An integrated ion-exchange membrane-based microfluidic device for irreversible dissociation and quantification of miRNA from ribonucleoproteins

Accelerating Cleavage Activity of CRISPR-Cas13 System on a Microfluidic Chip for Rapid Detection of RNA

It is extremely advantageous to detect nucleic acid levels in the early phases of disease management; such early detection facilitates timely treatment, and it can prevent altogether certain cancers and infectious diseases. A simple, rapid, and versatile detection platform without enzymatic amplification for both short and long sequences would be highly desirable in this regard. Our study addresses this need by introducing IMACC, an ICP-based Microfluidic Accelerator Combined with CRISPR, for amplification-free nucleic acid detection. It exploits electrokinetically induced ion concentration polarization (ICP) to concentrate target nucleic acids and CRISPR reagents near the depletion zone boundary within a microfluidic channel. This localized accumulation accelerates the CRISPR-guided promiscuous cleavage of reporter molecules while enhancing their fluorescence signals simultaneously. Simultaneous accumulation of RNA and ribonucleoproteins (RNP) in confined spaces was validated experimentally and numerically, showing overlapping regions. IMACC enabled detection of miRNA-21 (22 bp) down to 10 pM within 2 min of ICP. IMACC ensured CRISPR specificity (single mismatch (N = 1) sensitivity) during ICP, as shown by off-target and mismatch sequence experiments. IMACC was applied to long RNA samples (i.e., SARS-CoV-2), but it statistically remained challenging at this point due to nonlinear intensity trends with copy numbers and large deviations. IMACC enabled rapid detection of short RNAs such as microRNAs using only basic CRISPR reagents in a single microfluidic channel, eliminating the need for extra enzymes or buffer sets, streamlining workflow and reducing turnaround time. IMACC has the potential to advance CRISPR diagnostics and holds promise for improved detection and future prescreening applications.

Microfluidic-based redesign of a humidity-driven energy harvester

Integrating microfluidic elements onto a single chip offers many advantages, including miniaturization, portability, and multifunctionality, making such systems highly useful for biomedical, healthcare, and sensing applications. However, these chips need redesigning for compatibility with microfluidic fabrication methods such as photolithography. To address this, we integrated microfluidics technology into our previously developed humidity-driven energy harvester to create a self-powered system and redesigned it so that it could be fabricated using photolithography and printing. The device comprises stacked electrodes, cation-exchange membranes, and microchannels. The multi-element version of the device generated ten times more voltage than the single-element version. Both versions produced stable patterns of voltage output with respect to the fluctuations in humidity in both controlled and real-world environments. Their potential as humidity sensors is supported by the correlations exhibited between humidity and voltage output. The capacity of the device to respond to changes in perspiration-induced changes in humidity suggests its usefulness as a power source for wearable sensors. This novel device element, which can be easily integrated into other microfluidic devices, is expected to provide a new approach to powering microfluidic-based wearable sensors.

Extracellular vesicle and lipoprotein diagnostics (ExoLP-Dx) with membrane sensor: A robust microfluidic platform to overcome heterogeneity

The physiological origins and functions of extracellular vesicles (EVs) and lipoproteins (LPs) propel advancements in precision medicine by offering non-invasive diagnostic and therapeutic prospects for cancers, cardiovascular, and neurodegenerative diseases. However, EV/LP diagnostics (ExoLP-Dx) face considerable challenges. Their intrinsic heterogeneity, spanning biogenesis pathways, surface protein composition, and concentration metrics complicate traditional diagnostic approaches. Commonly used methods such as nanoparticle tracking analysis, enzyme-linked immunosorbent assay, and nuclear magnetic resonance do not provide any information about their proteomic subfractions, including active proteins/enzymes involved in essential pathways/functions. Size constraints limit the efficacy of flow cytometry for small EVs and LPs, while ultracentrifugation isolation is hampered by co-elution with non-target entities. In this perspective, we propose a charge-based electrokinetic membrane sensor, with silica nanoparticle reporters providing salient features, that can overcome the interference, long incubation time, sensitivity, and normalization issues of ExoLP-Dx from raw plasma without needing sample pretreatment/isolation. A universal EV/LP standard curve is obtained despite their heterogeneities.

Recent advances in nano/microfluidics-based cell isolation techniques for cancer diagnosis and treatments

Miniaturization has improved significantly in the recent decade, which has enabled the development of numerous microfluidic systems. Microfluidic technologies have shown great potential for separating desired cells from heterogeneous samples, as they offer benefits such as low sample consumption, easy operation, and high separation accuracy. Microfluidic cell separation approaches can be classified into physical (label-free) and biological (labeled) methods based on their working principles. Each method has remarkable and feasible benefits for the purposes of cancer detection and therapy, as well as the challenges that we have discussed in this article. In this review, we present the recent advances in microfluidic cell sorting techniques that incorporate both physical and biological aspects, with an emphasis on the methods by which the cells are separated. We first introduce and discuss the biological cell sorting techniques, followed by the physical cell sorting techniques. Additionally, we explore the role of microfluidics in drug screening, drug delivery, and lab-on-chip (LOC) therapy. In addition, we discuss the challenges and future prospects of integrated microfluidics for cell sorting.

Bubble nucleation and growth on microstructured surfaces under microgravity

Understanding the dynamics of surface bubble formation and growth on heated surfaces holds significant implications for diverse modern technologies. While such investigations are traditionally confined to terrestrial conditions, the expansion of space exploration and economy necessitates insights into thermal bubble phenomena in microgravity. In this work, we conduct experiments in the International Space Station to study surface bubble nucleation and growth in a microgravity environment and compare the results to those on Earth. Our findings reveal significantly accelerated bubble nucleation and growth rates, outpacing the terrestrial rates by up to ~30 times. Our thermofluidic simulations confirm the role of gravity-induced thermal convective flow, which dissipates heat from the substrate surface and thus influences bubble nucleation. In microgravity, the influence of thermal convective flow diminishes, resulting in localized heat at the substrate surface, which leads to faster temperature rise. This unique condition enables quicker bubble nucleation and growth. Moreover, we highlight the influence of surface microstructure geometries on bubble nucleation. Acting as heat-transfer fins, the geometries of the microstructures influence heat transfer from the substrate to the water. Finer microstructures, which have larger specific surface areas, enhance surface-to-liquid heat transfer and thus reduce the rate of surface temperature rise, leading to slower bubble nucleation. Our experimental and simulation results provide insights into thermal bubble dynamics in microgravity, which may help design thermal management solutions and develop bubble-based sensing technologies.