Aloke Kumar

Analytical solution for transient electroosmotic flow in a rotating microchannel

An analytical solution is developed for the unsteady flow of fluid through a parallel rotating plate microchannel, under the influence of electrokinetic force using the Debye–Huckel (DH) approximation. Transient Navier–Stokes equations are solved exactly in terms of the cosine Fourier series using the separation of variables method. The effects of frame rotation frequency and electroosmotic force on the fluid velocity and the flow rate distributions are investigated. The rotating system is found to have a damped oscillatory behavior. It is found that the period and the decay rate of the oscillations are independent of the DH parameter (κ). A time dependent structure of the boundary layer is observed at higher rotational frequencies. Furthermore, the rotation is shown to generate a secondary flow and a parameter is defined (β(t)) to examine the ratio of the flow in the y and x directions. It showed that both the angular velocity and the Debye–Huckel parameters are influential on the induced transient secondary flow in the y direction. At high values of the Debye–Huckel parameter and the rotation parameter the flow rates in the x and y directions are found to be identical. The analytical solution results are found to be in good agreement with the numerical method results and previously published work in this field.

Dynamics of bacterial streamers induced clogging in microfluidic devices

Using a microfabricated porous media mimic platform, we investigated the clogging dynamics of bacterial biomass that accumulated in the device due to the formation of bacterial streamers. Particularly, we found the existence of a distinct clogging front which advanced via pronounced stick-slip of the viscoelastic bacterial biomass over the solid surface of the micro pillar. Thus, the streamer, the solid surface, and the background fluidic media defined a clear three-phase front influencing these advancing dynamics. Interestingly, we also found that once the clogging became substantial, contrary to a static homogenous saturation state, the clogged mimic exhibited an instability phenomena marked by localized streamer breakage and failure leading to extended water channels throughout the mimic. These findings have implications for design and fabrication of biomedical devices and membrane-type systems such as porous balloon catheters, porous stents and filtration membranes prone to bacteria induced clogging as well as understanding bacterial growth and proliferation in natural porous media such as soil and rocks.

Type-IV Pilus Deformation Can Explain Retraction Behavior

Polymeric filament like type IV Pilus (TFP) can transfer forces in excess of 100 pN during their retraction before stalling, powering surface translocation(twitching). Single TFP level experiments have shown remarkable nonlinearity in the retraction behavior influenced by the external load as well as levels of PilT molecular motor protein. This includes reversal of motion near stall forces when the concentration of the PilT protein is loweblack significantly. In order to explain this behavior, we analyze the coupling of TFP elasticity and interfacial behavior with PilT kinetics. We model retraction as reaction controlled and elongation as transport controlled process. The reaction rates vary with TFP deformation which is modeled as a compound elastic body consisting of multiple helical strands under axial load. Elongation is controlled by monomer transport which suffer entrapment due to excess PilT in the cell periplasm. Our analysis shows excellent agreement with a host of experimental observations and we present a possible biophysical relevance of model parameters through a mechano-chemical stall force map.

Near wall void growth leads to disintegration of colloidal bacterial streamer

We investigated the failure of thick bacterial floc-mediated streamers in a microfluidic device with micropillars. It was found that streamers could fail due to the growth of voids in the biomass that originate near the pillar walls. The quantification of void growth was made possible by the use of 200u202fnm fluorescent polystyrene beads. The beads get trapped in the extracellular matrix of the streamer biomass and acted as tracers. Void growth time-scales could be characterized into short-time scales and long time-scales and the crack/void propagation showed several instances of fracture-arrest ultimately leading to a catastrophic failure of the entire streamer structure. This mode of fracture stands in strong contrast to necking-type instability observed before in streamers.

Special Issue on Microfluidics: Theory and Applications

This special issue from the Journal of the Indian Institute of Science is dedicated to the topic of microfluidics, which essentially deals with fundamentals and applications of fluid dynamics over miniaturized (typically, micron or sub-micron) scales. With phenomenal advancements in microfabrication technology over the past decade, rapid developments have taken place in the practical realization of microfluidic systems on a small portable credit card sized device, typically known as lab-on-a-chip or micro-total-analysis-system. Unlike large-scale flows, for flows at these diminutive length scales, physical issues such as interfacial interactions and transport of charged species can become the dominant phenomena. These interactions change the nature of fluid flow significantly and add interesting perspectives to the fundamental governing equations of hydrodynamics. On an application side, it is said that microfluidics is to small-scale flow what the wind tunnel is for large-scale flows. Thus, microfluidic platforms have increasingly being used as mimics to understand flows through complex systems such as porous media and membranes. Finally, the application of microfluidic systems to biomedical applications is widely expected to be the holy grail of research this domain. In particular, the advent of microfluidics is expected to revolutionize the realm of point-of-care diagnostics altogether, especially in the perspectives of their applications in low-cost resource-limited settings. This special issue brings together six manuscripts belonging to the domain of microfluidics that also elucidate these varied research issues within the discipline. Bandopadhayay and Ghosh discuss the intricacies of interactions between external and induced electric fields and fluid motion. These interactions, which are generally studied under the umbrella of electrokinetics (essentially, electrostatics + hydrodynamics), open up a novel paradigm of actuating pump-free flow in lab-on-a-chip devices. The authors review many interesting facets of electrokinetic flows. Chakraborty and co-workers review fundamental research in the area of flows in micro-confinements with deformable boundaries. The interaction of fluids and walls can have a substantial effect on the underlying fluid physics and the authors discuss multiple coupled phenomena belonging to this realm. In innovative uses of microfluidics, Debnath and Sadrzadeh discuss how microfluidic platforms can be designed to mimic membranes. Using small microposts separated by a sub-micron distances, microfiltration systems have been successfully mimicked in microfluidic channels. These devices can provide great insights into pore-scale phenomena in membranes, which are otherwise not easily accessible to analytical systems. Williams and co-workers discuss an innovative opto-electrofluidic technology called rapid electrokinetic patterning (REP). REP utilizes optically generated landscapes to drive electrothermal vortices, which can act as a tweezer and manipulate micro/nano-scale particulates. REP is today advancing biomedical research by allowing researchers to detect low-abundance biomarkers for disease diagnosis. Agrawal and co-workers focus on applications of microfluidic technologies for platelet separation and enrichment. Such technologies allow the development of rapid diagnostic devices with one drop of blood as the test sample. Finally, Toley and co-workers review low-cost paper microfluidic platforms that are enabling a host of assays by simply using microfluidic channels created on paper. These platforms can operate often with zero or very low energy requirements and can be deployed by non-experts. Overall, these six manuscripts provide a very nice review of the current advancing frontiers of microfluidics. We would like to thank Prof. Guru Row for his support in conceptualizing this special Edition. We would also like to thank the office staff of the Journal, especially Ms. Kavitha Harish, for her outstanding support during the whole process.

Impact of bacterial streamers on biofouling of microfluidic filtration systems

We investigate the effect of biofouling in a microfluidic filtration system. The microfluidic platform consists of cylindrical microposts with a pore-spacing of 2u2009μm, which act as the filtration section of the device. One of our key findings is that there exists a critical pressure difference above which pronounced streamer formation is observed, which eventually leads to rapid clogging of the device with an accompanying exponential decrease in permeate flow. Moreover, when streamers do form, de-clogging of pores also occurs intermittently, which leads to small time scale fluctuations [O(101u2009s)] superimposed upon the large time scale [O(102u2009min)] clogging of the system. These de-clogging phenomena lead to a sharp increase in water permeation through the microfluidic filtration device but rates the water quality as biomass debris is transported in the permeate. Streamer-based clogging shares similarities with various fouling mechanisms typically associated with membranes. Finally, we also show that the pH of the feed strongly affects biofouling of the microfluidic filtration system.

Failure through expanding voids in bacterial streamers

We investigate the failure of thick bacterial floc-mediated streamers in a microfluidic device with micro-pillars. We found that streamers could fail due to the growth of voids in the biomass that originate near the pillar walls. The quantification of void growth was made possible by the use of 200 nm fluorescent polystyrene beads. The beads get trapped in the extra-cellular matrix of the streamer biomass and act as tracers. Void growth time-scales could be characterized into short-time scales and long time-scales and the crack/void propagation showed several instances of fracture-arrest ultimately leading to a catastrophic failure of the entire streamer structure. This mode of fracture stands in strong contrast to necking-type instability observed before in streamers.

Sporosarcina pasteurii can form nanoscale crystals on cell surface

Using a semi-solid 0.5% agar column, we study the phenomenon of microbially induced mineral (calcium carbonate) by the bacteria Sporosarcina pasteurii. Our platform allows for in-situ visualization of the phenomena, and we found clear evidence of bacterial cell surface facilitating formation of nanoscale crystals. Moreover, in the bulk agar we found the presence of microspheres, which seem to arise from an aggregation of nanoscale crystals with needle like morphology. Extensive chemical characterization confirmed that the crystals to be calcium carbonate, and two different polymorphs (calcite and vaterite) were identified.

Bacteria can enhance mechanical strength of a porous medium

T critical challenge of current nanoscale oxide super thermal insulation materials, such as SiO2 and Al2O3 nano-particle aggregates and their composites, is the critical trade-off between extremely low thermal conductivity and unsatisfied thermal stability (nanostability typically below 1100oC). It is crucially important to modify current materials and further discover novel candidates which could balance the two key properties. This presentation shows progresses on optimal thermal stability of modified Al2O3 nano-particle aggregate; and in addition, new candidates of super thermal insulation materials, such as nano-Si3N4 and nanoSiC, which are commonly believed as excellent heat conductors. Especially, the new nano-systems exhibited good nanostability up to 1500°C. The striking results incorporated superior sintering stability of structural ceramics as SiC and Si3N4 with multiple phonon scattering mechanisms in nano-materials. It is possible to put forward this novel concept to design and search new types of high temperature thermal insulation materials through nano-scale morphology engineering of structural ceramics with excellent thermal stability, regardless their high intrinsic lattice thermal conductivities.Deok-Won Lee is an Oral and Maxillofacial Surgery Specialist and Associate Professor of Kyung Hee University College of Dentistry. His expertise is in treating and improving the oral and maxillofacial health and wellbeing of people. His research on dental implant materials creates new pathways for improving healthcare. He is continually building and investigating on adequate material for implantation through in-vivo and in-vitro models based on years of experience in research, evaluation, teaching and administration both in hospital and education institutions.Statement of the Problem: Nanoindentation of WC-12Co thermal spray coatings has been used to evaluate the elastic modulus and hardness of coating on the polished surface of the coatings. While there has been much progress overall, limited research has been reported on the deposition and evaluation of WC-cermet coatings. The aim of this study was to evaluate the microstructural and nanohardness characteristics of tungsten carbide-cobalt (WC-Co) cermet coatings deposited by liquid suspension spraying.Statement of the Problem: A more ubiquitous application of Ti-6Al-4V in the aerospace industry has been hindered by its poor set of surface properties. The cold spray coating (CSC) process is suitable for improvements in the surface properties but the process is very complex, and highly dependent and sensitive to small changes in its many process parameters. Moreover, the CSC is also very selective of the choice of powder materials. The choice is not only based on application requirements but also on plastic deformability of the powder.W developed an optically controllable organic field transistor (OFET) by employing photochromic diarylethene (DAE) molecules as a transistor channel layer. DAE molecules are known to undergo photochromic reaction, i.e., reversible conformational change between closedand open-ring isomers by alternating ultraviolet (UV) and visible (VIS) light irradiation. We found that the drain current in the DAE-based OFET also showed reversible change accompanied by this conformational change; the closed-ring isomer produced by UV light exhibited a transistor operation under appropriate gate and drain bias voltages, meanwhile the open-ring isomer produced by VIS light showed no drain current. As a result, a remarkably high on/off ratio of 1,000 was achieved. The drain current modulation can be attributed to the drastic transformation in the π-conjugation system in association with the photo-isomerization. These results present two important messages. The first one is that this compound has dual properties: organic semiconductor and photochromism. The second is that a phase transition between semiconductor and insulator can be induced by light irradiation. Based on these achievements, we demonstrate laser drawing of one-dimensional (1D) channels on an OFET with a photochromic DAE layer. The main findings are: i) a number of 1D channels can be written and erased repeatedly in the DAE layer by scanning UV and VIS focused laser spots alternately between the source and drain electrodes, ii) the conductivity of the 1D channel can be controlled by the illumination conditions, and iii) it is possible to draw an analogue adder circuit by optically writing 1D channels so as to overlap a portion of the channels and perform optical summing operations by local laser illumination on the respective channels. These findings will open new possibilities of various optically reconfigurable low-dimensional organic transistor circuits, which are not possible with conventional thin film OFETs.G nanoparticles of different shape and size have been designed and applied as contrast-enhancing agents for various imaging techniques: optical coherence tomography, fluorescence imaging, optical microscopy, photoacoustic imaging and sensing; and recently, for experimental cancer therapy as enhancers of thermal and radiation modes. In this presentation, we are focusing on different sides of gold nanorods (GNRs) applications, as well as their synthesis, functionalization, and specific targeting. The role of GNRs in comprehensive cancer diagnostics and treatment was analyzed and created the novel GNRs’ modifications of wide-ranging aspects ratio, size with high yield and quality. The GNRs were assessed by their toxicity for altered categories, such as amount of gold, surface area, optical density of their solutions and number of particles. GNRs have been reviewed as contrast agents with near-infrared absorption as highly efficient transformers of light energy into heat. Here, we present the use of GNRs as plasmonic nanoparticles for selective photothermal therapy of human acute and chronicle leukemia cells using a near-infrared laser. We have investigated GNRs as potential enhancers of radiotherapy. We have demonstrated high impact of external surface chemistry, role of molecules size and thickness of surfactant layer for damage of cancer cells by electromagnetic radiation. GNRs were evaluated as theranostic agents for imaging, photothermal and radiation modalities. The results may impact pre-clinical GNRs’ applications, molecular imaging, and quantitative sensing of biological analytes.W have done much work about silicon (Si) in solar cells and lithium ion batteries (LIBs). In the aspect of solar cell, we used silver (Ag)-assisted chemical etching method to fabricate black silicon solar cells with efficiency over 18% in 2013 and large-scale production was carried out. Besides, nickel, which is cheaper than Ag, was used as assisted metal to fabricate black silicon structure for the first time and surface reflectance of 1.59% was obtained. In the aspect of LIBs, we used Si powders made from broken Si wafers with different electrical resistivity in semiconductor industry as anode material in LIBs. We found that Si powders made from Si wafers with lower electrical resistivity show better electrochemical performance (higher capacity, and better rate performance) in LIBs. Therefore, broken Si wafers in semiconductor industry should be classified according to their electrical resistivity, which can be convenient for being used as anode raw materials for LIBs.T design of spines from some reef inhabiting sea urchins (Heterocentrotus mamilatus, Phyllacanthus imperialis) has shown to be responsible for high energy dissipation during compressive straining. It is shown that unusually high stresses are required to compress the material, which fails in a graceful manner during an overall straining of several tens of percent. The principal behind the mechanism involves the layering/gradation/ordering of pore space within a basically brittle material (Calcite). We will show the details of the structures and the results of the characterization by uniaxial compression and pin indentation. The natural material has a hierarchical design including a structuring on the nano-scale to prevent a failure by simple cleavage. It would therefore be difficult to scale up all structural features of this brittle material. We will discuss how improvements of material can nonetheless be implemented by abstracting only the more macroscopic features and choosing a suitable material. First efforts to apply this biomimetic principle to concrete as a modification of functional graded concretes confirm the effectiveness in construction materials. The design is not only beneficial for failure tolerance in cases of impacting objects, but improves at the same time thermal insulation properties and lowers the total weight of constructions. The concrete was realized by spraying and slip casting methods. We will also present a recently developed alternative method for the manufacture of 3D concrete constructions (“hydroplotting”), which allows the realization of very detailed designs.Introduction: Si clathrate compounds have been widely studied due to their unique open-framework structures of Si polyhedrons. Two types of Si clathrates encapsulating Na atoms have been known: type I (Na8Si46) and type II (NaxSi136, 0 < x ≤ 24). These Na-Si clathrates have been generally synthesized by thermal decomposition of a Na-Si binary compound, Na4Si4, at 673–823 K under high-vacuum conditions (< 10−2 Pa), and the obtained samples were in the form of powder with a particle size in the micrometer range.I cold forming, die materials are subjected to severe wear because of high contact temperature and pressure. D2 steel is used as die material for cold forming applications. However, its friction and wear properties have not been studied fully under high stress and high temperature conditions. Friction and wear behavior of D2 steel against AISI 52100 and Alumina have been studied under dry sliding conditions in temperature range of RT – 150°C, using ball-on-disc universal tribometer. For sliding distance test the wear rate of D2 with AISI 52100 is less than the Alumina for entire range at 150°C. The wear volume of D2 steel increases with the increase in sliding distance from 200 m to 1000 m against AISI 52100 and Alumina. For D2 steel, highest coefficient of friction (μ) 0.751 and 0.754 against AISI 52100 and Alumina was obtained at 5 N, whereas minimum μ of 0.32 and 0.43 against AISI 52100 and Alumina was obtained at 25 N, these tests were carried out at 150°C. For temperature test, highest coefficient of friction (μ) of 0.92 and 0.7671 against AISI 52100 and Alumina was obtained at 50°C, whereas minimum μ of 0.77 and 0.52 against AISI 52100 and Alumina was obtained at RT. Optical microscopy, SEM, EDXA and 3D profilometery have been used to understand the friction and wear mechanism of tribopair. From these observations it is concluded that wear of D2 steel is minimum for particular range of load and temperature. The results obtained are useful for designers and engineers working in the field of cold forming.N allotropes of carbon, including carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs), show a great deal of promise as functional fillers in nanocomposite materials. The extreme linear aspect ratios, strong sp2 carbon bonds, and high chemical stability all contribute to making CNTs ideal reinforcement fillers for mechanical applications. Conversely, the high aspect ratio planar nature of graphene and GNPs, along with their high impermeabilities, suggests applications as barrier materials. In this talk, we discuss our work on CNT – aluminum oxide (AO) composites for mechanical applications, including as ballistic armour, and GNP – polymer composites for high barrier applications, including oxygen barriers for food packaging and anti-corrosion coatings. CNT – AO hybrid structures are produced by depositing CNTs as conformal coatings on various AO materials, including powders and fabrics. The deposition is carried out in a large-volume chemical vapor deposition reactor, following a conformal catalyst deposition from solution or via an atomic layer deposition process. The CNT – AO hybrids are sintered into composite materials under high pressure and characterized for mechanical enhancements. Increase in fracture toughness of as high as 71% have been found from these CNT – AO composites. GNP materials are melt-processed with polyethylene (PE) and extruded into packaging films, which are characterized for their oxygen transmission rates. It is found that the GNP – PE films show comparable oxygen transmission rates to the neat PE films, indicating that further processing will be necessary to realize the desired enhancements. The GNP materials are also solution processed with epoxy (EP), cast onto steel substrates, and cured to form coatings. The efficacy of these coatings as anti-corrosion barriers is established by electrochemical and salt-fog corrosion tests. Early results suggest that the GNPs are enhancing the anti-corrosion performance of the EP films.Statement of the Problem: Antimicrobial materials based on various nanoparticles has attracted huge attention in last few decades because of the cheapness, easiness to use, and effectiveness in preventing annexation and proliferation of microbes on material surfaces. Paper has been used in many applications as a matrix to carry the nanoparticles due to its high porosity, considerable mechanical strength, and high availability. Silver nanoparticles (AgNPs) have widely been used as antibacterial/ antifungal agents in a varied range of consumer products because of their large active surface area. However, effective methods for immobilizing AgNPs on cellulose paper or similar surfaces for various applications are inadequately advanced.C features of certain materials are self-similar. This phenomenon is recognizable by scaling of measurement data corresponding to the considered self-similar feature. To perform scaling, we apply notion of homogenous function in general sense. For two independent variables such a function reads P(f,B)=Bβ F(f/Bα), where P is a considered magnitude, α and β are scaling exponents, F(∙) is an arbitrary continuous function, where α, β and F(∙) have to be determined by the measurement data. Definition of P(f,B) enables us to transform all characteristics P(f,B) to the one universal function of the one variable: P(f,B)/ Bβ =F(f/Bα). This effect is so called the data collapse and can be applied for comparison of measurement, data measured in different laboratories, which enable us to estimate quality of each laboratory series. Another application of the data collapse is compression of large experimental data. If the considered data are produced by a self-similar system then one can store them in a form of continuous curve. The data collapse enables us to introduce an absolute dimensionless characteristic: P = f• (f+1), where P and f are dimensionless P and f, respectively. This characteristic divide {P, f } space into the two independent subspaces of material’s characteristics. Finally, the scaling supplemented by pseudo-equation of states plays basic role in creation of algorithms for designing of modern materials. The presented results are based on experimental data of soft magnetic materials and soft magnetic composites. Where, P (f,B) is density of power loss, f is frequency of the field’s modulation and B is maximum of magnetic induction. One can apply this simple mathematics to any self-similar object. However, ultimately one must say that the degree of success achieved when applying the scaling depends on the property of the data. The data must obey the scaling.A homeostasis and pH regulation inside the body is precisely controlled by kidney, lungs and buffer systems, because even a minor change from the normal value could severely affect many organs. Blood and urine pH tests are common in day-to-day clinical trials without much effort. Still, there is great demand for in-vivo pH testing to understand more about body metabolism and to provide effective treatments during diagnosis. The detection of pH at the single-cell level is hoping for the great level of clinical importance for the early detection of many diseases like cancer, diabetes, etc. In this research work, we have fabricated a micro region pH sensor by series of processes like electrolytic polishing to create needle structure, deposition of electrode materials using RF magnetron sputtering for pH measurements and finally testing in various biological mediums. Working and reference electrodes were Ag/AgIO3 and Sb/Sb2O3 deposited on microneedles under optimized deposition parameters. The structural, elemental and morphological properties were analyzed using XRD, XPS, EDS and FE-SEM. The fabricated tip of the microneedle probe is around 5 μM analyzed by FE-SEM which size is comparable with the biological cells. pH testing initially began with using fish egg and various biological cells. The obtained pH sensing results were adequate with theoretical values. Since the sensor works at micro region, the potential difference is easily disturbed by atmospheric anomalies. Hence, many steps have been taken to improve the stability of the sensor. Besides that, fabricated microneedle sensor ability is proved through in-vivo testing in mice cerebrospinal fluid (CSF) and bladder. The pH sensor reported here is totally reversible and results were reproducible after several routine tests.I closed cycle gas turbine, turbine blades are subjected to severe wear because of high contact temperature and pressure. Inconel 718 is used as a blade material for closed cycle gas turbine applications; however, its friction and wear properties have been studied fully under high stress and high temperature conditions. Friction and wear behavior of Inconel 718 against silicon nitride and alumina have been studied under dry sliding conditions in temperature range of 40-500°C using ball-ondisc universal tribometer. For sliding distance test the wear rate of Inconel 718 with alumina is less than silicon nitride for the entire range at 500°C. The wear volume of Inconel 718 increases with the increase in sliding distance increases from 200 m to 1000 m against alumina and silicon nitride. For Inconel 718 highest coefficient of friction (μ) of 0.88 and 0.52 against alumina and silicon nitride was obtained at 10 N, whereas minimum μ of 0.45 and 0.40 against alumina and silicon nitride was obtained at 20 N, these tests carried out at 500°C. For temperature test highest coefficient of friction (μ) 0.75 at 400°C and lowest μ 0.46 at 200°C against silicon nitride whereas highest coefficient of friction (μ) 0.88 at 200°C and lowest μ 0.54 at 500°C against alumina. Optical microscopy, SEM, EDXA, and 3-D profilometery have been used to understand the friction and wear mechanism of tribopair. From these observations it is concluded that wear of Inconel 718 is minimumW a growing number of high precision tools for studying biological systems, it is important to develop traceable quantitative methods that result in accurate measurements. Because biological systems are both complex and fluxional, context is vitally important for such measurements in order for them to be accurate. Correlation of measurements through space and time can provide such quantitative assessments. Metallic nanoparticles pose many challenges for measurement in cellular systems. The metal can interfere with the detection method and the particles can change in size and shape over time and in association with different biological molecules. At the National Research Council, we seek to correlate detailed physical characterization of silver nanoparticles with biological measurements to generate methods for measuring the impact of nanosilver on different cell types and quantifying the specific interactions of nanosilver with biological molecules. Correlating changes in nanoparticles over time in biological fluids helps to provide an understanding of nanoparticle behaviour and results in higher reproducibility of observed biological endpoints. Surface coatings play a pivotal role in recognition of the particles by cellular receptors suggesting active transport plays a critical role in the nanosilver life cycle. Physical and chemical differences between silver nanoparticles and changes that occur in biological test media can be correlated to toxicity, and different mechanisms for toxicity are apparent. Uptake rates and localization is also different between different cell lines. Uptake and localization of particles provides evidence that nanosilver should not be treated as a single material but should be studied as an array of materials with different properties in different biological systems.

Optoelectrokinetic Manipulation for Cell Analysis

Rapid advancement of microfluidic technology in the recent years has opened a new era for biological diagnostics. The demands for fast response, multi-functionality, non-invasiveness, and programmability boost the developments in many fields, such as tissue engineering, cell analysis, and molecular biology. For this trend, an appropriate manipulation tool is pivotal to the success of all applications. In this chapter, we explore two newly developed optoelectrokinetic techniques, termed rapid electrokinetic patterning (REP) and optoelectronic tweezers (OETs), from the fundamental principles to their applications in cell-related research. Details about fabrications, setups, and assessments are also thoroughly discussed. Both techniques are enabled by a deliberate integration of light and electric fields, therefore imparting them the unique abilities to dynamically manipulate biological targets. Unlike some well-adopted techniques, such as dielectrophoresis (DEP), REP and OETs feature high flexibility in manipulation. Their repertoire of manipulation includes, but not limited to, micro/nano concentration, sorting, translation, single particle trapping, and patterning. By combining with optoelectrowetting (OEW), a cross-scale platform suitable for multiple purposes can be even achieved. The multi-functionality endows the optoelectrokinetic manipulation the potential to further extend the cell analysis in all aspects.