Holographic Sensor Based on Bayfol HX200 Commercial Photopolymer for Ethanol and Acetic Acid Detection.

This paper presents a holographic sensor based on reflection holograms recorded in the commercial photopolymer Bayfol HX 200. The recording geometry and index modulation of the hologram were optimised to improve accuracy for this specific application. The sensor was subjected to tests using various analytes, and it exhibited sensitivity to acetic acid and ethanol.

Contribution to the Improvement of the Correlation Filter Method for Modal Analysis with a Spatial Light Modulator.

Modal decomposition of light is essential to study its propagation properties in waveguides and photonic devices. Modal analysis can be carried out by implementing a computer-generated hologram acting as a match filter in a spatial light modulator. In this work, a series of aspects to be taken into account in order to get the most out of this method are presented, aiming to provide useful operational procedures.

Stacked volume holographic gratings for extending the operational wavelength range in LED and solar applications.

A novel stacking procedure is presented for volume phase holographic gratings (VPHGs) recorded in photopolymer material using Corning Willow Glass as a flexible substrate in order to achieve broader angular and spectral selectivity in a diffractive device with high efficiency for solar and LED applications. For the first time to our knowledge, we have shown a device designed for use with a white LED that has the same input and output angles and high efficiency when illuminated by different wavelengths. In this paper, two VPHGs were designed, experimentally recorded, and tested when illuminated at normal incidence.

Full modeling and experimental validation of cylindrical holographic lenses recorded in Bayfol HX photopolymer and partly operating in the transition regime for solar concentration.

Concentrating photovoltaics for building integration can be successfully carried out with Holographic Optical Elements (HOEs) because of their behavior analogous to refractive optical elements and their tuning ability to the spectral range that the photovoltaic (PV) cell is sensitive to. That way, concentration of spectral ranges that would cause overheating of the cell is avoided. Volume HOEs are usually chosen because they provide high efficiencies.

Characterization of volume holographic optical elements recorded in Bayfol HX photopolymer for solar photovoltaic applications.

Volume Holographic Optical Elements (HOEs) present interesting characteristics for photovoltaic applications as they can select spectrum for concentrating the target bandwidth and avoiding non-desired wavelengths, which can cause the decrease of the performance on the cell, for instance by overheating it. Volume HOEs have been recorded on Bayfol HX photopolymer to test the suitability of this material for solar concentrating photovoltaic systems. The HOEs were recorded at 532 nm and provided a dynamic range, reaching close to 100% efficiency at 800 nm.

Broadband behavior of transmission volume holographic optical elements for solar concentration.

A ray tracing algorithm is developed to analyze the energy performance of transmission and phase volume holographic lenses that operate with broadband illumination. The agreement between the experimental data and the theoretical treatment has been tested. The model has been applied to analyze the optimum recording geometry for solar concentration applications.

Generation of stable orthogonal gradients of chemical concentration and substrate stiffness in a microfluidic device.

Cellular responses to chemical cues are at the core of a myriad of fundamental biological processes ranging from embryonic development to cancer metastasis. Most of these biological processes are also influenced by mechanical cues such as the stiffness of the extracellular matrix. How a biological function is influenced by a synergy between chemical concentration and extracellular matrix stiffness is largely unknown, however, because no current strategy enables the integration of both types of cues in a single experiment.

Quantitative analysis of chemotaxis towards toluene by Pseudomonas putida in a convection-free microfluidic device.

Chemotaxis has been shown to be beneficial for the migration of soil-inhabiting bacteria towards industrial chemical pollutants, which they degrade. Many studies have demonstrated the importance of this microbial property under various circumstances; however, few quantitative analyses have been undertaken to measure the two essential parameters that characterize the chemotaxis of bioremediation bacteria: the chemotactic sensitivity coefficient χ(0) and the chemotactic receptor constant K(c). The main challenge to determine these parameters is that χ(0) and K(c) are coupled together in non-linear mathematical models used to evaluate them.

A facile route to the synthesis of monodisperse nanoscale liposomes using 3D microfluidic hydrodynamic focusing in a concentric capillary array.

A novel microscale device has been developed to enable the one-step continuous flow assembly of monodisperse nanoscale liposomes using three-dimensional microfluidic hydrodynamic focusing (3D-MHF) in a concentric capillary array. The 3D-MHF flow technique displays patent advantages over conventional methods for nanoscale liposome manufacture (i.e.

Pneumatic valves in folded 2D and 3D fluidic devices made from plastic films and tapes.

We present a rapid prototyping technique that expands elastomeric valving capabilities to devices made from thin materials such as plastic films and tapes. The time required from conception to full fabrication of functional devices is within a few hours. A key characteristic of this technology is that devices are thin (typically less than 0.

Holographic optical element to generate achromatic vortices.

A compound holographic optical element to generate achromatic vortices with high efficiency, based on the combination of two volume phase holograms, is designed and constructed. This element is compact and easy to align. It has high damage threshold, so it can be used with ultraintense laser pulses.

Measurement and validation of cell-based assays with microfluidics at the National Institute of Standards and Technology.

The National Institute of Standards and Technology (NIST) is the National Metrology Institute for the USA. Our mission is to advance measurement science, standards and technology in ways that enhance economic security and improve quality of life in the USA. Due to the increased need for technologies that advance biological research and the many new and exciting innovations in microfluidics, our projects are aimed at engineering well-controlled microenvironments for quantitative measurements of cell behavior in microfluidic systems.

A robust diffusion-based gradient generator for dynamic cell assays.

This manuscript describes a new method to generate purely diffusive chemical gradients that can be modified in time. The device is simple in its design and easy to use, which makes it amenable to study biological processes that involve static or dynamic chemical gradients such as chemotaxis. We describe the theory underlying the convection-free gradient generator, illustrate the design to implement the theory, and present a protocol to align multiple layers of double sided tape and laminates to fabricate the device.

2D separations on a 1D chip: gradient elution moving boundary electrophoresis-chiral capillary zone electrophoresis.

A new method is described for two-dimensional (2D) separations using a microfluidic chip normally employed for single dimension electrophoresis. The method employs a combination of gradient elution moving boundary electrophoresis (GEMBE) and chiral capillary zone electrophoresis (CZE). The simplicity of the first dimension GEMBE method enables its implementation in the injection channel of a conventional electrophoresis chip, simplifying the design and operation of the device.

Magnetic connectors for microfluidic applications.

We present a new type of microfluidic connector that employs a ring magnet on one side of the microfluidic chip and a disc magnet on the other side to produce a sealed connection between external tubing and inlets or outlets of microfluidic devices. The connectors are low-cost, simple to use and assemble, and reusable. We used numerical (finite element) simulations in order to optimize their geometry.

The microfluidic palette: a diffusive gradient generator with spatio-temporal control.

This paper describes a new microfluidic device called the "microfluidic palette", capable of generating multiple spatial chemical gradients simultaneously inside a microfluidic chamber. The unique aspect of this work is that chemical gradients are generated by diffusion, without convection, and can either be held constant over long periods, or modified dynamically. We characterized a representative device with a 1.

Characterization of transmission volume holographic gratings recorded in Slavich PFG04 dichromated gelatin plates.

We characterize Slavich PFG-04 dichromated gelatin plates to make transmission volume holographic elements recorded with a 532 nm laser source, obtaining high efficiency gratings with a high signal to noise ratio. The linear dynamic range of the material is studied by measuring the efficiency of multiplexed gratings. Results obtained are applied to the recording of holographic elements with high efficiency when they are illuminated with a 800 nm light source.

A vacuum manifold for rapid world-to-chip connectivity of complex PDMS microdevices.

The lack of simple interfaces for microfluidic devices with a large number of inlets significantly limits production and utilization of these devices. In this article, we describe the fabrication of a reusable manifold that provides rapid world-to-chip connectivity. A vacuum network milled into a rigid manifold holds microdevices and prevents leakage of fluids injected into the device from ports in the manifold.

Field improvement in a uniaxial centered lens composed of two stacked-volume holographic elements.

Arrangements are described for the recording of volume holograms with two sections that, when stacked together, work as uniaxial centered lenses and allow one to solve the problem of angular selectivity in the imaging of wide objects. The performance of such systems is examined qualitatively, and suggestions aimed at improving these designs are proposed.

Using pattern homogenization of binary grayscale masks to fabricate microfluidic structures with 3D topography.

Because fluids at the microscale form three dimensional interfaces and are subject to three dimensional forces, the ability to create microstructures with modulated topography over large areas could greatly improve control over microfluidic phenomena (e.g., capillarity and mass transport) and enable exciting novel microfluidic applications.

Anamorphic white light Fourier processor with holographic lenses.

Two anamorphic and achromatic Fourier processors were designed and constructed using diffractive and refractive cylindrical lenses. The diffractive lenses are holographic lenses recorded on silver halide material. In both processors the achromatic one-dimensional Fourier transform plane was obtained with two holographic lenses and one refractive cylindrical lens.

Capillary inserts in microcirculatory systems.

Microfluidic loops (i.e. closed fluid paths) pose specific practical challenges such as priming, introducing analytes or reagents in a controlled way and sampling products.

Steady flow generation in microcirculatory systems.

In this paper we explore the mechanical generation of steady-non pulsatile-flow in microfluidic systems. The rationale of the paper is inspired in the example of cardiovascular systems where at the microscale (i.e.

Controlled microfluidic interfaces.

The microfabrication technologies of the semiconductor industry have made it possible to integrate increasingly complex electronic and mechanical functions, providing us with ever smaller, cheaper and smarter sensors and devices. These technologies have also spawned microfluidics systems for containing and controlling fluid at the micrometre scale, where the increasing importance of viscosity and surface tension profoundly affects fluid behaviour. It is this confluence of available microscale engineering and scale-dependence of fluid behaviour that has revolutionized our ability to precisely control fluid/fluid interfaces for use in fields ranging from materials processing and analytical chemistry to biology and medicine.

Magnetically-driven biomimetic micro pumping using vortices.

Planar micropumps utilizing vortices shed by an oscillating ferromagnetic bar are presented. The movement of the bar is induced by magnetic coupling with an external spinning magnet. Thus, energy transfer is achieved without physical contact or need of any on-chip power source.