Deterministic Lateral Displacement Arrays Research Articles

Trajectory analysis of circulating tumor cells through contorted deterministic lateral displacement array for unruptured trapping: a simulation study

During the multistage process of cancer spread, fragments of cells branch out from the primitive tumor tissue and scatter throughout the body by blood flow stream or lymph, which are termed as circulating tumor cells (CTCs), regarded as an important biomarker for early cancer diagnosis. Deterministic lateral displacement (DLD) is one of the most efficient passive type particle isolation techniques which functions on asymmetrical laminar flow diversion around the placed microposts forming an array, based on the critical dimeter of the device. In this simulation study, complete trajectory analysis of CTCs and WBCs has been performed using COMSOL Multiphysics software with respect to the angular orientation of sample inlet channel. A simulated model of an asymmetric DLD array-based microfluidic device with latest empirical expression for critical diameter has been presented with optimized sample inlet orientation so as to maintain perfect separation efficiency of CTCs along with arrangement for unruptured trapping of CTCs and WBCs. The approximate CTC isolation efficiency was obtained above 95% for sample inlet inclinations up to 0.5°, and further tilt showed reduction in efficiency. Migration angle of CTC trajectory for the modeled device was obtained around 15° for both the sample inlet orientations leading to least intermingling of CTCs and WBCs. A smaller number of CTC–WBC interaction points was observed for clockwise sample inlet tilt compared to the anticlockwise displacement reducing possibilities of cell rupture. The shear rate around central microposts was found to be higher as well in clockwise sample inlet orientation. This simulation study establishes that sample inlet clockwise tilting of maximum around 0.5°–0.7° leads to better CTC isolation and provides better chances of unruptured trapping of cells at the designated outlets. The results of this study provide an approach toward further optimization of DLD devices' functioning and, thus, could help fabricate better DLD-based microfluidic devices for efficient trapping of CTCs.

A Novel Microfluidic Strategy for Efficient Exosome Separation via Thermally Oxidized Non-Uniform Deterministic Lateral Displacement (DLD) Arrays and Dielectrophoresis (DEP) Synergy.

Exosomes, with diameters ranging from 30 to 150 nm, are saucer-shaped extracellular vesicles (EVs) secreted by various type of human cells. They are present in virtually all bodily fluids. Owing to their abundant nucleic acid and protein content, exosomes have emerged as promising biomarkers for noninvasive molecular diagnostics. However, the need for exosome separation purification presents tremendous technical challenges due to their minuscule size. In recent years, microfluidic technology has garnered substantial interest as a promising alternative capable of excellent separation performance, reduced reagent consumption, and lower overall device and operation costs. In this context, we hereby propose a novel microfluidic strategy based on thermally oxidized deterministic lateral displacement (DLD) arrays with tapered shapes to enhance separation performance. We have achieved more than 90% purity in both polystyrene nanoparticle and exosome experiments. The use of thermal oxidation also significantly reduces fabrication complexity by avoiding the use of high-precision lithography. Furthermore, in a simulation model, we attempt to integrate the use of dielectrophoresis (DEP) to overcome the size-based nature of DLD and distinguish particles that are close in size but differ in biochemical compositions (e.g., lipoproteins, exomeres, retroviruses). We believe the proposed strategy heralds a versatile and innovative platform poised to enhance exosome analysis across a spectrum of biochemical applications.

Investigating the impact of pillar shape on flexible erythrocyte separation through deterministic lateral displacement

The deterministic lateral displacement (DLD) method has gradually moved beyond the separation of spherical rigid particles and has been successfully applied to the field of biological cells, especially to the separation of disc-shaped flexible erythrocytes. Different shapes of micropillars in the DLD device significantly affect the sorting performance of erythrocytes. We investigated the effect of the flow field in the gap of micropillars of different shapes (circular, triangular, I-shaped) on the behavior of erythrocyte tumbling motion. The simulation results showed that in the I-shaped pillar DLD device, compared with the circular and triangular pillars, the erythrocytes exhibited a stable and continuous flipping motion during the movement along the array offset direction, which enabled the effective separation size to be maintained at a high level. In addition, the formula for calculating the critical diameter of the I-shaped pillar DLD array for separating erythrocytes was obtained by fitting, which provides strong support for a more efficient design of the I-shaped pillar DLD device dedicated to erythrocyte sorting.

Isolation of Extracellular Vesicles from Cell Culture and Blood Through Nano-Targeted DLD Microfluidic Device.

Extracellular vesicles (EVs) are secreted by cells and found in biological fluids such as blood, with concentration correlated with oncogenic signals, making them attractive biomarkers for liquid biopsy. The current gold-standard method for EVs isolation requires an ultracentrifugation (UC) step among others. The cost and complexity of this technique are forbiddingly high for many researchers, as well as for routine use in biological laboratories and hospitals. This chapter reports on a simple microfluidic method for EVs isolation, based on a microfluidic size sorting technique named Deterministic Lateral Displacement (DLD). With the design of micrometric DLD array, we demonstrated the potential of our DLD devices for the isolation of nano-biological objects such as EVs, with main population size distribution consistent with UC technique.

Computational analysis of differently sized circulating tumor cells seclusion using cascaded deterministic lateral displacement array approach in microfluidics

Computational analysis of differently sized circulating tumor cells seclusion using cascaded deterministic lateral displacement array approach in microfluidics

Mesoscopic simulation of multi-scheme particle separation in deterministic lateral displacement devices using two-piece hybrid pillars

Pillar shape exploration in deterministic lateral displacement (DLD) technique holds great promise for developing high-performance microfluidic devices with versatile sorting schemes. A recent innovative design using filter-like micropillars was proposed to improve cell separation, but its significance might be greatly underestimated due to an inaccurate understanding of the underlying mechanism. In this study, we employ mesoscopic hydrodynamic simulations to explore the movement and separation of rigid spherical particles in DLD arrays using various two-piece hybrid (TPH) pillars, where each pillar consists of two individual pieces separated by a tunable inter-piece channel. In comparison with the conventional one-piece pillars, the back piece of TPH-pillars is found to hierarchically tailor the flow profile of the front piece on the basis of the row shift fraction and the inter-piece channel width, resulting in unique tunable multi-scheme separation at low, intermediate, and high row shift fractions, respectively. At the intermediate regime, in particular, the first flow lane that determines the critical separation size could be physically fenced out by the inter-piece channel, and a delicate coupling of hydrodynamic filtration and DLD has been revealed to induce a constant critical size in the whole regime. This work theoretically demonstrates the feasibility and significance of TPH-pillars, which may open up a new direction of the geometry design by exploiting rich multi-piece hybrid structures to expand the versatility of the DLD technique.

Low-frequency electrokinetics in a periodic pillar array for particle separation

Deterministic Lateral Displacement (DLD) exploits periodic arrays of pillars inside microfluidic channels for high-precision sorting of micro- and nano-particles. Previously we demonstrated how DLD separation can be significantly improved by the addition of AC electrokinetic forces, increasing the tunability of the technique and expanding the range of applications. At high frequencies of the electric field (>1 kHz) the behaviour of such systems is dominated by Dielectrophoresis (DEP), whereas at low frequencies the particle behaviour is much richer and more complex. In this article, we present a detailed numerical analysis of the mechanisms governing particle motion in a DLD micropillar array in the presence of a low-frequency AC electric field. We show how a combination of Electrophoresis (EP) and Concentration-Polarisation Electroosmosis (CPEO) driven wall-particle repulsion account for the observed experimental behaviour of particles, and demonstrate how this complete model can predict conditions that lead to electrically induced deviation of particles much smaller than the critical size of the DLD array.

A layout-dependent formula for the critical separation size of parallelogram-type deterministic lateral displacement arrays

The accurate and general formulation of the critical separation size is crucial for the effective design and application of passive microfluidic devices. However, the current formulas for the deterministic lateral displacement (DLD) technique are inadequate in accounting for its structural complexity. To address this limitation, we conducted mesoscopic hydrodynamics simulations to assess the separation performance of various parallelogram-type circular post arrays. Based on the simulation results, we developed a new layout-dependent formula that takes into account key geometric parameters, such as the lateral gap size, row shift fraction, and aspect ratio of downstream and lateral post-post distances, to characterize the lateral gap dimension, periodicity, and asymmetry of DLD arrays, respectively. This formula demonstrated high accuracy over a wide design space, precisely predicting the critical separation sizes of many asymmetric DLD devices in experiments. Furthermore, it is worth noting that when the downstream gap size expands, the veering flow strengthens, which, in turn, results in an increase in the critical separation size. These findings shed light on the unique separation mechanism induced by array asymmetry and present a powerful design tool for maximizing the potential of asymmetric DLD devices.

A sheathless high precise particle separation chip integrated contraction–expansion channel and deterministic lateral displacement

Cell sorting plays an important role in medical and biological research. This study aimed to propose a novel approach combining a contraction–expansion array (CEA) channel and a deterministic lateral displacement (DLD) array to achieve high-throughput and high-precision particle separation of different sizes. The CEA channel could realize the focusing and preliminary sorting of particles with different sizes under the joint action of inertia force and Dean resistance. The separation purity and efficiency could be further improved by coupling triangular microcolumn DLD. The finite element simulation analysis was carried out using commercial software COMSOL Multiphysics 5.4. The flow field distribution and the particle movement trajectory under the CEA channel and DLD array were simulated, respectively. The simulation results showed that this structure could achieve high-throughput and high-precision particle separation of different sizes. Finally, the separation experiments showed that the separation efficiency of 5 µm polystyrene microspheres as the target particles was more than 99%, and the separation purity was 96.1% under a high flow velocity. The microfluidic chip had the advantages of low cost, simple preparation process, and label-free, sheathless characteristics, thus realizing high-efficiency, high-throughput particle separation of different sizes. In general, the proposed approach provided a new pathway for sheathless particle separation with high precision and high throughput.

High-Throughput Separation of Long DNA in Deterministic Lateral Displacement Arrays.

Length-based separation of DNA remains as relevant today as when gel electrophoresis was introduced almost 100 years ago. While new, long-read genomics technologies have revolutionised accessibility to powerful genomic data, the preparation of samples has not proceeded at the same pace, with sample preparation often constituting a considerable bottleneck, both in time and difficulty. Microfluidics holds great potential for automated, sample-to-answer analysis via the integration of preparatory and analytical steps, but for this to be fully realised, more versatile, powerful and integrable unit operations, such as separation, are essential. We demonstrate the displacement and separation of DNA with a throughput that is one to five orders of magnitude greater than other microfluidic techniques. Using a device with a small footprint (23 mm × 0.5 mm), and with feature sizes in the micrometre range, it is considerably easier to fabricate than parallelized nano-array-based approaches. We show the separation of 48.5 kbp and 166 kbp DNA strands achieving a significantly improved throughput of 760 ng/h, compared to previous work and the separation of low concentrations of 48.5 kbp DNA molecules from a massive background of sub 10 kbp fragments. We show that the extension of DNA molecules at high flow velocities, generally believed to make the length-based separation of long DNA difficult, does not place the ultimate limitation on our method. Instead, we explore the effects of polymer rotations and intermolecular interactions at extremely high DNA concentrations and postulate that these may have both negative and positive influences on the separation depending on the detailed experimental conditions.

Topology optimization based deterministic lateral displacement array design for cell separation

Circulating tumor cell (CTC) can be used to guide cancer theranostics. How to isolate efficiently CTCs from blood owns great clinical requirement. Deterministic lateral displacement (DLD) is a pillar-array-based effective passive microfluidic method to separate cells based on their sizes. DLD is a potential CTC isolation tool. Pillar shape is one of the key priorities in DLD array design. Altered zigzag mode is a normally undesired phenomenon that leads zigzag particles away from flow direction. This work makes use of the altered zigzag mode to manipulate zigzag particles for the first time, and developed a novel DLD chip with topology optimized pillar shape and a wide DLD channel. The novel designing method based on topology optimization (TO) greatly increases lateral displacement of different sized cells, meanwhile demonstrates its universality and expansibility. The proposed structure has the ability to shorten the device and to manipulate cells flexibly. Bead experiment has been applied to determine the critical diameter of the DLD array. Numerical, bead and cell experiment have been carried out to verify the separation efficiency of the structure. The TO-based wide DLD channel promotes the separation efficiency.

Effect of process parameters on separation efficiency in a deterministic lateral displacement device

Deterministic lateral displacement (DLD) is a hydrodynamic method known for its high-resolution sorting of particles. It achieves this through a periodic array of obstacles and laminar flow that passively directs particles along in two different directions depending on the particles’ diameter. Many prior publications have been dedicated to the structural and geometrical development of DLD arrays to improve separation performance; however, a successful separation requires much more than a well-designed array. This paper shows how separation performance is affected by process parameters. For this purpose, the design and fabrication of a DLD device are described. Then three experiments show how process parameters affect the performance of the device. The first experiment uses dye solutions to visualize the formation of a hydrodynamically focused sample stream. The second experiment shows that the particle separation performance (of 7- & 15-µm particles) is affected by the way output fluids are collected. Finally, the third experiment looks at the particle separation efficiency as the input flow rates and the ratio of buffer to sample are changed. The results show that the proper range for buffer and sample flow rate in this device is 1–10 and 0.1–1 (µl/min), respectively. The buffer to sample flow rate ratio of 10 gives the highest separation efficiency, but at a lower sample throughput. The optimized values are specific for our device but demonstrate processes that we believe are universal for DLD separations.

Ultra-high precision passive particle sorting chip coupling inertial microfluidics and single row micropillar arrays

In this work, we propose a chip for high-throughput and high-precision particle sorting through coupled inertial microfluidics and a single-row micropillar array. The effect of a single-row micropillar array arrangement on the separation effect was studied in order to optimize the structure. The micropillar array was set to be 1/4 away from the outlet. The offset single row micropillar array can achieve higher precision sorting effect after optimization. Compared with cascaded deterministic lateral displacement arrays to the outer spiral, this structure not only reduces the chip size, but also has a lower blocking probability. In addition, the problem of flow resistance mismatch is avoided. Our chip sorting efficiency is higher in comparison with pure inertial microfluidic chip. Our chip successfully completely separated a small amount of 20 μm particles from the mixture of 5 μm particles and 20 μm particles through experiments, and the separation efficiency was close to 100%. Our chip structure has simple processing technology and low cost, which is suitable for the high-precision separation of two different particle sizes. High flux can be achieved by using passive separation technology. The chip can withstand a maximum flow rate of 9.4 m s−1. In general, it provides a new idea for ultra-high precision particle separation and microfluidic chip manufacturing at high flow rates.

Accurate Isolation of Circulating Tumor Cells via a Heterovalent DNA Framework Recognition Element-Functionalized Microfluidic Chip.

Detection of circulating tumor cells (CTCs) has provided a noninvasive and efficient approach for early diagnosis, treatment, and prognosis of cancer. However, efficient capture of CTCs in the clinical environment is very challenging because of the extremely rare and heterogeneous expression of CTCs. Herein, we fabricated a multimarker microfluidic chip for the enrichment of heterogeneous CTCs from peripheral blood samples of breast cancer patients. The multimarker aptamer cocktail DNA nanostructures (TP-multimarker) were modified on a deterministic lateral displacement (DLD)-patterned microfluidic chip to enhance the capture efficiency through the size selection effect of DLD arrays and the synergistic effect of multivalent aptamers. As compared to a monovalent aptamer-modified chip, the multimarker chip exhibits enhanced capture efficiency toward both high and low epithelial cell adhesion molecule expression cell lines, and the DNA nanostructure-functionalized chip enables the accurate capture of different phenotypes of CTCs. In addition, the DNA nanoscaffold makes nucleases more accessible to the aptamers to release cells with molecular integrity and outstanding cell viability.

Deterministic Lateral Displacement Using Hexagonally Arranged, Bottom-Up-Inspired Micropost Arrays.

Size-based separation of particles in microfluidic devices can be achieved using arrays of micro- or nanoscale posts using a technique known as deterministic lateral displacement (DLD). To date, DLD arrays have been limited to parallelogram or rotated-square arrangements of posts, with various post shapes having been explored in these two principal arrangements. This work examines a new DLD geometry based on patterning obtainable through self-assembly of single-layer nanospheres, which we call hexagonally arranged triangle (HAT) geometry. Finite element simulations are used to characterize the DLD separation properties of the HAT geometry. The relationship between the array angle, the gap spacing, and the critical diameter for separation is derived for the HAT geometry and expressed in a similar mathematical form as conventional parallelogram and rotated-square DLD arrays. At array angles <7°, HAT structures demonstrate smaller particle sorting capability (smaller critical diameter-to-gap spacing ratio) compared to published experimental results for parallelogram-type DLD arrays with circular posts. Experimental validation of DLD separation confirms the separation ability of the HAT array geometry. It is envisioned that this work will provide the first step toward future implementation of nanoscale DLD arrays fabricated by low-cost, bottom-up self-assembly approaches.

A microfluidic device for label-free separation sensitivity enhancement of circulating tumor cells of various and similar size

Due to the heterogeneity in the size of circulating tumor cells (CTCs), label-free, high-throughput, and efficient separation of CTCs for post-processing analysis is challenging. Recent advances in hybrid microfluidics have demonstrated enormous potential for the separation of complex samples. This paper presents a hybrid microfluidic platform for label-free cell separation that utilizes a cascade deterministic lateral displacement (DLD) array in conjunction with a traveling wave dielectrophoresis (twDEP) system. CTC clusters and red blood cells are separated from the blood sample in the cascade DLD unit. Other white blood cells (WBCs) and CTCs are classified according to their diameters, ranging from 10 to 15 µm, 15 to 20 µm, and 20 to 25 µm. Each category is connected via an outlet to a twDEP unit to separate CTCs from WBCs (even the same size cells). Our proposed structure outperforms conventional designs. Among them are the uniform pressure distribution at the DLD unit's outlets and the cell viability in the twDEP unit. The effect of flow rate and Reynolds number on the separation dynamics of a cascade DLD unit is investigated in this study, as is surveyed the effect of flow rate and variation in the applied voltage to the array of electrodes on the recovery rate of the twDEP units. According to numerical simulations, a recovery rate of nearly 93% for MDA-MB-231 cells spiked into the blood sample is achievable, which is a high recovery rate for systems that can separate cells of the same and different sizes.

Unannotated small RNA clusters associated with circulating extracellular vesicles detect early stage liver cancer

ObjectiveSurveillance tools for early cancer detection are suboptimal, including hepatocellular carcinoma (HCC), and biomarkers are urgently needed. Extracellular vesicles (EVs) have gained increasing scientific interest due to their involvement in...

A Novel Approach for Tuning of Fluidic Resistance in Deterministic Lateral Displacement Array for Enhanced Separation of Circulating Tumor Cells

A Novel Approach for Tuning of Fluidic Resistance in Deterministic Lateral Displacement Array for Enhanced Separation of Circulating Tumor Cells

Label-Free Multitarget Separation of Particles and Cells under Flow Using Acoustic, Electrophoretic, and Hydrodynamic Forces.

Multiplex separation of mixed biological samples is essential in a considerable portion of biomedical research and clinical applications. An automated and operator-independent process for the separation of samples is highly sought after. There is a significant unmet need for methods that can perform fractionation of small volumes of multicomponent mixtures. Herein, we design an integrated chip that combines acoustic and electric fields to enable efficient and label-free separation of multiple different cells and particles under flow. To facilitate the connection of multiple sorting mechanisms in tandem, we investigate the electroosmosis (EO)-induced deterministic lateral displacement (DLD) separation in a combined pressure- and DC field-driven flow and exploit the combination of the bipolar electrode (BPE) focusing and surface acoustic wave (SAW) sorting modules. We successfully integrate four sequential microfluidic modules for multitarget separation within a single platform: (i) sorting particles and cells relying on the size and surface charge by adjusting the flow rate and electric field using a DLD array; (ii) alignment of cells or particles within a microfluidic channel by a bipolar electrode; (iii) separation of particles based on compressibility and density by the acoustic force; and (iv) separation of viable and nonviable cells using dielectric properties via the dielectrophoresis (DEP) force. As a proof of principle, we demonstrate the sorting of multiple cell and particle types (polystyrene (PS) particles, oil droplets, and viable and nonviable yeast cells) with high efficiency. This integrated microfluidic platform combines multiple functional components and, with its ability to noninvasively sort multiple targeted cells in a label-free manner relying on different properties, is compatible with high-definition imaging, showing great potential in diverse diagnostic and analysis applications.

Numerical simulation of critical particle size in asymmetrical deterministic lateral displacement

Microfluidics devices are widely used for particle separation. Deterministic Lateral Displacement (DLD) is a passive method for particle separation. DLD devices mainly separate particles based on their sizes. There are two main modes of movement in DLD arrays; the small particles move in a zigzag path, and the larger particles separate in the displacement mode. It is therefore important to estimate the critical particle size for the transition of modes before the fabrication of DLD devices. Asymmetry in the design of the arrays can affect the fluid behavior and the critical particle size. In this study, we investigate the effects of the asymmetry caused by changing the downstream gap size to the lateral gap size ratio on the fluid behavior and particle trajectories in DLD devices. We used two dimensional (2D) Finite Element Method (FEM) to study the variations in the flow lane's widths and combined the fluid analysis with structural mechanics to model the contact between the particles and the posts in DLD arrays. We simulated the spherical particles' trajectories with diameters ranging from 1.4 to 19.2 μm in circular post DLD arrays with a lateral gap size of 20μm. In contrast to the previous works, in these simulations, the effect of particle movement on the fluid flow profiles was considered. We evaluated the particle movement mode in seven different values of the downstream gap size to the lateral gap size ratio (ranging from 0.5 to 2) and eight different row shift fraction (ranging from 0.025 to 0.3). Our simulations showed that increasing the value of the downstream gap while the lateral gap is fixed increases the veering flow rate and width. By finding the particle with the largest diameter in the zigzag mode and the particle with the smallest diameter in the displacement mode, we estimated the critical particle diameter for each value of shift fraction in different values of the downstream gap to the lateral gap size ratio. Using these data, a curve was fitted for predicting the critical particle diameter in each ratio. Finally, a more general form of the formula for the critical particle diameter was proposed, which considers an extra parameter compared to the previous ones. The results of this study can lead to a better understanding of DLD devices' functions and, thus, save time and costs for better designs and experiments.