Electrorheological Sensor Encapsulating Microsphere Media for Plague Diagnosis with Rapid Visualization

Sensors and Sensing Devices Utilizing Electrorheological Fluids and Magnetorheological Materials-A Review

This paper comprehensively reviews sensors and sensing devices developed or/and proposed so far utilizing two smart materials: electrorheological fluids (ERFs) and magnetorheological materials (MRMs) whose rheological characteristics such as stiffness and damping can be controlled by external stimuli; an electrical voltage for ERFs and a magnetic field for MRMs, respectively. In this review article, the MRMs are classified into magnetorheological fluids (MRF), magnetorheological elastomers (MRE) and magnetorheological plastomers (MRP). To easily understand the history of sensing research using these two smart materials, the order of this review article is organized in a chronological manner of ERF sensors, MRF sensors, MRE sensors and MRP sensors. Among many sensors fabricated from each smart material, one or two sensors or sensing devices are adopted to discuss the sensing configuration, working principle and specifications such as accuracy and sensitivity. Some sensors adopted in this article include force sensors, tactile devices, strain sensors, wearable bending sensors, magnetometers, display devices and flux measurement sensors. After briefly describing what has been reviewed in a conclusion, several challenging future works, which should be undertaken for the practical applications of sensors or/and sensing devices, are discussed in terms of response time and new technologies integrating with artificial intelligence neural networks in which several parameters affecting the sensor signals can be precisely and optimally tuned. It is sure that this review article is very helpful to potential readers who are interested in creative sensors using not only the proposed smart materials but also different types of smart materials such as shape memory alloys and active polymers.

Ultrafast absorption mechanism of oil-emulsified micelles onto ferrous absorbents with dielectrophoresis force in the presence of polarization

Absorption and desorption rates were generally dependent on the concentration gradient from bulk to absorbents. A novel methodology based on a capacitor with an alternating electric field (AEF) is developed to accelerate the absorption and desorption rates with the frequency manipulation. Ferrous polystyrene microspheres (PISMs) are synthesized as absorbents, which could enhance the complex permittivities as well as dielectric properties. Theoretically, the attractive force and viscous force predominately determine the particle and micelles movement in the medium under an AEF. Oil-emulsified micelles (OEM) with various viscosities were selected as absorbates. Both the OEM and microspherical absorbents assembled through the external attractive force in the presence of the AEF. When the attractive force is equal to viscous force in the medium at the characteristic frequency, the optimal absorption rate could be obtained. The absorption rate constants of pseudo-first-order for OEMs under the polarization at 50 V and 120 kHz of frequency are ca. 10 times higher than that in absence of the polarization. The desorption rate as well as recycling efficiency could be also improved at 800 kHz. The ferrous PISMs with high complex permittivity prevented the damage from the AEF, which could be recycled 10 times of absorption and desorption with frequency manipulation under the AEF. Our methodology provides novel insights for ultrafast wastewater treatment.

Enhanced Electrorheological Performance of Core-Shell-Structured Polymerized Ionic Liquid@Doubly Polymerized Ionic Liquid Microspheres Prepared via Evaporation-Assisted Dispersion Polymerization

A polymerized ionic liquid (PIL) provides a platform for the development of a high-performance water-free polyelectrolyte-based electrorheological fluid (ERF) because of the presence of large-size hydrophobic ion pairs. However, the large-size hydrophobic ion pairs also easily result in a low glass-transition temperature of an ordinary linear PIL, and consequently, the PIL-based ERF has to be subject to a high leaking current density and a narrow working temperature range. In this paper, we prepared a kind of core-shell-structured polymerized ionic liquid@doubly polymerized ionic liquid (PIL@D-PIL) microsphere with a linear PIL as the core and a physically cross-linked D-PIL as the shell via an evaporation-assisted dispersion polymerization method. The core-shell structure of the sample was observed by scanning electron microscopy and transmission electron microscopy. The thermal properties of the sample were tested by differential scanning calorimetery and thermogravimetric analysis. The ER effect and dielectric polarization of PIL@D-PIL microspheres when dispersed in an insulating nonpolar liquid were studied by a rheometer and dielectric spectroscopy. It shows that the glass-transition temperature and thermal stability of a PIL increased after coating with the D-PIL shell. Under electric fields, the ERF of the PIL@D-PIL microspheres exhibits a significantly reduced leaking current density and an enhanced operating temperature range compared to the ERF of single-PIL microspheres. The PIL@D-PIL microspheres can still maintain good ER effect even if the temperature is higher than the glass-transition point of the PIL core due to the protection of the D-PIL shell.

One-step Photocatalytic Synthesis of Fe3O4@Polydiallyl Isophthalate Magnetic Microspheres for Magnetocaloric Tumor Ablation and Its Potential for Tracing on MRI and CT

Allyl monomers that were previously considered to be difficult to polymerize are applied, and Fe₃O₄@polydiallyl isophthalate (Fe₃O₄@PDAIP) magnetic were synthesized by one-step photopolymerization. The skeleton of the microspheres is made of diallyl isophthalate (DAIP). We obtained the microspheres using the photo-click technique in a soft template with Nano-Fe₃O₄ evenly disseminated in hydrophobic DAIP by cation-π and polar interaction. The obtained Fe₃O₄@PDAIP magnetic microspheres can achieve tumor cell necrosis temperatures (41-52 ℃) in an alternating magnetic field due to their inherent magnetic response. The results of in vitro CT and MR imaging indicate that the microspheres might be monitored accurately in vivo. Then the structural characteristics of the microspheres were confirmed by morphological analysis and physicochemical property analysis. Experiments in vitro and in vivo revealed that the microspheres had an anti-tumor effect and their biocompatibility satisfies the standards. The stability experiment proves that the microspheres have the potential for long-term effectiveness in vivo. It demonstrates the promise of Fe₃O₄@PDAIP magnetic microspheres in clinical applications.

Performance Enhancement of Electrochemiluminescence with the Immunosensor Controlled Using Magnetized Masks for the Determination of Epithelial Cancer Biomarker EpCAM

The performance of an electrochemiluminescence (ECL) immunosensor was improved with a particle gradient. SiO₂-coated magnetic beads were adopted as nanocarriers for gradient manipulation and immobilized with the primary antibody. Cadmium telluride quantum dots were coated with a layer of protein G for conjugation and orientation of the secondary antibody as signal labels. ECL immunosensor gradients on the electrode were formed by magnetolithography (ML) with magnetized nickel masks of column and stripe arrays. The immunosensor generally aggregated as an island on the substrate, leading to a decrease of efficiency in the characteristic signals. Stripe arrays of magnetized nickel were designed to generate cylindrical magnetic flux on the substrate to improve the particle manipulation with the gradient. Various gradients of the sandwich-structured immunosensor substantially affected the electrochemical performance. Compared to the gradient-free immunosensor, the gradient of the immunosensor generated by ML using a 3 μm stripe array mask enhanced the ECL intensity ∼2.2 times. The results of quantification of epithelial cell adhesion molecules (EpCAM) with the gradient immunosensor showed a broad linear range (15-420 pg mL^-1), a low limit of detection (5.5 pg mL^-1), and high reliability for EpCAM-spiked serum samples, indicating that the immunosensor gradient substantially enhances the performance of the ECL assay.

Low-filled suspensions of α-chitin nanorods for electrorheological applications

Highly anisometric α-chitin nanoparticles isolated by TEMPO-oxidation were investigated as filler for electrorheological fluids. The dimensions of rod-like particles were determined by AFM and cryo-TEM methods. The rheological behavior of α-chitin nanoparticles in polydimethylsiloxane changes from viscous to elastic under electric field. The yield stress reaches about 220 Pa at 7 kV/mm for 1.0 wt% fluid. Despite the nanosize of particles, the suspensions sedimentation ratio was found to be low (~23%). The electrorheological behavior of the fluids was discussed in terms of the Mason numbers. The stability of fluids response under switching electric field was shown. The activation energy of polarization processes in suspensions was calculated as 58 ± 2 and 64 ± 1 kJ/mol for 0.5 and 1.0 wt% filler content from the impedance spectra. The high aspect ratio (~70) and dielectric permittivity result in high electrorheological activity of α-chitin suspensions at extremely low concentrations (≤1.0 wt%).

Inorganic reinforced poly(ionic liquid) microcapsules: confined cooling-assisted phase separation self-assembly and enhanced electro-responsive property

We report a simple preparation of inorganic reinforced poly(ionic liquid) (PIL) microcapsules by combining dispersion polymerization and confined cooling-assisted phase separation self-assembly. Silane coupling agent-modified PIL microbeads were first prepared by dispersion polymerization. Then, the microbeads were dissolved in a mixed solvent composed of good solvent and non-solvent to form hollow SiO_x microcapsules at a relatively high temperature. Finally, the solution was cooled to induce the nucleation and growth of dissolved PIL chains on the inner and outer surface of hollow SiO_x microcapsules to form inorganic reinforced microcapsules with asymmetric PIL/SiO_x /PIL sandwich-like shell. The morphology of microcapsules can be controlled by adjusting PIL concentration and cooling rate. The inorganic reinforced microcapsules show enhanced suspended stability and electro-responsive characteristic when used as the dispersed phase of smart suspensions. This article is protected by copyright. All rights reserved.

A microfluidic colorimetric biosensor for in-field detection of Salmonella in fresh-cut vegetables using thiolated polystyrene microspheres, hose-based microvalve and smartphone imaging APP

A microfluidic colorimetric biosensor was developed using thiolated polystyrene microspheres (SH-PSs) for aggregating of gold nanoparticles (AuNPs), a novel hose-based microvalve for controlling the flow direction, and a smartphone imaging APP for monitoring colorimetric signals. Aptamer-PS-cysteamine conjugates were used as detection probes and reacted with Salmonella in samples. Complementary DNA - magnetic nanoparticle (cDNA - MNP) conjugates were used as capture probes, reacted with the free aptamer-PS-cysteamine conjugates. AuNPs were aggregated on the surface of Salmonella-aptamer-PS-cysteamine conjugates, resulting in a visible color change in the detection chamber, which indicating different concentrations of Salmonella. The limit of detection was low to 6.0 × 10¹ cfu/mL. The microfluidic biosensor exhibited a good specificity. It was evaluated by analyzing salad samples spiked with Salmonella. The recoveries ranged from 91.68% to 113.76%, which indicated its potential application in real samples.

Enhanced electrorheological activity of porous chitosan particles

Novel porous filler for electrorheological fluids was fabricated from chitosan via freeze drying technique. An exceptional electrorheological effect was discovered in suspensions of polydimethylsiloxane (silicone oil) filled by highly porous chitosan particles. The electrorheological activity was studied by rotational rheometry and visualized by optical microscopy. High porosity of the filler allows preparing highly efficient electrorheological fluids at rather low (< 1 wt%) concentration of dispersed phase. The mechanism of chain-like structure formation was considered. The electrorheological behavior of suspensions and the filler structural organization at different concentration were comprehended in terms of dielectric properties. The rheological data were approximated by Bingham and Cho-Choi-Jhon equations. The sedimentation stability of chitosan suspensions in polydimethylsiloxane was significantly affected by particles porosity.

Cr(VI) visualization via transmittance of electrorheological display medium with core/shell polystyrene/polyvinyltetrazole microspheres

In the course of time, significant amounts of heavy-ion pollutants have been dispersed into the environment. Rapid on-site detection of heavy metal ions is crucial to monitor their dispersion in the nascent stages. In this study, 2.2-μm-diameter polystyrene microspheres (PSM) were synthesized via emulsifier-free polymerization to coat polyacrylonitrile (PSM@PAN) and form core/shell-structured microspheres. Core/shell polystyrene/polyvinyltetrazole (PSM@PVT) microspheres were obtained after a cyano-to-tetrazole conversion reaction, loaded in an electrorheological device (ERD) display constructed using two indium tin oxide glasses with a spacer seal. The ERD loading dispersed the microsphere solution by scattering light through the ERD, resulting in a low transmittance in the absence of an alternating electric field (AEF). Particles in the fluid medium were polarized to induce negative and positive charges at each end of the particles under the AEF, and the resultant particle chains enhanced transmittance. The optimal frequency to generate the highest degree of particle chaining in the presence of an AEF is defined as its characteristic frequency (Fc), which also serves as an indicator to identify the shell materials. The Fc of PSM@PVT shifted from 350 kHz to 30 kHz after adsorbing Cr(VI) from the PVT coating. Transmittance of the ERD loading of PSM@PVT with Cr(VI) increased linearly with the concentration of Cr(VI). Approximately 40 ng mL^-1 of the limit of detection was calculated in the linear range of 10-540 ng mL^-1. The Fc of the PSM@PVT adsorbing the Cr(VI) was not influenced by Na(I), K(I), Ca(II), Mg(II), Fe(III), and Zn(II) coexisting in the ERD.