Ultrafast High-pressure AC Electro-osmotic Pumps for Portable Biomedical Microfluidics

This paper details the development of an integrated AC electro-osmotic (ACEO) microfluidic pump for dilute electrolytes consisting of a long serpentine microchannel lined with three dimensional (3D) stepped electrode arrays. Using low AC voltage (1 Volt rms, 1 kHz), power (5 mW) and current (3.5 mA) in water, the pump is capable of generating a 1.4 kPa head pressure, a 100-fold increase over prior ACEO pumps, and a 1.37 mm/sec effective slip velocity over the electrodes without flow reversal. The integrated ACEO pump can utilize low ionic strength solutions such as distilled water as the working solution to pump physiological strength (100 mM) biological solutions in separate microfluidic devices, with potential applications in portable or implantable biomedical microfluidic devices. As a proof-of-concept experiment, the use of the ACEO pumps for DNA hybridization in a microfluidic microarray is demonstrated

Microfluidics for Biosensing

There are 12 papers published with 8 research articles, 3 review articles and 1 perspective. The topics cover: Biomedical microfluidics Lab-on-a-chip Miniaturized systems for chemistry and life science (MicroTAS) Biosensor development and characteristics Imaging and other detection technologies Imaging and signal processing Point-of-care testing microdevices Food and water quality testing and control We hope this collection could promote the development of microfluidics and point-of-care testing (POCT) devices for biosensing

Novel titania nanotube based electrochemical detection in micrototal analysis system

reportWe report the modification of titania (TiO2) nanotubes for quantitative electrochemical (EC) detection of biomolecules on a microfluidic platform

Simulation of cell seeding and retention in a disordered polymeric scaffold

Historically, bone repair has been performed using materials like metals, ceramics, cements and bioactive glass. The major problem with all these materials is that they do not perform the necessary non-structural functions of bone. Engineered tissue, created by growing bone cells on porous biodegradable material (scaffold), will address this issue with current bone repair techniques. Improving engineered tissue treatments requires a thorough understanding of factors affecting cell seeding and proliferation inside a disordered porous material which is not feasible using current experimental techniques. A model for particle transport in a disordered porous material that can predict the particle deposition pattern will be useful to understand the factors influencing particle transport and retention. Such a model has applications ranging from biomedical, microfluidics, environmental and water treatment. Currently available models for filtration or contaminant transport in a porous media either consider the porous media to be uniform or do not predict the particle deposition pattern. We develop an image-based computational model, which incorporates the structure of a disordered porous material, to study the effect of flow and material internal structure on particle transport and deposition, which was then applied to cell seeding. Particle motion and attachment inside the porous material is controlled by a deterministic convection component, obtained by numerically solving the Stokes Equation using FEM; a stochastic diffusion component, modeled using a random walk process, and an electrostatic component estimated using analytical expressions for the interaction of a colloid particle with a surface. Our simulations show that the Peclet number has a significant effect on the cell attachment pattern in a scaffold. At low Peclet numbers, cell attachment is concentrated at the inlet region of the scaffold, while cells penetrate deeper into the scaffold with increasing Peclet number. Additionally, the seeding pattern is found to vary considerably with internal pore structure. Visualization of the data indicates that attachment clusters at low velocity diffusion dominated zones

Micropatterning and dynamic swelling of photo-crosslinkable electroactive Pluronic hydrogel

AbstractThis paper presents the controlled swelling of a novel combination of materials for microsystems: a photopatternable electroactive polymer gel. It is very promising as an actuator material for e.g. biomedical or microfluidic applications as it shows a volume swelling of over 50% upon application of very modest voltages in a liquid environment. We present the synthesis of the novel material, the development of a MEMS compatible fabrication process and the measurements on fabricated test structures

Applications of polarized metallic nanostructures.

Gold nanostructures exhibit technologically useful properties when they are polarized in an electric field. In two projects we explore instances where the polarized metal can be used in real world applications. The first project involves gold nanoparticles (GNP) for use in light actuated microelectromechanical systems (MEMS) applications. Although the GNPs were originally designed for volumetric heating in biomedical applications, we treat them as a thin film coating, opening the door for these particles to be used in MEMS applications. This work characterizes the thermal properties of gold nanoparticles on surfaces for spatially-targeted thermal actuation in MEMS systems. The second project deals with metalized nanopore membranes for use in microfluidic applications. For this project several models and experiments were performed on electroosmotic flows driven by charge separation at polarized nanopore surfaces. Until this work, the flow-through geometry remained unexplored for induced charge electroosmotic flow (ICEO)

Effective Symmetry Breaking of Flow in AC Electro-Osmotic Pump Using a Ratchet Structure

AC electro-osmotic (ACEO) pumps play an important role in a wide diversity of microfiuidic applications. To produce high flow velocities, an effective breaking of symmetry is prerequisite. Here, we introduced a ratchet-structured electrode for achieving high flow velocities and developed a ratchet ACED pump containing both ratchet and plane electrodes. The performance of our new ACED pump is evaluated experimentally. At an ac voltage of 30 V at 10kHz, a maximum net flow velocity of 1.1 mm/s is measured along the inclined direction of the ratchet teeth. Furthermore, we also directly observed the flow fields due to the slip velocity of ACEO, which provide a physical insight on the ratchet-type ACED pumps.ArticleJOURNAL OF THE PHYSICAL SOCIETY OF JAPAN.88(8):084602(2019)journal articl

Optimization and characterization of a microscale thermal field-flow fractionation system

Journal ArticleA thorough investigation of the design considerations for microscale thermal field-flow fractionation and characterization of a 25 μm thin microscale thermal field-flow fractionation system is reported. A 4-50 times volume reduction from mesoscale and macroscale systems warrants customized design and operational conditions for microscale separation systems. Theoretical calculations are done to illustrate the importance of the increased dispersion due to extra-column tubing, off-chip detection and sample injection volume with reduced channel dimensions. An optimized microscale thermal field-flow fractionation (ThFFF) channel is fabricated using rapid and cost effective manufacturing and assembly processes. Specifically, improvements in material selection and arrangement are implemented to achieve higher particle retentions. The new instrument arrangement includes high conductivity silicon as the cold wall and a thin polymer layer with low thermal conductivity as the hot wall which results in high temperature gradients (~ 106 ºC/m) across the microchannel and subsequently high retention. Single particle retention separations are carried out with polystyrene nanoparticle samples in an aqueous carrier to characterize the device and demonstrate the improvements

Electroosmotic Flow Pump

Electroosmotic flow (EOF) pumping has been widely used to manipulate fluids such as liquid sample reagents in microfluidic systems. In this chapter, we will introduce the research progress on EOF pumps in the fields of microfluidic science and technology and briefly present their microfluidic applications in recent years. The chapter focuses on pump channel materials, electrodes, and their fabrication techniques in microfluidics