Electrokinetic particle trapping in microfluidic wells using conductive nanofiber mats.

The frequency dependence of electrokinetic particle trapping using large-area (>mm) conductive carbon nanofiber (CNF) mat electrodes is investigated. The fibers provide nanoscale geometric features for the generation of high electric field gradients, which is necessary for particle trapping via dielectrophoresis (DEP). A device was fabricated with an array of microfluidic wells for repeated experiments; each well included a CNF mat electrode opposing an aluminum electrode.

An electrospun nanofiber mat as an electrode for AC-dielectrophoretic trapping of nanoparticles.

In order to trap nanoparticles with dielectrophoresis, high electric field gradients are needed. Here we created large area (>mm) conductive carbon nanofiber mats to trap nanoparticles with dielectrophoresis. The electrospun fiber mats had an average diameter of 267 ± 94 nm and a conductivity of 2.

A microfluidic impedance platform for real-time, characterization of endothelial cells undergoing fluid shear stress.

We introduce a microfluidic impedance platform to electrically monitor in real-time, endothelium monolayers undergoing fluid shear stress. Our platform incorporates sensing electrodes (SEs) that measure cell behavior and cell-free control electrodes that measure cell culture media resistance simultaneously but independently from SEs. We evaluated three different cellular subpopulations sizes through 50, 100, and 200 μm diameter SEs.

Particle-Induced Electrostatic Repulsion within an Electric Curtain Operating below the Paschen Limit.

The electric curtain is a platform developed to lift and transport charged particles in air. Its premise is the manipulation of charged particles; however, fewer investigations isolate dielectric forces that are observed at lower voltages (i.e.

Development of Inspired Therapeutics Pediatric VAD: Computational Analysis and Characterization of VAD V3.

Purpose: Pediatric heart failure patients remain in critical need of a dedicated mechanical circulatory support (MCS) solution as development efforts for specific pediatric devices continue to fall behind those for the adult population. The Inspired Pediatric VAD is being developed as a pediatric specific MCS solution to provide up to 30-days of circulatory or respiratory support in a compact modular package that could allow for patient ambulation during treatment.

Methods: Hydrodynamic performance (flows, pressures), impeller/rotor mechanical properties (torques, forces), and flow shear stress and residence time distributions of the latest design version, Inspired Pediatric VAD V3, were numerically predicted and investigated using computational fluid dynamics (CFD) software (SolidWorks Flow Simulator).

Membrane tension may define the deadliest virus infection.

This manuscript describes the potentially significant role of interfacial tension in viral infection. Our hypothesis is based on evidence from drop coalescence hydrodynamics. A change in membrane tension can trigger fusion between the vesicle and cell such that genetic material, like viral RNA, can subsequently be transported to the cell interior.

Cyclic force driven colloidal self-assembly near a solid surface.

Hypothesis: Self-assembled colloidal mobility out of a non-equilibrium system can depend on many external and interparticle forces including hydrodynamic forces. While the driving forces guiding colloidal suspension, translation and self-assembly are different and unique, hydrodynamic forces are always present and can significantly influence particle motion. Unfortunately, these interparticle hydrodynamic interactions are typically overlooked.

Development of Inspired Therapeutics Pediatric VAD: Benchtop Evaluation of Impeller Performance and Torques for MagLev Motor Design.

Purpose: Despite the availability of first-generation extracorporeal mechanical circulatory support (MCS) systems that are widely used throughout the world, there is a need for the next generation of smaller, more portable devices (designed without cables and a minimal number of connectors) that can be used in all in-hospital and transport settings to support patients in heart failure. Moreover, a system that can be universally used for all indications for use including cardiopulmonary bypass (CPB), uni- or biventricular support (VAD), extracorporeal membrane oxygenation (ECMO) and respiratory assist that is suitable for use for adult, neonate, and pediatric patients is desirable. Providing a single, well designed, universal technology could reduce the incidence of human errors by limiting the need for training of hospital staff on a single system for a variety of indications throughout the hospital rather than having to train on multiple complex systems.

Time-resolved particle image velocimetry analysis and computational modeling of transient optically induced electrothermal micro vortex.

Trapping, sorting, transportation, and manipulation of synthetic microparticles and biological cells enable investigations in their behavior and properties. Microfluidic techniques like rapid electrokinetic patterning (REP) provide a non-invasive means to probe into the nature of these micro and nanoparticles. The opto-electrically induced nature of a REP micro vortex allows tuning of the trap characteristics in real-time.

Rapid detection of SARS-CoV-2 antibodies using electrochemical impedance-based detector.

Coronavirus disease (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was classified as a pandemic by the World Health Organization and has caused over 550,000 deaths worldwide as of July 2020. Accurate and scalable point-of-care devices would increase screening, diagnosis, and monitoring of COVID-19 patients. Here, we demonstrate rapid label-free electrochemical detection of SARS-CoV-2 antibodies using a commercially available impedance sensing platform.

Advances and applications of isomotive dielectrophoresis for cell analysis.

Isomotive dielectrophoresis (isoDEP) is a unique electric field such that the gradient of the field-squared ([Formula: see text]) is constant, resulting a uniform dielectrophoretic force. The current status of isoDEP is presented in this review, and we will highlight the progress that has been achieved over the past 60 years in various avenues of isoDEP since H.A.

Multiscale Self-Assembly of Distinctive Weblike Structures from Evaporated Drops of Dilute American Whiskeys.

When a sessile droplet of a complex mixture evaporates, its nonvolatile components may deposit into various patterns. One such phenomena, the coffee ring effect, has been a topic of interest for several decades. Here, we identify what we believe to be a fascinating phenomenon of droplet pattern deposition for another well-known beverage-what we have termed a "whiskey web".

Scaling law analysis of electrohydrodynamics and dielectrophoresis for isomotive dielectrophoresis microfluidic devices.

Isomotive dielectrophoresis (isoDEP) is a unique DEP geometrical configuration where the gradient of the field-squared ( ) is constant. IsoDEP analyzes polarizable particles based on their magnitude and direction of translation. Particle translation is a function of the polarizability of both the particles and suspending medium, the particles' size and shape, and the frequency of the electric field.

Isomotive dielectrophoresis for parallel analysis of individual particles.

Two dielectrophoresis systems are introduced where the induced dielectrophoretic force is constant throughout the experimental region, resulting in uniform (isomotive) microparticle translation. Isomotive dielectrophoresis (isoDEP) is accomplished through a unique geometry where the gradient of the field-squared (∇Erms2) is constant, a characteristic that is otherwise highly nonuniform in traditional DEP platforms. The governing isoDEP equations were derived herein and applied to two different isoDEP prototypes: (i) one fabricated from deep reactive ion etching (DRIE) of a conductive silicon wafer (1-10 Ω-cm) whose patterned features served as electrodes and microchannel sidewalls simultaneously; (ii) a second where the electric field is applied lengthwise through a PDMS microchannel whose geometry follows a specific curvature.

Dynamic optoelectric trapping and deposition of multiwalled carbon nanotubes.

In the path toward the realization of carbon nanotube (CNT)-driven electronics and sensors, the ability to precisely position CNTs at well-defined locations remains a significant roadblock. Highly complex CNT-based bottom-up structures can be synthesized if there is a method to accurately trap and place these nanotubes. In this study, we demonstrate that the rapid electrokinetic patterning (REP) technique can accomplish these tasks.

An orbital shear platform for real-time, in vitro endothelium characterization.

Electrical impedance techniques have been used to characterize endothelium morphology, permeability, and motility in vitro. However, these impedance platforms have been limited to either static endothelium studies and/or induced laminar fluid flow at a constant, single shear stress value. In this work, we present a microfabricated impedance sensor for real-time, in vitro characterization of human umbilical vein endothelial cells (HUVECs) undergoing oscillatory hydrodynamic shear.

Optoelectric patterning: Effect of electrode material and thickness on laser-induced AC electrothermal flow.

Rapid electrokinetic patterning (REP) is an emerging optoelectric technique that takes advantage of laser-induced AC electrothermal flow and particle-electrode interactions to trap and translate particles. The electrothermal flow in REP is driven by the temperature rise induced by the laser absorption in the thin electrode layer. In previous REP applications 350-700 nm indium tin oxide (ITO) layers have been used as electrodes.

Characterization of 2D colloid aggregations created by optically induced electrohydrodynamics.

Rapid electrokinetic patterning (REP) is a technique for creating self-assembled monolayers (SAMs) of spherical particles in a liquid medium, and dynamically controlling them though the simultaneous application of an electric field and optically induced temperature gradients. Previous work has investigated and characterized REP axisymmetric aggregations generated from a focus laser within a uniform electric field; work herein characterizes line-shaped particle assemblies derived from the application of a linearly scanned laser. The resulting aggregations of spherical polystyrene particles (1 μm) suspended in low-conductivity aqueous potassium chloride solution (KCl, 2.

Electrothermal pumping with interdigitated electrodes and resistive heaters.

Interdigitated electrodes are used in electrokinetic lab-on-a-chip devices for dielectrophoretic trapping and characterization of suspended particles, as well as the production of field-induced fluid flow via AC electroosomosis and electrothermal mechanisms. However, the optimum design for dielectrophoresis, that if symmetrical electrodes, cannot induce bulk electrohydrodynamic pumping. In addition, the mechanism of intrinsic electrothermal pumping is affected by the properties of the fluid, with thermal fields being generated by Joule Heating.

Characterization of 2D colloids assembled by optically-induced electrohydrodynamics.

We report the results of a study characterizing the behavior of colloid aggregations under manipulation of a technique known as Rapid Electrokinetic Patterning (REP) - this technique is capable of dynamically manipulating the crystallinity of 2D colloid aggregations, potentially enabling dynamically tunable photonic crystals. Herein, aggregations of spherical polystyrene particles 1.0 μm in diameter suspended in a low conductivity aqueous solution were collected at the surface of an indium-tin oxide coated glass slide.

An optoelectrokinetic technique for programmable particle manipulation and bead-based biosignal enhancement.

Technologies that can enable concentration of low-abundance biomarkers are essential for early diagnosis of diseases. In this study, an optoelectrokinetic technique, termed Rapid Electrokinetic Patterning (REP), was used to enable dynamic particle manipulation in bead-based bioassays. Various manipulation capabilities, such as micro/nanoparticle aggregation, translation, sorting and patterning, were developed.

Dielectrophoretic trapping of nanoparticles with an electrokinetic nanoprobe.

A high aspect ratio 3D electrokinetic nanoprobe is used to trap polystyrene particles (200 nm), gold nanoshells (120 nm), and gold nanoparticles (mean diameter 35 nm) at low voltages (<1 V(rms)). The nanoprobe is fabricated using room temperature self-assembly methods, without the need for nanoresolution lithography. The nanoprobe (150-500 nm in diameter, 2-150 μm in length) is mounted on the end of a glass micropipette, enabling user-specified positioning.

Enhanced electrothermal pumping with thin film resistive heaters.

This work demonstrates the use of thin film heaters to enhance electrothermal pumping in microfluidic systems. Thin film heating electrothermal pumping is more efficient than Joule heating alone. Numerical simulations of an asymmetric electrode array are performed to demonstrate the advantages of incorporating thin film heaters.