With many emerging applications such as chemical reactions and ultrasound therapy, acoustic cavitation plays a vital role in having improved energy efficiency. For example, acoustic cavitation results in substantial enhancement in the rates of various chemical reactions. In this regard, an applied acoustic field within a medium generates acoustic streaming, where cavitation bubbles appear due to preexisting dissolved gas in the working fluid. Upon cavitation inception, bubbles can undergo subsequent growth and collapse. During the last decade, the studies on the effects of different parameters on acoustic cavitation such as applied ultrasound frequency and power have been conducted. The bubble growth and collapse mechanisms and their distribution within the medium have been classified. Yet, more research is necessary to understand the complex mechanism of multi-bubble behavior under an applied acoustic field. Various parameters affecting acoustic cavitation such as surface roughness of the acoustic generator should be investigated in more detail in this regard. In this study, single bubble lifetime, bubble size and multi-bubble dynamics were investigated by changing the applied ultrasonic field. The effect of surface roughness on bubble dynamics was presented. In the analysis, images from a high-speed camera and fast video recording techniques were used. Numerical simulations were also done to investigate the effect of acoustic field frequency on bubble dynamics. Bubble cluster behavior and required minimum bubble size to be affected by the acoustic field were obtained. Numerical results suggested that bubbles with sizes of 50 µm or more could be aligned according to the radiation potential map, whereas bubbles with sizes smaller than 10 µm were not affected by the acoustic field. Furthermore, it was empirically proven that surface roughness has a significant effect on acoustic cavitation phenomena.

The separation of circulating tumor cells (CTCs) from blood samples is crucial for the early diagnosis of cancer. During recent years, hybrid microfluidics platforms, consisting of both passive and active components, have been an emerging means for the label-free enrichment of circulating tumor cells due to their advantages such as multi-target cell processing with high efficiency and high sensitivity. In this study, spiral microchannels with different dimensions were coupled with surface acoustic waves (SAWs). Numerical simulations were conducted at different Reynolds numbers to analyze the performance of hybrid devices in the sorting and separation of CTCs from red blood cells (RBCs) and white blood cells (WBCs). Overall, in the first stage, the two-loop spiral microchannel structure allowed for the utilization of inertial forces for passive separation. In the second stage, SAWs were introduced to the device. Thus, five nodal pressure lines corresponding to the lateral position of the five outlets were generated. According to their physical properties, the cells were trapped and lined up on the corresponding nodal lines. The results showed that three different cell types (CTCs, RBCs, and WBCs) were successfully focused and collected from the different outlets of the microchannels by implementing the proposed multi-stage hybrid system.

Control channels on microfluidic large-scale integration (mLSI) chips are prone to blockage and leakage defects. In this work, we propose a built-in self-test (BIST) method that drastically improves the test efficiency. Given n to-be-tested control channels, we reduced the number of test patterns for blockage and leakage tests from [EQUATION] to 1, and from ⌈log₂(n + 1)⌉ to ⌈log₂(χ^{(G) + 1)}⌉, respectively, where χ(G) denotes the vertex chromatic number of a graph G consisting of n vertices. We fabricated our design and demonstrated the feasibility and efficiency of our method.

A variety of hollow microneedle (HMN) designs has emerged for minimally invasive therapies and monitoring systems. In this study, a design change limiting the indentation depth of the (3D) printed custom microneedle assembly (circular array of five conical frusta with and without a stopper, aspect ratio = 1.875) fabricated using stereolithography has been experimentally validated and modeled in silico. The micro-indentation profiles generated in confined compression on 1 mm ± 0.073 mm alginate films enabled the generation of a Prony series, where displacement ranged from 100 to 250 µm. These constants were used as intrinsic properties simulating experimental ramp/release profiles. Puncture occurred on two distinct hydrogel formulations at the design depth of 150 µm and indentation rate of 0.1 mm/s characterized by a peak force of 3.5 N (H = 31 kPa) and 8.3 N (H = 36.5 kPa), respectively. Experimental and theoretical alignments for peak force trends were obtained when the printing resolution was simulated. Higher puncture force and uniformity inferred by the stopper was confirmed via microscopy and profilometry. Meanwhile, poroviscoelasticity characterization is required to distinguish mass loss vs. redistribution post-indentation through pycnometry. Results from this paper highlight the feasibility of insertion-depth control within the epidermis thickness for the first time in solid HMN literature.

After decades of development, flow-based microfluidic biochips have become an increasingly attractive platform for biochemical experiments. The fluid transportation and the on-chip device operation are controlled by microvalves, which are driven by external pneumatic controllers. To meet the increasingly complex experimental demands, the number of microvalves has significantly increased, making it necessary to adopt multiplexers (MUXes) for the actuation of microvalves. However, existing MUX designs have limited coding capacities, resulting in area overhead and excessive chip-to-world interface. This paper proposes a novel gate structure for modifying the current MUX architecture, along with a mixed coding strategy that achieves the maximum coding capacity within the modified MUX architecture. Additionally, an efficient synthesis tool for the mixed-coding-based MUXes (LaMUXes) is presented. Experimental results demonstrate that the LaMUX is exceptionally efficient, substantially reducing the usage of pneumatic controllers and microvalves compared to existing MUX designs.