Joe Bailey

Separation of blood cells with differing deformability using deterministic lateral displacement(

Determining cell mechanical properties is increasingly recognized as a marker-free way to characterize and separate biological cells. This emerging realization has led to the development of a plethora of appropriate measurement techniques. Here, we use a fairly novel approach, deterministic lateral displacement (DLD), to separate blood cells based on their mechanical phenotype with high throughput. Human red blood cells were treated chemically to alter their membrane deformability and the effect of this alteration on the hydrodynamic behaviour of the cells in a DLD device was investigated. Cells of defined stiffness (glutaraldehyde cross-linked erythrocytes) were used to test the performance of the DLD device across a range of cell stiffness and applied shear rates. Optical stretching was used as an independent method for quantifying the variation in stiffness of the cells. Lateral displacement of cells flowing within the device, and their subsequent exit position from the device were shown to correlate with cell stiffness. Data showing how the isolation of leucocytes from whole blood varies with applied shear rate are also presented. The ability to sort leucocyte sub-populations (T-lymphocytes and neutrophils), based on a combination of cell size and deformability, demonstrates the potential for using DLD devices to perform continuous fractionation and/or enrichment of leucocyte sub-populations from whole blood.

Coined quantum walks on percolation graphs

Quantum walks, both discrete (coined) and continuous time, form the basis of several quantum algorithms and have been used to model processes such as transport in spin chains and quantum chemistry. The enhanced spreading and mixing properties of quantum walks compared with their classical counterparts have been well studied on regular structures and also shown to be sensitive to defects and imperfections in the lattice. As a simple example of a disordered system, we consider percolation lattices, in which edges or sites are randomly missing, interrupting the progress of the quantum walk. We use numerical simulation to study the properties of coined quantum walks on these percolation lattices in one and two dimensions. In one dimension (the line), we introduce a simple notion of quantum tunnelling and determine how this affects the properties of the quantum walk as it spreads. On two-dimensional percolation lattices, we show how the spreading rate varies from linear in the number of steps down to zero as the percolation probability decreases towards the critical point. This provides an example of fractional scaling in quantum-walk dynamics.

Absorption modulation of terahertz metamaterial by varying the conductivity of ground plane

Most research focuses on varying the resonator and dielectric spacer to configure the absorption and resonant frequency of terahertz (THz) metamaterial absorbers (MAs), where a metal ground plane is used as a perfect reflector of incident THz waves. In this paper, we modulate the MAs absorption by varying the conductivity of the ground plane. Two THz MAs were fabricated by replacing the gold ground planes with cobalt silicide films, and the measured absorptivity decreases by 4% for the electric resonance and increases by 44% for the dipole resonance. Our quantitative analysis reveals that when the conductivity of the ground plane decreases from 1.8 × 107 S/m to 3.0 × 105 S/m, the absorptivity of the electric resonance decreases by 23%, while that of the dipole resonance increases by 62%. Our approach also provides a practical method to measure the electric conductivity of conductive films in the THz regime.

Real-time dielectrophoretic signaling and image quantification methods for evaluating electrokinetic properties of nanoparticles

Real‐time image signaling and quantification methods are described that allow easy‐to‐use, fast extraction of the electrical properties of nanoparticles. Positive dielectrophoretic (pDEP) collection rate analysis enables the dielectric properties of very small samples of nanoparticles to be accurately quantified. Advancing earlier work involving dual‐cycle pulsed pDEP collection experiments, we report the development of a statistical image quantification method that significantly advances the evaluation of nanoparticle dielectric properties. Compared with traditional methods that require information about the geometry of the electrode array to be entered for semiautomated quantification , the new statistical approach described does not require a priori knowledge of device geometry. The efficacy of the statistical method is experimentally demonstrated using 200 nm diameter latex nanospheres, suspended in low conductivity medium, that are attracted by pDEP onto planar castellated electrode arrays with 5‐micron‐sized features. The method is shown to yield estimates for the nanoparticle conductivity and surface conductance, σp=25.8 mS/m and KS=1.29 nS, that concur closely with those obtained using traditional geometric methods previously reported . Consequently, the statistical method is accurate, fast, robust, supervisor‐free, and useful for determining nanoparticle electrokinetic parameters.

Surface mediated cooperative interactions of drugs enhance mechanical forces for antibiotic action

The alarming increase of pathogenic bacteria that are resistant to multiple antibiotics is now recognized as a major health issue fuelling demand for new drugs. Bacterial resistance is often caused by molecular changes at the bacterial surface, which alter the nature of specific drug-target interactions. Here, we identify a novel mechanism by which drug-target interactions in resistant bacteria can be enhanced. We examined the surface forces generated by four antibiotics; vancomycin, ristomycin, chloroeremomycin and oritavancin against drug-susceptible and drug-resistant targets on a cantilever and demonstrated significant differences in mechanical response when drug-resistant targets are challenged with different antibiotics although no significant differences were observed when using susceptible targets. Remarkably, the binding affinity for oritavancin against drug-resistant targets (70 nM) was found to be 11,000 times stronger than for vancomycin (800 μM), a powerful antibiotic used as the last resort treatment for streptococcal and staphylococcal bacteria including methicillin-resistant Staphylococcus aureus (MRSA). Using an exactly solvable model, which takes into account the solvent and membrane effects, we demonstrate that drug-target interactions are strengthened by pronounced polyvalent interactions catalyzed by the surface itself. These findings further enhance our understanding of antibiotic mode of action and will enable development of more effective therapies.

Direct and alignment-insensitive measurement of cantilever curvature

We analytically derive and experimentally demonstrate a method for the simultaneous measurement of deflection for large arrays of cantilevers. The Fresnel diffraction patterns of a cantilever independently reveal tilt, curvature, cubic, and higher order bending of the cantilever. It provides a calibrated absolute measurement of the polynomial coefficients describing the cantilever shape, without careful alignment and could be applied to several cantilevers simultaneously with no added complexity. We show that the method is easily implemented, works in both liquid media and in air, for a broad range of displacements and is especially suited to the requirements for multi-marker biosensors.

Corrigendum: Surface mediated cooperative interactions of drugs enhance mechanical forces for antibiotic action

Scientific Reports 7:Article number: 41206; published online: 03 February 2017; updated: 23 March 2017 This Article contains errors. An additional affiliation for Samadhan B. Patil was omitted. The correct affiliations for this Author are listed below: Departments of Medicine, UCL Institute for Liver and Digestive Health, Royal Free Hospital, London NW3 2QG, UK.

Information Processing Tools for Extracting the Electrical Properties of Nanoparticles

Newly developed information processing tools are described that enable easy-to-use, fast extraction of the electrical properties of nanoparticles. Positive dielectrophoretic (pDEP) collection rate analysis enables the dielectric properties of very small samples of nanoparticles to be accurately quantified. We report the latest advances of semi-automated image quantification methods that are applied to pDEP collection experiments using dual-cycle pulsed pDEP [1]. Compared to traditional methods that require information about the geometry of the electrode array to be entered for semi-automated quantification [2], the new statistic-based approach described does not require a priori knowledge of device geometry. Consequently, the statistical method is supervisor-free, fast and suitable for laboratory application. The statistical method gives estimates for the nanoparticle conductivity and surface conductance that agree closely to those obtained using more complex geometric methods. The efficacy of the method ...

Planar broadband terahertz metamaterial absorber using single nested resonator

We report a broadband terahertz metamaterial absorber with two nested back-to-back split-ring resonators constituting a single planar resonator. Bandwidths of 0.66THz and 0.98THz with the absorptivity above 0.8 and 0.6 were experimentally obtained respectively.

Dual-band metamaterial absorbers at terahertz frequency based on gold/parylene-C/silicide structure

We design, fabricate and characterize dual-band terahertz (THz) metamaterial absorbers with high absorption based on a structures consisting of a cobalt silicide (Co-Si) ground plane, a parylene-C dielectric spacer and a metal top layer. By combining two periodic metal resonators that couple separately within a single unit cell, a polarization-independent absorber with two distinct absorption peaks was obtained. By varying the thickness of the dielectric layer, we obtain absorptivity of 0.76 at 0.76THz and 0.97 at 2.30THz, which indicates the Co-Si ground plane absorbers present good performance.