viable cooling technology for the thermal management of electronic devices, owing to their low power consumption, minimal noise emission, and small and configurable dimensions.Piezoelectric fans are investigated for application in the cooling of low-power electronics. Different experimental configurations are considered, and the effect of varying the fan amplitude, the distance between the fan and the heat source, the fan length, its frequency offset from resonance, and the fan offset from the center of the heat source are studied to assess the cooling potential of the fans. A Design-Of-Experiments (DOE) analysis revealed the fan frequency offset from resonance and the fan amplitude as the critical parameters. Transfer functions are obtained from the DOE analysis for the implementation of these fans in electronics cooling. For the best case, an enhancement in convective heat transfer coefficient exceeding 375% relative to natural convection was observed, resulting in a temperature drop at the heat source of more than 36.4°C. A computational model for the flow field and heat transfer induced by the piezoelectric fan is also developed. Effects of the flow on convection heat transfer for different fan-to-heat source distances and boundary conditions are analyzed. Transition between distinct convection patterns is observed with changes in the parameters. The computational results are validated against experimental measurements, with good agreement.

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Miniaturized resonating slender beams are finding increased applications as fluidic actuators for portable electronics cooling. Piezoelectric and ultrasonic "fans" drive a flexural mode of the beam into resonance thus inducing a streaming flow, which can be used to cool microelectronic components. This paper presents analytical, computational, and experimental investigations of the incompressible two-dimensional streaming flows induced by resonating thin beams. Closed-form analytical streaming solutions are presented first for an infinite beam. These are used to motivate a computational scheme to predict the streaming flows from a baffled piezoelectric fan. Experiments are conducted to visualize the asymmetric streaming flows from a baffled piezoelectric fan and the experimental results are found to be in close agreement with the predicted results. The findings are expected to be of relevance in the optimal design and positioning of these solid-state devices in cooling applications.

The cooling performance of piezoelectric actuators is evaluated for low-form-factor electronics in this work. A piezoelectric actuator is a cantilever made from metal or plastic with a piezoelectric material bonded to it. Under an alternating electrical current, the piezo actuator oscillates back and forth, generating airflow. Compared to conventional fans, these actuators have the advantages of low power consumption, low noise, and smaller dimensions. The parameters investigated in the experiments are actuator orientation, actuator-to-heat source distance, and actuator amplitude. For an actuator power consumption of 31 mW, the heat source temperature was lowered by more than 25°C compared to natural convection conditions (for a 2.45 W heater power dissipation). Performance comparisons against axial fans and natural convection heat sinks show that the piezo actuators perform significantly better in terms of power consumption and cooling volume.   This paper was also originally published as part of the Proceedings of the ASME 2005 Heat Transfer Summer Conference.

A stainless steel direct liquid contact microchannel cold plate is investigated for the thermal management of bare die packages.Experiments are conducted for a prototype microchannel cold plate in contact with a 1.18cm 2 uniformly heated thermal test vehicle. The junction-to-fluid thermal resistance is measured to be 0.21 C/W for a water flow rate of 1 L/min thru the cold plate. Dynamic thermal characterization of the microchannel cooling solution has also been conducted and compared against static models to predict temperature response fro m a d ynamic po wer profile .