Key Engineering Materials Vols. 645-646

Abstract: A low power low noise CMOS amplifier with integrated filter for neural signal recording is designed and fabricated with CSMC 0.5 μm CMOS process. DC offsets introduced by electrode-tissue interface are rejected through a feedback low-pass filter. The bandwidth of the amplifier is in 3.5Hz-5.5KHz range, and the gain is about 48dB in the midband. AC input differential mode voltage range is 10mV, and DC input differential mode voltage range is 180mV. The amplifier can accommodate 180mV DC offsets drift and 10mV neural spikes. The neural probe array is integrated directly on the surface of the amplifier array chip, and is tested in saline solution, and also is implanted in rats in vivo , the results of the experiments show that the amplifier is suitable for neural signal recording. The power dissipation is about 14μW while consuming 0.16 mm² of chip area, which satisfies implantable devices requirements.

Abstract: In this paper, we proposed a four-electrode microdevice for precise isolating and trapping of a single cell using negative dielectrophoresis (nDEP) forces. To generate appropriate nDEP forces, sinusoidal alternating currents (AC) signals with various phase shifting were applied to the microelectrodes, and the finite element analysis (FEA) techniques were used to analyze the resulted electric field distribution. The simulation results implied that effective trapping and rotation forces can be realized by the proposed device structure under specific excitation condition. The geometry effect on the electric field distributions of electrodes was further studied in details. For the electrodes with 50 μm width, the maximum value of the gradient of the squared field strength could reach 10⁶ V²/m³, which is higher than that for electrodes with 20 μm width. The influences of applied voltage to electric field gradient were also simulated and the result shows that the dielectrophoresis (DEP) force increased significantly with the magnitude of applied voltage. These preliminary results may provide useful insight and design guidelines for the future DEP microstructure design and fabrication.

Abstract: The clinical applications of tissue engineering are still limited by the lack of a functional vascular supply in tissue-engineered constructs. In order to improve the pre-vascularization of tissue-engineered scaffold during in vitro culture, in this study, based on three-dimensional (3D) printing technology, using the crosslinking effect of coaxial fluids (sodium alginate and CaCl₂) to prepare vessel-like hollow gel fibers, then layer by layer overlapping into 3D scaffold. The biological 3D printing platform was successfully developed and a coaxial nozzle module was introduced to generate a CaCl₂-in-Alginate coaxial microfluidic. The inner core diameters of the prepared hollow gel fibers were 220~380 micrometers. In addition, the influence of materials concentration and dispensing rates on hollow fiber dimension were investigated, the cell-encapsulated in the printed hollow fibers was realized and the viability of endothelial cells (ECs) was studied with Laser scanning confocal microscopy (LSCM) and Live-Dead cell staining. The 3D scaffold built by hollow fibers could improve the phenomenon of diffusion constrain and enhance the survival rate of those ECs growing at a greater depth in the construct. This study provides a new theoretical basis for the vascularization of bone scaffold.

Abstract: In this paper, an aptasensor with high sensitivity and rapid response was developed for the detection of staphylococcus enterotoxin B (SEB) by using thiol-modified piezoresistive cantilever. Thiol-modified aptamers, acting as the functionalized sensing elements, were immobilized on the nanogold-coated surface of the sensing cantilever as agents for detecting SEB. By using the functionalized aptasensors, different concentrations of SEB were detected with a wide detection range of 6-100 ng/mL and a quick response in milk. The experimental results indicated that the cantilever-based aptasensors had sufficient sensitivity for the detection of SEB in real food commodities and might provide an economical platform for on-site detections of different toxicants with the advantages of portability, high sensitivity, and rapid response.

Abstract: The defective repairing and restructuring of some tissues and organs is becoming a livelihood issue which need settling urgently at present. Using polytechnics to design and prepare regenerated biological scaffolds is now facing a big bottleneck. In this paper, by the study and analyzing of CAD/CAM technology, 3D printing and electro-spinning technology, a new bionic CAD/CAM/3D printing integrated molding platform is expressed to meet the reunification of design and manufacture of regenerated bone scaffolds. Using the integrated molding platform, the Gelatin/chitosan – PVA scaffold were prepared with macro to micro structure. This molding method will help to develop the bio-manufacturing, biological 3D printing and their equipment, and has a realistic significance on pushing human health.

Abstract: In this paper, a low-voltage automatic gain control (AGC) circuits is presented. The proposed circuit uses a novel approximated exponential function to increase the dB-linear output range. The three-stage AGC is fabricated in 0.18μm CMOS technology and shows the maximum gain variation of more than 100dB and a 67dB linear range with linearity error of less than ±1dB. The range of gain variation can be controlled from 34 to 101dB. The AGC dissipates less than 2.3mA under 1.8V supply voltage while occupying 0.4mm² of chip area.

Abstract: Cu/TiO₂ nanocomposite was first prepared by photocatalytic reduction according to optimal processing condition selected via orthogonal test: 2.0% of glucose, 0.25% of TiO₂, 0.3% of CuCl ₂ and reaction time of 12 h. Multiple characterization methods were utilized to confirm the structure of Cu/TiO₂ nanocomposite, and its antibacterial property against Escherichia coli (E.coli) was then investigated in detail. The obtained Cu/TiO₂ (ca. 50 nm) was composed of elemental copper, TiO₂ and a small amount of unreacted CuCl₂. EDTA titration and XRF indicated that solid content of Cu was about 61.68%. Antibacterial test showed that the inhibition zone diameter of Cu/TiO₂ with 1% solid content is 15.77 mm and the minimum bactericidal concentration (MBC) of which is 5 mg/mL. Furthermore, Cu/TiO₂ (1.0 wt%) was added into a super-hydrophilic coating for the aluminum cooling fin of air conditioner. The antibacterial ability of the fin can be significantly improved without obvious changes of hydrophilicity, which can reach the national standard (grade I).

Abstract: Identification and characterization of CTCs can be used as a tool for the study of cancer metastases. A novel design of microfluidic chip used for enrichment of circulating tumor cells is presented in this paper. An integration of DLD method and negative enrichment method were designed to improve the throughput and recovery rate while getting intact CTCs. The DLD stage is used to separate CTCs from blood cells preliminarily, and the negative enrichment stage is used to acquire purified CTCs. Both of them were simulated with COMSOL Multiphysics. Simulation results showed that triangular micro-posts have better performance in DLD stage, and wave structures could generate better disturbance effect than herringbone structures. This chip provides a potential approach with high throughput and purity for the enrichment of CTCs.

Abstract: Carbon nanotubes (CNTs) have been used in a variety of industrial areas as a kinds of new nanometer materials. Algal growth test was developed to determine the biological effect of single-walled carbon nanotubes (SWNTs) on Skeletonema costatum and Prorocentrum donghaiense. The results showed that SWNTs stimulated the growth of S. costatum within 72 h and 24 h as theirs concentrations were smaller than 0.5 mg/L and 10 mg/L respectively, While the growth of S. costatum was inhibited within 48 h and 96 h as theirs concentrations were higher than 10 mg/L and 0.5mg/L respectively (p＜0.05). The concentrations of chlorophyll were the same as the density of phytoplankton cells. The growth of P. donghaiense was inhibited as SWNTs concentrations were higher than 100 mg/L within 72 h, while SWNTs promoted the growth of P. donghaiense within 48 h after SWNTs were added as their concentrations were smaller than 5 mg/L（p＜0.05). The results of chlorophyll were similar to the density of P. donghaiense cells. The roles of SWNTs on the growth of algae were suggested to be associated with the active of some enzymes and the physical properties, such as agglomeration and shading.

Abstract: In-stent restenosis still remains an obsession to cardiologist, especially in tapered vessels. In this paper, we designed a novel balloon-expandable stent for tapered vessel and proposed a finite element method (FEM) to study the expansion of the novel stent. The effect of stent design parameters on stent tapering and foreshortening were also researched. Results show that the radial displacement of stent proximal end was always larger than that of stent distal end during stent expansion, and the stent had a tapered shape as a whole after expansion. The degree of stent tapering observed increased with the expansion pressure increase. Besides, increasing the gradient of ring amplitude not only could increase the tapering degree of stent after expansion, but also could decrease stent foreshortening, improving the positioning accuracy after stent implantation. In conclusion, FEM can quantify expansion performance of novel balloon-expandable stents and help designers to devise and assess new stent designs for tapered vessel.