Miniaturized biological assays using microfluidics have the potential to enhance assay sensitivity, reduce reagent consumption, and increase throughput. However, challenges to miniaturization include increased platform complexity and increased surface to volume ratios leading to risk of evaporation and analyte loss through surface binding. Exclusive Liquid Repellency (ELR) enables open microfluidic systems that minimize these challenges through an oil phase that protects small aqueous volumes from temperature fluctuation and evaporation while eliminating surface fouling that leads to sample loss. Here we report a novel microfluidic platform leveraging ELR and Exclusion-based Sample Preparation (ESP) for the miniaturization of CUT&Tag, a complex multistep biological assay. The resultant Lossless Altered Histone Modification Analysis System (LAHMAS) employs a PDMS-silane treated glass surface immersed in silicone oil to facilitate lossless liquid handling and prevent sample evaporation. The device design, compatible with standard laboratory equipment, allows effective processing of cell inputs as low as 100 cells with higher specificity than macroscale CUT&Tag facilitating accurate chromatin profiling of low input and rare cell samples.

Improving food safety is crucial in the context of a "One Health" approach. To guarantee product quality and safety, the food industry, which has a very high turnover rate, needs short time-to-result analyses. Therefore, user-friendly systems at the point-of-need are necessary, presenting relevant analytical information and fulfilling the current regulations. To answer these challenges, a microfluidic platform integrating sample preparation and subsequent multiplex qPCR detection has been developed for on-site testing. The system consists of a fully automated instrument driving a microfluidic cartridge dedicated to the detection of multiple allergens in complex food matrices. The first part of the microfluidic cartridge contains pumps, reservoirs, valves and a filter to achieve DNA extraction, concentration and purification. Multiplex qPCR detection is carried out in the second part of the cartridge including a negative control chamber and five chambers for target analyte detection. The in-house developed instrument contains all functions to autonomously drive the microfluidic cartridge: pneumatic control for fluid actuation, thermal control for qPCR amplification and an optical system using three fluorescent wavelengths for multiplex detection of the target analytes and controls. We demonstrate the simultaneous detection of four different allergens - gluten, sesame, soy and hazelnut - from various complex food matrices. The turn-around-time from sample to result is close to two hours and controls in place validate the obtained results. For gluten, a direct comparison with ELISA shows that the regulatory threshold of 20 ppm is comfortably fulfilled. Moreover, all results are in agreement with external laboratory analyses performed in parallel on the same samples. Our findings confirm that the system can be used safely on-site without the risk of cross contamination between the various samples being analysed. In conclusion, our microfluidic platform offers a robust method for on-site allergen management.

The design, fabrication, simulation, and experimental characterization of a microfabricated, fluidically-driven microturbine mixer are presented. The mixer was engineered to achieve rapid mixing (<1 ms), enabling control over kinetically-limited chemical reactions. The microturbine is microfabricated in silicon using a sequence of photolithographic patterning and deep reactive ion etching (DRIE) steps. The device features two fluidic inlets, each supplying chemical reagents, that drive a microturbine through momentum transfer, generating shear forces within the reaction chamber to induce mixing. By systematically varying the flow rates of the reagents, the rotational velocities of the microturbine were experimentally and computationally determined. Mixing profiles were analyzed using fluorescence colocalization, an established biological imaging technique that was adopted for this application. Characterization results were leveraged to optimize the synthesis of ultra-small, monodisperse silver nanoparticles (AgNPs), i.e. particles of 1 nm to 3 nm in diameter. These nanoparticles have very large surface-to-volume ratios, making them ideal candidates for applications in catalysis, sensing, and antimicrobial agents. The microturbine mixer provides a scalable and reproducible method for the production of ultra-small AgNPs through precise control of mixing conditions, overcoming challenges associated with traditional synthesis routes that struggle to attain size control, size distribution and reproducibility.

There is a growing demand for reliable, efficient, and easily integrated micropumps for microfluidics. Despite the demonstrated potential of acoustic wave-driven devices for on-chip pumping, current prototypes lack the practicality and integratability for deployment in microfluidic systems. This study presents an acoustic micropump based on the resonance of arrays of on-substrate sharp-edge micropillars prepared in a fluid-filled channel and driven by a piston ultrasonic transducer. At an operating frequency of 80.5 kHz and a driving voltage of 54 Vp-p, a flow rate of 16.2 μL min-1 is achieved in a downstream straight channel with dimensions 12(L) × 0.6(W) × 0.2(H) mm3. The corresponding pumping pressure exceeds 1.3 kPa, more than an order of magnitude higher than its predecessors. In experimental demonstrations, two micropumps are employed as feeding units for an acoustofluidic particle separation device based on tilted-angle standing surface acoustic waves (TaSSAWs). The current micropump exhibits advantages of high pumping pressure, fast response time, and high reliability, making it a promising pumping unit for lab-on-a-chip systems.

Owing to the high carbon emissions associated with the production of Portland cement clinker and its use in concrete, the construction industry is interested in the development of more sustainable materials and processes. One area of research is on the curing of cements through carbonation rather than hydration in order to offset emissions by sequestering CO2 in the built environment. Here, we present a simple 3D-printed gas-flow microreactor to facilitate rapid studies of the carbonation curing of millimeter-thin cement samples (also known as carbon curing or CO2 curing). The device is paired with a gas and humidity control system to deliver precise environmental conditions. It can be coupled with various analytical techniques, including X-ray diffraction and Raman spectroscopy, thus allowing in situ monitoring of carbonation processes. We validate and characterize the carbonation system and measurement sensitivity and subsequently utilize the microreactor to investigate a large parameter space in the carbonation curing of a hydrated lime model system. Finally, we demonstrate the potential industrial utility of the device by following the carbonation curing of ordinary Portland cement (OPC) paste.

Acoustic waves provide an effective method for object manipulation in microfluidics, often requiring high-frequency ultrasound in the megahertz range when directly handling microsized objects, which can be costly. Micro-air-bubbles in water offer a solution toward low-cost technologies using low-frequency acoustic waves. Owing to their high compressibility and low elastic modulus, these bubbles can exhibit significant expansion and contraction in response to even kilohertz acoustic waves, leading to resonances with frequencies determined and tuned by air-bubble size. The resonances amplify vibrational amplitude and generate localized turbulence, enabling selective, non-invasive, and high-precision manipulation of microsized objects. However, conventional bubble formation relies on the shear force of the liquid flow and bubble surface tension, facing challenges of instability and random vibration that can impair manipulation precision and performance. To address these issues, we propose a coupled vibration structure with 3D-printed circular microsized air holes encapsulated by a PDMS film. These airholes act as artificial micro-air-bubbles, with their expansion and contraction stabilized by acoustic hard boundaries. The PDMS film further regulates vibration modes through the interaction between air movement and the film's vibration, eliminating randomness. Compared to conventional air-bubbles held by surface tension, these artificial air-bubbles are mechanically stable, allowing for enhanced gas volume changes and stronger forces for object manipulation. We experimentally confirm the stable vibration modes and their frequency-dependent behavior using laser Doppler vibrometry. Precise aggregation, rotation, and separation of micro-objects are demonstrated by adjusting the film's vibration mode. Furthermore, we propose a metasurface design featuring a multi-size microbubble array for frequency-selective manipulation, enabling flexible control of sample trajectory by changing the exciting frequency of an embedded piezoelectric transducer. Our low-frequency acoustic metasurface device offers a versatile, cost-effective solution for drug screening and automated sample handling.

Acoustic tweezers, with the capability to manipulate tiny objects without physical contact, hold substantial potential for biomedical and biological research. However, current acoustic tweezers platforms face challenges in precise, selective, and multi-degree-of-freedom (multi-DoF) manipulation of objects in Petri dishes, making it difficult to integrate them into typical laboratory workflows. This paper presents an acoustic vortex tweezers platform that enables contactless, precise, multi-DoF, and multifunctional manipulation of micro-to-millimeter-scale objects within a Petri dish. The platform features an acoustic holography-based module, which uses a holographic lens to transform acoustic waves and generate a focused acoustic vortex beam. This beam carries sufficient energy to propagate through a Petri dish's bottom wall, creating a ring-shape intensity field for trapping tiny objects. Using lenses encoded with different topological charge numbers, vortex beams with varying diameters can be generated, allowing for trapping various-sized objects. Additionally, in combination with a 3-DoF linear motion module, our integrated platform enables high-resolution translation of acoustically trapped objects along complex paths. We experimentally demonstrated our platform's diverse capabilities, including concentrating micro-objects, trapping flowing micro-objects to create an agglomerate, translating a microparticle and an agglomerate along complex paths, as well as trapping, rotating and translating a zebrafish larva in horizontal and vertical postures. With these capabilities, we expect our in-Petri-dish acoustic vortex tweezers to emerge as a valuable tool for the contactless, high-resolution, programmable handling of tiny biomaterials in biomedical and biological research.

Bacterial detection is pivotal for the timely diagnosis and effective treatment of infectious diseases. Microfluidic platforms offer advantages over traditional methods, including heightened sensitivity, rapid analysis, and minimal sample volume requirements. Traditional clinical methods for bacterial identification often involve extended processing times and necessitate high pathogen concentrations, resulting in delayed diagnoses and missed treatment opportunities. Microfluidic technology overcomes these limitations by facilitating rapid bacterial identification at lower biomass levels, thus ensuring prompt and precise treatment interventions. Additionally, bacteria-driven inflammation has been associated with the development and progression of various diseases, including cancer. Elucidating the complex interplay between bacteria, inflammation, and disease is essential for devising effective disease models and therapeutic strategies. Microfluidic platforms have been used to construct in vitro disease models that accurately replicate the intricate microenvironment that bacteria-driven inflammation affects. These models offer valuable insights into bacteria-driven inflammation and its impact on disease progression, such as cancer metastasis and therapeutic responses. This review examines recent advancements in bacterial detection using microfluidics and assesses the potential of this technology as a robust tool for exploring bacteria-driven inflammation in the context of cancer.

Open droplet microfluidics is an emerging technology that generates, manipulates, and analyzes droplets in open configuration systems. Droplets function as miniaturized reactors for high-throughput analysis due to their compartmentalization and parallelization, while openness enables addressing and accessing the targeted contents. The convergence of two technologies facilitates the localization and intricate manipulation of droplets using external tools, showing great potential in large-scale chemical and biological applications, particularly in cell analysis. In this review, we first introduce various methods of droplet generation and manipulation in open environments. Next, we summarize the typical applications of open droplet systems in cell culture. Then, a comprehensive overview of cell analysis is provided, including nucleic acids, proteins, metabolites, and behaviors. Finally, we present a discussion of current challenges and perspectives in this field.

Immunoassays are widely utilized in various settings, from clinics and emergency rooms to remote and resource-limited environments, such as patients' homes. However, they often present a significant trade-off: while offering simplicity, speed, and cost-effectiveness, they generally lack sensitivity. This study introduces an innovative electrokinetic preconcentration device that employs ion concentration-polarization in micro- and nanofluidic systems to continuously capture and preconcentrate target biomolecules. The system then facilitates their transfer with minimal dilution to standard immunoassays, increasing analyte concentration and enhancing transport kinetics and immunoreaction rates. Designed for cost-effectiveness and ease of use, the device does not require sophisticated equipment such as pumps, making it suitable for point-of-care (POC) commercially available immunoassays. By using this device as a preliminary step for various immunoassays, including enzyme-linked immunosorbent assay (ELISA) and lateral flow assay (LFA), we achieved substantial signal enhancement, improving the limit of detection of these assays by an order of magnitude. The obtained enhancement factor correlated with processed sample volume, operational duration, and assay binding kinetics. Our experimental validations and theoretical analysis lay the groundwork for enhancing commercially available immunoassays without modifying the assays themselves, promising significant advancements in biomedical POC diagnostics.