Aptamer decorated PDA@magnetic silica microparticles for bacteria purification.

One significant constraint in the advancement of biosensors is the signal-to-noise ratio, which is adversely affected by the presence of interfering factors such as blood in the sample matrix. In the present investigation, a specific aptamer binding was chosen for its affinity, while exhibiting no binding affinity towards non-target bacterial cells. This selective binding property was leveraged to facilitate the production of magnetic microparticles decorated with aptamers. A novel assay was developed to effectively isolate S. pneumoniae from PBS or directly from blood samples using an aptamer with an affinity constant of 72.8 nM. The capture experiments demonstrated efficiencies up to 87% and 66% are achievable for isolating spiked S. pneumoniae in 1 mL PBS and blood samples, respectively.

Biosensor for ATP detection via aptamer-modified PDA@POSS nanoparticles synthesized in a microfluidic reactor.

This study introduces aptamer-functionalized polyhedral oligomeric silsesquioxane (POSS) nanoparticles for adenosine triphosphate (ATP) detection where the POSS nanoparticles were synthesized in a one-step, continuous flow microfluidic reactor utilizing thermal polymerization. A microemulsion containing POSS monomers was generated in the microfluidic reactor which was designed to prevent clogging by using a continuous oil flow around the emulsion during thermal polymerization. Surfaces of POSS nanoparticles were biomimetically modified by polydopamine. The aptamer sequence for ATP was successfully attached to POSS nanoparticles. The aptamer-modified POSS nanoparticles were tested for affinity-based biosensor applications using ATP as a model molecule. The nanoparticles were able to capture ATP molecules successfully with an affinity constant of 46.5 [Formula: see text]M. Based on this result, it was shown, for the first time, that microfluidic synthesis of POSS nanoparticles can be utilized in designing aptamer-functionalized nanosystems for biosensor applications. The integration of POSS in biosensing technologies not only exemplifies the versatility and efficacy of these nanoparticles but also marks a significant contribution to the field of biorecognition and sample preparation.

Novel 3D-Printed Microfluidic Magnetic Platform for Rapid DNA Isolation.

This study presents a novel miniaturized device as a 3D-printed microfluidic magnetic platform specifically designed to manipulate magnetic microparticles in a microfluidic chip for rapid deoxyribonucleic acid (DNA) isolation. The novel design enables the movement of the magnetic particles in the same or opposite directions with the flow or suspends them in continuous flow. A computational model was developed to assess the effectiveness of the magnetic manipulation of the particles. Superparamagnetic monodisperse silica particles synthesized in-house are utilized for the isolation of fish sperm DNA and human placenta DNA. It was demonstrated that the proposed platform can perform DNA isolation within 10 min with an isolation efficiency of 50% at optimum operating conditions.

Real-Time Biosensing Bacteria and Virus with Quartz Crystal Microbalance: Recent Advances, Opportunities, and Challenges.

Continuous monitoring of pathogens finds applications in environmental, medical, and food industry settings. Quartz crystal microbalance (QCM) is one of the promising methods for real-time detection of bacteria and viruses. QCM is a technology that utilizes piezoelectric principles to measure mass and is commonly used in detecting the mass of chemicals adhering to a surface. Due to its high sensitivity and rapid detection times, QCM biosensors have attracted considerable attention as a potential method for detecting infections early and tracking the course of diseases, making it a promising tool for global public health professionals in the fight against infectious diseases. This review first provides an overview of the QCM biosensing method, including its principle of operation, various recognition elements used in biosensor creation, and its limitations and then summarizes notable examples of QCM biosensors for pathogens, focusing on microfluidic magnetic separation techniques as a promising tool in the pretreatment of samples. The review explores the use of QCM sensors in detecting pathogens in various samples, such as food, wastewater, and biological samples. The review also discusses the use of magnetic nanoparticles for sample preparation in QCM biosensors and their integration into microfluidic devices for automated detection of pathogens and highlights the importance of accurate and sensitive detection methods for early diagnosis of infections and the need for point-of-care approaches to simplify and reduce the cost of operation.

Assessment of silicon, glass, FR4, PDMS and PMMA as a chip material for acoustic particle/cell manipulation in microfluidics.

In the present study, the capabilities of different chip materials for acoustic particle manipulation have been assessed with the same microfluidic device architecture, under the same actuator and flow conditions. Silicon, glass, epoxy with fiberglass filling (FR4), polydimethylsiloxane (PDMS) and polymethyl methacrylate (PMMA) are considered as chip materials. The acoustophoretic chips in this study were manufactured with four different fabrication methods: plasma etching, chemical etching, micromachining and molding. A novel chip material, FR4, has been employed as a microfluidic chip material in acoustophoretic particle manipulation for the first time in literature, which combines the ease of manufacturing of polymer materials with improved acoustic performance. The acoustic particle manipulation performance is evaluated through acoustophoretic focusing experiments with 2µm and 12µm polystyrene microspheres and cultured breast cancer cell line (MDA-MB-231). Unlike the common approach in the literature, the piezoelectric materials were actuated with partitioned cross-polarized electrodes which allowed effective actuation of different family of chip materials. Different from previous studies, this study evaluates the performance of each acoustophoretic device through the perspective of synchronization of electrical, vibrational and acoustical resonances, considers the thermal performance of the chip materials with their effects on cell viability as well as manufacturability and scalability of their fabrication methods. We believe our study is an essential work towards the commercialization of acoustophoretic devices since it brings a critical understanding of the effect of chip material on device performance as well as the cost of achieving that performance.

DC-electrokinetic motion of colloidal cylinder(s) in the vicinity of a conducting wall.

The boundary effects on DC-electrokinetic behavior of colloidal cylinder(s) in the vicinity of a conducting wall is investigated through a computational model. The contribution of the hydrodynamic drag, gravity, electrokinetic (i.e., electrophoretic and dielectrophoretic), and colloidal forces (i.e., forces due to the electrical double layer and van der Waals interactions) are incorporated in the model. The contribution of electrokinetic and colloidal forces are included by introducing the resulting forces as an external force acting on the particle(s). The colloidal forces are implemented with the prescribed expressions from the literature, and the electrokinetic force is obtained by integrating the corresponding Maxwell stress tensor over the particles' surfaces. The electrokinetic slip-velocity together with the thin electrical double layer assumption is applied on the surfaces. The position and velocity of the particles and the resulting electric and flow fields are obtained and the physical insight for the behavior of the colloidal cylinders are discussed in conjunction with the experimental observations in the literature.

An extended view for acoustofluidic particle manipulation: Scenarios for actuation modes and device resonance phenomenon for bulk-acoustic-wave devices.

For the manipulation of microparticles, ultrasonic devices, which employ acoustophoretic forces, have become an essential tool. There exists a widely used analytical expression in the literature which does not account for the effect of the geometry and acoustic properties of the chip material to calculate the acoustophoretic force and resonance frequencies. In this study, we propose an analytical relationship that includes the effect of the chip material on the resonance frequencies of an acoustophoretic chip. Similar to the analytical equation in the literature, this approach also assumes plane wave propagation. The relationship is simplified to a form which introduces a correction term to the acoustophoretic force equation for the presence of the chip material. The proposed equations reveal that the effect of the chip material on the resonance frequency is significant-and is called the device resonance-for acoustically soft materials. The relationship between the actuation modes of the piezoelectric actuator(s) and position of the nodal lines inside the channel are discussed. Finite element simulations are performed to verify the proposed equations. Simulations showed that even if some of the assumptions in the derivations are removed, the general conclusions about the motion of the microparticles are still valid.

ß-Dispersion of blood during sedimentation.

Aggregation of human red blood cells (RBC) is central to various pathological conditions from bacterial infections to cancer. When left at low shear conditions or at hemostasis, RBCs form aggregates, which resemble stacks of coins, known as 'rouleaux'. We experimentally examined the interfacial dielectric dispersion of aggregating RBCs. Hetastarch, an RBC aggregation agent, is used to mimic conditions leading to aggregation. Hetastrach concentration is incrementally increased in blood from healthy donors to measure the sensitivity of the technique. Time lapse electrical impedance measurements were conducted as red blood cells form rouleaux and sediment in a PDMS chamber. Theoretical modeling was used for obtaining complex permittivity of an effective single red blood cell aggregate at various concentrations of hetastarch. Time response of red blood cells' impedance was also studied to parametrize the time evolution of impedance data. Single aggregate permittivity at the onset of aggregation, evolution of interfacial dispersion parameters, and sedimentation kinetics allowed us to distinguish differential aggregation in blood.

A portable microfluidic platform for rapid determination of microbial load and somatic cell count in milk.

Microfluidics systems that have been emerged in the last 20 years and used for processing the fluid in a microchannel structure at microliter levels are alternative to the conventional methods. The objective of the study is to develop a microfluidic platform for determination of the microbial load and the number of somatic cells in milk. For this purpose, a polydimethylsiloxane (PDMS) chip with a channel size of 300 µm × 60 µm was produced. Cells/bacteria labeled with fluorescent stain in milk were counted with the proposed microfluidic platform and the results were compared with the reference cell concentration/the bacterial counts by conventional method. It was found that our platform could count somatic and bacterial cells with an accuracy above 80% in 20 min run for each analysis. The portable overall platform has an overall dimension of 25x25x25 cm and weighs approximately 9 kg.

Assessment of Lagrangian Modeling of Particle Motion in a Spiral Microchannel for Inertial Microfluidics.

Inertial microfluidics is a promising tool for a label-free particle manipulation for microfluidics technology. It can be utilized for particle separation based on size and shape, as well as focusing of particles. Prediction of particles' trajectories is essential for the design of inertial microfluidic devices. At this point, numerical modeling is an important tool to understand the underlying physics and assess the performance of devices. A Monte Carlo-type computational model based on a Lagrangian discrete phase model is developed to simulate the particle trajectories in a spiral microchannel for inertial microfluidics. The continuous phase (flow field) is solved without the presence of a discrete phase (particles) using COMSOL Multi-physics. Once the flow field is obtained, the trajectory of particles is determined in the post-processing step via the COMSOL-MATLAB interface. To resemble the operation condition of the device, the random inlet position of the particles, many particles are simulated with random initial locations from the inlet of the microchannel. The applicability of different models for the inertial forces is discussed. The computational model is verified with experimental results from the literature. Different cases in a spiral channel with aspect ratios of 2.0 and 9.0 are simulated. The simulation results for the spiral channel with an aspect ratio of 9.0 are compared against the experimental data. The results reveal that despite certain limitations of our model, the current computational model satisfactorily predicts the location and the width of the focusing streams.

A Novel, Low-Cost Anesthesia and Injection System for Zebrafish Researchers.

In this study, we designed and developed a novel low-cost system for anesthetizing and injecting adult zebrafish. The system utilizes a gradual cooling method for the anesthesia and maintains the fish in a stable anesthetic plane, as well as stabilizes the animal so that intraperitoneal injections can be consistently performed. It is a system that any laboratory with access to a workshop can build for their group. Moreover, it is a safe system for researchers, as well as a reliable one for repeated experiments since multiple fish can be injected quickly and there is little physical contact necessary between the investigator and the animal. This will likely reduce any unnecessary stress in the fish, as compared with manual methods of injection. Finally, the system is adaptable so that as the investigators' procedural needs change due to different research questions, that is, gradual rewarming or something of that nature, it could be modified.

Modeling of dielectrophoretic particle motion: Point particle versus finite-sized particle.

Dielectrophoresis (DEP) is a very popular technique for microfluidic bio-particle manipulation. For the design of a DEP-based microfluidic device, simulation of the particle trajectory within the microchannel network is crucial. There are basically two approaches: (i) point-particle approach and (ii) finite-sized particle approach. In this study, many aspects of both approaches are discussed for the simulation of direct current DEP, alternating current DEP, and traveling-wave DEP applications. Point-particle approach is implemented using Lagrangian tracking method, and finite-sized particle is implemented using boundary element method. The comparison of the point-particle approach and finite-sized particle approach is presented for different DEP applications. Moreover, the effect of particle-particle interaction is explored by simulating the motion of closely packed multiple particles for the same applications, and anomalous-DEP, which is a result of particle-wall interaction at the close vicinity of electrode surface, is illustrated.

Ablation-cooled material removal with ultrafast bursts of pulses.

The use of femtosecond laser pulses allows precise and thermal-damage-free removal of material (ablation) with wide-ranging scientific, medical and industrial applications. However, its potential is limited by the low speeds at which material can be removed and the complexity of the associated laser technology. The complexity of the laser design arises from the need to overcome the high pulse energy threshold for efficient ablation. However, the use of more powerful lasers to increase the ablation rate results in unwanted effects such as shielding, saturation and collateral damage from heat accumulation at higher laser powers. Here we circumvent this limitation by exploiting ablation cooling, in analogy to a technique routinely used in aerospace engineering. We apply ultrafast successions (bursts) of laser pulses to ablate the target material before the residual heat deposited by previous pulses diffuses away from the processing region. Proof-of-principle experiments on various substrates demonstrate that extremely high repetition rates, which make ablation cooling possible, reduce the laser pulse energies needed for ablation and increase the efficiency of the removal process by an order of magnitude over previously used laser parameters. We also demonstrate the removal of brain tissue at two cubic millimetres per minute and dentine at three cubic millimetres per minute without any thermal damage to the bulk.

An integrated acoustic and dielectrophoretic particle manipulation in a microfluidic device for particle wash and separation fabricated by mechanical machining.

In this study, acoustophoresis and dielectrophoresis are utilized in an integrated manner to combine the two different operations on a single polydimethylsiloxane (PDMS) chip in sequential manner, namely, particle wash (buffer exchange) and particle separation. In the washing step, particles are washed with buffer solution with low conductivity for dielectrophoretic based separation to avoid the adverse effects of Joule heating. Acoustic waves generated by piezoelectric material are utilized for washing, which creates standing waves along the whole width of the channel. Coupled electro-mechanical acoustic 3D multi-physics analysis showed that the position and orientation of the piezoelectric actuators are critical for successful operation. A unique mold is designed for the precise alignment of the piezoelectric materials and 3D side-wall electrodes for a highly reproducible fabrication. To achieve the throughput matching of acoustophoresis and dielectrophoresis in the integration, 3D side-wall electrodes are used. The integrated device is fabricated by PDMS molding. The mold of the integrated device is fabricated using high-precision mechanical machining. With a unique mold design, the placements of the two piezoelectric materials and the 3D sidewall electrodes are accomplished during the molding process. It is shown that the proposed device can handle the wash and dielectrophoretic separation successfully.

Fabrication of continuous flow microfluidics device with 3D electrode structures for high throughput DEP applications using mechanical machining.

Microfluidics is the combination of micro/nano fabrication techniques with fluid flow at microscale to pursue powerful techniques in controlling and manipulating chemical and biological processes. Sorting and separation of bio-particles are highly considered in diagnostics and biological analyses. Dielectrophoresis (DEP) has offered unique advantages for microfluidic devices. In DEP devices, asymmetric pair of planar electrodes could be employed to generate non-uniform electric fields. In DEP applications, facing 3D sidewall electrodes is considered to be one of the key solutions to increase device throughput due to the generated homogeneous electric fields along the height of microchannels. Despite the advantages, fabrication of 3D vertical electrodes requires a considerable challenge. In this study, two alternative fabrication techniques have been proposed for the fabrication of a microfluidic device with 3D sidewall electrodes. In the first method, both the mold and the electrodes are fabricated using high precision machining. In the second method, the mold with tilted sidewalls is fabricated using high precision machining and the electrodes are deposited on the sidewall using sputtering together with a shadow mask fabricated by electric discharge machining. Both fabrication processes are assessed as highly repeatable and robust. Moreover, the two methods are found to be complementary with respect to the channel height. Only the manipulation of particles with negative-DEP is demonstrated in the experiments, and the throughput values up to 105 particles / min is reached in a continuous flow. The experimental results are compared with the simulation results and the limitations on the fabrication techniques are also discussed.

The moss flora of Akdag Mountain (Amasya, Turkey).

The moss flora of Akdag Mountain (Amasya, Turkey) was investigated. At the result of identifications of 1500 moss specimens, collected from the research area, 178 taxa belonging to 69 genera and 26 families were determined. Among them, 94 taxa are new for A3 grid square according to the Turkey grid system which was adopted by Henderson. The location data of Grimmia crinitoleucophaea Cardot and Barbula enderesii Garov. are the first records for Turkey, and Encalypta spathulata Müll. Hal., Schistidium dupretii (Thér.) W. A. Weber, Weissia condensa var. armata (Thér. & Trab.) M. J. Cano, Ros & J. Guerra, Tortella bambergeri (Schimp.), Barbula enderesii Garov., Hedwigia ciliata var. leucophaea Bruch & Schimp., and Campyliadelphus elodes (Lindb.) Kanda are recorded for the second time to the byroflora of Turkey.

Dielectrophoresis in microfluidics technology.

Dielectrophoresis (DEP) is the movement of a particle in a non-uniform electric field due to the interaction of the particle's dipole and spatial gradient of the electric field. DEP is a subtle solution to manipulate particles and cells at microscale due to its favorable scaling for the reduced size of the system. DEP has been utilized for many applications in microfluidic systems. In this review, a detailed analysis of the modeling of DEP-based manipulation of the particles is provided, and the recent applications regarding the particle manipulation in microfluidic systems (mainly the published works between 2007 and 2010) are presented.

Lab-on-a-chip device for continuous particle and cell separation based on electrical properties via alternating current dielectrophoresis.

A novel alternating current-dielectrophoresis microfluidic chip was developed to separate particles and cells continuously by their electric properties. The flow is induced by pressure gradient. A pair of simple, 3-D electrodes was used to achieve a localized nonuniform electric field. Dielectrophoretic force is generated in the transverse direction to the flow by inserting the electrodes along the channel side walls. The localized electric field is important to reduce the Joule heating and any adverse effects of electrical field on biological cells. Latex particles of different sizes and white blood cells (8-12 µm) were manipulated successfully and the separation of 10 µm latex particles and white blood cells based on their different electrical properties was demonstrated.

Continuous particle separation based on electrical properties using alternating current dielectrophoresis.

A design of a microchannel for continuous separation of particles based on alternating current dielectrophoretic is studied. The geometric design parameters are determined by analyzing the dielectrophoresis force field inside the microchannel corresponding to the most efficient separation. The trajectories of 5 and 10 microm spherical particles are derived analytically using Lagrangian tracking method to examine the feasibility and the effectiveness of the design. The effects of the mean flow velocity inside the channel and the applied voltage across the channel on the performance of the separation are also discussed.

Continuous particle separation by size via AC-dielectrophoresis using a lab-on-a-chip device with 3-D electrodes.

In this paper, we present a novel, simple lab-on-a-chip device for continuous separation of particles by size. The device is composed of a straight rectangular microchannel connecting two inlet reservoirs and two exit reservoirs. Two asymmetric, 3-D electrodes are embedded along the channel wall to generate a non-uniform electrical field for dielectrophoresis. Particles with different sizes are collected at the different exit reservoirs. Main flow is induced by pressure difference between the inlet and the exit reservoirs. The device is used successfully for the separation of the 5 and 10 mum latex particles and for the separation of yeast cells and white blood cells. A numerical simulation based on Lagrangian tracking method is used to simulate the particle motion and the results showed a good agreement with the experimental data.