1,262 research outputs found
Creating tissue on chip constructs in microtitre plates for drug discovery
We report upon a novel coplanar dielectrophoresis (DEP) based cell patterning system for generating transferrable hepatic cell constructs, resembling a liver-lobule, in culture. The use of paper reinforced gel substrates provided sufficient strength to enable these constructs to be transfered into 96-well plates for long term functional studies, including in the future, drug development studies. Experimental results showed that hepatic cells formed DEP field-induced structures corresponding to an array of lobule-mimetic patterns. Hepatic viability was observed over a period of 3 days by the use of a fluorescent cell staining technique, whilst the liver specific functionality of albumin secretion showed a significant enhancement due to the layer patterning of cell lines (HepG2/C3A), compared to 2D patterned cells and un-patterned control. This âbuild and transferâ concept could, in future, also be adapted for the layer-by-layer construction of organs-on-chip in microtitre formats
Acoustically controlled enhancement of molecular sensing to assess oxidative stress in cells
We demonstrate a microfluidic platform for the controlled aggregation of colloidal silver nanoparticles using surface acoustic waves (SAWs), enabling surface enhanced Raman scattering (SERS) analysis of a cell based model for oxidative damage. We show that by varying the frequency and the power of the acoustic energy, it is possible to modulate the aggregation of the colloid within the sample and hence to optimise the SERS analysis
Acoustic suppression of the coffee-ring effect
We study the influence of acoustic fields on the evaporative self-assembly of solute particles suspended inside sessile droplets of complex fluids. The self-assembly process often results in an undesirable ring-like heterogeneous residue, a phenomenon known as the coffee-ring effect. Here we show that this ring-like self-assembly can be controlled acoustically to form homogeneous disc-like or concentrated spot-like residues. The principle of our method lies in the formation of dynamic patterns of particles in acoustically excited droplets, which inhibits the evaporation-driven convective transport of particles towards the contact line. We elucidate the mechanisms of this pattern formation and also obtain conditions for the suppression of the coffee-ring effect. Our results provide a more general solution to suppress the coffee-ring effect without any physiochemical modification of the fluids, the particles or the surface, thus potentially useful in a broad range of industrial and analytical applications that require homogenous solute depositions
Ultrasonic Wave Mixing for Nonlinear Ultrasonics in a Microfluidic Capillary
In this study we show that nonlinear ultrasonics,
based on nonlinear wave mixing, can enable the measurement of
the interactions between acoustic waves and a microliter liquid
sample in a glass capillary microchannel. This has the potential to
deliver new techniques with a high sensitivity to acoustic material
propertie
Channel integrated optoelectronic tweezer chip for microfluidic particle manipulation
Light patterned electrical fields have been widely used for the manipulation of microparticles,
from cells to microscopic electronic components. In this work, we explore a novel
electromechanical phenomenon for particle focusing and sorting where the electrical field
patterns are shaped by a combination of the light patterned photoconductor and the channel
geometry. This effect results from the combination of particle polarisation described by
the ClausiusâMossotti relation and the engineering of large electric gradients produced by
choosing the channels height to suit the size of the particles being manipulated. The matched
geometry increases the distortion of the field created by a combination of the illuminated
photoconductor and the particles themselves and hence the non-uniformity of the field they
experience. We demonstrate a new channel integration strategy which allows the creation of
precisely defined channel structures in the OET device. By defining channels in photoresist
sandwiched between upper and lower ITO coated glass substrates we produce robust channels
of well controlled height tailored to the particle. Uniquely, the top substrate is attached before
photolithographically defining the channels. We demonstrate versatile control using this effect
with dynamically reconfigurable light patterns allowing the retention against flow, focusing
and sorting of micro particles within the channels. Contrary to traditional designs, this channel
integrated device allows patterned micro channels to be used in conjunction with conductive
top and bottom electrodes producing optimal conditions for the dielectrophoretic manipulation
as demonstrated by the rapid flow (up to 5mm sâ1
) in which the particles can be focuse
Green-function Method for Nonlinear Interactions of Elastic Waves
In the linear wave propagation regime, an analytical
mesh-free Green-function decomposition has been shown as a
viable alternative to FDTD and FEM. However, its expansion into
nonlinear regimes has remained elusive due to the inherent linear
properties of the Green-function approach. This work presents
a novel frequency-domain Green function method to describe
and model nonlinear wave interactions in isotropic hyperelastic
media. As an example of the capabilities of the method, we
detail the generation of sum frequency waves when initial quasimonochromatic waves are emitted in a fluid by finite sources.
The method is supported by both numerical and experimental
results using immersion ultrasonic techniques
Creating tissue on chip constructs in microtitre plates for drug discovery
We report upon a novel coplanar dielectrophoresis (DEP) based cell patterning system for generating
transferrable hepatic cell constructs, resembling a liver-lobule, in culture. The use of paper reinforced gel
substrates provided sufficient strength to enable these constructs to be transfered into 96-well plates for
long term functional studies, including in the future, drug development studies. Experimental results
showed that hepatic cells formed DEP field-induced structures corresponding to an array of lobulemimetic patterns. Hepatic viability was observed over a period of 3 days by the use of a fluorescent cell
staining technique, whilst the liver specific functionality of albumin secretion showed a significant
enhancement due to the layer patterning of cell lines (HepG2/C3A), compared to 2D patterned cells and
un-patterned control. This âbuild and transferâ concept could, in future, also be adapted for the layer-bylayer construction of organs-on-chip in microtitre formats
Cycling of Rational Hybridization Chain Reaction To Enable Enzyme-Free DNA-Based Clinical Diagnosis
In order to combat the growing threat of
global infectious diseases, there is a need for rapid
diagnostic technologies that are sensitive and that can
provide species specific information (as might be needed to
direct therapy as resistant strains of microbes emerge).
Here, we present a convenient, enzyme-free amplification
mechanism for a rational hybridization chain reaction,
which is implemented in a simple format for isothermal
amplification and sensing, applied to the DNA-based
diagnosis of hepatitis B virus (HBV) in 54 patients. During
the cycled amplification process, DNA monomers selfassemble in an organized and controllable way only when a
specific target HBV sequence is present. This mechanism is
confirmed using super-resolution stochastic optical reconstruction microscopy. The enabled format is designed in a
manner analogous to an enzyme-linked immunosorbent assay, generating colored products with distinct tonality and with
a limit of detection of ca. five copies/reaction. This routine assay also showed excellent sensitivity (>97%) in clinical
samples demonstrating the potential of this convenient, low cost, enzyme-free method for use in low resource settings
Frequency dependence of microflows upon acoustic interactions with fluids
Rayleigh surface acoustic waves (SAWs), generated on piezoelectric substrates, can interact with
liquids to generate fast streaming flows. Although studied extensively, mainly phenomenologically,
the effect of the SAW frequency on streaming in fluids in constrained volumes is not fully understood,
resulting in sub-optimal correlations between models and experimental observations. Using microfluidic structures to reproducibly define the fluid volume, we use recent advances modeling the body
force generated by SAWs to develop a deeper understanding of the effect of acoustic frequency on
the magnitude of streaming flows. We implement this as a new predictive tool using a finite element
model of fluid motion to establish optimized conditions for streaming. The model is corroborated
experimentally over a range of different acoustic excitation frequencies enabling us to validate a
design tool, linking microfluidic channel dimensions with frequencies and streaming efficiencies.
We show that in typical microfluidic chambers, the length and height of the chamber are critical in
determining the optimum frequency, with smaller geometries requiring higher frequencies
Low-cost, multispectral imaging mini-microscope for longitudinal oximetry in small animals
We present a multispectral imaging mini-microscope for longitudinal oximetry in small animals. By replacing expensive and complex imaging systems using a low-cost imaging system
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