Qianqian Duan

Portable microsystem integrates multifunctional dielectrophoresis manipulations and a surface stress biosensor to detect red blood cells for hemolytic anemia

Hemolytic anemia intensity has been suggested as a vital factor for the growth of certain clinical complications of sickle cell disease. However, there is no effective and rapid diagnostic method. As a powerful platform for bio-particles testing, biosensors integrated with microfluidics offer great potential for a new generation of portable point of care systems. In this paper, we describe a novel portable microsystem consisting of a multifunctional dielectrophoresis manipulations (MDM) device and a surface stress biosensor to separate and detect red blood cells (RBCs) for diagnosis of hemolytic anemia. The peripheral circuit to power the interdigitated electrode array of the MDM device and the surface stress biosensor test platform were integrated into a portable signal system. The MDM includes a preparing region, a focusing region, and a sorting region. Simulation and experimental results show the RBCs trajectories when they are subjected to the positive DEP force, allowing the successful sorting of living/dead RBCs. Separated RBCs are then transported to the biosensor and the capacitance values resulting from the variation of surface stress were measured. The diagnosis of hemolytic anemia can be realized by detecting RBCs and the portable microsystem provides the assessment to the hemolytic anemia patient.

Highly Sensitive and Stretchable Strain Sensor Based on Ag@CNTs

Due to the rapid development and superb performance of electronic skin, we propose a highly sensitive and stretchable temperature and strain sensor. Silver nanoparticles coated carbon nanowires (Ag@CNT) nanomaterials with different Ag concentrations were synthesized. After the morphology and components of the nanomaterials were demonstrated, the sensors composed of Polydimethylsiloxane (PDMS) and CNTs or Ag@CNTs were prepared via a simple template method. Then, the electronic properties and piezoresistive effects of the sensors were tested. Characterization results present excellent performance of the sensors for the highest gauge factor (GF) of the linear region between 0–17.3% of the sensor with Ag@CNTs1 was 137.6, the sensor with Ag@CNTs2 under the strain in the range of 0–54.8% exhibiting a perfect linearity and the GF of the sensor with Ag@CNTs2 was 14.9.

Detection system based on magnetoelastic sensor for classical swine fever virus

In this paper, a magnetoelastic (ME) sensing system for the detection of classical swine fever virus (CSFV) is presented. The detection system comprises a test paper and a measurement circuit. The test paper consists mainly of an ME biosensor to detect the CSFV. Based on the impedance analysis technique, the measurement circuit is designed to measure the resonance frequency of the ME biosensor. The anti-CSFV IgG is immobilized onto the ME sensor surface to form the ME biosensor through a physical absorption approach. The experimental results show that the shift in the resonance frequency of the ME biosensor increases with the augmentation of the CSFV concentration. The effectiveness of the combination between the anti-CSFV IgG and CSFV is confirmed by the scanning electron microscopy (SEM) images, the sandwich-based enzyme-linked immunosorbent assay (ELISA) analysis, the interference study and the reference biosensor test method. The resonance frequency shift is linearly proportional to the concentration in the range from 0 to 2.5μg/ml, and becomes sub-linear at higher concentrations. The ME biosensor for CSFV detection has a sensitivity of about 95Hz/μg·ml(-1), with a detection limit of 0.6μg/ml.

A magnetoelastic biosensor based on E2 glycoprotein for wireless detection of classical swine fever virus E2 antibody

A wireless magnetoelastic (ME) biosensor immobilized with E2 glycoprotein was first developed to detect classical swine fever virus (CSFV) E2 antibody. The detection principle is that a sandwich complex of CSFV E2 – rabbit anti-CSFV E2 antibody – alkaline phosphatase (AP) conjugated goat anti-rabbit IgG formed on the ME sensor surface, with biocatalytic precipitation used to amplify the mass change of antigen–antibody specific binding reaction, induces a significant change in resonance frequency of the biosensor. Due to its magnetostrictive feature, the resonance vibrations and resonance frequency can be actuated and wirelessly monitored through magnetic fields. The experimental results show that resonance frequency shift increases with the augmentation of the CSFV E2 antibody concentration. Scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) and fluorescence microscopy analysis proved that the modification and detection process were successful. The biosensor shows a linear response to the logarithm of CSFV E2 antibody concentrations ranging from 5 ng/mL to 10 μg/mL, with a detection limit (LOD) of 2.466 ng/mL and the sensitivity of 56.2 Hz/μg·mL−1. The study provides a low-cost yet highly-sensitive and wireless method for selective detection of CSFV E2 antibody.

Utilizing Fullerenols as Surfactant for Carbon Nanotubes Dispersions Preparation

Dispersions of individual carbon nanotubes (CNTs) are crucial for nanodevices and polymer/CNTs nanocomposites. In this paper, stable and homogenous dispersions of individual multiwalled carbon nanotubes (MWCNTs) have been synthesized. The factors influencing the dispersibility mechanism, including the surfactant concentration and the pH value, have been investigated. SEM images display the impurities sticking on MWCNTs which have been removed. The oxygen-containing groups on the surface of MWCNTs sample have been detected through FT-IR and Raman spectra. All experimental results illustrate that using fullerenols as surfactant can greatly improve the dispersibility of MWCNTs. Moreover, the prepared dispersions exhibit good stability that the sediment percentage of fullerenols-MWCNTs is only 5.2% after 5 days.

Preparation and Property Research of Strain Sensor Based on PDMS and Silver Nanomaterials

Based on the advantages and broad applications of stretchable strain sensors, this study reports a simple method to fabricate a highly sensitive strain sensor with Ag nanomaterials-polydimethylsiloxane (AgNMs-PDMS) to create a synergic conductive network and a sandwich-structure. Three Ag nanomaterial samples were synthesized by controlling the concentrations of the FeCl3 solution and reaction time via the heat polyols thermal method. The AgNMs network’s elastomer nanocomposite-based strain sensors show strong piezoresistivity with a high gauge factor of 547.8 and stretchability from 0.81% to 7.26%. The application of our high-performance strain sensors was demonstrated by the inducting finger of the motion detection. These highly sensitive sensors conform to the current trends of flexible electronics and have prospects for broad application.

Simulation Study on the Controllable Dielectrophoresis Parameters of Graphene

The method of using dielectrophoresis (DEP) to assemble graphene between micro-electrodes has been proven to be simple and efficient. We present an optimization method for the kinetic formula of graphene DEP, and discuss the simulation of the graphene assembly process based on the finite element method. The simulated results illustrate that the accelerated motion of graphene is in agreement with the distribution of the electric field squared gradient. We also conduct research on the controllable parameters of the DEP assembly such as the alternating current (AC) frequency, the shape of micro-electrodes, and the ratio of the gap between electrodes to the characteristic/geometric length of graphene (λ). The simulations based on the Clausius–Mossotti factor reveal that both graphene velocity and direction are influenced by the AC frequency. When graphene is close to the electrodes, the shape of micro-electrodes will exert great influence on the velocity of graphene. Also, λ has a great influence on the velocity of graphene. Generally, the velocity of graphene would be greater when λ is in the range of 0.4–0.6. The study is of a theoretical guiding significance in improving the precision and efficiency of the graphene DEP assembly.

Micro-Mechanism of Silicon-Based Waveguide Surface Smoothing in Hydrogen Annealing*

The micro-mechanism of the silicon-based waveguide surface smoothing is investigated systematically to explore the effects of silicon-hydrogen bonds on high-temperature hydrogen annealing waveguides. The effect of silicon-hydrogen bonds on the surface migration movement of silicon atoms and the waveguide surface topography are revealed. The micro-migration from an upper state to a lower state of silicon atoms is driven by silicon-hydrogen bonding, which is the key to ameliorate the rough surface morphology of the silicon-based waveguide. The process of hydrogen annealing is experimentally validated based on the simulated parameters. The surface roughness declines from 1.523 nm to 0.461 nm.