Experiment study on focusing pattern prediction of particles in asymmetric contraction-expansion array channel.

Contraction-expansion array (CEA) microchannel is a typical structure applied on particle/cell manipulation. The prediction of the particle focusing pattern in CEA microchannel is worthwhile to be investigate deeply. Here, we demonstrated a virtual boundary method by flow field analysis and theoretical derivation. The calculating method of the virtual boundary location, related to the Reynolds number (Re) and the structure parameter RW, was proposed. Combining the approximate Poiseuille flow pattern based on the virtual boundary method with the simulation results of Dean flow, the main line pattern and the main/lateral lines pattern were predicted and validated in experiments. The transformation from the main line pattern to the main/lateral lines pattern can be facilitated by increasing Re, decreasing RW , and decreasing α. An empirical formula was derived to characterize the critical condition of the transformation. The virtual boundary method can provide a guidance for asymmetric CEA channel design and contribute to the widespread application of microfluidic particle focusing.

Glass-Blowing-Inspired Upcycling of Thermosetting Polymer to Neuron-Like Hierarchical Carbon for Microwave Absorption and Conversion.

Upgrading thermosetting polymer waste and harvesting unwanted electromagnetic energy are of great significance in solving environmental pollution and energy shortage problems. Herein, inspired by the glass-blowing art, a spontaneous, controllable, and scalable strategy is proposed to prepare hollow carbon materials by inner blowing and outside blocking. Specifically, hierarchically neuron-like hollow carbon materials (HCMSs) with various sizes are fabricated from melamine-formaldehyde sponge (MS) waste. Benefiting from the synergistic of the hollow "cell body" and the connected "protrusions" networks, HCMSs reveal superior electromagnetic absorption performance with a strong reflection loss of -54.9 dB, electromagnetic-heat conversion ability with a high conversion efficiency of 34.4%, and efficient energy storage performance in supercapacitor. Furthermore, a multifunctional device integrating electromagnetic-heat-electrical energy conversion is designed, and its feasibility is proved by experiments and theoretical calculations. The integrated device reveals an output voltage of 34.5 mV and a maximum output power of 0.89 µW with electromagnetic radiation for 60 s. This work provides a novel solution to recycle polymer waste, electromagnetic energy, and unwanted thermal energy.

Boarding pyroptosis onto nanotechnology for cancer therapy.

Pyroptosis, a non-apoptotic programmed cellular inflammatory death mechanism characterized by gasdermin (GSDM) family proteins, has gathered significant attention in the cancer treatment. However, the alarming clinical trial data indicates that pyroptosis-mediated cancer therapeutic efficiency is still unsatisfactory. It is essential to integrate the burgeoning biomedical findings and innovations with potent technology to hasten the development of pyroptosis-based antitumor drugs. Considering the rapid development of pyroptosis-driven cancer nanotherapeutics, here we aim to summarize the recent advances in this field at the intersection of pyroptosis and nanotechnology. First, the foundation of pyroptosis-based nanomedicines (NMs) is outlined to illustrate the reliability and effectiveness for the treatment of tumor. Next, the emerging nanotherapeutics designed to induce pyroptosis are overviewed. Moreover, the cross-talk between pyroptosis and other cell death modalities are discussed, aiming to explore the mechanistic level relationships to provide guidance strategies for the combination of different types of antitumor drugs. Last but not least, the opportunities and challenges of employing pyroptosis-based NMs in potential clinical cancer therapy are highlighted.

Nano-Interfacial Supramolecular Adhesion of Metal-Organic Framework-Based Separator Enables High-Safety and Wide-Temperature-Range Lithium Batteries.

Polyolefin separators are the most commonly used separators for lithium batteries; however, they tend to shrink when heated, and their Li+ transference number (t Li +) is low. Metal-organic frameworks (MOFs) are expected to solve the above problems due to their high thermal stability, abundant pore structure, and open metal sites. However, it is difficult to prepare high-porosity MOF-based membranes by conventional membrane preparation methods. In this study, a high-porosity free-standing MOF-based safety separator, denoted the BCM separator, is prepared through a nano-interfacial supramolecular adhesion strategy. The BCM separator has a large specific surface area (450.22 m2 g-1) and porosity (62.0%), a high electrolyte uptake (475 wt%), and can maintain its morphology at 200 °C. The ionic conductivity and t Li + of the BCM separator are 1.97 and 0.72 mS cm-1, respectively. Li//LiFePO4 cells with BCM separators have a capacity retention rate of 95.07% after 1100 cycles at 5  C, a stable high-temperature cycling performance of 300 cycles at 80 °C, and good capacity retention at -40 °C. Li//NCM811 cells with BCM separators exhibit significantly improved rate performance and cycling performance. Pouch cells with BCM separators can work at 120 °C and have good safety at high temperature.

Vortex-Enhanced Microfluidic Chip for Efficient Mixing and Particle Capturing Combining Acoustics with Inertia.

Vortex-based microfluidics has received significant attention for its unique characteristics of high efficiency, flexible control, and label-free properties for the past decades. Herein, we present a vortex-based acousto-inertial chip that allows both fluid and particle manipulation within a significantly wider flow range and lower excitation voltage. Composed of contraction-expansion array structures and vibrating microstructures combined with bubbles and sharp edges, such a configuration results in more vigorous vortical fluid motions. The overall improvement in device performance comes from the synergistic effect of acoustics and inertia, as well as the positive feedback loop formed by vibrating bubbles and sharp edges. We characterize flow patterns in the microchannels by fluorescence particle tracer experiments and uncover single- and double-vortex modes over a range of sample flow rates and excitation voltages. On this basis, the ability of rapid and efficient sample homogenization up to a flow rate of 200 µL/min under an excitation voltage of 15 Vpp is verified by a two-fluid fluorescence mixing experiment. Moreover, the recirculation motion of particles in microvortices is investigated by using a high-speed imaging system. We also quantitatively measure the particle velocity variation on the trajectory and illustrate the capturing mechanism, which results from the interaction of the microvortices, particle dynamics, and composite microstructure perturbations. Further utilizing the shear forces derived by microvortices, our acousto-inertial chip is demonstrated to lysis red blood cells (RBCs) in a continuous, reagent-free manner. The high controllability and multifunction of this technology allow for the development of multistep miniaturized "lab-on-chip" analytical systems, which could significantly broaden the application of microvortex technology in biological, chemical, and clinical applications.

Combination of deep learning and 2D CARS figures for identification of amyloid-ß plaques.

In vivo imaging and accurate identification of amyloid-ß (Aß) plaque are crucial in Alzheimer's disease (AD) research. In this work, we propose to combine the coherent anti-Stokes Raman scattering (CARS) microscopy, a powerful detection technology for providing Raman spectra and label-free imaging, with deep learning to distinguish Aß from non-Aß regions in AD mice brains in vivo. The 1D CARS spectra is firstly converted to 2D CARS figures by using two different methods: spectral recurrence plot (SRP) and spectral Gramian angular field (SGAF). This can provide more learnable information to the network, improving the classification precision. We then devise a cross-stage attention network (CSAN) that automatically learns the features of Aß plaques and non-Aß regions by taking advantage of the computational advances in deep learning. Our algorithm yields higher accuracy, precision, sensitivity and specificity than the results of conventional multivariate statistical analysis method and 1D CARS spectra combined with deep learning, demonstrating its competence in identifying Aß plaques. Last but not least, the CSAN framework requires no prior information on the imaging modality and may be applicable to other spectroscopy analytical fields.

Non-flammable solvent-free liquid polymer electrolyte for lithium metal batteries.

As a replacement for highly flammable and volatile organic liquid electrolyte, solid polymer electrolyte shows attractive practical prospect in high-energy lithium metal batteries. However, unsatisfied interface performance and ionic conductivities are two critical challenges. A common strategy involves introducing organic solvents or plasticizers, but this violates the original intention of security design. Here, an electrolyte concept called liquid polymer electrolyte without any small molecular solvents is proposed for safe and high-performance batteries, based on the design of a room-temperature liquid-state brush-like polymer as the sole solvent of lithium salts. This liquid polymer electrolyte is non-flammable and exhibits high ionic conductivity (1.09 [Formula: see text] 10-4 S cm-1 at 25 °C), significant lithium dendrite suppression, and stable long-term cycling over a wide operating temperature range ( ≥ 1000 cycles at 60 °C and 90 °C). Moreover, the pouch cell can resist thermal abuse, vacuum environment, and mechanical abuse. This electrolyte and design strategy are expected to provide enlightening ideas for the development of safe and high-performance polymer electrolytes.

Degeneration of flow pattern in acousto-elastic flow through sharp-edge microchannels.

Acoustic streaming (AS) is the steady time-averaged flow generated by acoustic field, which has been widely used in enhancing mixing and particle manipulation. Current researches on acoustic streaming mainly focus on Newtonian fluids, while many biological and chemical solutions exhibit non-Newtonian properties. The acoustic streaming in viscoelastic fluids has been studied experimentally for the first time in this paper. We found that the addition of polyethylene oxide (PEO) polymer to the Newtonian fluid significantly altered the flow characteristics in the microchannel. The resulting acousto-elastic flow showed two modes: positive mode and negative mode. Specifically, the viscoelastic fluids under acousto-elastic flow exhibit mixing hysteresis features at low flow rates, and degeneration of flow pattern at high flow rates. Through quantitative analysis, the degeneration of flow pattern is further summarized as time fluctuation and spatial disturbance range reduction. The positive mode in acousto-elastic flow can be used for the mixing enhancement of viscoelastic fluids in the micromixer, while the negative mode provides a potential method for particle/cell manipulation in viscoelastic body fluids such as saliva by suppressing unstable flow.

A pH-Responsive Asymmetric Microfluidic/Chitosan Device for Drug Release in Infective Bone Defect Treatment.

Bacterial infection is currently considered to be one of the major reasons that leads to the failure of guided bone regeneration (GBR) therapy. Under the normal condition, the pH is neutral, while the microenvironment will become acid at the sites of infection. Here, we present an asymmetric microfluidic/chitosan device that can achieve pH-responsive drug release to treat bacterial infection and promote osteoblast proliferation at the same time. On-demand release of minocycline relies on a pH-sensitive hydrogel actuator, which swells significantly when exposed to the acid pH of an infected region. The PDMAEMA hydrogel had pronounced pH-sensitive properties, and a large volume transition occurred at pH 5 and 6. Over 12 h, the device enabled minocycline solution flowrates of 0.51-1.63 µg/h and 0.44-1.13 µg/h at pH 5 and 6, respectively. The asymmetric microfluidic/chitosan device exhibited excellent capabilities for inhibiting Staphylococcus aureus and Streptococcus mutans growth within 24 h. It had no negative effect on proliferation and morphology of L929 fibroblasts and MC3T3-E1 osteoblasts, which indicates good cytocompatibility. Therefore, such a pH-responsive drug release asymmetric microfluidic/chitosan device could be a promising therapeutic approach in the treatment of infective bone defects.

A multi-vortex micromixer based on the synergy of acoustics and inertia for nanoparticle synthesis.

Mixing is one of the most important steps in chemical reaction, sample preparation and emulsification. However, achieving complete mixing of fluids at high throughput is still a challenge for acoustic micromixers, which are limited by the intensity of the acoustic streaming. In this study, we proposed an acoustic-inertial micromixer based on multi-vortex synergy by introducing inertia into acoustic micromixer. The device contains side-wall sharp-edge structure and contraction-expansion array structure (SCEA) in the microchannel to enhance the acoustic streaming with inertial vortices. The mixing mechanism of SCEA was explored and the mixing process showed three modes: acoustic streaming dominant mode, acoustic-inertial synergy mode and inertial vortex dominant mode. On the basis of the "vortex seed" provided by the contraction-expansion structure, stronger chaotic advection was produced by the synergy of acoustic streaming and inertial vortices (including Dean vortex and horizontal vortex). Rapider mixing (0.20 m s) and wider operating ranges (0-3000 µL/min) were achieved in SCEA at lower driving voltages compared with conventional acoustic micromixers. Finally, more homogeneous and tunable chitosan nanoparticles and shellac nanoparticles were synthesized based on this device. The micromorphology, particle size distribution and drug loading properties of the products were measured and compared. This work provides a platform for control of mixing process in specific application environments with high operational flexibility, indicating potentially wider application of SCEA in multi-functional integration of lab-on-a-chip systems.

An Asymmetric Microfluidic/Chitosan Device for Sustained Drug Release in Guided Bone Regeneration Applications.

One of the major challenges of guided bone regeneration (GBR) is infections caused by pathogen colonization at wound sites. In this paper, an asymmetric microfluidic/chitosan device was developed to release drugs to inhibit infections and to ensure that guided bone regeneration can be realized. The microfluidic technique was introduced into the GBR membrane for the first time, which demonstrated more controllable drug release, more flexible clinical use and had a lower cost compared with surface treatments and embedded nanoparticles. Based on the theory of diffusion and Fick's first law, the contact area and concentration gradient were adjusted to realize sustained drug release. The standard deviation of minocycline release over 5 days was only 12.7%, which was lower than the joint effect of porous chitosan discs and nanospheres. The in vitro experiments against E. coli and Streptococcus mutans showed the excellent antibacterial performance of the device (>95%). The in vitro experiments for fibroblasts at the microfluidic side and osteoblasts at the chitosan side showed the satisfactory biocompatibility and the ability of the device to enhance bone regeneration. Therefore, this microfluidic/chitosan device is a promising therapeutic approach to prevent infection and guide bone regeneration.

A needle tip CCEA microfluidic device based on enhanced Dean flow for cell washing.

Particle/cell washing is an essential technique in biological and clinical manipulations. Herein, we propose a novel circular contraction-expansion array (CCEA) microdevice. It can be directly connected to a needle tip without connection tubes. Its small size and centrosymmetric structure are beneficial to low sample consumption, high connection stability, and a wide application range. Computational fluid dynamics (CFD) simulation results show that the CCEA structure can produce a stronger Dean flow and lead to faster particle/cell focusing than the circle structure and CEA structure with the same length. Experimentally, an optimal flow rate ratio of 1:3 and an optimal total flow rate of 120 µL/min were found to ensure a stable fluid distribution. Under these conditions, rapid focusing of 10-20 µm particles with high efficiencies was achieved. Compared with a normal CEA device using tubes, the particle loss rate could be reduced from 64 to 7% when washing 500 µL of a rare sample. Cell suspensions with concentrations from 3 × 105/mL to 1 × 103/mL were tested. The high cell collection efficiency (>85% for three cell lines) and stable waste removal efficiency (>80%) reflected the universality of the CCEA microfluidic device. After the washing, the cell activities of H1299 cells and MCF-7 cells were calculated to be 93.8 and 97.5%, respectively. This needle-tip CCEA microfluidic device showed potential in basic medical research and clinical diagnosis.

A weak shear stress microfluidic device based on Viscoelastic Stagnant Region (VSR) for biosensitive particle capture.

Particle manipulation in microfluidic devices is of great significance in biological research. However, currently available inertial capture methods require relatively high flow rates, which will cause damage to biological particles, especially for single-celled organisms that are sensitive to environments. Herein, we demonstrate a label-free, size-based, low shear stress manipulation method using the Viscoelastic Stagnant Region (VSR) to capture sensitive bioparticles. This method uses the deformation of molecular chains in the polymer solution which can generate elastic stresses to form vortices which is called VSR because of the extremely low velocity in the contraction-expansion array (CEA) microchannel. Formation and evolution of VSR was observed experimentally using the Micro-PIV system in polyethylene oxide (PEO) solutions with different concentrations. On this basis, 20 µm and 5 µm polystyrene (PS) particles were confined to a certain area in the microchamber and the trajectory of particles motion in VSR was observed. Both the inertial lift force and the viscoelastic force are affected by the particle size, so the method also presented size selectivity. By quantitatively studying the velocity distribution of the particles on the orbit of motion, it was found that the maximum velocity of the particles in the VSR was about 0.02 m s-1, which is only about 1/100 of that in inertial vortices. Moreover, the spiral motion of particles captured by VSR with variable trajectories was first observed, which is different from the equilibrium orbit in inertial vortices and can provide more motion paths for the particles. This method was further applied to the research of Crypthecodinium cohnii (C. cohnii), which is vulnerable but has high nutritious value. We found that the activity of the C. cohnii decreased slightly after being processed by VSR, but was lost after being processed by the inertial vortices. This research, as a simple and low shear stress particle manipulation method, will provide useful guidance for the manipulation, capture and separation of sensitive biological cells under higher biocompatibility, which is of great significance for the study of cellular and molecular biology.

Separation of exfoliated tumor cells from viscoelastic pleural effusion using a microfluidic sandwich structure.

A microfluidic device with a sandwich structure is proposed to achieve label-free and size-selective separation of tumor cells from pleural effusion. The sandwich structure is a co-flow system incorporating an initial sample layer, an isolation layer and the target sample layer. The isolation layer is used to provide a size-selective interface between the initial sample layer and the isolation layer. The relative magnitude of the inertial lift force and the interfacial lift force at the interface only allows exfoliated tumor cells to migrate out of the sample layer. The high interfacial elastic lift force of the isolation layer also enables the device to be used for pleural effusion samples, whose properties usually vary across a wide range. The target sample layer is used for large migration distances of exfoliated tumor cells in the contraction-expansion array (CEA) channel and high separation efficiency. Cell washing is also achieved with the target sample layer, demonstrating the integration of our device. Experimentally, an optimal flow rate ratio of 1:1:6 was obtained to ensure the stability of the sandwich structure, and the collected fluid was all from the target sample layer. A critical polyethylene oxide (PEO) concentration of the isolation layer (500 ppm, η0 = 1.37 mPa·s) was then obtained by particle tests. Twenty-micrometer particles were efficiently separated from different viscoelastic samples (PEO concentration changes from 0 to 400 ppm) at this concentration. For the cell test, exfoliated tumor cells from different pleural effusion samples were successfully separated and washed. The separation efficiency of exfoliated tumor cells and blood cells was about 100% and over 90%, respectively. Compared with a conventional co-flow system of two fluids, this device has great advantages in 1) wide applicability for pleural effusion samples of various viscoelasticity and 2) focusing performance. It shows potential for use in medical research and clinical diagnosis of cancer.

Ultralight Three-Dimensional Hierarchical Cobalt Nanocrystals/N-Doped CNTs/Carbon Sponge Composites with a Hollow Skeleton toward Superior Microwave Absorption.

It is extremely desirable but remains greatly challenging to obtain high-performance microwave absorption (MA) materials with thin thickness, lightweight, wide frequency bandwidth, and strong absorption by facile and low-cost preparing methods. In this work, by utilizing an inexpensively commercial melamine-formaldehyde sponge (MFS) as a template for growth of a Co-based metal-organic framework (ZIF-67) and subsequently carbonizing this ZIF-67-decorated MFS in a nitrogen atmosphere, an ultralight (8 mg cm-3), three-dimensional hybrid carbon sponge composite with a hierarchical micro/nanostructure and hollow skeleton is successfully prepared to acquire excellent MA performances for the first time. The as-obtained composite consisted of interconnected carbon microtubes as a skeleton, intertwined N-doped carbon nanotubes (CNTs) grew on the outer surface of the carbon microtubes, and metallic Co nanocrystals encapsulated at the tips of the CNTs. Benefiting from the unique architecture and hierarchical composite which contribute to a good conductive network, moderate magnetic loss, strong matched impedance, and multiple polarization, the composite (Co/CNTs/CS) exhibited a minimum reflection loss (RL) of -51.2 dB and an effective absorption bandwidth (EAB, RL < -10 dB) of 4.1 GHz with a matching thickness of 2.2 mm at a filler loading of as low as 10 wt % in paraffin wax. Even with the thickness of 1.6 mm or at the filler loading of 5 wt %, the composites can also gain the low minimum RL value of -30.9 or -17.9 dB, respectively. In addition, the largest EAB was 5.4 GHz at the thickness of 2.0 mm, and the tunable EAB can be achieved in the range of 3.6-18 GHz, covering 90% of the measured frequency range via adjusting the absorber thickness between 1 and 5.5 mm. The results offer new insights for designing advanced microwave absorbers with lightweight, thin thickness, strong RL, and wide absorption frequency range.

A Dean-flow-coupled interfacial viscoelastic fluid for microparticle separation applied in a cell smear method.

We propose a novel microfluidic device for continuous, label-free and size-selective particle separation. The process consists of two stages: the particle separation based on the pre-focus of sheath flow and the size-selective interface between a Newtonian sample fluid and non-Newtonian poly(ethylene oxide) (PEO) solution (1st stage), and separation distance expansion due to the contraction-expansion structure (2nd stage). The force balance has been analyzed to explore the mechanism and the factors in the particle migration. In the 1st stage, the inertial lift force and the interfacial elastic lift force are a couple of counter forces which only allow the target particles to penetrate the interface. By controlling the flow rate ratio and the PEO concentration, all unwanted particles can be confined to the sample layer. In the 2nd stage, the elastic lift force is used to counteract the inertial lift force, which increases the predomination of the Dean drag force in the lateral migration of the target particles. We conclude that the separation distance is not monotonically increasing with the elastic lift force but peaks at 50-150 ppm. Thus, an optimal parameter for particle separation in our device is obtained. Compared to a similar method without the 2nd stage and the same device without the 1st stage, the distance between the target particles and the unwanted particles could increase by approximately 35.8% and 101.2%, respectively. Finally, a sensitive, time saving and no background-interfering cell smear method is approved to diagnose the malignant pleural effusion efficiently.

Insight into hydrogen bonds and characterization of interlayer spacing of hydrated graphene oxide.

The number of hydrogen bonds and detailed information on the interlayer spacing of graphene oxide (GO) confined water molecules were calculated through experiments and molecular dynamics simulations. Experiments play a crucial role in the modeling strategy and verification of the simulation results. The binding of GO and water molecules is essentially controlled by hydrogen bond networks involving functional groups and water molecules confined in the GO layers. With the increase in the water content, the clusters of water molecules are more evident. The water molecules bounding to GO layers are transformed to a free state, making the removal of water molecules from the system difficult at low water contents. The diffuse behaviors of the water molecules are more evident at high water contents. With an increase in the water content, the functional groups are surrounded by fewer water molecules, and the distance between the functional groups and water molecules increases. As a result, the water molecules adsorbed into the GO interlamination will enlarge the interlayer spacing. The interlayer spacing is also affected by the number of GO layers. These results were confirmed by the calculations of number of hydrogen bonds, water state, mean square displacement, radial distribution function, and interlayer spacing of hydrated GO. Graphical Abstract This work research the interaction between GO functional groups and confined water molecules. The state of water molecules and interlayer spacing of graphene oxide were proved to be related to the number of hydrogen bonds.

Dewatering of drilling sludge by ultrasound assisted Fe(ii)-activated persulfate oxidation.

An ultrasound assisted Fe(ii)-activated persulfate oxidation method was put forward to improve the dewaterability of drilling sludge in this research. The water content in the filter cake and specific resistance to filtration (SRF) were measured to evaluate the sludge dewaterability. Volatile suspended solids (VSS), transmittance of supernatant, microstructure, particle size distribution and zeta potential were tested to justify the proposed mechanism. The results showed that appropriate ultrasound assisted Fe(ii)-activated persulfate oxidation could not only further enhance the sludge dewaterability but also reduce the reaction time as well. The optimal conditions for this method were 1.6% sodium persulfate, 0.8% ferrous sulfate, 40 W ultrasonic power and 45 min reaction time. Reduction of VSS and an increase of transmittance were further achieved compared to oxidation alone. SEM results and the decrease of particle size after the treatment confirmed the disintegration of sludge flocs, which promoted the release of bound water. A synergistic effect mechanism of ultrasound and chemical oxidation was proposed, with ultrasonic cavitation disintegrating the flocs, exposing the interior organics and persulfate further oxidizing the released organics.

Correction: The effect of wall depletion and hydrodynamic interactions on stress-gradient-induced polymer migration.

Correction for 'The effect of wall depletion and hydrodynamic interactions on stress-gradient-induced polymer migration' by Hossein Rezvantalab et al., Soft Matter, 2016, 12, 5883-5897.

The effect of wall depletion and hydrodynamic interactions on stress-gradient-induced polymer migration.

We generalize our recent continuum theory for the stress-gradient-induced migration of polymers [Zhu et al., J. Rheol., 2016, 60, 327-343] by incorporating the effect of solid boundaries on concentration variations. For a model flow in a channel with periodic slip wall velocity, which can in principle be produced by an electric field in the presence of a sinusoidal wall charge, we obtain theoretical results for the steady-state distribution of dilute solutions of polymer dumbbells using a systematic perturbation analysis in Weissenberg number Wi. We find that the presence of a thin wall depletion zone changes the lowest order solution from second to first in Wi and drastically affects the concentration field far from the depletion layer, due both to a coupling of the second derivative of the velocity field to the concentration gradient, and to convection of the polymer-depleted fluid in this layer into the bulk of the fluid. Additional effects induced by wall hydrodynamic interaction (HI) are assessed by incorporating polymer flux from the wall-HI migration theory of Ma and Graham into our continuum theory. We establish the range of validity of our theory by comparing the theoretical results with Brownian dynamics (BD) simulations: excellent agreement is achieved for relatively small molecules, while the theory breaks down when the Gradient number Gd is greater than 0.5, where Gd is the ratio of polymer coil size to the length scale over which the velocity gradient changes. The BD simulations are also extended to the case of long Hookean chains with numbers of springs per chain ranging from 1 to 32, where it is found that for fixed Gd and Wi, the results are nearly identical, showing that all important phenomena are captured by a simple dumbbell model, thus supporting the continuum theory which was derived for the case of dumbbells. In addition, the Stochastic Rotation Dynamics (SRD) method is employed to evaluate the role of HI on the migration pattern, producing effects consistent with the continuum theory incorporating the wall-migration flux. In general, we demonstrate that the polymer concentrates in drastically different regions of the channel depending on Gd and Wi.