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Non-intrusive load monitoring technology is the key technology to realize smart grid construction. The identification and classification of similar electrical appliances and low-power small-current...

Unstable liquid flow in syringe pump-driven systems due to the low-speed vibration of the step motor is commonly observed as an unfavorable phenomenon, especially when the flow rate is relatively small. Upon the design of a convenient and cost-efficient microfluidic standing air bubble system, this paper studies the physical principles behind the flow stabilization phenomenon of the bubble-based hydraulic capacitors. A bubble-based hydraulic capacitor consists of three parts: tunable microfluidic standing air bubbles in specially designed crevices on the fluidic channel wall, a proximal pneumatic channel, and porous barriers between them. Micro-bubbles formed in the crevices during liquid flow and the volume of the bubble can be actively controlled by the pneumatic pressure changing in the proximal channel. When there is a flowrate fluctuation from the upstream, the flexible air-liquid interface would deform under the pressure variation, which is analogous to the capacitive charging/discharging process. The theoretical model based on Euler law and the microfluidic equivalent circuit was developed to understand the multiphysical phenomenon. Experimental data characterize the liquid flow stabilization performance of the flow stabilizer with multiple key parameters, such as the number and the size of microbubbles. The developed bubble-based hydraulic capacitor could minimize the flow pulses from syringe pumping by 75.3%. Furthermore, a portable system is demonstrated and compared with a commercial pressure-driven flow system. This study can enhance the understanding of the bubble-based hydraulic capacitors that would be beneficial in microfluidic systems where the precise and stable liquid flow is required.

The manipulation of microscale bioentities is desired in many biological and biomedical applications. However, the potential unobservable damage to bioparticles due to rigid contact has always been a source of concern. Herein, a soft-contact acoustic microgripper to handle microparticles to improve the interaction safety is introduced. The system takes advantage of the acoustic-enhanced adhesion of flexible gas-liquid interfaces to capture-release, transport, and rotate the target, such as microbeads (20-65 µm) and zebrafish embryos (from 950 µm to 1.4 mm). The gas-liquid interface generated at the tip of a microcapillary can be precisely controlled by a pneumatic pressure source. The gas-liquid interface oscillation excited by acoustic energy imposes coupled radiation force and drag force on the microparticles, enabling multidimensional movements. Experiments with the microbeads are conducted to evaluate the claimed function and quantify the key parameters that influence the manipulation result. Additionally, 250 zebrafish embryos are captured, transported, and rotated. The hatching rate of the 250 manipulated embryos is approximately 98% similar to that of the nonmanipulated group, which proves the noninvasiveness of the method. The derived theories and experimental data indicate that the developed soft-contact microgripper is functional and beneficial for biological and medical applications.

The syringe pump is widely used in microfluidic systems as a liquid sample handling method. However, the step motors in syringe pumps often produce undamped pulses, resulting in the unstable fluid delivery in micro-channel. In this paper, a novel active flow regulation system has been proposed, which functions as a micro damper. A bubble-based micro-damper consists of three parts: a liquid channel, a gas channel as a control section beside it, and specially designed crevice structures on liquid channel walls. The standing air bubbles originate in these crevice structures, and the size adjustment of the air bubble can be used to realise the alignment of the hydraulic resistance. The presented pneumatic damping method is not only low-cost and practical but can also be used in elastomeric and rigid micro-channels without complex microstructure.

Microbubbles are often used in chemistry, biophysics, and medicine. Properly controlled microbubbles have been proved beneficial for various applications by previous scientific endeavors. However, there is still a plenty of room for further development of efficient microbubble handling methods. Here, this paper introduces a tunable, stable, and robust microbubble interface handling mechanism, named as microfluidic standing air bubbles (μSABs), by studying the multiphysical phenomena behind the gas-liquid interface formation and variation. A basic μSAB system consists specially structured fluidic channels, pneumatic channels, and selectively permeable porous barriers between them. The μSABs originate inside the crevice structures on the fluidic channel walls in a repeatable and robust manner. The volumetric variation of the μSAB is a multiphysical phenomenon that dominated by the air diffusion between the pneumatic channel and the bubble. Theoretical analysis and experimental data illustrate the coupling processes of the repeatable and linear μSAB volumetric variation when operated under common handling conditions (control pneumatic pressure: -90 kPa to 200 kPa). Furthermore, an adjustable acoustic microstreaming is demonstrated as an application using the alterable μSAB gas-liquid interface. Derived equations and microscopic observations elucidate the mechanism of the continuous and linear regulation of the acoustic microstreaming using varying μSAB gas-liquid interfaces. The μSAB system provides a new tool to handle the flexible and controllable gas-liquid interfaces in a repeatable and robust manner, which makes it a promising candidate for innovative biochemical, biophysical, and medical applications.