Particle manipulation under X-force fields.

Particle manipulation is a central technique that enhances numerous scientific and medical applications by exploiting micro- and nanoscale control within fluidic environments. In this review, we systematically explore the multifaceted domain of particle manipulation under the influence of various X-force fields, integral to lab-on-a-chip technologies. We dissect the fundamental mechanisms of hydrodynamic, gravitational, optical, magnetic, electrical, and acoustic forces and detail their individual and synergistic applications.

Micro-fluidic covalent immobilization of multi-gradient RGD peptides on a gelatin surface for studying endothelial cell migration.

Collective endothelial migration is a hallmark of wound healing, which is regulated by spatial concentration gradients of extracellular biochemical factors. Arginine-glycine-aspartate (RGD) peptides play a vital role in regulating cell migration through specific binding to integrins. In this study, a micro-fluidic technology combined with a photopolymerization technique is developed to create gelatin methacryloyl (GelMA)-based substrates with various concentration gradients of RGD peptides.

Long-Term Stable and Multifeature Microfluidic Impedance Flow Cytometry Based on a Constricted Channel for Single-Cell Mechanical Phenotyping.

The microfluidic impedance flow cytometer (m-IFC) using constricted microchannels is an appealing choice for the high-throughput measurement of single-cell mechanical properties. However, channels smaller than the cells are susceptible to irreversible blockage, extremely affecting the stability of the system and the throughput. Meanwhile, the common practice of extracting a single quantitative index, i.

Droplet drinking in constrictions.

Droplets generated through microfluidics serve as a common platform for assembling artificial cells, which are feasibly tailored using microfluidic methodology. The ability of natural cells to undergo shape changes, such as phagocytosis, is a typical characteristic that researchers aim to mimic in artificial cells. However, simulating the deformation behavior of natural cells within droplets is exceptionally challenging.

Effects of accumulated exercise on the stiffness and hemodynamics of the common carotid artery.

This research aims to study and compare the effects of moderate-intensity continuous exercise and accumulated exercise with different number of bouts on common carotid arterial stiffness and hemodynamic variables. Thirty healthy male adults were recruited to complete four trials in a randomized crossover design: no-exercise (CON); continuous exercise (CE, 30-min cycling); accumulated exercise including two or three bouts with 10-min rest intervals (AE15, 2 × 15-min cycling; AE10, 3 × 10-min cycling). The intensity in all the exercise trials was set at 45%-55% heart rate reserve.

Microfluidic characterization of single-cell biophysical properties and the applications in cancer diagnosis.

Single-cell biophysical properties play a crucial role in regulating cellular physiological states and functions, demonstrating significant potential in the fields of life sciences and clinical diagnostics. Therefore, over the last few decades, researchers have developed various detection tools to explore the relationship between the biophysical changes of biological cells and human diseases. With the rapid advancement of modern microfabrication technology, microfluidic devices have quickly emerged as a promising platform for single-cell analysis offering advantages including high-throughput, exceptional precision, and ease of manipulation.

Temperature-mediated diffusion of nanoparticles in semidilute polymer solutions.

The temperature is often a critical factor affecting the diffusion of nanoparticles in complex physiological media, but its specific effects are still to be fully understood. Here, we constructed a temperature-regulated model of semidilute polymer solution and experimentally investigated the temperature-mediated diffusion of nanoparticles using the particle tracking method. By examining the ensemble-averaged mean square displacements (MSDs), we found that the MSD grows gradually as the temperature increases while the transition time from sublinear to linear stage in MSD decreases.

A microfluidic array enabling generation of identical biochemical stimulating signals to trapped biological cells for single-cell dynamics.

Microfluidic-based analyses of single-cell dynamics in response to dynamic biochemical signals are emerging as pivotal approaches for investigating the effects of extracellular microenvironmental biochemical factors on cellular structure, function, and behavior. However, current devices often fail to consistently apply identical dynamic biochemical signals to trapped cells. In this study, we introduce a novel radially distributed single-cell trapping microfluidic array, designed to quantitatively and consistently apply identical biochemical stimulating signals to each trapped cell.

A mathematical model for intracellular NO and ROS dynamics in vascular endothelial cells activated by exercise-induced wall shear stress.

Vascular endothelial cells (ECs) residing in the innermost layer of blood vessels are exposed to dynamic wall shear stress (WSS) induced by blood flow. The intracellular nitric oxide (NO) and reactive oxygen species (ROS) in ECs modulated by the dynamic WSS play important roles in endothelial functions. Mathematical modeling is a popular methodology for biophysical studies.

Effect of the uronic acid composition of alginate in alginate/collagen hybrid hydrogel on chondrocyte behavior.

Developing a culture system that can effectively maintain chondrocyte phenotype and functionalization is a promising strategy for cartilage repair. An alginate/collagen (ALG/COL) hybrid hydrogel using different guluronate/mannuronate acid ratio (G/M ratio) of alginates (a G/M ratio of 64/36 and a G/M ratio of 34/66) with collagen was developed. The effects of G/M ratios on the properties of hydrogels and their effects on the chondrocytes behaviors were evaluated.

A high-throughput microfluidic device inspired by the Wheatstone bridge principle for characterizing the mechanical properties of single cells.

The mechanical properties of single cells have been recognized as biomarkers for identifying individual cells and diagnosing human diseases. Microfluidic devices based on the flow cytometry principle, which are not limited by the vision field of a microscope and can achieve a very high throughput, have been extensively adopted to measure the mechanical properties of single cells. However, these kinds of microfluidic devices usually required pressure-driven pumps with a very low flow rate and high precision.

Hopping Behavior Mediates the Anomalous Confined Diffusion of Nanoparticles in Porous Hydrogels.

Diffusion is an essential means of mass transport in porous materials such as hydrogels, which are appealing in various biomedical applications. Herein, we investigate the diffusive motion of nanoparticles (NPs) in porous hydrogels to provide a microscopic view of confined diffusion. Based on the mean square displacement from particle tracking experiments, we elucidate the anomalous diffusion dynamics of the embedded NPs and reveal the heterogeneous pore structures in hydrogels.

Fabricating a multi-component microfluidic system for exercise-induced endothelial cell mechanobiology guided by hemodynamic similarity.

Generating precise in vivo arterial endothelial hemodynamic microenvironments using microfluidics is essential for exploring endothelial mechanobiology. However, a hemodynamic principle guiding the fabrication of microfluidic systems is still lacking. We propose a hemodynamic similarity principle for quickly obtaining the input impedance of the microfluidic system in vitro derived from that of the arterial system in vivo to precisely generate the desired endothelial hemodynamic microenvironments.

A passive pump-assisted microfluidic assay for quantifying endothelial wound healing in response to fluid shear stress.

There as an urgent need to quantify the endothelial wound-healing process in response to fluid shear stress to improve the biological and clinical understanding of healing mechanisms, which is of great importance for preventing healing impairment, chronic wounds, and postoperative in-stent restenosis. However, current experimental platforms not only require expensive, cumbersome, and powered pumping devices (to, e.g.

Vortex evolution patterns for flow of dilute polymer solutions in confined microfluidic cavities.

Flow instability in confined cavities has attracted extensive interest due to its significance in many natural and engineering processes. It also has applications in microfluidic devices for biomedical applications including flow mixing, nanoparticle synthesis, and cell manipulation. The recirculating vortex that characterizes the flow instability is regulated by the fluid rheological properties, cavity geometrical characteristics, and flow conditions, but there is a lack of quantitative understanding of how the vortex evolves as these factors change.

Raman Spectroscopic Characterization of Polymerization Kinetics of Cyanoacrylate Embolic Glues for Vascular Embolization.

Endovascular glue embolization is a minimally invasive technique used to selectively reduce or block the blood supply to specific targeted vessels. Cyanoacrylate glues, mixed with radiopaque iodized oil, have been widely used for vascular embolization owing to their rapid polymerization rate, good penetration ability and low tissue toxicity. Nevertheless, in clinical practice, the selection of the glue-oil proportion and the manual injection process of mixtures are mostly based on empirical knowledge of operators, as the crucial physicochemical effect of polymerization kinetics has rarely been quantitatively investigated.

A microfluidic system for precisely reproducing physiological blood pressure and wall shear stress to endothelial cells.

To reproduce hemodynamic stress microenvironments of endothelial cells is of vital significance, by which one could exploit the quantitative impact of hemodynamic stresses on endothelial function and seek innovative approaches to prevent circulatory system diseases. Although microfluidic technology has been regarded as an effective method to create physiological microenvironments, a microfluidic system to precisely reproduce physiological arterial hemodynamic stress microenvironments has not been reported yet. In this paper, a novel microfluidic chip consisting of a cell culture chamber with on-chip afterload components designed by the principle of input impedance to mimic the global hemodynamic behaviors is proposed.

A microfluidic generator of dynamic shear stress and biochemical signals based on autonomously oscillatory flow.

Biological cells in vivo typically reside in a dynamic flowing microenvironment with extensive biomechanical and biochemical cues varying in time and space. These dynamic biomechanical and biochemical signals together act to regulate cellular behaviors and functions. Microfluidic technology is an important experimental platform for mimicking extracellular flowing microenvironment in vitro.

The intracellular calcium dynamics in a single vascular endothelial cell being squeezed through a narrow microfluidic channel.

Revealing the mechanisms underlying the intracellular calcium responses in vascular endothelial cells (VECs) induced by mechanical stimuli contributes to a better understanding for vascular diseases, including hypertension, atherosclerosis, and aneurysm. Combining with experimental measurement and Computational Fluid Dynamics simulation, we developed a mechanobiological model to investigate the intracellular [Ca] response in a single VEC being squeezed through narrow microfluidic channel. The time-dependent cellular surface tension dynamics was quantified throughout the squeezing process.

Breakup Dynamics of Semi-dilute Polymer Solutions in a Microfluidic Flow-focusing Device.

Droplet microfluidics involving non-Newtonian fluids is of great importance in both fundamental mechanisms and practical applications. In the present study, breakup dynamics in droplet generation of semi-dilute polymer solutions in a microfluidic flow-focusing device were experimentally investigated. We found that the filament thinning experiences a transition from a flow-driven to a capillary-driven regime, analogous to that of purely elastic fluids, while the highly elevated viscosity and complex network structures in the semi-dilute polymer solutions induce the breakup stages with a smaller power-law exponent and extensional relaxation time.

Diffusion of Nanoparticles with Activated Hopping in Crowded Polymer Solutions.

A long-distance hop of diffusive nanoparticles (NPs) in crowded environments was commonly considered unlikely, and its characteristics remain unclear. In this work, we experimentally identify the occurrence of the intermittent hops of large NPs in crowded entangled poly(ethylene oxide) (PEO) solutions, which are attributed to thermally induced activated hopping. We show that the diffusion of NPs in crowded solutions is considered as a superposition of the activated hopping and the reptation of the polymer solution.

Separation of micro and sub-micro diamagnetic particles in dual ferrofluid streams based on negative magnetophoresis.

In the present study, we numerically demonstrate an approach for separation of micro and sub-micro diamagnetic particles in dual ferrofluid streams based on negative magnetophoresis. The dual streams are constructed by an intermediate sheath flow, after which the negative magnetophoretic force induced by an array of permanent magnets dominates the separation of diamagnetic particles. A simple and efficient numerical model is developed to calculate the motions of particles under the action of magnetic field and flow field.