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In recent years, magnetic levitation is finding interesting applications in various fields related to microdevices. Producing inexpensive microfabricated magnetic films is of high importance to all magnetically levitated microdevices. This paper introduces a microlevitation system and presents the fabrication of Co–Ni–Mn–P films using electrodeposition. The fabrication parameters are varied such that magnetization direction of the film is varied by changing the crystal structure. The magnetic properties of the films such as coercivity, remanence, and maximum energy product demonstrate that hexagonal structure promotes out-of-plane magnetization whereas cubic structure reinforces in-plane magnetization. The performance of the Co–Ni–Mn–P films is evaluated by magnetic levitation experiments of silicon samples. Satisfactory results are obtained toward the goal of realization of a magnetically levitated microgripper. [ABSTRACT FROM AUTHOR]

Droplet-based microfluidic systems offer tremendous benefits for high throughput biochemical assays. Despite the wide use of electrical detection for microfluidic systems, application of impedimetric sensing for droplet systems is very limited. This is mainly due to the insulating oil-based continuous phase used for most aqueous samples of interest. We present modelling and experimental verification of impedimetric detection of hemagglutination in microdroplets. We have detected agglutinated red blood cells in microdroplets and screened whole blood samples for multiple antibody sera using conventional microelectrodes. We were able to form antibody and whole blood microdroplets in PDMS microchannels without any tedious chemical surface treatment. Following the injection of a blood sample into antibody droplets, we have detected the agglutination-positive and negative droplets in an automated manner. In order to understand the characteristics of impedimetric detection inside microdroplets, we have developed the lumped electrical circuit equivalent of an impedimetric droplet content detection system. The empirical lumped element values are in accordance with similar models developed for single phase electrical impedance spectroscopy systems. The presented approach is of interest for label-free, quantitative analysis of droplets. In addition, the standard electronic equipment used for detection allows miniaturized detection circuitries that can be integrated with a fluidic system for a quantitative microdroplet-based hemagglutination assay that is conventionally performed in well plates. [ABSTRACT FROM AUTHOR]

This paper proposes a novel method for measuring blood plasma and serum viscosity with a microcantilever-based MEMS sensor. MEMS cantilevers are made of electroplated nickel and actuated remotely with magnetic field using an electro-coil. Real-time monitoring of cantilever resonant frequency is performed remotely using diffraction gratings fabricated at the tip of the dynamic cantilevers. Only few nanometer cantilever deflection is sufficient due to interferometric sensitivity of the readout. The resonant frequency of the cantilever is tracked with a phase lock loop (PLL) control circuit. The viscosities of liquid samples are obtained through the measurement of the cantilever’s frequency change with respect to a reference measurement taken within a liquid of known viscosity. We performed measurements with glycerol solutions at different temperatures and validated the repeatability of the system by comparing with a reference commercial viscometer. Experimental results are compared with the theoretical predictions based on Sader’s theory and agreed reasonably well. Afterwards viscosities of different Fetal Bovine Serum and Bovine Serum Albumin mixtures are measured both at 23°C and 37°C, body temperature. Finally the viscosities of human blood plasma samples taken from healthy donors are measured. The proposed method is capable of measuring viscosities from 0.86cP to 3.02cP, which covers human blood plasma viscosity range, with a resolution better than 0.04cP. The sample volume requirement is less than 150μl and can be reduced significantly with optimized cartridge design. Both the actuation and sensing are carried out remotely, which allows for disposable sensor cartridges. [ABSTRACT FROM AUTHOR]

This is the first part of a two-part study on the generation of droplets at a microfluidic T-junction operating in the transition regime where confinement of the droplet creates a large squeezing pressure that influences droplet formation. In this regime, the operation of the T-junction depends on the geometry of the intersection (height-to-width ratio, inlet width ratio), capillary number, flow ratio, and viscosity ratio of the two phases. Here in paper I we presented our experimental observations through the analysis of high-speed videos of the droplet formation process. Various parameters are tracked during the formation cycle such as the shape of the droplet (penetration depth and neck), interdroplet spacing, production rate, and flow of both phases across several T-junction designs and flow conditions. Generally, the formation process is defined by a two-stage model consisting of an initial filling stage followed by a necking stage. However, video evidence suggests the inclusion of a third stage, which we term the lag stage, at the beginning of the formation process that accounts for the retraction of the interface back into the injection channel after detachment. Based on the observations made in this paper, a model is developed to describe the formation process in paper II, which can be used to understand the design and operation of T-junction generators in the transition regime. [ABSTRACT FROM AUTHOR]

This is the second part of a two-part study on the generation of droplets at a microfluidic T-junction operating in the transition regime. In the preceding paper [Phys. Rev. E 85, 016322 (2012)], we presented our experimental observations of droplet formation and decomposed the process into three sequential stages defined as the lag, filling, and necking stages. Here we develop a model that describes the performance of microfluidic T-junction generators working in the squeezing to transition regimes where confinement of the droplet dominates the formation process. The model incorporates a detailed geometric description of the drop shape during the formation process combined with a force balance and necking criteria to define the droplet size, production rate, and spacing. The model inherently captures the influence of the intersection geometry, including the channel width ratio and height-to-width ratio, capillary number, and flow ratio, on the performance of the generator. The model is validated by comparing it to speed videos of the formation process for several T-junction geometries across a range of capillary numbers and viscosity ratios. [ABSTRACT FROM AUTHOR]

Abstract: Detection of the presence, size and speed of microdroplets in microfluidic devices is presented using commercially available capacitive sensors which make the droplet based microfluidic systems scalable and inexpensive. Cross-contamination between the droplets is eliminated by introducing a passivation layer between the sensing electrodes and droplets. A simple T-junction generator is used to generate droplets in microchannels. Coplanar electrodes are used to form a capacitance through the microfluidic channel. The change in capacitance due to the presence of a droplet in the sensing area is detected and used to determine the size and speed of the droplet. The design of a single pair of electrodes is used to detect the presence of a droplet and the interdigital finger design is used to detect the size and speed of the droplet. An analytical model is developed to predict the detection signal and guide the experimental optimization of the sensor geometry. The measured droplet information is displayed through a Labview interface in real-time. The use of capacitance sensors to monitor droplet sorting at a T-junction is also presented. The discussions in this paper can be generalized to any droplet detection application and can serve as a guideline in sensor selection. [Copyright &y& Elsevier]

Abstract: This paper presents the modeling, simulation and characterization of a photo-thermally actuated bent-beam microactuator. The microactuator consists of a single polymeric layer (SU-8) fabricated with conventional photolithography techniques. The principle of operation is based on the thermal expansion of the bent-beams that absorb the required heat by laser illumination. This provides an effective non-contact actuation mechanism by laser beam focusing. A theoretical model of the microactuator is derived and verified by finite element simulations and experiments. The experiments show that a bent-beam actuator with 800 m long, 40 m wide, 100 m thick and 6 bent arms achieves a tip displacement of 16 m with an incident laser beam of 50mW power while keeping the maximum temperature less than 125 C. This study merges the advantages of photo-thermal actuation with practicality of polymeric materials. To verify the effectiveness of the proposed microactuator mechanism, a microgripper with bent-beam actuator was fabricated and characterized. It has been demonstrated that the opening of the gripping fingers can be increased from 20 to 50 m for a microgripper with 1000 m long fingers with an incident laser power of 50mW. This polymeric microgripper with photo-thermal actuation provides a way of gentle grasping with electrical isolation, high repeatability and low temperature operation that is particularly crucial for biomanipulation applications. The polymeric photo-thermal actuator described in this study expands the practical applications of microactuators/microgrippers which are critical tools in bioMEMS devices. [Copyright &y& Elsevier]

This paper presents modeling and analysis of eddy-current damping that is formed by a conductive plate placed below the levitating object in order to suppress vibrations and ensure stability. It is demonstrated that vibrations should be damped to preserve stability and precision especially for stepwise motion. The levitated object is a small permanent magnet in our experiments. A magnetic drive unit is used for vertical motion of the magnet. Eddy-current distribution in the plate is calculated by solving diffusion equation for vector magnetic potential. The eddy force applied to the object is derived by a coil model representation. It is shown that if a 20 mm radius, 9 mm thick aluminum circular plate is used for eddy-current damping, the levitated object can closely follow a step input with a steady- state precision varying between 0.04 and 0.07 mm depending on the plate object distance. Eddy-current damping is a key technique that improves levitation performance to increase the diversity of applications of magnetic levitation systems in micromanipulation and microelectronic fabrication. [ABSTRACT FROM AUTHOR]

Targeted, on‐demand delivery has been of interest using materials responsive to environmental stimuli. A delivery technique based on precise release of aqueous microdroplets from a liquid crystal (LC) medium with contactless stimulation is presented. A nematic LC is doped with a photothermal dye that produces heat under near IR light exposure. The heat is used to overcome the elastic strains in the LC phase, promoting the release of initially entrapped water droplets to the neighboring aqueous solution. Designing the geometry of LC‐based emulsions and tuning the light intensity and position allows for manipulation of the release in two distinct modes defined as pulsated and continuous. In the pulsated mode, water droplets are released transiently from the casted water‐in‐LC emulsion layer based on sweeping by the moving isotropic‐nematic phase boundary controlled by light. In the continuous mode, water droplets are ejected continuously from a droplet‐shaped water‐in‐LC emulsion, due to a heating‐induced internal flow controlled by light. The droplet release by contactless stimulation is used for the on‐demand dosing of dopamine and its oxidizing reagent from isolated reservoirs to obtain an in situ reaction signal for a hydrogen peroxide assay. A new dual‐mode release system developed with photothermal LCs holds potential in drug release, controlled mixing, and photothermal therapy. [ABSTRACT FROM AUTHOR]

Organoids are emerging as a powerful tool to investigate complex biological structures in vitro. Vascularization of organoids is crucial to recapitulate the morphology and function of the represented human organ, especially in the case of the kidney, whose primary function of blood filtration is closely associated with blood circulation. Current in vitro microfluidic approaches have only provided initial vascularization of kidney organoids, whereas in vivo transplantation to animal models is problematic due to ethical problems, with the exception of xenotransplantation onto a chicken chorioallantoic membrane (CAM). Although CAM can serve as a good environment for vascularization, it can only be used for a fixed length of time, limited by development of the embryo. Here, we propose a novel lab on a chip design that allows organoids of different origin to be cultured and vascularized on a CAM, as well as to be transferred to in vitro conditions when required. Mouse embryonic kidneys cultured on the CAM showed enhanced vascularization by intrinsic endothelial cells, and made connections with the chicken vasculature, as evidenced by blood flowing through them. After the chips were transferred to in vitro conditions, the vasculature inside the organoids was successfully maintained. To our knowledge, this is the first demonstration of the combination of in vivo and in vitro approaches applied to microfluidic chip design. [ABSTRACT FROM AUTHOR]

The flow behavior of blood is determined mainly by red blood cell (RBC) deformation and aggregation as well as blood viscoelasticity. These intricately interdependent parameters should be monitored by healthcare providers to understand all aspects of circulatory flow dynamics under numerous cases including cardiovascular and infectious diseases. Current medical instruments and microfluidic systems lack the ability to quantify these parameters all at once and in physiologically relevant flow conditions. This work presents a handheld platform and a measurement method for quantitative analysis of multiple of these parameters from 50 μl undiluted blood inside a miniaturized channel. The assay is based on an optical transmission analysis of collective RBC deformation and aggregation under near-infrared illumination during a 1 s damped oscillatory flow and at stasis, respectively. Measurements with blood of different hemo-rheological properties demonstrate that the presented approach holds a potential for initiating simultaneous and routine on-chip blood flow analysis even in resource-poor settings. [ABSTRACT FROM AUTHOR]

Particle cross-stream migration in electrohydrodynamic microfluidic systems exhibits intriguing behaviors, which makes it interesting when viewed from a fundamental perspective and promising for nanoparticle focusing and separation applications. So far, particle behavior in such systems has been explained with the slip-induced lift force model (Saffman model), which predicts particle central or side focusing based on the direction of electric field and fluid flow. However, in our previous work, we observed particle migration patterns that did not adhere to the prediction of the Saffman model. In this work, we further studied this novel particle lateral migration behavior, which we termed the "anti-Saffman" behavior. We experimentally investigated how changing the conductivity of the suspending medium influences particle behavior and quantitatively measured the net lateral force experienced by the particles. Then, we compared this net force with the prediction of the relevant lift force models in the literature. We concluded that the anti-Saffman behavior is positively correlated with medium conductivity and shear rate (∝ γ ̇ 2 ). Furthermore, the comparison with the existing force models revealed that none of them can predict the experimentally observed particle lift. The net lift predicted by hydrodynamic lift models indicated that the underlying mechanism behind our experiments also potentially has a hydrodynamic origin. We believe this phenomenon offers the possibility of manipulating and separating nanoparticles suspended in standard aqueous electrolyte solutions, which makes it applicable to various biological samples. [ABSTRACT FROM AUTHOR]

In this article, we report a method to damp microfluidic hydrodynamic fluctuations caused by flow sources. We demonstrate that compliance of elastomeric off-chip tubings can be used to damp fluctuations and lead to steady flow rates. We analyze the whole microfluidic system using electrical circuit analogies, and demonstrate that off-chip compliances are significant, especially for displacement pump driven systems. We apply this hydrodynamic damping method to microfluidic droplet generation. Our results show that highly monodisperse microdroplets can be obtained by syringe pump driven systems utilizing this damping effect. We reached a coefficient of variation of 0.39% for the microdroplet area using a standard T-junction geometry. Additionally, we demonstrated that pressure pumps inherently use this effect, and have so far led the high performances reported in the literature in terms of droplet monodispersity. The presented off-chip hydrodynamic damping method is not only low-cost and practical, but can also be used in elastomeric and rigid microchannels without need to introduce additional components to the fluidic circuit. [ABSTRACT FROM AUTHOR]

Transfusion of red blood cells (RBCs) is one of the most valuable and widespread treatments in modern medicine. Lifesaving RBC transfusions are facilitated by the cold storage of RBC units in blood banks worldwide. Currently, RBC storage and subsequent transfusion practices are performed using simplistic workflows. More specifically, most blood banks follow the "first-in-first-out" principle to avoid wastage, whereas most healthcare providers prefer the "last-in-first-out" approach simply favoring chronologically younger RBCs. Neither approach addresses recent advances through -omics showing that stored RBC quality is highly variable depending on donor-, time-, and processing-specific factors. Thus, it is time to rethink our workflows in transfusion medicine taking advantage of novel technologies to perform RBC quality assessment. We imagine a future where lab-on-a-chip technologies utilize novel predictive markers of RBC quality identified by -omics and machine learning to usher in a new era of safer and precise transfusion medicine. [ABSTRACT FROM AUTHOR]

Most of the available microvalves include complicated fabrication steps and multiple materials. We present a microvalve which is inspired from macroplug valves. The plug microvalve is fabricated by boring a hole through a rigid cylindrical rod and inserting it through a microfluidic chip. It simply functions by rotating the rod which aligns or misaligns the valve port with the microchannel. The rod is made up of a rigid material for applying the valve to an elastic polydimethylsiloxane (PDMS) microchannel. The valve can also be used for a rigid channel by inserting the rod into an elastic tubing. Therefore, the presented microvalve can be used for both elastomeric and thermoplastic channels. The plug microvalve can be applied to a prefabricated microchannel and does not require modification of the mold design. We have verified the repeatability and robustness of the valve by repetitive operation cycles using a servo motor. The plug microvalve is adaptable to numerous microfluidic applications. We have shown three modes of operation for the microvalve including fluid flow control across multiple intersecting channels. Integrating the microvalve to some commonly used microfluidic designs, we demonstrated the versatility and the practicality of the microvalve for controlling flow focusing, microdroplet sorting and rapid chemical agent detection. This low-cost microvalve significantly minimizes the prototyping time for microfluidic systems. [ABSTRACT FROM AUTHOR]

The erythrocyte sedimentation rate (ESR) is a frequently used 30 min or 60 min clinical test for screening of several inflammatory conditions, infections, trauma, and malignant diseases, as well as non-inflammatory conditions including prostate cancer and stroke. Erythrocyte aggregation (EA) is a physiological process where erythrocytes form face-to-face linear structures, called rouleaux, at stasis or low shear rates. In this work, we proposed a method for ESR measurement from EA. We developed a microfluidic opto-electro-mechanical system, using which we experimentally showed a significant correlation (R2 = 0.86) between ESR and EA. The microfluidic system was shown to measure ESR from EA using fingerprick blood in 2 min. 40 μl of whole blood is filled in a disposable polycarbonate cartridge which is illuminated with a near infrared emitting diode. Erythrocytes were disaggregated under the effect of a mechanical shear force using a solenoid pinch valve. Following complete disaggregation, transmitted light through the cartridge was measured using a photodetector for 1.5 min. The intensity level is at its lowest at complete disaggregation and highest at complete aggregation. We calculated ESR from the transmitted signal profile. We also developed another microfluidic cartridge specifically for monitoring the EA process in real-time during ESR measurement. The presented system is suitable for ultrafast, low-cost, and low-sample volume measurement of ESR at the point-of-care. [ABSTRACT FROM AUTHOR]

• Revealed the root cause for droplet volume variation in fluidic systems. • Presented a universal novel method to achieve ultra-high monodispersity of droplets. • The novel method implemented for the most common droplet generators and flow sources. • Easily applicable method with no additional cost for existing droplet systems. Despite the importance of droplet monodispersity, a universal methodology for high monodispersity droplet generation does not exist yet. We have recently demonstrated that unlike the conventional method of droplet generation, applying an identical pressure from a single source makes the microfluidic droplet system immune to the external fluctuations that originate from the imperfection of the flow source. In this work, we show that our method is universal and applicable to other common microfluidic devices and flow sources. We applied this method to flow-focusing and coflow devices that are commonly used for high-frequency microdroplet generation. In addition to the pressure pump, we used a syringe pump to show that our method is applicable to flow rate controllable systems as well. We compared the monodispersity of droplets formed by the conventional methods and the novel method explained in this work. [ABSTRACT FROM AUTHOR]

Pazopanib (PAZ), a tyrosine kinase inhibitor, is used to treat advanced renal cell carcinoma (RCC) and advanced soft tissue sarcoma (STS). The FDA approved PAZ for RCC in 2009 and for STS in 2012. The antitumor activity of pazopanib, according to the degree of inhibition, shows different results depending on the dose. Renal cell carcinoma is the most sensitive carcinoma to pazopanib, with 77% inhibition at the 10 mg/kg dose. Clinical studies have shown 53% to 65% inhibition in carcinomas such as breast carcinoma, prostate carcinoma, and melanoma. Plasma proteins such as human serum albumin (HSA) have a critical role in transporting and storing bioactive components. This feature of HSA is very important for the development of cancer therapy. Here, we investigated the interaction between PAZ and HSA to evaluate their binding strength, binding types, and conformational change in HSA. We used spectroscopic methods to assess the drug–protein interaction. Fluorescence measurements revealed that the interaction of PAZ with HSA occurred via the static quenching mechanism. The calculated binding number and binding constants were 1.041 and 1.436 × 106 M−1, respectively, at 298.15 K based on fluorescence screening. The high binding constant and calculated Gibbs free energy at different temperatures showed spontaneous and strong binding. Circular dichroism measurements showed that the α-helix structure of HSA was retained as the secondary structure, with a slight reduction in its percentage after adding PAZ. Furthermore, molecular modeling studies suggested that the docking score of PAZ is higher than those of bicalutamide and ibuprofen, the drugs that were chosen as model competitors against PAZ. Accordingly, PAZ was found to replace bicalutamide and ibuprofen on the HSA binding site, which was also confirmed by UV absorption spectroscopy. [ABSTRACT FROM AUTHOR]

The article discusses the need for objective tools to assess the quality of stored red blood cells (RBCs) for transfusion medicine. The authors highlight the potential of lab-on-a-chip (LOC) technologies to quantitatively evaluate RBC quality using multidimensional metrics. They acknowledge the development of a point-of-care device called Erysense, which assesses the flow properties and morphological abnormalities of stored RBCs. However, they also mention limitations and challenges that need to be addressed, such as the need for extensive validation, automation of the workflow, and addressing storage lesions. The authors suggest that while scalable strategies for in vitro erythropoiesis are promising, other steps can be taken to address blood shortages and improve transfusion practices. [Extracted from the article]

Simple, low-cost, robust, and scalable fabrication of microscopic linear barcodes with high levels of complexity and multiple authentication layers is critical for emerging applications in information security and anti-counterfeiting. This manuscript presents a novel approach for fabrication of microscopic linear barcodes that can be visualized under Raman microscopy. Microfluidic channels are used as molds to generate linear patterns of end-grafted polymers on a substrate. These patterns serve as templates for area-selective binding of colloidal gold nanoparticles resulting in plasmonic arrays. The deposition of multiple taggant molecules on the plasmonic arrays via a second microfluidic mold results in a linear barcode with unique Raman fingerprints that are enhanced by the underlying plasmonic nanoparticles. The width of the bars is as small as 10 μm, with a total barcode length on the order of 100 μm. The simultaneous use of geometric and chemical security layers provides a high level of complexity challenging the counterfeiting of the barcodes. The additive, scalable, and inexpensive nature of the presented approach can be easily adapted to different colloidal nanomaterials and applications. [ABSTRACT FROM AUTHOR]

Droplet-based microfluidic systems require a precise control of droplet physical properties; hence, measuring the morphological properties of droplets is critical to obtain high sensitivity analysis. The ability to perform such measurements in real-time is another demand which has not been addressed yet. In this study, we used coplanar electrodes configured in the differential measurement mode for impedimetric measurement of size and velocity. To obtain the size of the droplets, detailed 3D finite element simulations of the system were performed. The interaction of the non-uniform electric field and the droplet was investigated. Electrode geometry optimization steps were described and design guideline rules were laid out. User-friendly software was developed for real-time observation of droplet length and velocity together with in situ statistical analysis results. A comparison between impedimetric and optical measurement tools is given. Finally, to illustrate the benefit of having real-time analysis, iDM was used to synthesize particles with a predefined monodispersity limit and to study the response times of syringe pump and pressure pump driven droplet generation devices. This analysis allows one to evaluate the 'warm-up' time for a droplet generator system, after which droplets reach the desired steady-state size required by the application of interest. [ABSTRACT FROM AUTHOR]

Coagulation is an essential physiological activity initiated by the interaction of blood components for clot formation. Prothrombin time (PT) measurement is a clinical test for the assessment of the extrinsic/common pathways of coagulation cascade. Periodic measurement of PT is required under numerous conditions including cardiovascular disorders. We present a self-powered microfluidic device for quantitative PT measurement from 50 μl whole blood. The entire platform is disposable and does not require any external pumping, power, or readout units. It consists of a 3D-printed effervescent pump for CO 2 generation from a chemical reaction, a cartridge for two-channel fluid flow (blood and water), and a grid for the quantification of fluid migration distance. Following the introduction of the fluids to the corresponding channel inlets, marking the coagulation start, an acid-base reaction is triggered for gas generation that drives the fluids within the channels. When the blood coagulates, its flow in the channel is halted. At that point, the distance water has travelled is measured using the grid. This distance correlates with PT as demonstrated through clinical tests with patient samples. This single-unit device has a potential for rapid evaluation and periodic monitoring of PT in the clinical settings and at the point-of-care. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Rapid determination of coagulation time using from erythrocyte aggregation that is monitored optically. • Proposing a new methodology for one of the most common point-of-care assays in the market. • Development of a truly portable system that only requires 50 μl of whole blood sample to perform the test. • Investigating the role of fibrinogen in erythrocyte aggregation and coagulation simultaneously. • Excellent correlation between the proposed coagulation time method and the results obtained from benchtop device. Abstract Coagulation, the process leading to clot formation with the interplay of blood constituents, is a self-regulating mechanism, requiring attentive and periodic monitoring for numerous clinical cases. Erythrocyte aggregation (EA) is a characteristic behaviour of erythrocytes forming reversible clumps especially in vitro at low shear rates. The effect of EA during coagulation is overlooked in whole blood (WB) clotting assays, and the relationship between the two mechanisms is not well understood. We present an optofluidic point-of-care device enabling quantitative investigation of EA from 50 μl WB during the coagulation process. Not only did we explain the coagulation mechanism considering EA, but we also demonstrated coagulation time measurement from optical EA analysis. The device consists of a disposable cartridge and a handheld analyzer containing a pinch valve for fluid motion and optics for transmitted light measurement. Following the sample introduction and cessation of the valve operation, the optical signal is the lowest due to shear-induced cell disaggregation. Then, the signal increases due to EA until reaching a peak, indicating blood clotting. The working principle was proven through clinical tests for prothrombin time measurement. In addition to revealing the relation between coagulation and aggregation, this device is promising for rapid WB coagulation time measurement. [ABSTRACT FROM AUTHOR]

In this study, a facile strategy for fabricating a microfluidic flow cytometer using two glass micropipettes with different sizes and a 3D printed millifluidic aligner was presented. Particle confinement was achieved by hydrodynamic focusing using a single sample and sheath flow. Device performance was extracted using the forward and side-scattered optical signals obtained using fiber-coupled laser and photodetectors. The 3-D printing assisted glass capillary microfluidic device is ultra-low-cost, not labor-intensive and takes less than 10 min to fabricate. The present device offers a great alternative to conventional benchtop flow cytometers in terms of optofluidic configuration. [ABSTRACT FROM AUTHOR]

We demonstrate a surface plasmon resonance imaging platform integrated with a smartphone to be used in the field with high-throughput biodetection. Inexpensive and disposable SPR substrates are produced by metal coating of commercial Blu-ray discs. A compact imaging apparatus is fabricated using a 3D printer which allows taking SPR measurements from more than 20.000 individual pixels. Real-time bulk refractive index change measurements yield noise equivalent refractive index changes as low as 4.12 × 10 −5 RIU which is comparable with the detection performance of commercial instruments. As a demonstration of a biological assay, we have shown capture of mouse IgG antibodies by immobilized layer of rabbit anti-mouse (RAM) IgG antibody with nanomolar level limit of detection. Our approach in miniaturization of SPR biosensing in a cost-effective manner could enable realization of portable SPR measurement systems and kits for point-of-care applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • New forms of particle behaviour were presented for colloidal solutions in microchannels. • The novel patterns are hypothesized to be due to nonuniformity of electric double layer and particle rotation due to shear flow. • The observations were done using Newtonian aqueous solutions and are applicable to a wide range of solutions. • These results challenge the Saffman-like slip velocity induced lift mechanisms used to explain the cross-stream particle migration. The lateral migration of colloidal particles inside a microfluidic channel has gained attention due to being both fundamentally intriguing and applicable for particle separation, such as cancer cell isolation or extracellular vesicle purification. Applying an external electric field combined with a pressure-driven flow induces such lateral migrations. In this study, new modes of lateral particle migration have been found by experimentally investigating 6 µm particles in the co-presence of electric field and pressure-driven flow. The experiments revealed the importance of the relative strengths of electric field and pressure gradient in determining particle lateral positioning. We hypothesize that the nonuniformity of the polarization caused by the external electric field and the rotation of the particle due to the background pressure-driven flow result in these modes of transverse migration. These new migration patterns are further utilized to perform microparticle separation and, more importantly, present a novel separation modality. [ABSTRACT FROM AUTHOR]

The isolation of extracellular vesicles (EVs) from milk, a complex mixture of colloidal structures having a comparable size to EVs, is challenging. Although ultracentrifugation (UC) has been widely used for EV isolation, this has significant limitations, including a long processing time at high g-force conditions and large sample volume requirements. We introduced a new approach based on nature nanoentities cellulose nanofibers (CNFs) and short time and low g-force centrifugation to isolate EVs from various milk fractions. The flexible and entangled network of CNFs forms nanoporous, which entraps the EVs. Further, positively charged CNFs interact with anionic EVs through an electrostatic attraction, promoting their isolation with efficiency comparable with UC. The functionality and toxicity of isolated milk EVs were tested in Caco2 cells. Overall, the newly developed approach provides straightforward isolation and biocompatibility and preserves the natural properties of the isolated EVs, enabling further applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Microfluidic capacitive sensors have been used for detection of droplets, however they have been lacking the sensitivity required for detecting the content of droplets. In this study, we developed a scalable, portable, robust and high sensitivity capacitive microdroplet content detection system using coplanar electrodes with nanometer thick silicon dioxide (SiO 2 ) passivation layer and off-the-shelf capacitive sensors. The microfluidic chip we have designed provides easy and rapid modification of droplet content by mixing two aqueous liquids at any given ratio. The change in dielectric constant of the droplet content leads to the change in capacitive signal. The dielectric content of droplets was modified continuously while corresponding capacitance signal was measured. The resolution of the system was measured as 3 dielectric permittivity units. The results were verified using a semiconductor parameter analyzer. The application specific integrated circuit used in this work enables a portable, low-cost detection system and matches the performance of bench-top analyzers. Automated and precise measurement of dielectric content in droplets for biochemical assay monitoring is a major application of the presented system. [ABSTRACT FROM AUTHOR]

[Display omitted] • Waste moth eggshells has been introduced to material science. • The eggshell has no cytotoxicity. • The elastic modulus of the inner part is much greater than the outer part. • Hexagonal part provides highly suitable template for growth of silver nanostructures. • Eggshell silver coating transforms the originally microbial surface to antimicrobial. Although over 80% of the world's existing animal species are insects, with each of these species having unique eggshell morphologies, limited information is available regarding the use of their eggshells in material science applications. The present research discusses using discarded eggshells of the Chinese oak silkworm (Antheraea pernyi) as a technological material. The 3-dimensional aspects of the insect's eggshell were examined in detail, demonstrating the complexity of their novel surface morphology. The outer surface of the eggshell was comprised of a hexagonal structure, whereas the inner surface consists of a mostly smooth surface. Distinctive layers of the eggshell were observed when cross sections of the surface were analyzed. The elastic modulus of the inner part of the eggshell is substantially greater than that of the outer part. The physicochemical properties of the eggshell were characterized and no toxic properties were found. The hexagonal structures found on the outer surface of the eggshell provide a highly suitable template for silver nanostructure deposition. The resulting silver decorated surfaces can be used to detect molecules via surface-enhanced Raman scattering (SERS) effects. The deposition of silver renders the surface antimicrobial, whereas the original surface was microbial. Collectively, the insights gained in this study will be key in developing advanced engineering applications of the insect eggshells. [ABSTRACT FROM AUTHOR]

Low proliferation capacity of corneal endothelial cells (CECs) and worldwide limitations in transplantable donor tissues reveal the critical need of a robust approach for in vitro CEC growth. However, preservation of CEC-specific phenotype with increased proliferation has been a great challenge. Here we offer a biomimetic cell substrate design, by optimizing mechanical, topographical and biochemical characteristics of materials with CEC microenvironment. We showed the surprising similarity between topographical features of white rose petals and corneal endothelium due to hexagonal cell shapes and physiologically relevant cell density (≈ 2000 cells/mm2). Polydimethylsiloxane (PDMS) substrates with replica of white rose petal topography and cornea-friendly Young's modulus (211.85 ± 74.9 kPa) were functionalized with two of the important corneal extracellular matrix (ECM) components, collagen IV (COL 4) and hyaluronic acid (HA). White rose petal patterned and COL 4 modified PDMS with optimized stiffness provided enhanced bovine CEC response with higher density monolayers and increased phenotypic marker expression. This biomimetic approach demonstrates a successful platform to improve in vitro cell substrate properties of PDMS for corneal applications, suggesting an alternative environment for CEC-based therapies, drug toxicity investigations, microfluidics and organ-on-chip applications. [Display omitted] • White rose petal relief topography exhibited CEC microenvironment-like patterns. • PDMS cell substrates were produced within a cornea-friendly stiffness range. • COL 4 and HA functionalization of PDMS were characterized. • Patterned and COL 4 modified PDMS enhanced CEC proliferation, morphology and functionality. [ABSTRACT FROM AUTHOR]

Porous, bioactive microspheres have always been a dream material to biomedical scientists for bone regeneration and drug delivery applications due to their interconnectivity, unique pore geometry, encapsulation ability and porosity spanning macroscopic, microscopic and nanoscopic length scales. Extensive efforts have been made to produce such materials synthetically at a great cost of money, time and labor. Herein, naturally-assembled multifunctional, open-channeled and hollow bioactive micro silica spheres (diameter 209.4 ± 38.5 µm) were discovered in a marine sponge (Geodia macandrewii), by peeling the outer surface of the sterrasters using hydrogen fluoride. The obtained micro silica spheres exhibited valuable characteristics such as homogeneously distributed pores, a cavity in the center of the sphere, and channels (approx. 3000) opening from each pore into the central cavity. Simulated body fluid analysis demonstrated the bioactivity of the micro silica spheres; whereas, no bioactivity was recorded for the original untreated sterrasters. The non-cytotoxicity and osteogenic ability of the isolated microspheres were confirmed through osteoblast cell culture. Finally, these silica based porous microspheres were tested for controlled drug release capacity. The spheres showed excellent loading and release abilities for an anti-cancer drug, carboplatin, in simulated solutions and in human cancer cell culture, HeLa, through a real time cell analyzer system. The drug loading capacity of the porous beads was determined as 10.59%. Considering the unique biological and physicochemical properties, these novel bioactive silica spheres, which we name as giant macroporous silica (GMS), are promising materials for a range of applications including bone tissue engineering and drug delivery. [ABSTRACT FROM AUTHOR]

• Investigated the underlying reasons for droplet volume variation in fluidic systems. • Presented 4 design recommendations to improve monodisperse droplet generation. • Presented practical limit of achieving absolute droplet monodispersity, i.e. 0% CV. • Achieved ultra-high droplet monodispersity, less than 0.2% CV in droplet size. • Fluidic evaluation chip design to test parameters under same experimental conditions. Droplet microfluidic systems are becoming routine in advanced biochemical studies such as single cell gene expression, immuno profiling, precise nucleic acid quantification (dPCR) and particle synthesis. For all these applications, ensuring droplet monodispersity is critical to minimize the uncertainty due to droplet volume variation. Despite the wide usage of droplet-based microfluidic systems, the limit of monodispersity for droplet generation systems is still unknown. Here, we present an analytical approach that takes into account all the system dynamics and internal/external factors that disturb monodispersity. Interestingly, we are able to model the dynamics of a segmented two-phase flow system using a single-phase flow analogy, electron flow, in electrical circuits. We offer a unique solution and design guidelines to ensure ultra-monodisperse droplet generation. Our analytical conclusions are experimentally verified using a T-junction droplet generator. Equally importantly, we show the limiting experimental factors for reaching the theoretical maximum of monodispersity. [ABSTRACT FROM AUTHOR]

• A focusing-free microfluidic impedance flow cytometry is presented based on geometrical optimization of channel design. • The system is able to differentiate similar size cell types at high precision: red blood cells and lymphocytes. • Position-independent impedance signal was obtained by using a shallow channel that generates homogenous field distribution. • The system uses conventional microelectrodes and does not require any complicated fabrication or high-end signal processing units. • The microfluidic device was formed by a reversible sealing technique, hence the channel and the electrodes are reusable. A focusing-free microfluidic impedimetric cell detection system is developed. The effect of the channel dimensions, solution conductivity, excitation voltage, and particle size on impedimetric signal outputs were optimized to increase the sensitivity of the system. Conventional microfabrication techniques were adapted to obtain low height, resealable microchannels. The geometry optimization was performed by a combination of analytical, numerical and experimental approaches. The results demonstrate that reliable impedimetric particle differentiation can be achieved without any labeling or particle focusing. The system parameters were studied and rule-of-thumb design criteria were provided. Finally, using the developed system, red blood cells and leukemia cells were experimentally detected and differentiated. Thanks to its simplicity, the focusing-free cell differentiation system may find applications in several cellular diagnostic uses. [ABSTRACT FROM AUTHOR]

• Inertial regime fluidics for 2D/3D structures: spiral, straight, squarel, helical, and double oriented 3D-spiral channels. • 3D orthogonal double spiral microchannel design to achieve single line inertial focusing. • Versatile and rapid fabrication method for adjustable transformation of any planar layout to 3D geometries. • A computational approach to model particle trajectory in 3D geometries. • A fabrication method that can be adapted by many domains of microfluidics. Particle focusing and separation in microfluidic devices are critical for biological and medical applications. Inertial microfluidics is used for high throughput bio-particle focusing and separation. Most of the inertial microfluidic systems use planar structures for squeezing the particles in streams. Particle manipulation in 3D structures is often overlooked due to the complexity of the fabrication. In this study, we introduce some novel microchannel designs for inertial microfluidics by using a simple fabrication method that allows construction of both 2D and 3D structures. First, inertial migration of particles in 2D layouts including straight, spiral, and square spiral channels is investigated. Afterward, by applying a "tape'n roll" method, helical and double oriented spiral channels are configured and unexplored inertial migration behaviours are observed. Thanks to the simplicity of the fabrication and the unique characteristics of the new designs, high performance microfluidic inertial migration results can be obtained without any need for complicated microfabrication steps. The design optimization cycle can also be shortened using a computational approach we introduce in this study. [ABSTRACT FROM AUTHOR]

Spectrally selective thermal emission is in high demand for thermophotovoltaics, radiative cooling, and infrared sensing applications. Spectral control of the emissivity is historically achieved by choosing the material with suitable infrared properties. The recent advancements in nanofabrication techniques that lead to enhanced light–matter interactions enable optical properties like infrared emissivity that are not naturally available. In this study, thermal emitters based on nanometer‐thick dielectrics on field‐enhancement surfaces as optical security features are proposed. Such a function is achieved by generating patterns by ultrathin dielectrics that are transparent in the visible and exhibit strong infrared absorption in the spectral range of thermal cameras. The invisible patterns are then revealed by thermal imaging. The field‐enhancement surfaces enhance the emissivity of the patterns, in turn reduce the minimum temperature to detect the thermal emission down to ≈30 °C from >150 °C to exploit ubiquitous heat sources like the human body. The study provides a framework for the use of thermal emitters as optical security features and demonstrates applications on rigid and flexible substrates. Nanometer‐thick SiO2 patterns are encrypted in the visible wavelength regime to be decrypted in the infrared. This study provides a framework for the use of thermal emitters as optical security features and demonstrates applications on rigid and flexible substrates. [ABSTRACT FROM AUTHOR]