Hetero-coated magnetic microcarriers for point-of-care diagnostics

Abstract Summary: We report on the latest advances in the development of our magnetic encoded microcarriers Introduction: Thin magnetic strips ('bits') are encapsulated in a biocompatible polymer backbone to form `tags'. The tags can be used to generate a large library of magnetically labelled bio-chemical analytes. Since the magnetic encoding can be applied post fabrication, all microcarriers are nominally identical, which makes them a cost effective micro-tagging strategy We will be focussing on some novel aspects of surface chemistry and the effects of various linker molecules on binding efficiency The microcarriers are read in-flow through a 50µm wide channel, which includes a TMR sensor able to detect the stray field (magnetic signature) of the passing microcarrie

Preparation and crystallization of hollow α-Fe<inf>2</inf>O<inf>3</inf> microspheres following the gas-bubble template method

In this work we report the formation of hollow α-Fe2O3 (hematite) microspheres by the gas-bubble template method. This technique is simple and it does not require hard templates, surfactants, special conditions of atmosphere or complex steps. After reacting Fe(NO3)3.9H2O and citric acid in water by sol-gel, the precursor was annealed in air at different temperatures between 180 and 600 ºC. Annealing at 550 and 600 ºC generates bubbles on the melt which crystallize and oxidizes to form hematite hollow spheres after condensation. The morphology and crystal evolution are studied by means of X-ray diffraction and scanning electron microscopy. We found that after annealing at 250-400 ºC, the sample consist of a mixture of magnetite, maghemite and hematite. Single hematite phase in the form of hollow microspheres is obtained after annealing at 500 and 600 ºC. The crystallization and crystal size of the hematite shells increase with annealing temperature. A possible mechanism for hollow sphere formation is presented.This work was supported by the Engineering and Physical Science Research Council (EPSRC No. EP/J003638/1). The work in Peru has been supported by CONCYTEC. The work in Brazil was supported by CNPq (307552/2012-8), CAPES (PNPD- 230.007518/2011-11) and FACEPE (APQ-0589-1.05/08).This is the author accepted manuscript. The final version is available from Elsevier via http://dx.doi.org/10.1016/j.matchemphys.2015.11.02

A composite element bit design for magnetically encoded microcarriers for future combinatorial chemistry applications

A composite element (CE) bit design for magnetically encoded microcarriers provides an increased coercivity range for longer bit codes as well as significant improvements to encoding density, reliability and read-out.The authors gratefully acknowledge the EPSRC for financial support and thank Dr Andrew Thompson for valuable discussions. DL, TM and CHWB acknowledge the Cambridge Philosophical Society, the Lundgren Research Award, the Development of Prototype Grant (Innovate UK), the Brian Mercer Feasibility Award (Royal Society) and Cambridge Bio- Magnetics Ltd. AFP acknowledges the Winton Programme for the Physics of Sustainability.This is the final published version. It first appeared at http://pubs.rsc.org/en/Content/ArticleLanding/RA/2015/C4RA16991C#!divAbstract

Fabrication of nanogap electrodes by electroless- and electro deposition

In this chapter, the fabrication of metal nano-spaced electrodes for electronic nanodevices by electro and electroless plating is discussed. The necessary reagents, conditions, and processes required to obtain nano and atomic gaps between soft and clean surfaces electrodes are described. In the electroless method, the plating process is performed catalytically after immersing the sample in a solution which contains the same metal ions. In the electrodeposition technique, metal ions of an electrolyte move towards the sample under an applied voltage. Both techniques are explained with examples, the first technique is described by demonstrating the formation of gold nanogap electrodes using common medical solutions as reactants, whereas the second technique is described by showing electrodeposition of nickel electrodes in a conventional electrochemical cell. Current voltage characteristics are also presented to evaluate possible applications of the nanogap electrodes in electronic nanodevices. 8.1 IntroductionNano and molecular electronics devices require the fabrication of symmetric metal electrodes separated by a nanogap (“nanogap electrodes”) in which a specific molecule or crystal can be placed in order to connect them to the macroscopic world. In the last two decades, vertical structures in which a self-assembled monolayer (SAM) of molecules is electrically connected on one side with a scanning tunneling microscope (STM) [1,2] or conductive probe atomic force microscope (C-AFM) [3] and on the other side by a metallic surface have been demonstrated. Even though this approach has yielded many important results, it suffers from limitations such as the enormous asymmetry of the electrodes, the requirement of high vacuum environment, difficulties in mass production, and difficulty in maintaining a stable chemical bond between the molecule and the microscope tip due to mechanical vibrations. To solve these problems, more recently, new coplanar metal/molecule/metal devices have been proposed. Nanogap electrodes are fabricated before the molecular components, and they are subsequently inserted. This methodology has the advantage that the junction can be characterized with and without the presence of the molecule, thus, allowing the characterization of the molecule. Among others, there are three most remarkable new approaches for making in-plane nanogaps: (i) controlling a break junction mechanically, (ii) electrical breakdown of thin metal wire via electromigration, and (iii) electroless and electrochemical plating. These techniques are schematically represented in Fig. 8.1. The first technique was first developed by Moreland and Ekin [4]. An Nb-Sn wire mounted on a flexible glass beam can be broken to form an electron tunneling junction between the fracture elements. The method was later improved by other researchers. Notched wires of different metals are obtained first with lithography, by bending the substrate with

Universal process-inert encoding architecture for polymer microparticles

Polymer microparticles with unique, decodable identities are versatile information carriers with a small footprint. Widespread incorporation into industrial processes, however, is limited by a trade-off between encoding density, scalability and decoding robustness in diverse physicochemical environments. Here, we report an encoding strategy that combines spatial patterning with rare-earth upconversion nanocrystals, single-wavelength near-infrared excitation and portable CCD (charge-coupled device)-based decoding to distinguish particles synthesized by means of flow lithography. This architecture exhibits large, exponentially scalable encoding capacities (&gt;10(6) particles), an ultralow decoding false-alarm rate (&lt;10(-9)), the ability to manipulate particles by applying magnetic fields, and pronounced insensitivity to both particle chemistry and harsh processing conditions. We demonstrate quantitative agreement between observed and predicted decoding for a range of practical applications with orthogonal requirements, including covert multiparticle barcoding of pharmaceutical packaging (refractive-index matching), multiplexed microRNA detection (biocompatibility) and embedded labelling of high-temperature-cast objects (temperature resistance).close1