Micro Particle Image Velocimetry Research Articles

Effect of Hydrogen Pressure on The Mass Transfer Characteristics of Hydrogen-Bromine Flow Battery Electrodes

The mass transfer characteristics of porous carbon electrodes in the liquid side of a hydrogen bromine redox flow battery (H2-Br2 RFB) were investigated under compressive deformation caused by operation at elevated hydrogen pressure. Here, flow cell measurements of permeability and micro-particle image velocimetry (μPIV), alongside electrochemical measurements of capacitance and battery discharge were used to characterize changes in the liquid side electrode compression, in-plane liquid flow, accessible surface area, polarization, and mass transfer scaling brought by hydrogen pressure. We studied two electrode types with different structures, carbon paper and carbon cloth, in untreated well as heat-treated forms in the pressure range 0–8 bar H2. It was found that pressure-induced compression of the liquid side electrode increases the accessible area of untreated electrodes, with little effect on heat-treated electrodes, but decreases the electrochemical performance of the battery in all cases by increasing the ohmic resistance of the cell and decreasing the mass transfer coefficient of the porous electrode. Overall, heat treatment is shown to affect the rigidity, saturation behavior, and generalized mass transfer of paper electrodes but not of cloth electrodes. Our findings will guide the selection of electrode materials and operation parameters for the H2-Br2 RFB.

Micro-PIV of viscoelastic fluid flow in microporous media

The present experimental investigation combines the bulk flow properties of polymer solutions and measurable rheological parameters as they flow through a distinctive micro-porous structure, with micro-PIV (micro-particle image velocimetry) to measure the velocity distribution and velocity fluctuations within individual pores of a novel porous glass structure. To investigate the effects of fluid elasticity at pore scale, aqueous solutions of a polyacrylamide (PAA) & polyethylene oxide (PEO) in the concentration range of 50–200 ppm, which were characterized in both shear and extensional flows using shear and capillary break-up extensional rheometers (CaBER) respectively, were used as working fluids. The velocity field measurement includes the velocity magnitude and fluctuation intensity in several different pores within the porous material across a Weissenberg number Wi range of approximately 0.01 to 1 for each of the test fluids. The global averaged fluctuation intensity increases with Wi but the critical value, which indicates the onset of significant unsteadiness (i.e. well above noise floor/Newtonian baseline) within the flow at pore scale gives an approximately constant value of Wi≈0.4, which is almost 40 times higher than the value that is observed in the pressure-drop measurements for the data to rise above the Newtonian base line. We therefore postulate that the enhanced pressure-drop behaviour of the bulk flow may not be due to local velocity fluctuations within the pores but due to mean flow effects, at least over a significant portion of the data (up to Wi≈0.4).

Stereoscopic Micro-PIV measurement of the flow dynamics in a spherical dimple

One way to increase the thermal efficiency of heat exchangers is to structure the heat transfer surfaces with dimples, resulting in an enlarged surface area and intensified turbulence in the fluid flow. The increased turbulence also causes higher wall shear stress, which potentially suppresses the deposition of particles and supports a self-cleaning of the surface. For a deeper understanding of these phenomena, the flow dynamics inside the dimple were observed experimentally with Stereoscopic Micro-Particle Image Velocimetry (Stereo µPIV). The formation of an unsteady oscillating vortex, which leads to an asymmetric trail downstream of the dimple, is visualized. The significant influence of the dimple geometry on heat transfer enhancement is shown, and the most beneficial geometric ratio of the spherical dimple regarding its ability to increase turbulence is identified. A comparison of the local flow velocities with the results of the numerically and experimentally observed patterns of the deposited particles caused by the dimple’s self-cleaning effect shows a good match.

The velocity studies in the pure viscoelastic liquid core in displacement flow with interfacial instabilities

The velocity profiles in the core of a pure viscoelastic liquid displacing a Newtonian oil in a 500 µm microchannel were measured with micro-particle image velocimetry (µPIV) to investigate the onset of elastic turbulence. During displacement, a film of the displaced phase remains on the channel wall while interfacial instabilities develop upstream of the displacing core. Two displacing phase flow rates were investigated at 0.1 ml/min and 0.2 ml/min, corresponding to elastic Mach numbers, Ma, of 0.43 and 0.86 respectively. It was found that the velocity profiles in the streamwise and wall-normal directions are almost symmetric with respect to the centre of the core phase, apart from the case at high Ma and at the position of maximum interface deformation. Velocity fluctuations are present for the 0.2 ml/min while they are almost zero for the 0.1 ml/min, indicating the presence of elastic turbulence at large flow rate. Similarly, the calculated turbulence strengths at different directions (which make up the turbulent kinetic energy) and the Reynolds stresses have significant values at 0.2 ml/min but are almost zero at the low flow rate. In both flow rates, a circulation pattern is formed below the interfacial instability.

Weather-related changes in the dehydration of respiratory droplets on surfaces bolster bacterial endurance

HypothesisThe study shows for the first time a fivefold difference in the survivability of the bacterium Pseudomonas Aeruginosa (PA) in a realistic respiratory fluid droplet on fomites undergoing drying at different environmental conditions. For instance, in 2023, the annual average outdoor relative humidity (RH) and temperature in London (UK) is 71 % and 11 °C, whereas in New Delhi (India), it is 45 % and 26 °C, showing that disease spread from fomites could have a demographic dependence. Respiratory fluid droplet ejections containing pathogens on inanimate surfaces are crucial in disease spread, especially in nosocomial settings. However, the interplay between evaporation dynamics, internal fluid flow and precipitation and their collective influence on the distribution and survivability of pathogens at different environmental conditions are less known. ExperimentsShadowgraphy imaging is employed to study evaporation, and optical microscopy imaging is used for precipitation dynamics. Micro-particle image velocimetry (MicroPIV) measurements reveal the internal flow dynamics. Confocal imaging of fluorescently labelled PA elucidates the bacterial distribution within the deposits. FindingsThe study finds that the evaporation rate is drastically impeded during drying at elevated solutal concentrations, particularly at high RH and low temperature conditions. MicroPIV shows reduced internal flow under high RH and low temperature (low evaporation rate) conditions. Evaporation rate influences crystal growth, with delayed efflorescence and extending crystallization times. PA forms denser peripheral arrangements under high evaporation rates and shows a fivefold increase in survivability under low evaporation rates. These findings highlight the critical impact of environmental conditions on pathogen persistence and disease spread from inanimate surfaces.

Blood viscometer using capillary blood flow under disposable compliance pump

Blood viscosity is considered a promising indicator of cardiovascular disease and helps predict disease risks. However, conventional methods require two highly precise pumps to maintain consistent flow rates in co-flowing streams. In this study, a low-cost and disposable compliance pump was fabricated by inserting three components (a syringe needle, a blood-loaded syringe, and an air compliance unit [ACU]) into a three-way valve. Since the pump induces transient blood flow, accurately obtaining the transient flow rate is necessary. A correction factor was employed to improve the blood velocity obtained by microparticle image velocimetry. Air pressure inside the ACU was estimated using the ideal gas law. A discrete fluid circuit model was constructed to estimate the flow rate and pressure in a microfluidic channel. Four types of fluid physical properties (fluid resistance, fluid viscosity, time constant, and compliance coefficient) were obtained by analysing flow rate and pressure. The proposed method was employed to detect several types of suspended blood (variations in haematocrit, thermal-shocked RBCs, and RBC aggregation-enhanced blood). From the quantitative comparison, the proposed method provides better results than the previous method. Therefore, the proposed method is a promising tool for detecting biophysical variations in suspended blood.

Pore-scale flooding experiments reveal the thermally regulated flow fields of the curdlan solution

Polymers can enhance oil recovery depending on viscoelasticity. In a field, during polymer flow through porous strata, continuous shear forces result in severe viscosity loss. However, polymers with great shear resistance result in limited migration distance. One solution to the above dilemma is to regulate viscosity, which enables a polymer to migrate long distances through pores with low viscosity and subsequently maintain high viscosity in deep reservoirs. The viscosity of curdlan can be regulated by changing temperature. By curdlan, we mean a biopolymer that shows applications in food industry. However, regarding oil reservoirs, it is unclear whether curdlan viscosity can be effectively regulated in pores. To reveal the feasibility of curdlan viscosity regulation to enhance oil recovery, flooding experiments combined with micro-particle image velocimetry were conducted in a two-dimensional pore network to investigate flow fields of curdlan solutions (0.25%, 0.5%, 1%, and 2%, w/v) at different temperatures (40, 65, and 85 °C). As a result, at 40 °C, curdlan solution (0.25%) easily migrated with low viscosity loss and low adsorption [88.3% original throat diameter (OTD)], and the mobility of curdlan was higher than hydrolyzed polyacrylamide. After heating (65 °C), the viscoelasticity, adsorption (55.1% OTD), and flow resistance (injection pressure, 2.2–8.8 kPa) of curdlan increased, and the greater adsorption capacity of curdlan than xanthan gum led to a more homogeneous flow field [average velocity ratio (Rm), from 2.6 to 1.1]. Since a homogeneous flow field indicated better sweep efficiency, curdlan regulated by temperature could achieve both long-distance migration and improved sweep efficiency in deep strata. These results suggested that viscosity regulation by curdlan could potentially improve oil recovery in water-flooded reservoirs.

Investigation of Multidimensional Fractionation in Microchannels Combining a Numerical DEM-LBM Approach with Optical Measurements

The fractionation in microchannels is a promising approach for the delivery of microparticles in narrow property distributions. The underlying mechanisms of the channels are however often not completely understood and are therefore subject to current research. These investigations are done using different numerical and experimental methods. In this work, we present and evaluate our method of combining a numerical Discrete Element Method (DEM)-Lattice Boltzmann Method (LBM) approach with experimental long-exposure fluorescence microscopy, micro-Particle Image Velocimetry (µPIV) and Astigmatism Particle Tracking Velocimetry (APTV) measurements. The suitability of the single approaches and their synergies are evaluated using the exemplary investigation of multidimensional fractionation in different channel geometries. It shows that both, numerical and experimental method are well suited to evaluate particle dynamics in microchannels. As they furthermore show strengths canceling out weaknesses of the respective other method, the combined method is very well suited for the comprehensive analysis of particle dynamics in microchannels.

Study on the Flow Field Distribution in Microfluidic Cells for Surface Plasmon Resonance Array Detection.

This research is dedicated to optimizing the design of microfluidic cells to minimize mass transfer effects and ensure a uniform flow field distribution, which is essential for accurate SPR array detection. Employing finite element simulations, this study methodically explored the internal flow dynamics within various microfluidic cell designs to assess the impact of different contact angles on flow uniformity. The cells, constructed from Polydimethylsiloxane (PDMS), were subjected to micro-particle image velocimetry to measure flow velocities in targeted sections. The results demonstrate that a contact angle of 135° achieves the most uniform flow distribution, significantly enhancing the capability for high-throughput array detection. While the experimental results generally corroborated the simulations, minor deviations were observed, likely due to fabrication inaccuracies. The microfluidic cells, evaluated using a custom-built SPR system, showed consistent repeatability.

Facile compliance-based pump for blood physiometer

The biomechanical properties of blood are considered promising label-free biomarkers for early disease detection. Disposable pumps have been suggested as replacements for bulky and expensive syringe pumps. However, they have limitations, including initial air bubble removal, simple stop-and-run flow control, and quantification of many rheological properties. In this study, a compliance-based pump (CP) is developed by fitting a blood-loaded syringe, an air-compliance unit, and a needle into each port of a three-way valve. When blood is loaded into the microfluidic channel from the CP, the initial air bubbles are removed from the channels. By manipulating the three-way valve, blood flow is stopped immediately. Red blood cell (RBC) aggregation index (AI) is obtained by analyzing microscopic blood images. The air-compliance unit induces a transient blood flow. The time-resolved micro-particle image velocimetry technique is employed to obtain the blood velocity. The flow rate and time constant are obtained by assuming the flow rate as Q (t) = Q1 exp(−t/λ1) + Q2 exp(t/λ2) and conducting nonlinear regression analysis. The proposed method is employed to obtain the properties (AI, Q1, Q2, λ1, and λ2) of suspended bloods (hematocrit = 30%–70%, 5–30 mg/ml dextran solution, and heat-shocked RBCs). It is also used to detect four different types of suspended blood prepared by adding two types of RBCs (normal or hardened RBCs) to two types of diluents (1 × phosphate-buffered saline or dextran). In conclusion, the proposed method can be used to detect differences in suspended blood by manipulating the CP and consistently analyzing microscopic blood images.

Relating ciliary propulsion morphology and flow to particle acquisition in marine planktonic ciliates I: the tintinnid ciliate Amphorides quadrilineata

Abstract The marine tintinnid ciliate Amphorides quadrilineata is a feeding-current feeder, creating flows for particle encounter, capture and rejection. Individual-level behaviors were observed using high-speed, high-magnification digital imaging. Cells beat their cilia backward to swim forward, simultaneously generating a feeding current that brings in particles. These particles are then individually captured through localized ciliary reversals. When swimming backward, cells beat their cilia forward (=ciliary reversals involving the entire ring of cilia), actively rejecting unwanted particles. Cells achieve path-averaged speeds averaging 3–4 total lengths per second. Both micro-particle image velocimetry and computational fluid dynamics were employed to characterize the cell-scale flows. Forward swimming generates a feeding current, a saddle flow vector field in front of the cell, whereas backward swimming creates an inverse saddle flow vector field behind the cell; these ciliary flows facilitate particle encounter, capture and rejection. The model-tintinnid with a full-length lorica achieves an encounter rate Q ~29% higher than that without a lorica, albeit at a ~142% increase in mechanical power and a decrease in quasi-propulsive efficiency (~0.24 vs. ~ 0.38). It is also suggested that Q can be approximated by π(W/2 + l)2U, where W, l and U represent the lorica oral diameter, ciliary length and swimming speed, respectively.

EXPERIMENTAL INVESTIGATION OF SECONDARY FLOW DURING THE DROPLET FORMATION IN THE FLOW-FOCUSING CHANNEL

In this study, we have investigated the complex dynamics of droplet formation in a flow-focusing channel. Experiment has been performed under micro-particle image velocimetry (μPIV). The growth of droplets has been observed at four stages: lagging, filling, necking, and detachment. The interaction of two immiscible fluids, de-aerated water and silicon oil, is used. Characteristics of the droplet thread have been analyzed. Length of dispersed thread and tip size decrease with increased flow rate ratio. Furthermore, the flow characteristics of the dispersed phase, the velocity fields, contour plots of vorticity (ω<sub>z</sub>) swirl strength (λ<sub>1</sub>), and circulation strength (Г/U<sub>d</sub>W) have been investigated. Vortex flow region is identified during the droplet formation in such flow conditions (Re ~ 1 and Ca < 0.01). The vortex flow region shrinks with increasing flow rate ratio. Our experimental methodology and results have illustrated the presence of a temporal vortex pair during droplet formation in dispersed phase, a phenomenon with potential to amplify the chaotic mixing of multiphase fluids in a microchannel.

Initial contact and spreading of a non-Newtonian drop on a solid surface

In this work, the very initial contact and spreading of drops of two non-Newtonian fluids on a hydrophilic stainless-steel surface were comparatively investigated. The fluids employed were respectively a polymer solution of polyacrylamide (PAAm) and an aqua dispersion of fine graphene oxide (GO) particles. Experimental studies involved visualizing and characterizing the spreading width over time on the substrate surface. A more precise investigation into the initial contact and spreading of non-Newtonian pendant drops on a solid surface was performed through a home-made ultra-high-speed direct current (DC) electrical device with an acquisition frequency up to 1.25 MHz (time interval of 0.8 μs), a high-speed camera and a home-developed high-speed micro-particle image velocimetry (micro-PIV). The competing mechanisms of related forces: inertial, viscous, and capillary forces were probed to lead to different scaling laws.

Conjugate heat transfer analysis of sidewall-heated rectangular microchannels with different bottom wall materials

In this study, the conjugate heat transfer in a microchannel under four sidewalls (left, right, top, and bottom wall facing upstream) heating conditions is investigated experimentally and numerically. The microchannel has a width of 500 μm and a depth of 100 μm. Micro-Particle Image Velocimetry (Micro-PIV) and Temperature Sensitive Paint (TSP) are respectively applied to measure the velocity and temperature fields at a Reynolds number (Re) of 20. The experimental results demonstrate that the temperature gradient exists in both the left, right, and bottom wall, indicating the existence of conjugate heat transfer. Thus, 3D conjugate heat transfer simulations are subsequently conducted. Good agreements are attained between numerical and experimental data only with the non-ideal boundary condition. Otherwise, there is a significant discrepancy between them. Further parametric studies on bottom wall to fluid thermal conductivity ratio (kb/kf) and Re show that the fully developed overall Nusselt number (Nu‾) in the conjugate heat transfer case is approximately 4.55, much higher than the analytical solution 0.87 without accounting for conjugate heat transfer. As kb/kf is varied from 0.21 to 6.48, there exists a critical kb/kf=1.79, before and beyond which the total heat flux respectively increases and decreases with kb/kf. However, Nu‾ is a monotonically increasing function of kb/kf, with a peak value of 5.75 occurring at kb/kf = 6.48.

On flow disturbances caused by pressure taps in highly elastic flows around a microfluidic cylinder

The objective of this work is to characterize the onset of laterally asymmetric flow of viscoelastic solutions around a confined microfluidic cylinder, which was encountered in a recent study [Rodrigues et al., J. Non-Newtonian Fluid Mech. 289, 104406 (2020)]. To this end, two non-Newtonian fluids were employed in the same micro-geometry. Two microchannels were studied, both with a cylinder of diameter 75 μm, aspect ratio (channel height over width) of 0.37, and blockage ratio (cylinder diameter over channel width) of 0.28, differing only on the width of the pressure taps, located 500 μm up- and downstream from the respective cylinder face, on opposing walls. The working fluids consist of two poly(ethylene oxide) solutions: an elastic weakly shear-thinning fluid and an elastic shear-thinning fluid. Micro-Particle Image Velocimetry and streak imaging techniques were used to evaluate the flow over a Weissenberg number range 100≤Wi≤500, while maintaining a low Reynolds number, Re < 1. The elastic shear-thinning solution showed laterally asymmetric flow past the cylinder with both pressure tap designs, while with the weakly shear-thinning solution asymmetric flow was only observed with the wider pressure tap intake. In both cases, the fluids preferentially chose the cylinder/wall gap opposing the upstream pressure tap, which was found to influence the flow greatly, seemingly associated with time-dependent flow and possibly the lateral flow asymmetry itself. This work brings to light the necessary compromise between optimal pressure tap design for quality pressure measurements and minimal flow interference, due to the increased susceptibility of elastic microfluidic flows to flow perturbations.

Co-effect of hydrophobicity and cavities on flow characteristics at microscale

Flowing characteristics of drag reduction are experimentally and numerically investigated with a combination of hydrophobic coating and various cavities in polydimethylsiloxane microchannels. Two typical types of cavities with different geometrical parameters, rectangular and triangular, are studied with a wide range of Reynolds numbers from 0 to 300. A promising hydrophobic processing method is proposed based on a comprehensive performance on surface morphology, water repellency, and structural distortion. In this method, hydrofluoric acid (40 wt. %) is adopted and the corrosion time is set to 5 min. The velocity field and streamlines are acquired by the micro-particle image velocimetry system and numerical models to explain the flow patterns in particular. The slip length is measured as 13.38 μm in the hydrophobic straight channel. For rectangular cavities, the drag reduction rate reaches nearly 14.1% under no-slip condition and 33.2% under slip condition. A critical turning point of the co-effect is found by numerical results when the slip length is about 15 μm, which is also determined by the cavities. The convergent and divergent angles of triangular cavities play a critical role in the pressure drop due to the competition of the vortex and flow impingement. A nonlinear model is developed based on the numerical results to predict Poiseuille number with the relevant important variables for a two-dimensional microchannel. Our results reveal the fundamental physics of flowing characteristics with the co-design of hydrophobicity and microstructures, predicting a composite design method for widespread applications in microfluids.

High-resolution microscale velocity field measurement using light field particle image-tracking velocimetry

Light field microparticle image velocimetry (LF-μPIV) can realize the three-dimensional (3D) microscale velocity field measurement, but the spatial resolution of the velocity field is low. Therefore, this study proposes a high-resolution LF particle image-tracking velocimetry (PIV–PTV) in combination with a cross-validation matching (CVM) algorithm. The proposed method performs motion compensation for the distribution of particle center position based on the low-resolution velocity field achieved by PIV and then conducts the CVM on tracer particles with the nearest neighbor method. The motion compensation reduces the particle displacement during the matching, while the CVM reduces the impact of missing particles on the matching accuracy. Thus, the proposed method enables precise tracking of individual particles at higher particle concentrations and improves the spatial resolution of the velocity field. Numerical simulations were conducted on the 3D displacement field reconstruction. The influence of interrogation window size, particle diameter, and concentration was analyzed. Experiments were conducted on the microscale 3D velocity field within the microchannel with right-angle bends. Results indicate that the proposed method provides the high-resolution measurement of the microscale 3D velocity field and improves the precision of the velocity field compared to the PTV at higher particle concentrations. It demonstrates that the proposed method outperforms PIV by 26% in resolution and PTV by 76% in precision at a higher particle concentration of 1.5 particles per microlens.

Experimental analysis of pulsatile flow effects on flow structure in transitional-type cavity

Studies combining flow separation and pulsatile flow phenomena are inherent in the field of biomedicine and have many engineering and biomedical applications. In this study, the pulsatile flow structure is investigated experimentally based on a transitional-type cavity with a length-to-depth ratio of 8 using a microparticle image velocimetry system. A pulsatile flow is generated by pulsating the inlet pressure in sinusoidal pulses using a pressure control unit. Stationary flow and four sets of pulsatile parameters are investigated: two pulsation amplitudes (A = 0.15 and 0.60) and two pulsation frequencies (f = 0.5 and 1 Hz) in the Reynolds range of 50–2000. The recirculation flow dynamics in a cavity are analyzed by investigating the effect of pulsations on the flow structure and statistical flow parameters such as vorticity, shear rate, and turbulence intensity. The analysis shows that the effect of the pulsation amplitude on the recirculation zone dynamics is more prominent than that of the pulsation frequency. The magnitude of the recirculation zone reduction achieved by the pulsatile flow is inversely proportional to the pulsation amplitude. A reduction in the recirculation zone length decreases the shear rate distribution along the cavity. Additionally, an analysis into the turbulence intensity shows that effect of pulsations is negligible when the flow approaches the turbulent flow regime.

The Path from Nasal Tissue to Nasal Mucosa on Chip: Part 2-Advanced Microfluidic Nasal In Vitro Model for Drug Absorption Testing.

The nasal mucosa, being accessible and highly vascularized, opens up new opportunities for the systemic administration of drugs. However, there are several protective functions like the mucociliary clearance, a physiological barrier which represents is a difficult obstacle for drug candidates to overcome. For this reason, effective testing procedures are required in the preclinical phase of pharmaceutical development. Based on a recently reported immortalized porcine nasal epithelial cell line, we developed a test platform based on a tissue-compatible microfluidic chip. In this study, a biomimetic glass chip, which was equipped with a controlled bidirectional airflow to induce a physiologically relevant wall shear stress on the epithelial cell layer, was microfabricated. By developing a membrane transfer technique, the epithelial cell layer could be pre-cultivated in a static holder prior to cultivation in a microfluidic environment. The dynamic cultivation within the chip showed a homogenous distribution of the mucus film on top of the cell layer and a significant increase in cilia formation compared to the static cultivation condition. In addition, the recording of the ciliary transport mechanism by microparticle image velocimetry was successful. Using FITC-dextran 4000 as an example, it was shown that this nasal mucosa on a chip is suitable for permeation studies. The obtained permeation coefficient was in the range of values determined by means of other established in vitro and in vivo models. This novel nasal mucosa on chip could, in future, be automated and used as a substitute for animal testing.

Dynamics of rigid achiral magnetic microswimmers in shear-thinning fluids

Here, we use magnetically driven self-assembled achiral swimmers made of two to four superparamagnetic micro-particles to provide insight into how swimming kinematics develop in complex, shear-thinning fluids. Two model shear-thinning polymer fluids are explored, where measurements of swimming dynamics reveal contrasting propulsion kinematics in shear-thinning fluids vs a Newtonian fluid. When comparing the velocity of achiral swimmers in polymer fluids to their dynamics in water, we observe kinematics dependent on (1) no shear-thinning, (2) shear-thinning with negligible elasticity, and (3) shear-thinning with elasticity. At the step-out frequency, the fluidic environment's viscoelastic properties allow swimmers to propel faster than their Newtonian swimming speed, although their swimming gait remains similar. Micro-particle image velocimetry is also implemented to provide insight into how shear-thinning viscosity fluids with elasticity can modify the flow fields of the self-assembled magnetic swimmers. Our findings reveal that flow asymmetry can be created for symmetric swimmers through either the confinement effect or the Weissenberg effect. For pseudo-chiral swimmers in shear-thinning fluids, only three bead swimmers show swimming enhancement, while four bead swimmers always have a decreased step-out frequency velocity compared to their dynamics in water.