Micro-magnet arrays coupled with external rotating magnetic fields have been reported for the manipulation of individual superparamagnetic particles in stationary microfluidics, requiring no fluidic actuation. In addition to their magnetic properties preventing particle aggregation, superparamagnetic particle size reduction advantageously increases their interaction with surrounding liquid environment. However, precise magnetophoresis of submicrometric particles is challenging, owing to their low magnetic content. We present a micro-magnetofluidic chip for fast and collective transport of superparamagnetic nanoparticles (SNPs) over centimetric distances. In our innovative approach, SNPs are captured on a line pattern on top of a micro-magnet array covered with a spacer, which allows for SNP precise positioning along the surface using a rotating external magnetic field. The impact of SNP size on magnetophoresis was explored by characterizing the velocility ranges of 100 nm and 200 nm SNPs. For 100 nm size, a critical speed of 500 μm s-1 was reached beyond which the particles get resuspended, whereas for the 200 nm size, our system maximum rotation speed conveys the particles at up to 1.4 mm s-1 without reaching a critical speed. The mobility of SNPs was investigated in different buffers commonly used for biological analysis, and shown to be enhanced in low ionic strength conditions. As an example of future application, we demonstrate nucleic acid detection by SNP accumulation enabling to concentrate the fluorescence signal. This system provides the opportunity to be easily integrated in lab-on-a-chip (LOC) devices and could help relieve current development limitations related to complex and costly fluidic actuation instrumentation.

Quantitative nucleic acid detection is widely used in molecular diagnostics for infectious diseases. Here, we demonstrate that the previously developed MLFIA (magnetically localized fluorescent immunoassay) has the potential to detect Polymerase Chain Reaction (PCR) and loop-mediated isothermal amplification (LAMP) products using biotinylated and fluorescent primers and streptavidin-coated magnetic nanoparticles. The functionalized nanoparticles separate amplified DNA from non-incorporated primers in situ, allowing the quantification of DNA products. We compare magnetically localized fluorescence detection to commercial technologies based on the DNA intercalation of fluorescent dyes. Our system allows the detection of PCR and LAMP products but is approximately 10 times less sensitive than standard commercial assays. Future optimizations, such as enhancing the signal-to-noise ratio and improving nanoparticle functionalization, could significantly increase sensitivity and bring it closer to current diagnostic standards. This work highlights the potential of magnetically localized fluorescence detection to detect DNA.

Two‐photon polymerization (2PP) allows precise 3D printing at the micrometer scale, and by associating it with magnetic materials, the creation of remotely actuatable micro‐structures. Such structures attract a growing interest for biomedical applications, thanks to their size and to the biocompatibility of some photoresist materials. Gelatin methacryloyl (Gel‐MA) is one such material, and can be used to create physiological scaffolds for cell culture. Here, the physico‐chemical properties of two resins are exploited, the first being a silica‐based hybrid polymer, the OrmoComp, and the second a Gel‐MA‐based hydrogel. A 2PP manufacturing protocol is defined and designed to print both materials in succession as a single structure, which is then linked to a neodymium‐iron‐boron (NdFeB) magnetic bead for actuation. By this combination, a magnetically deformable 3D culture substrate is created to study cells in an environment that mimics soft, curved, and dynamic properties of tissues in vivo. The structure is actuated via an external magnetic field and bends back and forth along its longest axis. Lastly, preliminary cell culture trials are conducted showing the proliferation of cells on the structures.

Immunoassays are used for many applications in various markets, from clinical diagnostics to the food industry, generally relying on gold-standard ELISAs that are sensitive, robust, and cheap but also time-consuming and labour intensive. As an alternative, we propose here the magnetically localized and wash-free fluorescence immunoassay (MLFIA): a no-wash assay to directly measure a biomolecule concentration, without mixing nor washing steps. To do so, a fluorescence no-wash measurement is performed to generate a detectable signal. It consists of a differential measurement between the fluorescence of fluorophores bound to magnetic nanoparticles specifically captured by micro-magnets against the residual background fluorescence of unbound fluorophores. Targeted biomolecules (antibodies or antigens) are locally concentrated on micro-magnet lines, with the number of captured biomolecules quantitatively measured without any washing step. The performance of the MLFIA platform is assessed and its use is demonstrated with several biological models as well as clinical blood samples for HIV, HCV and HBV detection, with benchmarking to standard analyzers of healthcare laboratories. Thus, we demonstrated for the first time the versatility of the innovative MLFIA platform. We highlighted promising performances with the successful quantitative detection of various targets (antigens and antibodies), in different biological samples (serum and plasma), for different clinical tests (HCV, HBV, HIV).

Only achievable with two photons' polymerization, 3D printing at the micrometer scale is essential for the fabrication of complex objects such as photonic components, deformable microstructures, or microscaffolds for biological cells. Integrating magnetic materials inside those structures has made their remote actuation with an external magnetic field possible. However, the nature of the magnetic material, its volume, and precise position in the structure are keys for the efficiency, dexterity, and compatibility with optical or biological functions. Herein, an original approach consisting in the bonding of discrete and fully magnetic microbeads to unaffected 3D-microprinted structures is presented. Implemented in combination with the fine control of optical and mechanical properties allowed by the careful design of the 3D architecture, it is applied to the fabrication of the first remotely tunable biconvex microlens (focal length of 18 mu m). Combined with the additional precise positioning and magnetic orientation of multiple microbeads, the presented technique enables the fabrication of complex actuators such as a 100 mu m microtweezer that can be translated, rotated, and opened with a single variable external magnetic field. The dexterity of this untethered micromanipulator is demonstrated through a pick-and-place operation of 40 mu m objects in a confined environment.

The detection of herpes simplex viruses and Treponemal pallidum from genital lesions requires efficient sampling of genetic material for a reliable molecular diagnosis. From 460 patients attending the Public Health clinic, two swabs (dry cotton swabs and Eswabs) per patient were collected in alternating order from the same lesion. Additionally, three storage conditions of Eswabs up to 28 days were evaluated to assess the stability of DNA over time. Out of the 830 PCRs performed, 20 (2.4%) PCRs were discordant between the two swabs. No significant differences were observed between the two sample types. HSV1 and HSV2 could be reliably detected from Eswabs up to 28 days when kept at room temperature. A single swab from a genital lesion is sufficient for reliable diagnosis of α-herpes viruses and Treponemal pallidum, for which both a dry cotton swab or Eswab could be used.

Micro-magnets producing magnetic field gradients as high as 106 T m-1 have been used to efficiently trap nanoparticles with a magnetic core of just 12 nm in diameter. Particle capture efficiency increases with increasing particle concentration. Comparison of measured capture kinetics with numerical modelling reveals that a threshold concentration exists below which capture is diffusion-driven and above which it is convectively-driven. This comparison also shows that two-way fluid-particle coupling is responsible for the formation of convective cells, the size of which is governed by the height of the droplet. Our results indicate that for a suspension with a nanoparticle concentration suitable for bioassays (around 0.25 mg ml-1), all particles can be captured in less than 10 minutes. Since nanoparticles have a significantly higher surface-to-volume ratio than the more widely used microparticles, their efficient capture should contribute to the development of next generation digital microfluidic lab-on-chip immunoassays.

In this paper, we compare different techniques to manufacture high-performance miniature disks of Terfenol-D aiming at self-powered IoT sensors. To reach large in-plane magnetostriction while maintaining low driving field, microstructure engineering is essential. This work covers monocrystalline, polycrystalline and hot-pressed powder materials whose performances are analyzed. A “performance phase diagram per technique” is reported at the end.

Open-circuit direct piezoelectric coefficients g31 of bi-axially stretched PVDF and chiral PLLA are reported. This measure is decisive for sensor, generator and energy harvesting applications. We use an in-situ method with contactless voltage measurement during a conventional tensile-test, greatly improving measurement precision (error less than 10%).

AIM:We present a fast magnetic immunoassay, combining magnetic nanoparticles and micromagnets. High magnetic field gradients from micromagnets are used to develop a new approach to the standard ELISA. Materials & methods/results: A proof-of-concept based on colorimetric quantification of antiovalbumin antibody in buffer is performed and compared with an ELISA. After optimization, the magnetic immunoassay exhibits a limit of detection (40 ng/ml) and a dynamic range (40-2500 ng/ml) similar to that of ELISAs developed using same biochemical tools.CONCLUSION:Micromagnets can be fully integrated in multiwell plates at low cost to allow the efficient capture of immunocomplexes carried by magnetic nanoparticles. The method is generic and permits to perform magnetic ELISA in 30 min.

We present an innovative, one-step, no-wash fast immunoassay exploiting functionalized nanoparticles, structured micro-magnets and fluorescent detection: MagIA. As a proof of concept, we compare MagIA and standard ELISA performances applied to ovalbumin monoclonal antibody detection (anti-OVA mAb) in buffer. We then achieve the detection of anti-OVA mAb in biological fluid (mouse serum 1:100). Finally, MagIA protocol is transferred to clinical parameters measurements: CRP and Toxoplasma gondii serology. Comparison of data obtained with automated immuno-analysers shows excellent correlation.

There can be a significant discrepancy between predicted and measured power conversion efficiency when using piezoelectric polymers for thermal energy harvesting. The influence of temperature and strain on electrical parameters can impact overall performances. We report the temperature and strain dependence of PVDF dielectric constant and losses and their impact on power conversion efficiency of composite thermal SMA-PVDF energy harvesters.

The interest in miniaturizing heat engines to harvest low-grade heat has grown up with the development of wireless sensors requiring little energy to work. The bimetallic strip heat engines exploit the thermo-mechanical instability of composite membranes to convert heat into mechanical energy and have been proposed as an alternative to Seebeck thermoelectric generators based on the properties of semiconductors like bismuth tellurides. This article aims to describe the theoretical operation of these heat engines by explaining the nature and the conditions of occurrence of the thermo-mechanical instability of simply-supported beams. The thermodynamic cycle of the heat engine is explained and the performances of nine types of bimetallic beams are evaluated.

Many recent researches have been focused on the development of thermal energy harvesters using thermo-mechanical or thermo-electrical coupling phenomena associated to a first-order thermodynamic transition. In the case of the bimetallic strip heat engine, the exploitation of the thermo-mechanical instability of bimetallic membranes placed in a thermal gradient enables to convert heat into kinetic energy. This paper is a contribution to the modeling and the comprehension of these heat engines. By restraining the study to the simply-supported bimetallic beams and using a Ritz approximation of the beam shape, this paper aims to give an analytical solution to the first mode of the composite beams and then to evaluate the efficiency of the harvesters exploiting these kinds of instability. (C) 2016 Published by Elsevier B.V.

ABSTRACTDirect piezoelectric g31 voltage coefficient was measured in situ as a function of applied tensile stress for films of polyvinylidene fluoride (PVDF). Measurements were performed under quasi‐static conditions with applied strain rates of 0.5–1.5 mm/min for strains up to 12%. Open‐circuit voltage was measured with a contact‐less electrostatic voltmeter. Obtained results show a strong dependence of the g31 coefficient of mono‐oriented PVDF films on the applied stress, with a maximum value of the coefficient in the transition region between elastic and plastic deformation zones. The effect of sample geometry on the apparent g31 coefficient is shown and discussed. The anisotropy of the piezoelectric effect is studied by means of g31 and g32 measurements. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43248.

A novel flexible composite thermal energy harvester is presented, which couples pyroelectric and piezoelectric effects of polyvinylidene fluoride (PVDF) with shape memory effect of TiNiCu alloy. The harvester combines superior flexibility of PVDF with large temperature-induced strain of the shape memory alloy to harvest small and quasi-static temperature variations. The post-stamp size harvester (27.5mm3) achieved an energy density of 0.41mJ/cm3 per event of temperature variation of 20°C. When reaching 70°C the harvester, consisting of a stack of four PVDF, powered a wireless node instantaneously without any storage unit. The use of PVDF quadruples the energy output, compared to previously reported PZT-based composites.

This paper deals with the analytical modeling of pyroelectric bimetallic strip heat engines. These devices are designed to exploit the snap-through of a thermo-mechanically bistable membrane to transform a part of the heat flowing through the membrane into mechanical energy and to convert it into electric energy by means of a piezoelectric layer deposited on the surface of the bistable membrane. In this paper, we describe the properties of these heat engines in the case when they complete a Stirling cycle, and we evaluate the performances (available energy, Carnot efficiency...) of these harvesters at the macro- and micro-scale.