Precise cellular analysis is one of the core goals in contemporary life science research. As a key prerequisite for achieving this goal, single-cell encapsulation effectively isolates individual cells from complex cell populations. Microfluidic technology, by precisely manipulating microscale flow dynamics, provides robust technical support for efficient and controllable single-cell isolation or encapsulation. From the perspective of microscale flow, this work systematically reviews microfluidic technologies for single-cell encapsulation, focusing on flow mechanisms, technological evolution, and performance regulation strategies for encapsulation methods and for enhancing encapsulation efficiency. Single-cell encapsulation achieves cell capture and encapsulation through hydrodynamic effects such as low-Reynolds-number flow and interface instability, while encapsulation enhancement technologies overcome the limitations of conventional encapsulation efficiency by regulating processes like cell separation and focusing, thereby enabling efficient cell encapsulation. Understanding flow mechanisms helps improve encapsulation performance. By elucidating flow mechanisms to enhance encapsulation efficacy, this study collates hydrodynamic distinctions across methodologies, articulates their cardinal advantages and inherent limitations, furnishes theoretical guidance for mechanistic research and experimental design in single-cell encapsulation, and fosters deeper integration of microfluidic approaches within biofluid mechanics.

The transport of micro- and nano- particles driven by magnetic fields has significant applications in fields such as microrobotics, flexible manufacturing, and precision medicine. In recent years, substantial progress has been made in experimental research, numerical simulations, and theoretical modeling. However, a systematic understanding of interface effects, multi-particle collective motion, motion mode regulation, and multi-field collaborative control remains lacking. This paper provides a systematic review of recent studies from the perspective of experimental fluid mechanics, focusing on the forces and dynamic behaviors of magnetic particles in low Reynolds number fluids. The review organizes three typical motion modes—translation, rotation, and near-wall rolling—corresponding to magnetic force and torque inputs. It outlines force models, velocity scaling relationships, and correction laws due to wall drag and lubrication effects under gradient and rotating fields. It also summarizes the collective dynamics of magnetic particles induced by magnetic–hydrodynamic coupling and interface geometric constraints in multi-particle systems, reflecting the non-equilibrium feedback between magnetic field input and fluid medium. The review discusses the traction transfer mechanisms between magnetic particles and droplets or vesicles in composite particle systems, presenting the interfacial dynamics of composite motion under magnetic driving. Furthermore, it summarizes the representative mechanisms and application scenarios of multi-field collaborative systems, such as magneto-acoustic, magneto-electric, and magneto-chemical systems, demonstrating the potential of cross-field driving to enhance control freedom under complex media or specific task constraints. This review aims to provide a reference for the mechanical understanding and system design of magnetic particle transport, offering foundational support for the further development of magnetically driven microsystems in biomedical fields.

To achieve metrological calibration of nL/min-level liquid ultra-microflow, a piston-type liquid ultra-microflow standard device based on the interference method has been developed. This device employs laser interference measurement technology to ensure precise capture of the syringe piston’s micrometer-level displacement. By establishing a flow calculation model based on the syringe's inner diameter and piston displacement, the uncertainty of each component in the device is analyzed and evaluated. The study used syringes of various specifications to test ultra-microflows in the range of 1–1000 nL/min. Experimental results demonstrate that the device can detect microscopic changes in ultra-microflow, exhibiting excellent flow response capability. Calibration errors for the syringe pump were below 1%, with an expanded uncertainty of less than 4% (k = 2). Finally, comparative experiments between gravimetric and interference method standard devices demonstrated consistent error trends in syringe pump calibration. Further calculation of normalized deviation validated the accuracy of the interference method device and the validity of its uncertainty assessment results.

To investigate the coupled effects of storage duration and cyclic tensile loading on the viscoelasticity and deformability of red blood cells (RBCs), a dielectrophoresis-based microfluidic platform for single-cell mechanical characterization was developed. RBCs stored for different durations (0, 4, 7, and 13 days) were subjected to controlled cyclic electrical deformation (period of 4 s, effective voltage of 2 V). Using the Kelvin−Voigt viscoelastic model, the deformation ratio–time curves were piecewise fitted with exponential functions to quantitatively determine the changes in shear modulus and shear viscosity of the RBCs membrane. The results show that as the number of cyclic stretching cycles increases, the maximum deformation ratio of RBCs continuously decreases. Both shear modulus and shear viscosity increase monotonically, with the shear modulus in the 13-day storage group rising to 5–6 times its initial value after 2250 cycles. Storage duration significantly affects the degradation rate of RBCs mechanical properties: short-term storage (0–7 days) results in relatively mild changes in mechanical parameters, while long-term storage (13 days) markedly enhances fatigue sensitivity, with the shear modulus increasing by more than 250%. This study reveals that cumulative membrane fatigue hardening induced by cyclic stretching is the primary cause of the decline in RBCs deformability, and that storage duration accelerates this process by reducing membrane structural stability, offering a new perspective for understanding the mechanical adaptation mechanism of RBCs in blood circulation.

Microstructured superhydrophobic surfaces represent an effective approach for drag reduction and reducing energy consumption of underwater vehicles. However, the gas film stability on microstructured surfaces remains insufficient, particularly under hydrodynamic shear conditions, which can lead to premature failure of drag reduction performance. Here, a superhydrophobic conical array surface (CAS) is proposed to enable effective underwater drag reduction in Couette flow and enhance the stability of the gas-film by altering the cone structure. The gas-liquid two-phase-flow over CAS in a planar Couette flow configuration is investigated by COMSOL multiphysics. The key parameters, such as the cone height, inclination angle, and wettability, are analyzed to investigate their effects on the flow velocity, slip length, and drag reduction performance. The results demonstrate that the CAS induces a significant boundary slip velocity, effectively reducing hydrodynamic drag under laminar flow conditions. The slip length exhibits a positive correlation with the cone height, while drag reduction increases with an increase in the inclination angle. The inclined CAS configuration enhances the contact-line pinning effect, and thus further improves the gas-film stability under fluid shear conditions, enhancing sustained drag reduction. These findings provide a theoretical basis for designing and manufacturing functional drag reduction superhydrophobic surfaces for underwater applications.

This study employed high-speed camera technology to observe the kinetic behaviour of micrometre-sized Fe₃O₄ particles traversing the oil–water interface under the influence of a non-uniform magnetic field. The experimental results show that the mass fraction of Span 80 surfactant alters interfacial properties (interfacial tension, viscosity, and oil–water–solid contact angle). As Span 80 mass fraction increases, the Ohnesorge number (Oh) rises while the magnetic Bond number (Bo_m) decreases. Particles exhibit five distinct motion modes at the interface: encapsulation and detachment, interfacial jet formation, cluster ejection, suspension ejection, and steady-state stretching. At low mass fractions (＜ 0.42%), the Marangoni effect predominates, enveloping particles within the oil phase to form magnetic emulsions; near the critical micelle concentration ($\approx$ 0.42%), particle aggregation intensifies, enabling them to overcome the interfacial energy barrier and traverse the interface; at high mass fractions (＞ 0.63%), liquid column necking is suppressed, with only deformation occurring. This study systematically reveals the mechanism by which surfactant mass fraction influences particle distribution and interfacial mechanical response through regulation of the Oh and Bo_m, providing theoretical foundations for the application of magnetic particles in multiphase flow and interfacial manipulation.

This study explores how optimized spacer design enhances heat and mass transfer efficiency in microscale flows within membrane distillation seawater desalination modules. Various microscale flow channels exist inside these modules, such as gaps between spacer filaments and spaces between the membranes, influencing the water production performance of the membrane modules significantly. A lab-scale direct contact membrane distillation system is built to assess key parameters including spacer structure, feed temperature, salt concentration, and flow conditions on permeate flux. Higher feed temperature markedly increases water production. Introducing spacers improves flow distribution near the membrane surface, reducing both concentration and temperature polarization. Optimized spacer structures under high-temperature and high-salinity conditions boost permeate flux by about 30% compared to configurations without spacers. Using spacer 2, the maximum water production can reach up to 15.38 L/(m²$ \cdot $h) under the following conditions: feed temperature of 60 ℃, saline concentration of 0%, and counter-current flow configuration. Counter-current flow outperforms co-current flow, with further efficiency gains when combined with optimized spacers. At elevated temperatures, bubble formation on spacer surfaces becomes more pronounced. Microscale roughness provides numerous nucleation sites for vapor, enhancing interfacial phase-change mass transfer. Spacers enhance membrane distillation performance by regulating flow fields, intensifying mass transfer, and providing mechanical support to membranes. These findings offer valuable experimental and theoretical insights for designing efficient membrane distillation systems for seawater desalination.

The compressive stress experienced by Circulating Tumor Cells (CTCs) in the microcirculation is a key mechanical factor affecting their metastatic potential. This study aims to investigate the independent regulatory effects of compressive stress intensity and duration on cell viability. Referring to the typical diameter of the MCF−7 cell line, microfluidic channels with different widths (9, 12 and 15 µm) and lengths (100 and 500 µm) were designed to construct an in vitro mechanical stimulation platform, simulating the capillary environment and decoupling the two mechanical parameters. The dynamic process and transit time of MCF−7 cells passing through the microchannels were recorded using high-speed microimaging technology. Fluorescence staining and image analysis were employed to quantitatively evaluate the proliferation and adhesion capabilities of cells after different mechanical stimulations. Results show that the cell transit time is primarily determined by the channel length, while a decrease in channel width increases the dispersion of transit velocities. Regarding cell viability, under short-duration compressive stimulation (approx. 3 ms), cell proliferation ability decreased with increasing stress intensity; whereas under long-duration stimulation (approx. 15 ms), it showed a trend of first enhancing and then weakening. Furthermore, compressive stress significantly inhibited cell adhesion ability, and the effect was more pronounced with prolonged stimulation. This study provides support for deciphering the regulation of cell fate by stress stimulation intensity and time, offering experimental evidence for a deeper understanding of the metastasis mechanism of circulating tumor cells.

Electro–elasto–microfluidic technology integrates the high controllability of electric fields with the viscoelasticity of non-Newtonian fluids, representing a frontier approach for precise manipulation of particles at the micro- and nanoscale. However, existing studies have predominantly focused on macroscopic rheological properties and particle size effects, while the influence of microscopic rheological parameters—such as polymer chain length—on particle migration behavior remains insufficiently understood. In particular, the coupling mechanism between the polymer chain length and slip-velocity-induced lift has yet to be elucidated. In this study, an electro–elasto–microfluidic system with tunable viscoelastic parameters was designed, and a control strategy incorporating polymer chain-scale parameters was established to systematically investigate the effects of polymer solutions with different chain lengths and concentrations on the migration of nano- and microparticles. Experimental results demonstrate that the polymer chain length plays a critical role in regulating the lift force balance in electro–elasto–coupled systems. Numerical simulations further reveal that the polymer chain length significantly influences the particle slip velocity. The particle slip velocity U_s exhibits an approximately linear dependence on the ratio between the force acting on the particle and its radius, F_p/R. With increasing polymer chain length, the slip velocity U_s decreases monotonically under identical F_p/R conditions. Theoretical analysis indicates that, as particle size decreases, the flow-induced elastic lift decays much more rapidly than the slip-induced lift, causing the latter to dominate nanoparticle manipulation. Based on these findings, efficient nanoparticle focusing at prescribed flow velocities, as well as high-throughput continuous separation of particles spanning the nano- to microscale, were achieved by appropriately matching polymer chain length and concentration. This work not only elucidates the microscopic regulatory role of the polymer chain length—a key microrheological parameter—on macroscopic particle dynamics, but also provides a new theoretical foundation and design strategy for electro–elasto–synergistically driven microfluidic sorting technologies.

The evaporation and migration of tiny droplets in non-uniform temperature fields involve the coupling of multi-physical fields such as heat and flow. These processes are crucial for applications in microfluidics, microscale heat dissipation, and biomedical engineering. To explore the interaction between contact line migration and internal thermal flow instability under temperature gradients, an experimental system was developed. The system includes an experimental substrate to control local temperature and combines high-speed microscopy, infrared thermography, and micro–PIV. Two droplets with distinct wettability, anhydrous ethanol and HFE–7200, were selected as study subjects. Their evaporation behaviors were investigated in both uniform and non-uniform temperature fields. Results show that under a temperature gradient of 0.41 K/mm, the HFE–7200 droplet, with a low contact angle hysteresis, migrates from the hot to the cold side. Its migration speed follows a trend consistent with classical lubrication theory. In contrast, the anhydrous ethanol droplet, which has a high contact angle hysteresis, only shows asymmetric retraction of the contact line, with no significant overall movement. Internal heat convection patterns reveal that the HFE–7200 droplet's flow structure shifts toward the cold side in the non-uniform field. The ethanol droplet displays hydrothermal waves propagating along the contact line and the range of these waves contracts toward the cold end in the non-uniform field. Analysis based on the Marangoni number, Rayleigh number, and dynamic and static Bond numbers shows that during the evaporation of HFE–7200, buoyancy effects and thermocapillary effects compete significantly. For the ethanol droplet, internal flow is primarily driven by thermocapillarity. And the evolution of dimensionless numbers correlates well with changes in internal flow patterns. This study clarifies the critical role of wettability and contact line dynamics in thermocapillary migration. It also provides insights into how temperature gradients influence internal flow modes and instability, offering a basis for predicting and controlling droplet behavior in non-uniform thermal environments.

Existing studies of droplet impact dynamics on superhydrophobic surfaces have predominantly focused on conventional substrates lacking macroscopic geometric features, while comparatively limited attention has been given to non-conventional surfaces with macro-structures that are common in practical engineering. In this study, we experimentally investigate the impact dynamics of droplets on superhydrophobic surfaces featuring a single macroscopic slot. We systematically examine the effects of the dimensionless slot width (the ratio of the actual slot width to the initial droplet diameter, 0.09–0.54) and the Weber number (4.03–36.59) on droplet spreading, retraction, penetration, and fragmentation. Four characteristic regimes are observed—complete rebound, rebound with partial penetration, fragmentation with partial penetration, and full penetration—and their corresponding parameter maps are constructed. The maximum spreading diameter decreases progressively as the slot width increases. By accounting for both the slot width and liquid penetration height, a modified theoretical model is developed to predict the maximum spreading coefficient as a function of the Weber number, achieving great agreement with experimental measurements. Moreover, partial liquid penetration during impact reduces the effective mass involved in spreading and retraction, leading to a significant reduction in the droplet–surface contact time.