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The Oscillation Dynamics of Droplets Subject to Electrowetting Actuation
摘要： The dynamic behavior of an Electrowetting-on-Dielectrics (EWOD) actuation process can be linked to certain fluid properties of the actuated polar liquid droplet. After actuation, inertia will lead to droplet oscillations where the contact angle asymptotically approaches the newly created surface tension equilibrium value. The decay behavior, frequency and amplitude of these oscillations can be related to material parameters such as density, viscosity and mass. In this work we study the characteristics of these oscillations, present simulation results and develop a measurement setup for first observations of oscillations on deionized water droplets. We show that there is a big difference between two grounding schemes, in particular regarding the dynamic movement of the liquid-gas interface. It turns out that only an electrical grounding from below leads to utilizable oscillations. Finally we point towards applications for future Lab-on-a-Chip applications.
关键词： actuator,FEM simulation,electrowetting,viscosity sensing,droplet oscillations,Lab-on-a-Chip
更新于2025-09-23 15:22:29
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Enzymatic method of urea determination in LTCC microfluidic system based on absorption photometry
摘要： In this paper a novel microanalytical system based on absorption photometry for urea determination in small-volume biological samples is described. The developed microsystem with built-in microreactor with urease immobilised on its surface was fabricated using low temperature co-fired ceramics (LTCC) technology. For detection of the ammonium ions – product of urea hydrolysis, the modified Berthelot’s reaction was applied and conditions of this reaction were optimised in a way to be suitable for analysis in microsystems and for particular application, with special regards to very small alternation of urea concentration in culture medium. The best results were obtained for reagent R1 composed of: 180 mM sodium salicylate, 15 mM sodium nitroprusside, 2 mM EDTA in phosphate buffer solution of pH 7 and reagent R2 containing 16.9 mM sodium hypochlorite in phosphate buffer solution of pH 12. Linear concentration range of urea detection with the use of the developed LTCC microfluidic system for the selected flow rate of 4 μl/min, was in the range up to 1 mM, and the calculated lower limit of detection – 0.002 mM. The developed microsystem enables urea determination in samples of post-culture medium and of cells lysates of minimised volume c.a. 1 μl. Preliminary studies related to determination of urea in real samples, performed using hepatic cells lysates and post-culture medium were successful. As reference methods, commercially available tests were applied. The determined urea concentration measured by means of the QuantiChrom? and BioMaxima test and by the developed method based on the LTCC microanalytical system differs by c.a. 9% and 2% respectively. To the best of our knowledge, this is the first urea analysis microsystem for use in cells culture studies characterised by: the smallest volume of sample – 1 μl, long lifetime with stable response - reduced by 14%, through experimental time span of 30 days as well as suitability for quasi-monitoring of cells in vitro with sampling rate - 6 samples per hour.
关键词： LTCC technology,enzymatic microreactor,microfluidic systems,lab-on-a-chip,enzymatic urea determination,absorption photometry
更新于2025-09-23 15:22:29
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Visible Laser on Silicon Optofluidic Microcavity
摘要： Optical readout within microfluidic chips is a bottleneck limiting their industrial development. The integration of lasers operating in the visible range within a microfluidic platform is crucial for enabling in situ optical measurements in lab-on-a-chip applications. In principle, microstructured single-crystal silicon is an excellent optofluidic platform, which allows integration of microfluidic channels together with optical circuits including micro-optics, waveguides, and resonant cavities. However, the silicon absorption below 1.1 μm is a fundamental limit that prohibits the use of silicon-based micro-cavities as the feedback element for visible lasers and restricts their use to the infrared only. In this work, an ultra-wide band silicon cavity enabled by two deeply etched hollow-core planar waveguides is demonstrated. The proposed microcavity shows a broad bandwidth extending from 500 to 1600 nm with quality factors up to 2067. A tubular microfluidic channel is inserted between the mirrors of the optofluidic cavity. The microfluidic channel is filled with Rhodamine 6G (R6G) at 20 μL min?1 flow rate allowing successful demonstration of lasing on silicon at 562.4 nm. The laser beam propagates in-plane (along the chip surface) and is handled with monolithically integrated input/output optical fiber grooves. This provides a unique silicon platform integrating hollow core optofluidic channels together with optical cavities, which is suitable for implementing optical readout in lab-on-a-chip devices.
关键词： visible lasers,microcavities,silicon,optofluidics,lab on a chip
更新于2025-09-23 15:21:01
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LiNbO3 integrated system for opto-microfluidic sensing
摘要： In this work, we realized and tested an integrated opto-microfluidics platform entirely made on lithium niobate (LiNbO3) crystals, able to detect the single droplet passage and estimate its size without the need of any imaging processing. It is based on the coupling of a self-aligned integrated optical stage, made of an array of optical waveguides, to a microfluidic circuit such as a T-junction or Cross-junction engraved in the same substrate. The platform presented high quality performances in terms of optical triggering, reproducibility and stability in time, allowing in real-time data analysis. The comparison with standard approaches using microscopes and fast camera imagining acquisition and relative post-processing, showed an increased capability better than 50%. The demonstrated feasibility of integration of these two stages will allow the realization of a Lab-On-a-Chip on a monolithic substrate of lithium niobate, exploiting its multiple applications for manipulation of droplets.
关键词： waveguide,Microfluidic,Droplet,optical trigger,lithium niobate,Lab-on-a-chip
更新于2025-09-23 15:21:01
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Photoactive Functional Soft Materials (Preparation, Properties, and Applications) || Soft Photoactuators in Microfluidics
摘要： Microfluidics, also known as lab‐on‐a‐chip (LOC) and micro‐total‐analysis‐system (μTAS), cover a set of multidisciplinary technologies dealing with the manipulation of small amounts of liquids to perform reactions, analyses, or fundamental investigations in biology, physics, and at the interdisciplinary frontiers. In contrast to the conventional bulky bench‐top instruments and the associated manual methods to handle large amounts of biological and chemical reagents that are pretty time consuming and not so environmentally friendly, a fine control over the motion of continuous fluids or nano/picoliter‐sized discrete droplets in microscale channels is beneficial in miniaturized systems. Therefore, there is a growing interest in downscaling the corresponding processes within LOCs and still retaining cost‐effectiveness and ease of fabrication. The microfluidic systems possess intrinsic features including minimized consumption of reagents, portability, increased automation, reduced time, and cost efficiency, which make them particularly attractive from a wide range of laboratory and industrial perspectives.
关键词： Microfluidics,Lab‐on‐a‐chip,Photoactuators,Soft materials,Micro‐total‐analysis‐system
更新于2025-09-23 15:21:01
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Single-Cell Optogenetic Control of Calcium Signaling with a High-Density Micro-LED Array
摘要： Precise optogenetic control, ideally down to single cells in dense cell populations, is essential in understanding the heterogeneity of cell networks. Devices with such capability, if built in a chip scale, will advance optogenetic studies at cellular levels in a variety of experimental settings. Here we demonstrate optogenetic control of intracellular Ca2+ dynamics at the single cell level using a 16-μm pitched micro-LED array that features high brightness, small spot size, fast response, and low voltage operation. Individual LED pixels are able to reliably trigger intracellular Ca2+ transients, confirmed by fluorescence microscopy, control experiments, and cross-checked by two genetically-coded Ca2+ indicators. Importantly, our array can optogenetically address individual cells that are sub-10 μm apart in densely packed cell populations. These results suggest the possible use of the micro-LED array towards a lab-on-a-chip for single-cell optogenetics, which may allow for pharmaceutical screening and fundamental studies on a variety of cell networks.
关键词： optogenetic control,lab-on-a-chip,calcium signaling,micro-LED array,single-cell
更新于2025-09-19 17:13:59
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Novel Nanoplasmonic Structure based Integrated Microfluidic Biosensors for Label-Free in Situ Immune Functional Analysis
摘要： The study of immune functional responses is essential to understanding the central role of the immune system in providing immunological host defense and its intercommunication with other systems. The recent development of integrated microfluidic cytokine biosensors has established a new paradigm to identify, isolate, and study immune cell subtypes, cell functions, and intercellular communications that constitute those responses. In this minireview, we highlight the most recent progress in label-free cytokine detection based on localized surface plasmon resonance optical sensing. We present the applications of newly identified plasmonic nanostructures and the integration with advanced microfluidic devices for novel lab-on-a-chip biosensing systems and discuss the associated challenges and future perspective of such integrative sensing technologies for next-generation immune functional analysis.
关键词： immune functional responses,localized surface plasmon resonance,microfluidic cytokine biosensors,plasmonic nanostructures,lab-on-a-chip biosensing systems
更新于2025-09-19 17:13:59
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Selective infiltration and storage of picoliter volumes of liquids into sealed SU-8 microwells
摘要： This paper describes the selective infiltration and storage of picoliter volumes of water and IPA in arrays of sealed SU-8 microwells. Microwells, with a volume of approximately 300 picoliters, are fabricated employing photolithography and a polymer onto polymer lamination method to seal the structures with a thin cover of SU-8 and PDMS in order to suppress the evaporation of the infiltrated liquids. A glass capillary is used to punch through the SU-8/PDMS cover and to infiltrate the liquid of interest into the microwells. The influence of the mixing ratio of the PDMS and its curing agent is studied and the results show that a lower ratio of 2:1 suppresses the evaporation more when compared to the standard mixing ratio of 10:1. In regards to water and IPA, the dwell time in the reservoirs was increased by approximately 50 % and 450 % respectively. Depending on the physical properties of the microwells and the liquids, the SU-8/PDMS cover suppresses the evaporation up to 32 mins for water and 463 mins for IPA, respectively, until the microwell is completely empty again. Additionally, multiple infiltrations of the same microwell are demonstrated using two immiscible liquids IPA and paraffin oil. Based on the popular polymers SU-8 and PDMS, the sealed microwell structures are scalable and combinable with different glass capillaries according to the needs of future analytical research and medical diagnostics.
关键词： microwells,Lab-on-a-chip,microfluidics,Selective infiltration,PDMS,SU-8
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - In Flow Manipulation and Characterization of Cancer Cells by Coherent Computational Microscopy
摘要： Liquid biopsy has shown remarkably promising in oncology for the early diagnosis of cancer through the detection of circulating biomarkers such as circulating tumor cells (CTCs). Recent evidences suggest that CTCs represent effective prognostic and predictive biomarkers to monitor/predict therapy efficacy in breast, colon and prostate cancers [1,2]. However, the frequency of CTCs in blood is approximately 1 to 10 cells per 10 mL of blood, which is as challenging as looking for a needle in a haystack. In microfluidics, Digital Holography (DH) has been shown to be a promising technique to characterize CTCs with the aim to detect them inside a heterogeneous liquid sample. DH is label-free, real-time and gives access to the complex amplitude of the object [3-6]. Thus, any classification approach based on the holographic signature can exploit a reach information content to take a decision. Moreover, the flexible refocusing capability of DH imaging allows to inspect an entire liquid volume with a single capture. This enables the high-throughput inspection of blood and other bodily fluids rapidly flowing inside microfluidic channels. In DH, the sample is probed from one single direction and the phase delay introduced by the sample in through transmission acts as a contrast agent. Hence, the optical thickness measurable by DH imaging is an integral information, i.e. the sum of all the contributions experienced by the coherent light during its passage through the sample. In order to decouple the refractive index from the physical thickness and to resolve its distribution along the optical axis, tomography exploits multiple recordings, probing the sample from different angles and combining the corresponding phase-contrast maps [7,8]. Various schemes have been proposed to minimize the number of sampling angles and to make the recording stage faster in order to match the requirements and time constraints imposed by real biological problems. Here we show the recent advances of in-flow holographic tomography, which exploits a controlled induced rotation of the sample inside the microfluidic channel to probe it from different view angles with no mechanical rotation of the source beam [8,9]. We introduce an effective algorithm to recover from the recorded phase maps the set of angles required as input of the optical projection tomography algorithm [7-9]. We show the application of holographic flow tomography to the characterization of different cancer cells [10], namely breast cancer cells, ovarian cancer cells and neuroblastoma. We also discuss different possibilities of Lab-on-a-Chip design and flow engineering that allow us to induce controlled rotations while maintaining the high-throughput nature of DH microscopy [9,11,12]. In the next future, the large amount of data obtainable by this approach will be used to train a neural network devoted to classify CTCs, distinguishing them from the other components of a blood stream.
关键词： liquid biopsy,cancer cells,microfluidics,circulating tumor cells,holographic tomography,Lab-on-a-Chip,digital holography
更新于2025-09-16 10:30:52
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Ultralow-Power Electrically Activated Lab-on-a-Chip Plasmonic Tweezers
摘要： We propose ultralow-power plasmonic tweezers with no external optical source. They consist of a one-dimensional array of graphene-based plasmonic units driven by the optical transitions within the underlying array of (Al, In)As/(Ga, In)As/(Al, In)As/(Ga, In)As/(Al, In)As quantum cascaded heterostructures (QCHs), electrically biased in series. Each QCH unit formed in a nanopillar can act as a built-in optical source required for exciting the localized surface plasmons (LSPs) at the surface of the overlying circular graphene nanodisk. The stimulated emission due to intersubband transition within each optical source evanesces through the top (Al, In)As cladding layer and interacts with the overlying graphene nanodisk, inducing the LSPs required for the formation of the plasmonic tweezers. Numerical simulations show, under 145–170 mV applied voltages, that the tweezers with graphene nanodisks of 16–30 nm in diameter and chemical potentials of 0.5–0.7 eV can trap polystyrene nanoparticles of 9 nm in diameter and larger, demonstrating acceptable sensitivities for variations in the nanoparticle diameter and refractive index. These lab-on-a-chip plasmonic tweezers, bene?ting from their small footprints and ultralow power consumptions, which are capable of sensing and trapping nanoparticles without requiring expensive external optical sources, open up a di?erent horizon for developing compact on-chip plasmonic tweezers.
关键词： plasmonic tweezers,localized surface plasmons,graphene,lab-on-a-chip,quantum cascade heterostructures
更新于2025-09-16 10:30:52