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Cellular biomechanical features contributed to the occurrence and development of various physiological and pathological phenomena. Micropillar arrays have emerged as an important tool for both the assessment and manipulation of cellular biomechanical characteristics. This comprehensive review provides an in-depth understanding of the fabrication methodologies of micropillar arrays and their applications in deciphering and fine-tuning cellular biomechanical properties and the innovative experimental platforms including organ-on-a-chip and organoids-on-a-chip. This review provides novel insights into the potential of micropillar technology, poised to update the landscape of stem cell research and tissue engineering. [ABSTRACT FROM AUTHOR]

In this study, we developed an optofluidic chip consisting of a guided-mode resonance (GMR) sensor incorporated into a microfluidic chip to achieve simultaneous blood plasma separation and label-free albumin detection. A sedimentation chamber is integrated into the microfluidic chip to achieve plasma separation through differences in density. After a blood sample is loaded into the optofluidic chip in two stages with controlled flow rates, the blood cells are kept in the sedimentation chamber, enabling only the plasma to reach the GMR sensor for albumin detection. This GMR sensor, fabricated using plastic replica molding, achieved a bulk sensitivity of 175.66 nm/RIU. With surface-bound antibodies, the GMR sensor exhibited a limit of detection of 0.16 μg/mL for recombinant albumin in buffer solution. Overall, our findings demonstrate the potential of our integrated chip for use in clinical samples for biomarker detection in point-of-care applications. [ABSTRACT FROM AUTHOR]

Increasing demands on the reproducibility and accuracy of lab-on-a-chip systems in the life science sector require new tools for the molding of polymer films with spatially selectively functionalized surfaces. By applying local micro- and nanostructuring to the molding tools, the aim is to achieve multifunctionality of the polymer films, by setting certain wetting properties. This means that fluid-affecting properties (hydrophobic, hydrophilic) should be possible. To functionalize polymer films, the replication tools were specifically microstructured using laser-based surface functionalization. The periodic micro- and nanostructures were produced with the help of nanosecond pulsed and picosecond pulsed laser systems using Direct Laser Interference Patterning. For this purpose, complex functional microstructures in the range of 0.1 µm to 100 µm were developed based on a bionic approach. The functional properties were transferred in a one-step replicative process using UV-imprinting and were subsequently verified by determining the wetting behavior of the molded microfluidic films and the corresponding laser microstructured replication tools. This publication presents the successfully developed processes and the promising results of this series of experiments. [ABSTRACT FROM AUTHOR]

Chemotherapy alone or in conjunction with surgery and radiation is often used to treat various cancer types. While effective at treating some tumors, the response varies across patients with different malignancies. For some cancers, such as glioblastoma, ovarian cancer, and soft tissue sarcoma, 85%-100% of patients experience cancer recurrence and develop chemotherapy resistance, which often leads to worse prognoses. These alarming statistics highlight an urgent need to better understand the landscape of therapy resistance in cancer, in order to develop improved treatment strategies and prevent recurrence. A central focus has been the investigation of resistant tumor subclones and whether the use of different alkylating agents and/or immune checkpoint inhibitors can ablate different clones. However, very little effort has been directed towards studies of the tumor microenvironment, a complex ecosystem of blood vessels, fibroblasts, immune cells, signaling molecules, and extracellular matrix, in the context of therapy resistance. In this perspective, we provide an overview of different platforms, tools, and techniques that have been developed and used to identify tumor microenvironment alterations due to therapy resistance. We also address potential therapeutic strategies that involve components of the tumor milieu and have been identified and tested to overcome treatment-induced resistance. Identifying microenvironmental changes post-resistance presents opportunities for new targeted treatment strategies. The current state of the literature suggests a dire need for more engineered models that probe specific microenvironment contributors to therapy resistance or ways in which the tumor tissue can be harnessed to mitigate resistance. [ABSTRACT FROM AUTHOR]

Introduction: There have been relatively few attempts to quantitatively assess if, and in which areas, the use of non-animal methods (NAMs) is increasing in biomedical research and importantly, how this compares to the use of live animals. Methods: We conducted a bibliometric analysis of the relative publication of papers reporting the use of NAMs-only compared to those reporting the use of animals, even if they also reported the use of NAMs, over the period 2003 to 2022 across seven research areas (breast cancer, lung disease, blood cancer, heart disease, neurodegenerative diseases, diabetes and toxicology) and five regions (USA, China, France, Germany, United Kingdom). Results: We found that the relative number of publications of research using NAMs-only has been higher than animal-based research for the last 20 years for all research areas and is growing. Research areas differed in their relative publication of NAMs-only based work, with breast cancer and lung disease having consistently the highest ratio of NAMs-only to animal-based publications and heart disease, diabetes and toxicology showing the greatest change over the time period. A key period of change was 2016--18. By 2022 the UK had the highest NAMs-only to animal-based research ratio than any other country for five of the seven research areas and China the lowest for six, accounting for publication rate. Tissue and in silico-based methods were the most common of all NAMs-only publications; lab-on-a-chip and stem cell models are increasing in their use but at much lower levels and rate of increase. Conclusion: We found that proportionately the reliance on animals in these research areas is decreasing, which will be encouraging to those that support the replacement of animal experiments. [ABSTRACT FROM AUTHOR]

Abstract In the in vitro motility assay (IVMA), actin filaments are observed while propelled by surface-adsorbed myosin motor fragments such as heavy meromyosin (HMM). In addition to fundamental studies, the IVMA is the basis for a range of lab-on-a-chip applications, e.g. transport of cargoes in nanofabricated channels in nanoseparation/biosensing or the solution of combinatorial mathematical problems in network-based biocomputation. In these applications, prolonged myosin function is critical as is the potential to repeatedly exchange experimental solutions without functional deterioration. We here elucidate key factors of importance in these regards. Our findings support a hypothesis that early deterioration in the IVMA is primarily due to oxygen entrance into in vitro motility assay flow cells. In the presence of a typically used oxygen scavenger mixture (glucose oxidase, glucose, and catalase), this leads to pH reduction by a glucose oxidase-catalyzed reaction between glucose and oxygen but also contributes to functional deterioration by other mechanisms. Our studies further demonstrate challenges associated with evaporation and loss of actin filaments with time. However, over 8 h at 21–26 °C, there is no significant surface desorption or denaturation of HMM if solutions are exchanged manually every 30 min. We arrive at an optimized protocol with repeated exchange of carefully degassed assay solution of 45 mM ionic strength, at 30 min intervals. This is sufficient to maintain the high-quality function in an IVMA over 8 h at 21–26 °C, provided that fresh actin filaments are re-supplied in connection with each assay solution exchange. Finally, we demonstrate adaptation to a microfluidic platform and identify challenges that remain to be solved for real lab-on-a-chip applications.

Abstract Flow-based microfluidic biochips (FMBs) are widely used in biomedical research and diagnostics. However, their security against potential material-level cyber-physical attacks remains inadequately explored, posing a significant future challenge. One of the main components, polydimethylsiloxane (PDMS) microvalves, is pivotal to FMBs' functionality. However, their fabrication, which involves thermal curing, makes them susceptible to chemical tampering-induced material degradation attacks. Here, we demonstrate one such material-based attack termed “BioTrojans,” which are chemically tampered and optically stealthy microvalves that can be ruptured through low-frequency actuations. To chemically tamper with the microvalves, we altered the associated PDMS curing ratio. Attack demonstrations showed that BioTrojan valves with 30:1 and 50:1 curing ratios ruptured quickly under 2 Hz frequency actuations, while authentic microvalves with a 10:1 ratio remained intact even after being actuated at the same frequency for 2 days (345,600 cycles). Dynamic mechanical analyzer (DMA) results and associated finite element analysis revealed that a BioTrojan valve stores three orders of magnitude more mechanical energy than the authentic one, making it highly susceptible to low-frequency-induced ruptures. To counter BioTrojan attacks, we propose a security-by-design approach using smooth peripheral fillets to reduce stress concentration by over 50% and a spectral authentication method using fluorescent microvalves capable of effectively detecting BioTrojans.

Flow-based microfluidic biochips (FMBs) are widely used in biomedical research and diagnostics. However, their security against potential material-level cyber-physical attacks remains inadequately explored, posing a significant future challenge. One of the main components, polydimethylsiloxane (PDMS) microvalves, is pivotal to FMBs' functionality. However, their fabrication, which involves thermal curing, makes them susceptible to chemical tampering-induced material degradation attacks. Here, we demonstrate one such material-based attack termed “BioTrojans,” which are chemically tampered and optically stealthy microvalves that can be ruptured through low-frequency actuations. To chemically tamper with the microvalves, we altered the associated PDMS curing ratio. Attack demonstrations showed that BioTrojan valves with 30:1 and 50:1 curing ratios ruptured quickly under 2 Hz frequency actuations, while authentic microvalves with a 10:1 ratio remained intact even after being actuated at the same frequency for 2 days (345,600 cycles). Dynamic mechanical analyzer (DMA) results and associated finite element analysis revealed that a BioTrojan valve stores three orders of magnitude more mechanical energy than the authentic one, making it highly susceptible to low-frequency-induced ruptures. To counter BioTrojan attacks, we propose a security-by-design approach using smooth peripheral fillets to reduce stress concentration by over 50% and a spectral authentication method using fluorescent microvalves capable of effectively detecting BioTrojans. [ABSTRACT FROM AUTHOR]

Bio/chemical mixture sensing in a water environment is of great importance in sensing applications. Relying on plentiful molecular fingerprints in mid‐infrared (MIR) and high integration potential, nanophotonic waveguide‐based MIR lab‐on‐a‐chip (LoC) provides a miniaturized and versatile solution for specific and label‐free bio/chemical detection. However, it is still challenging to implement an MIR LoC with on‐chip photodetection for chemical sensing in water, due to the strong MIR water absorption and limited MIR on‐chip photodetector scheme, let alone the spectral overlap issue in mixture analysis. Here, a MIR LoC integrating zero‐bias graphene photodetector is reported and the real‐time monitoring of three analytes in water leveraging the MIR LoC is demonstrated. Besides, using machine learning, the on‐chip collected spectra of the ternary mixture in water with 27 mixing ratios are successfully classified with an accuracy of 95.77%. Moreover, concentration prediction of individual analytes in a mixture is performed by developing a convolution regression network for mixture spectrum decomposition: 83.33% of the single‐component concentration predictions are within the 1 vol% error range, and an average root‐mean‐squared error of 1 vol% for mixture concentration predictions is achieved. The MIR LoC offers new opportunities for highly integrated intelligent sensing systems in various sensing scenarios in the Internet of Things era. [ABSTRACT FROM AUTHOR]

In the past decades, microfluidic chips have been one of the hottest research topics in the "lab-on-a-chip" field. However, it is still a challenge for design the perfect microchannels with high functional integration, complex geometry, and high production efficiency. This review paper provides a comprehensive overview of microfluidic structural models and designs, manufacturing techniques, and bonding methods. The effect of three types of microfluidic channel structure models and their configuration parameters on the fluid behaviors of microfluidics was investigated. Surface-to-volume ratio of the flow channel is a critical parameter for determining the mixing and diffusion capabilities of the microfluidic devices (MDs). Thereafter, the main manufacturing techniques for microstructures were discussed, including etching, photolithography, soft lithography, molding, mechanical micro-machining, laser beam micromachining, printing, and 3D printing. We performed a statistical analysis to discuss the relative advantages and disadvantages of these manufacturing methods. In addition, the current bonding methods for MDs were also summarized, including thermal bonding, solution adhesive bonding, dry adhesive bonding, plasma bonding, and anodic bonding. a comparison of different bonding methods was presented to provide a reference to select a suitable bonding method for the assembly of microfluidic device. Finally, the tendencies and challenges of microchannel manufacturing were discussed, and the prospects were also provided. [ABSTRACT FROM AUTHOR]

Mycotoxins are toxic secondary metabolites produced by certain molds and fungi that contaminate various food commodities, posing serious adverse effects on humans and animals. Aflatoxin, ochratoxin, trichothecene, fumonisin, zearalenone, patulin, and citrinin are some of the major mycotoxins affecting food and feed. The scientific community has focused on regulating food and feed materials due to their potential risks. Conventional techniques for mycotoxin detection have certain limitations in terms of sensitivity, specificity, and speed. In recent years, nanotechnology has emerged as a promising approach to revolutionize mycotoxin detection. This review provides an overview of nanotechnology‐based detection methods for mycotoxins in food and feed, discussing the basic aspects of mycotoxins, their health hazards, and conventional methods. It also explores various nanosensors and nanodevices developed to improve the sensitivity, selectivity, and speed of mycotoxin detection, thereby enhancing food safety and security. [ABSTRACT FROM AUTHOR]

Microfluidic systems have become integral for lab‐on‐a‐chip and organ‐on‐a‐chip applications across numerous disciplines. These systems, typically fabricated using polydimethylsiloxane (PDMS) chips on glass substrates, lack the bioactivity required for such applications. To overcome this, biomolecules are immobilized using either oxygen (O2) plasma treatment or chemical reagents like amino silanes. However, O2 plasma treatments are unstable and cannot covalently immobilize biomolecules, while wet‐chemistry approaches are toxic, time‐consuming, and expensive. A novel microfluidic platform that combines two plasma surface treatments: Plasma‐activated coating (PAC) and atmospheric pressure plasma jet (APPJ), to enable reagent‐free covalent immobilization of biomolecules is described here. These surface treatments, unlike O2 plasma, covalently immobilized fibronectin on PDMS and glass, and significantly improved endothelial cell attachment and proliferation. By combining PAC and APPJ, a hybrid microfluidic platform with equivalent bond strength to standard O2 plasma devices, but with significantly enhanced endothelial cell growth in and artery‐on‐a‐chip model, is developed. This platform is also amenable to high‐shear applications such as coronary shear, with endothelial cells aligning with flow, as seen in human arteries. By providing reagent‐free covalent immobilization of biomolecules within a microfluidic system, this technology has the potential to radically improve organ‐on‐a‐chip development as well as lab‐on‐a‐chip systems, point‐of‐care diagnostics, and sensors. [ABSTRACT FROM AUTHOR]

Conventional magnetophoresis techniques for manipulating biocarriers and cells predominantly rely on large‐scale electromagnetic systems, which is a major obstacle to the development of portable and miniaturized cell‐on‐chip platforms. Herein, a novel magnetic engineering approach by tailoring a nanoscale notch on a disk micromagnet using two‐step optical and thermal lithography is developed. Versatile manipulations are demonstrated, such as separation and trapping, of carriers and cells by mediating changes in the magnetic domain structure and discontinuous movement of magnetic energy wells around the circumferential edge of the micromagnet caused by a locally fabricated nano‐notch in a low magnetic field system. The motion of the magnetic energy well is regulated by the configuration of the nanoscale notch and the strength and frequency of the magnetic field, accompanying the jump motion of the carriers. The proposed concepts demonstrate that multiple carriers and cells can be manipulated and sorted using optimized nanoscale multi‐notch gates for a portable magnetophoretic system. This highlights the potential for developing cost‐effective point‐of‐care testing and lab‐on‐chip systems for various single‐cell‐level diagnoses and analyses. [ABSTRACT FROM AUTHOR]

A new screen-printed electrode (SPE) modified with carbon black and ternary oxide (SiO2/TiO2/Nb2O5), denominated SPE/CB/SiTiNb and was developed for the direct detection of triclosan in tap water and mouthwash samples. The morphological characterization and electrochemical behavior of the sensors were performed by scanning electron microscopy, energy dispersive spectroscopy, and cyclic voltammetry. Differential pulse voltammetry was used to evaluate the proposed sensor in Britton–Robinson buffer 0.1 mol L−1 and showed a limit detection of 1.23 nmol L−1 in a linear range from 0.025 to 57.01 µmol L−1. Studies with possible interferents were performed demonstrating a significant selectivity of the sensor to the triclosan oxidation reaction. The sensor was applied in tap water and mouthwash real sample analyses, whose recoveries ranged from 93.4 to 98.8%, demonstrating that the sensor shows promise in the detection of triclosan in different matrices allied to high sensitivity, selectivity, low-cost, portability, disposability, and low sample volume, without pre-treatment, per analysis. [ABSTRACT FROM AUTHOR]

Introduction: The microfluidic device is highly optimized to remove oocytes from the cumulus-corona cell mass surrounding them. Additionally, it effectively captures and immobilizes the oocytes, aiding in assessing their quality and facilitating the injection of sperm into the oocyte. In this study, a novel microfluidic chip was designed and manufactured using conventional soft lithography methods. Methods: This research proposes the utilization of a microfluidic chip as a substitute for the conventional manual procedures involved in oocyte denudation, trapping, and immobilization. The microfluidic chip was modeled and simulated using COMSOL Multiphysics® 5.2 software to optimize and enhance its design and performance. The microfluidic chip was fabricated using conventional injection molding techniques on a polydimethylsiloxane substrate by employing soft lithography methods. Results: A hydrostatic force was applied to guide the oocyte through predetermined pathways to eliminate the cumulus cells surrounding the oocyte. The oocyte was subsequently confined within the designated trap region by utilizing hydraulic resistance along the paths and immobilized by applying vacuum force. Conclusion: The application of this chip necessitates a lower level of operator expertise compared to enzymatic and mechanical techniques. Moreover, it is feasible to continuously monitor the oocyte's state throughout the procedure. There is a reduced need for cultural media compared to more standard approaches. [ABSTRACT FROM AUTHOR]

Microfluidics, a multidisciplinary field at the intersection of physics, engineering and biology is reshaping drug discovery. This review delves into its historical evolution, fundamental principles, components and manufacturing techniques. Microfluidics operates with precision, offering laminar flow, efficient mass transfer and scaling laws. Platforms like microscale cell culture systems, high-throughput screening techniques, lab-on-a-chip devices and organ-on-a-chip systems are driving advancements in disease modeling and pharmacokinetics. Despite challenges in device fabrication, regulation and costs, microfluidics promises an efficient, patient-centric future for drug discovery. Collaborative innovation can unlock its potential, making drug development faster, more precise and accessible. Microfluidics stands as a transformative force with the potential to revolutionize the drug development process. [ABSTRACT FROM AUTHOR]

This study presents a novel absorption cell with a circular geometry that can be integrated into microfluidic devices for optical spectroscopy applications. The absorption cell is made of PDMS/SU8 and offers an optical path length that is 8.5 times its diameter, resulting in a significant increase in the sensitivity of the measurements. Overall, this design provides a reliable and efficient solution for optical spectroscopy in microfluidic systems, enabling the precise detection and analysis of small quantities of analytes. [ABSTRACT FROM AUTHOR]

Intracellular and extracellular sensing of physical and chemical variables is important for disease diagnosis and the understanding of cellular biology. Optical sensing utilizing fluorescent nanodiamonds (FNDs) is promising for probing intracellular and extracellular variables owing to their biocompatibility, photostability, and sensitivity to physicochemical quantities. Based on the potential of FNDs, we outlined the optical properties, biocompatibility, surface chemistry of FNDs and their applications in intracellular biosensing. This review also introduces biosensing platforms that combine FNDs and lab-on-a-chip approaches to control the extracellular environment and improve sample/reagent handling and sensing performance. [ABSTRACT FROM AUTHOR]

Abstract Chronic kidney disease (CKD) is a significant global health concern, impacting over 10% of the world population. Despite advances in home‐based treatments, CKD diagnosis and monitoring remain centralized in large laboratories. This work reports on the development of a Graphene‐based Lab‐On‐a‐Chip (G‐LOC) for the self‐testing of multiple renal function biomarkers in capillary blood. G‐LOC integrates bioelectronic sensors with a 3D‐printed microfluidic system that enables the multiplex quantification of urea, potassium, sodium, and chloride, from one drop of blood. The potentials of three graphene sensors modified with ion‐selective membranes and enzymes are simultaneously measured. The analytical performance of the test is evaluated in terms of linearity, accuracy, and coefficient of variability (CV). Accuracy values higher than 98.7%, and CV values lower than 10.8% are obtained for all the biomarkers. Correlation and Bland–Altman plots show good correlation (slopes in the range of 0.94–1.15) and high agreement of G‐LOC with a reference method. It is also demonstrated that the test can correctly differentiate biomarker levels normally obtained for healthy people, early‐stage CKD, and end‐stage CKD. Finally, user experience is studied with a group of untrained volunteers who highlight the simple usability of the test and its suitability for at‐home diagnostics.

Chemotherapy alone or in conjunction with surgery and radiation is often used to treat various cancer types. While effective at treating some tumors, the response varies across patients with different malignancies. For some cancers, such as glioblastoma, ovarian cancer, and soft tissue sarcoma, 85%–100% of patients experience cancer recurrence and develop chemotherapy resistance, which often leads to worse prognoses. These alarming statistics highlight an urgent need to better understand the landscape of therapy resistance in cancer, in order to develop improved treatment strategies and prevent recurrence. A central focus has been the investigation of resistant tumor subclones and whether the use of different alkylating agents and/or immune checkpoint inhibitors can ablate different clones. However, very little effort has been directed towards studies of the tumor microenvironment, a complex ecosystem of blood vessels, fibroblasts, immune cells, signaling molecules, and extracellular matrix, in the context of therapy resistance. In this perspective, we provide an overview of different platforms, tools, and techniques that have been developed and used to identify tumor microenvironment alterations due to therapy resistance. We also address potential therapeutic strategies that involve components of the tumor milieu and have been identified and tested to overcome treatment-induced resistance. Identifying microenvironmental changes post-resistance presents opportunities for new targeted treatment strategies. The current state of the literature suggests a dire need for more engineered models that probe specific microenvironment contributors to therapy resistance or ways in which the tumor tissue can be harnessed to mitigate resistance.

Microfluidic and lab-on-a-chip devices offer exquisite temporal and spatial control over chemical and physical processes that are important in mineral exploration and mining. These include mineral-water interfacial reactions, dissolution, and adsorption/desorption in pores, fractures, or other micro/nanostructures. Microfluidic mineral studies offer advantages of small sample and reagent volumes, high throughout, and short analytical cycles that may enable in-field mining decisions. However, not many microfluidic studies have targeted these mining sector challenges for mineral leaching. In this review, special attention is given to microscale experimental platforms for predicting extraction and leaching of industrially-relevant samples (real ore samples). Advantages and challenges of these platforms are given. The review concludes that there are significant opportunities for microfluidics in mineral analysis, screening, process intensification, and process control in the resource and minerals sector.

Lab-on-a-chip devices have become pivotal in various scientific disciplines due to their compactness and efficiency. However, their reliance on traditional materials raises environmental concerns. This perspective explores the shift towards biodegradable materials in these devices, highlighting their benefits, challenges, and potential for a more sustainable scientific approach. Biodegradable alternatives like natural polymers (e.g. cellulose-based compounds) offer eco-friendly characteristics and the ability to naturally decompose without harming the environment. Yet, integrating these materials presents challenges in maintaining device functionality and cost-effectiveness. Nonetheless, this transition signifies a crucial step towards more sustainable scientific practices, ensuring that advancements in research align with environmental conservation.

Abstract This review reports diverse microfluidic systems utilizing surface-enhanced Raman scattering (SERS) detection for disease diagnosis. Integrating SERS detection technology, providing high-sensitivity detection, and microfluidic technology for manipulating small liquid samples in microdevices has expanded the analytical capabilities previously confined to larger settings. This study explores the principles and uses of various SERS-based microfluidic devices developed over the last two decades. Specifically, we investigate the operational principles of documented SERS-based microfluidic devices, including continuous-flow channels, microarray-embedded microfluidic channels, droplet microfluidic channels, digital droplet channels, and gradient microfluidic channels. We also examine their applications in biomedical diagnostics. In conclusion, we summarize the areas requiring further development to translate these SERS-based microfluidic technologies into practical applications in clinical diagnostics.

In this paper, we design and optimize a single-mode photonic crystal (PhC) nanobeam-grating (NBG) structure with antisymmetric quarter-elliptical walls geometry based on the computational finite element method (FEM). This structure is capable of providing a wide bandwidth spectrum for chemical sensing (ChS) operation due to the 2∆λ ≈ 110 nm wide bandgap (with a Bragg wavelength center of λB ≈ 1550 nm) and filtering out the undesired optical modes. Due to the ChS mode intensification (fundamental mode TE1 wavelength λ = 1550 nm) with a high quality (Q) factor Q = 3.565 × 103 and a very small modal volume (MVol) Vmode = 0.0012(λres/nSi)3 in the cavity area as well as confinement of the evanescent wave mode (EWM) in the air grating near the cavity (where chemical analyte, ChAn, is placed) supporting a very high confinement factor (CFac), Γ ≈ 0.45, the single-mode PhC nanobeam resonator offers a very good platform for ChS operation with very low light dissipation. The proposed nanobeam photonic resonator structure can analyze a very small surface analyte, 0.01199 µm2 of ChAn such as ethanol (C2H5OH) and water (H2O) with extremely high sensitivities SEthanol ≈ 1554.22 nm/RIU and SWater ≈ 1549.49 nm/RIU, respectively. The high sensitivity S and high Q/Vmode ratio, the capability of Label-Free sensing operation as well as being ultra-compact, indicate that the single-mode nanobeam structure as a passive photonic structure is a very practical candidate in the Lab-on-a-Chip (LOC) chemical sensor systems. [ABSTRACT FROM AUTHOR]

Heart failure represents a primary cause of hospitalization and mortality in both developed and developing countries, often necessitating heart transplantation as the only viable recovery path. Despite advances in transplantation medicine, organ rejection remains a significant post-operative challenge, traditionally monitored through invasive endomyocardial biopsies (EMB). This study introduces a rapid prototyping approach to organ rejection monitoring via a sensor-integrated flexible patch, employing electrical impedance spectroscopy (EIS) for the non-invasive, continuous assessment of resistive and capacitive changes indicative of tissue rejection processes. Utilizing titanium-dioxide-coated electrodes for contactless impedance sensing, this method aims to mitigate the limitations associated with EMB, including procedural risks and the psychological burden on patients. The biosensor's design features, including electrode passivation and three-dimensional microelectrode protrusions, facilitate effective monitoring of cardiac rejection by aligning with the heart's curvature and responding to muscle contractions. Evaluation of sensor performance utilized SPICE simulations, scanning electron microscopy, and cyclic voltammetry, alongside experimental validation using chicken heart tissue to simulate healthy and rejected states. The study highlights the potential of EIS in reducing the need for invasive biopsy procedures and offering a promising avenue for early detection and monitoring of organ rejection, with implications for patient care and healthcare resource utilization. [ABSTRACT FROM AUTHOR]

Legionella pneumophila has been pinpointed by the World Health Organization as the highest health burden of all waterborne pathogens in the European Union and is responsible for many disease outbreaks around the globe. Today, standard analysis methods (based on bacteria culturing onto agar plates) need several days (~12) in specialized analytical laboratories to yield results, not allowing for timely actions to prevent outbreaks. Over the last decades, great efforts have been made to develop more efficient waterborne pathogen diagnostics and faster analysis methods, requiring further advancement of microfluidics and sensors for simple, rapid, accurate, inexpensive, real-time, and on-site methods. Herein, a lab-on-a-chip device integrating sample preparation by accommodating bacteria capture, lysis, and DNA isothermal amplification with fast (less than 3 h) and highly sensitive, colorimetric end-point detection of L. pneumophila in water samples is presented, for use at the point of need. The method is based on the selective capture of viable bacteria on on-chip-immobilized and -lyophilized antibodies, lysis, the loop-mediated amplification (LAMP) of DNA, and end-point detection by a color change, observable by the naked eye and semiquantified by computational image analysis. Competitive advantages are demonstrated, such as low reagent consumption, portability and disposability, color change, storage at RT, and compliance with current legislation. [ABSTRACT FROM AUTHOR]

This review reports diverse microfluidic systems utilizing surface-enhanced Raman scattering (SERS) detection for disease diagnosis. Integrating SERS detection technology, providing high-sensitivity detection, and microfluidic technology for manipulating small liquid samples in microdevices has expanded the analytical capabilities previously confined to larger settings. This study explores the principles and uses of various SERS-based microfluidic devices developed over the last two decades. Specifically, we investigate the operational principles of documented SERS-based microfluidic devices, including continuous-flow channels, microarray-embedded microfluidic channels, droplet microfluidic channels, digital droplet channels, and gradient microfluidic channels. We also examine their applications in biomedical diagnostics. In conclusion, we summarize the areas requiring further development to translate these SERS-based microfluidic technologies into practical applications in clinical diagnostics. [ABSTRACT FROM AUTHOR]

Electro‐coalescence is the fusion phenomenon between a pair or more microfluidic droplets that are immersed in an immiscible medium under an electric field. This technique is frequently used to merge confined droplets in surfactant‐stabilized microfluidic emulsions using local electric fields. Despite the necessity of miniaturized electrodes, this method has proven highly successful in microfluidics and lab‐on‐a‐chip applications. Miniaturized electrodes severely curtail the spatial and temporal flexibility of the electric potential, thus hindering real‐time and flexible operation and leading to high production costs. The current study addresses this problem with reconfigurable electric field potential by light‐driven functional virtual electrodes. These electrodes are light‐induced on a non‐centrosymmetric ferroelectric photovoltaic crystal placed below a microfluidic droplet channel. The photovoltaic effect in the crystal is responsible for the space charge distributions that act as virtual electrodes, whose evanescent field is screened by free charges into the two liquids inside the channel. A numerical model is developed to describe the evolution of the evanescent electric field causing electro‐coalescence. Based on this prediction, two coalescence processes occur at two different timescales and with different numbers of droplets involved. Controlled exposure time modulation allows either rapid on‐demand coalescence of droplet pairs or breakup of the entire emulsion. [ABSTRACT FROM AUTHOR]

Microfluidics has emerged as a robust technology for diverse applications, ranging from bio-medical diagnostics to chemical analysis. Among the different characterization techniques that can be used to analyze samples at the microfluidic scale, the coupling of photonic detection techniques and on-chip configurations is particularly advantageous due to its non-invasive nature, which permits sensitive, real-time, high throughput, and rapid analyses, taking advantage of the microfluidic special environments and reduced sample volumes. Putting a special emphasis on integrated detection schemes, this review article explores the most relevant advances in the on-chip implementation of UV–vis, near-infrared, terahertz, and X-ray-based techniques for different characterizations, ranging from punctual spectroscopic or scattering-based measurements to different types of mapping/imaging. The principles of the techniques and their interest are discussed through their application to different systems. [ABSTRACT FROM AUTHOR]

The study of steady and unsteady microflows plays an important role in micromixing applications. In this paper, Computational Fluid Dynamics (CFD) simulations using OpenFOAM have been carried out to investigate mixing efficiency and flow characteristics with rectangular geometry of three different wall conditions. The geometries of the microchannels were rectangular with the dimensions of 4000 μ length, 1000 μ depth and 1000 μ width. The first channel does not have a hydro-active patch along the length of the channel. In the second channel, hydro-active patches of 1000 μ are placed symmetrically on the top and bottom along the length of the microchannel. In the third channel, hydro-active patches of 1000 μ are placed asymmetrically on the top and bottom along the length of the microchannel. A three-dimensional (3D) model was created for three geometries and simulations were performed to investigate the mixing effect for mixing two different fluids. The developed mathematical model was based on modified wall surface boundary conditions with an unsteady state of the flow field. The effect of introducing hydro-active patches in the form of symmetric boundary conditions led to a reduction in micromixer length approximately by a factor of three. The enhancement in the mixing efficiency in shorter lengths is due to surface modification, which significantly affects the unsteady behaviour of the flow field. In symmetric and asymmetric geometries with hydro-active patches, swirling vortexes were developed providing good mixing results. [ABSTRACT FROM AUTHOR]

Given the growing importance of lab-on-a-chip in a number of fields, such as medical diagnosis or environmental analysis, the fact that the current fabrication process relies mainly on oil-based polymers raises an ecological concern. As an eco-responsible alternative, we presented, in this article, a manufacturing process for microfluidic devices from chitosan, a bio-sourced, biodegradable, and biocompatible polysaccharide. From chitosan powder, we produced thick and rigid films. To prevent their dissolution and reduce their swelling when in contact with aqueous solutions, we investigated a film neutralization step and characterized the mechanical and physical properties of the resulting films. On these neutralized chitosan films, we compared two micropatterning methods, i.e., hot embossing and mechanical micro-drilling, based on the resolution of microchannels from 100 µm to 1000 µm wide. Then, chitosan films with micro-drilled channels were bonded using a biocompatible dry photoresist on a glass slide or another neutralized chitosan film. Thanks to this protocol, the first functional chitosan microfluidic devices were prepared. While some steps of the fabrication process remain to be improved, these preliminary results pave the way toward a sustainable fabrication of lab-on-a-chip. [ABSTRACT FROM AUTHOR]

Shrink film is a thin sheet of polystyrene plastic that shrinks to 25–40% of its original size when heated. This study investigated the shrinkage factor of the film at different temperatures and baking times to determine the optimal fabrication recipe for shrink film microfluidic device production. Additionally, this study characterized the properties of shrink film, including minimum possible feature size and cross-section geometries, using manual engraving and the CAMEO 4 automated cutting machine. The optimal shrinkage factor ranged from 1.7 to 2.9 at 150 °C and a baking time of 4 min, producing the ideal size for microfluidic device fabrication. The X- and Y-axes shrank ~2.5 times, while Z-axis thickened by a factor of ~5.8 times. This study achieved a minimum feature size of 200 microns, limited by the collapsing of channel sidewalls when shrunk, leading to blockages in the microchannel. These findings demonstrate the feasibility and versatility of using shrink film as a cost-effective and efficient material for the rapid fabrication of microfluidic devices. The potential applications of this material in various fields such as the medical and biomedical industries, bacteria and algae culture and enumeration are noteworthy. [ABSTRACT FROM AUTHOR]

Phosphorus, an essential rare element in aquatic ecosystems, plays a key role in maintaining ecosystem balance. However, excess phosphorus leads to eutrophication and algal proliferation. To prevent eutrophication, the pretreatment and measuring of the concentration of total phosphorus (TP) is crucial. Compared to conventional TP pretreatment equipment (autoclave), a lab-on-a-chip detection device fabricated using micro-electromechanical system technology and titania (TiO2) as a photocatalyst is more convenient, efficient, and cost-effective. However, the wide bandgap of TiO2 (3.2 eV) limits photocatalytic activity. To address this problem, this paper describes the preparation of a TiO2/Au nanocomposite film using electron-beam evaporation and atomic-layer deposition, based on the introduction of gold film and TiO2 to a quartz substrate. The photocatalytic degradation properties of TiO2/Au nanocomposite films with thicknesses of 1, 2, 3, and 4 nm were assessed using rhodamine B as a pollutant. The experimental results demonstrate that the deposition of gold films with different thicknesses can enhance photocatalytic degradation efficiency through synergetic reactions in the charge separation process on the surface. The optimal photocatalytic efficiency is achieved when the deposition thickness is 2 nm, and it decreases with further increase in the thickness. When the photocatalytic reaction time is 15 min, the lab-on-a-chip (LOC) device with a 2-nm-thick gold layer and autoclave exhibits a similar TP pretreatment performance. Therefore, the proposed LOC device based on photocatalytic technology can address the limitations of conventional autoclave equipment, such as large volumes, long processing times, and high costs, thereby satisfying the growing demand for on-site evaluation. [ABSTRACT FROM AUTHOR]

Molecular diagnostic systems for point-of-care (POC) testing are nowadays routinely used and are part of many labs. Although often intended for bedside use outside of the microbiology lab, there is still room for expansion. This review discusses the two techniques that are currently the most widespread, real-time polymerase-chain reaction (RT-PCR) and loop-mediated isothermal amplification (LAMP). An overview is provided of the various manufacturers and products as well as the evidence and current use in clinical practice. The article further sheds light on some newer techniques, such as CRISPR-based diagnostics and lab-on-a-chip, which are still in development. With many new platforms and techniques still in the pipeline and their potential currently not yet fully exploited, we expect the use of molecular POC testing to increase in the years to come. However, even when used in hospital – in lab, the main advantages of the tests being fast and easy to perform already provide significant benefits in terms of patient outcome. [ABSTRACT FROM AUTHOR]

Efficient healthcare management demands prompt decision-making based on fast diagnostics tools, astute data analysis, and informatics analysis. The rapid detection of analytes at the point of care is ensured using microfluidics in synergy with nanotechnology and biotechnology. The nanobiosensors use nanotechnology for testing, rapid disease diagnosis, monitoring, and management. In essence, nanobiosensors detect biomolecules through bioreceptors by modulating the physicochemical signals generating an optical and electrical signal as an outcome of the binding of a biomolecule with the help of a transducer. The nanobiosensors are sensitive and selective and play a significant role in the early identification of diseases. This article reviews the detection method used with the microfluidics platform for nanobiosensors and illustrates the benefits of combining microfluidics and nanobiosensing techniques by various examples. The fundamental aspects, and their application are discussed to illustrate the advancement in the development of microfluidics-based nanobiosensors and the current trends of these nano-sized sensors for point-of-care diagnosis of various diseases and their function in healthcare monitoring. [ABSTRACT FROM AUTHOR]

Thanks to recent and continuing technological innovations, modern microfluidic systems are increasingly offering researchers working across all fields of biotechnology exciting new possibilities (especially with respect to facilitating high throughput analysis, portability, and parallelization). The advantages offered by microfluidic devices—namely, the substantially lowered chemical and sample consumption they require, the increased energy and mass transfer they offer, and their comparatively small size—can potentially be leveraged in every sub-field of biotechnology. However, to date, most of the reported devices have been deployed in furtherance of healthcare, pharmaceutical, and/or industrial applications. In this review, we consider examples of microfluidic and miniaturized systems across biotechnology sub-fields. In this context, we point out the advantages of microfluidics for various applications and highlight the common features of devices and the potential for transferability to other application areas. This will provide incentives for increased collaboration between researchers from different disciplines in the field of biotechnology. [ABSTRACT FROM AUTHOR]

IntroductionThere have been relatively few attempts to quantitatively assess if, and in which areas, the use of non-animal methods (NAMs) is increasing in biomedical research and importantly, how this compares to the use of live animals.MethodsWe conducted a bibliometric analysis of the relative publication of papers reporting the use of NAMs-only compared to those reporting the use of animals, even if they also reported the use of NAMs, over the period 2003 to 2022 across seven research areas (breast cancer, lung disease, blood cancer, heart disease, neurodegenerative diseases, diabetes and toxicology) and five regions (USA, China, France, Germany, United Kingdom).ResultsWe found that the relative number of publications of research using NAMs-only has been higher than animal-based research for the last 20 years for all research areas and is growing. Research areas differed in their relative publication of NAMs-only based work, with breast cancer and lung disease having consistently the highest ratio of NAMs-only to animal-based publications and heart disease, diabetes and toxicology showing the greatest change over the time period. A key period of change was 2016–18. By 2022 the UK had the highest NAMs-only to animal-based research ratio than any other country for five of the seven research areas and China the lowest for six, accounting for publication rate. Tissue and in silico-based methods were the most common of all NAMs-only publications; lab-on-a-chip and stem cell models are increasing in their use but at much lower levels and rate of increase.ConclusionWe found that proportionately the reliance on animals in these research areas is decreasing, which will be encouraging to those that support the replacement of animal experiments.

Abstract Nowadays, droplet microfluidics has become widely utilized for high-throughput assays. Efficient mixing is crucial for initiating biochemical reactions in many applications. Rapid mixing during droplet formation eliminates the need for incorporating micromixers, which can complicate the chip design. Furthermore, immediate mixing of substances upon contact can significantly improve the consistency of chemical reactions and resulting products. This study introduces three innovative designs for droplet generators that achieve efficient mixing and produce small droplets. The T-cross and cross-T geometries combine cross and T junction mixing mechanisms, resulting in improved mixing efficiency. Numerical simulations were conducted to compare these novel geometries with traditional T and cross junctions in terms of mixing index, droplet diameter, and eccentricity. The cross-T geometry exhibited the highest mixing index and produced the smallest droplets. For the flow rate ratio of 0.5, this geometry offered a 10% increase in the mixing index and a decrease in the droplet diameter by 10% compared to the T junction. While the T junction has the best mixing efficiency among traditional droplet generators, it produces larger droplets, which can increase the risk of contamination due to contact with the microchannel walls. Therefore, the cross-T geometry is highly desirable in most applications due to its production of considerably smaller droplets. The asymmetric cross junction offered a 8% increase in mixing index and around 2% decrease in droplet diameter compared to the conventional cross junction in flow rate ratio of 0.5. All novel geometries demonstrated comparable mixing efficiency to the T junction. The cross junction exhibited the lowest mixing efficiency and produced larger droplets compared to the cross-T geometry (around 1%). Thus, the novel geometries, particularly the cross-T geometry, are a favorable choice for applications where both high mixing efficiency and small droplet sizes are important.

In this study, we developed an optofluidic chip consisting of a guided-mode resonance (GMR) sensor incorporated into a microfluidic chip to achieve simultaneous blood plasma separation and label-free albumin detection. A sedimentation chamber is integrated into the microfluidic chip to achieve plasma separation through differences in density. After a blood sample is loaded into the optofluidic chip in two stages with controlled flow rates, the blood cells are kept in the sedimentation chamber, enabling only the plasma to reach the GMR sensor for albumin detection. This GMR sensor, fabricated using plastic replica molding, achieved a bulk sensitivity of 175.66 nm/RIU. With surface-bound antibodies, the GMR sensor exhibited a limit of detection of 0.16 μg/mL for recombinant albumin in buffer solution. Overall, our findings demonstrate the potential of our integrated chip for use in clinical samples for biomarker detection in point-of-care applications.

We demonstrate an optofluidic device which utilizes the optical scattering and gradient forces for particle trapping in microchannels featuring 300 nm thick membranes. On-chip waveguides are used to direct light into microfluidic trapping channels. Radiation pressure is used to push particles into a protrusion cavity, isolating the particles from liquid flow. Two different designs are presented: the first exclusively uses the optical scattering force for particle manipulation, and the second uses both scattering and gradient forces. Trapping performance is modeled for both cases. The first design, referred to as the orthogonal force design, is shown to have a 80% capture efficiency under typical operating conditions. The second design, referred to as the gradient force design, is shown to have 98% efficiency under the same conditions.

Nowadays, droplet microfluidics has become widely utilized for high-throughput assays. Efficient mixing is crucial for initiating biochemical reactions in many applications. Rapid mixing during droplet formation eliminates the need for incorporating micromixers, which can complicate the chip design. Furthermore, immediate mixing of substances upon contact can significantly improve the consistency of chemical reactions and resulting products. This study introduces three innovative designs for droplet generators that achieve efficient mixing and produce small droplets. The T-cross and cross-T geometries combine cross and T junction mixing mechanisms, resulting in improved mixing efficiency. Numerical simulations were conducted to compare these novel geometries with traditional T and cross junctions in terms of mixing index, droplet diameter, and eccentricity. The cross-T geometry exhibited the highest mixing index and produced the smallest droplets. For the flow rate ratio of 0.5, this geometry offered a 10% increase in the mixing index and a decrease in the droplet diameter by 10% compared to the T junction. While the T junction has the best mixing efficiency among traditional droplet generators, it produces larger droplets, which can increase the risk of contamination due to contact with the microchannel walls. Therefore, the cross-T geometry is highly desirable in most applications due to its production of considerably smaller droplets. The asymmetric cross junction offered a 8% increase in mixing index and around 2% decrease in droplet diameter compared to the conventional cross junction in flow rate ratio of 0.5. All novel geometries demonstrated comparable mixing efficiency to the T junction. The cross junction exhibited the lowest mixing efficiency and produced larger droplets compared to the cross-T geometry (around 1%). Thus, the novel geometries, particularly the cross-T geometry, are a favorable choice for applications where both high mixing efficiency and small droplet sizes are important. [ABSTRACT FROM AUTHOR]