1. Piezoelectric Actuators for Sensing
TIAN Lab explores innovative methods for enhancing mass transfer and mixing within small-scale systems, particularly sessile droplets and microfluidic devices, to improve performance in electrochemical sensing and other applications. One approach utilizes vibrating air bubbles to generate streaming flows, leading to a twelvefold increase in mass transfer rates for electrochemical sensors. Another technique involves vibration of sessile droplets to induce internal flows, achieving fivefold improvements in mass transfer rates and significantly enhancing the sensitivity of heavy metal ion and protein detection. A third method employs substrate oscillation to drive internal vortices within sessile droplets, enabling complete mixing in as little as 1.35 seconds and achieving a sevenfold enhancement in mass transfer rates. Together, these methods demonstrate significant potential for improving the efficiency and accuracy of sensing, mixing, and reaction processes in microfluidic and electrochemical systems.
These studies collectively advance the field of microfluidics by offering scalable, cost-effective, and versatile solutions for enhancing mass transfer and mixing in small volumes. The vibrating bubble technique provides a contact-free and energy-efficient method applicable to a wide range of electrochemical sensing scenarios. The sessile droplet approaches, leveraging either direct vibration or substrate oscillation, are to address the challenges of slow molecular diffusion and poor mixing in droplet-based systems. These advancements have broad implications for applications to biosensing, environmental monitoring, and chemical synthesis, offering improved sensitivity, reduced reaction times, and simplified device integration, thereby paving the way for next-generation lab-on-a-chip technologies.
2. Piezoelectric Actuators for Electronics Cooling
TIAN Lab studied an active heat sink system employing piezoelectric translational agitators, piezoelectric synthetic jets, and micro pin fins was introduced, and its thermal performance was experimentally validated. Increasing heat dissipation of modern power electronics drives continuous development of a variety of passive and active cooling technologies using air, water, and other non-conductive liquids, as coolants. Liquid cooling, such as single-phase, direct spray, microchannel geometries, and boiling heat transfer, can provide substantial cooling capability. However, liquid cooling adds considerable cost, weight, volume, and complexity to complete an entire cooling loop, such as pumps, pipes, hoses, reservoirs, nozzles, and orifices. Reliability is another issue as leakage, condensation, and corrosion can cause critical failures to electronics. On the other hand, air possesses many advantages over liquid cooling due to its inherent characteristics. Though cooling with air-using traditional methods is less effective than liquid cooling, there is still strong motivation for further advancing air cooling to maximize its capacity. Without moving to liquid cooling, one can consider incorporating active and passive cooling components into a blower-driven heat sink system. Effective active components disturb thermal boundary layers to enhance surface heat transfer beyond those in simple channel flows. An oval loop shell coupled with a piezoelectric stack actuator was used to drive translational agitators and synthetic jets, resulting in a significant reduction of thermal resistance with much lower fan power. These results indicate that the active heat sink is a more efficient method than the traditional fan-assisted system.
3. Demonstration