Processing and Characterization of Micromachined Actuators Based on Proton-Irradiated P(VDF-TrFE) Copolymer

ABSTRACT

Copolymers of vinylidene fluoride and trifluoroethylene (P(VDF-TrFE)) have been used in a variety of devices such as transducers, actuators and sensors because of their good electroactive properties. Our earlier work showed that the electric field-induced strain in P(VDF-TrFE) copolymers can be enhanced significantly after high energy proton irradiation. In this study, micromachined actuators using proton-irradiated P(VDF-TrFE) copolymer as the active element have been fabricated. P(VDF-TrFE) 70/30 mol% copolymer film with a thickness of ～ 3.3 μ m was spin-coated on a silicon (Si) substrate. After etching the Si substrate by bulk micromachining, an actuator in the form of a suspended membrane was obtained. High energy proton irradiation with a dose of 107 Mrad was carried out to modify the properties of the copolymer film. The resonance characteristics of the actuators based on these irradiated copolymer films were studied and the displacement induced in the actuators was measured using a laser vibrometer. These types of polymer-based micromechanical systems have the advantages of being lightweight and have high toughness, thereby reducing the risk of breakage. By applying different d.c. bias voltages, the magnitude of the displacement induced in the actuator can be varied.     

Pulsed Laser Deposition of Ba0.6Sr0.4TiO3 Thin Films and Their Optical Properties

ABSTRACT

Barium strontium titanate [Ba_0.6Sr_0.4TiO₃ or BST (60/40)] thin films were deposited on MgO (100) substrates using pulsed laser deposition. X-ray diffraction (XRD) measurements revealed that the BST thin films had epitaxially grown on the MgO (100) substrates. The surface morphology of the thin films was observed using an atomic force microscope and the grain size was found to be about 100–150 nm. The surface roughness was around 4.9 nm for a 250 nm thick film. The optical transmittance of the BST thin film was measured using a transmission mode ellipsometer. The BST/MgO configuration was highly transparent in the visible region. The optical band gap energy of the BST film, calculated by applying the Tauc relation, was 3.56 eV. Optical waveguide characteristics of the BST (60/40) thin film were determined using a prism coupler. The electro-optic (E-O) properties were measured at 632.8 nm wavelength using a phase modulation detection method. The BST film exhibited a predominately quadratic E-O behavior and the quadratic E-O coefficient was found to be 0.58 × 10^{? 17} m²/V².     

基于谐波闭锁涌流的样本电流分析

分析了二次谐波励磁涌流制动使用的2种差电流：Y,d转换差电流ia-ib和D,y转换差电流ia-i0。分析表明,2种方法识别涌流效果相当,存在转换过程中造成二次谐波减小情况,空投时容易出现误动情况,不宜采用分相闭锁。在基于更真实反映励磁电流的基础上,提出了采用样本电流ia＋xi0判断励磁涌流的方法。理论证明该方法能够有效...     

Prevention of Hot Cracking by Trailing Cooling along the Weld

ＰｒｅｖｅｎｔｉｏｎｏｆＨｏｔＣｒａｃｋｉｎｇｂｙＴｒａｉｌｉｎｇＣｏｏｌｉｎｇａｌｏｎｇｔｈｅＷｅｌｄ￥（田锡唐）（杨愉平）（张忠）ＴＩＡＮＨｉｔａｎｇ；ＹＡＮＧＹｕｐｉｎｇＺＨＡＮＧＺｈｏｎｇ（Ｄｅｐｔ．ｏｆＭａｔｅｒｉａｌＳｃｉｅｎｃｅａｎｄＥ...     

2-Aminopyridine functionalized cellulose based Pd nanoparticles: An efficient and ecofriendly catalyst for the Suzuki cross-coupling reaction

A palladium catalyst supported on 2-aminopyridine functionalized cellulose was synthesized and fully characterized by inductively coupled plasma atomic emission spectroscopy, transmission electron microscope, Fourier transform infrared spectroscopy, thermogravimetric analysis and X-ray photoelectron spectrometry. This catalyst can be applied in the Suzuki cross-coupling reaction of aryl halides with arylboronic acids in 50% ethanol to afford biaryls in good yields, and easily recycled by simple filtration after reaction without the loss of metal Pd.

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Metabolomic Profiling of Plasma from Melioidosis Patients Using UHPLC-QTOF MS Reveals Novel Biomarkers for Diagnosis

To identify potential biomarkers for improving diagnosis of melioidosis, we compared plasma metabolome profiles of melioidosis patients compared to patients with other bacteremia and controls without active infection, using ultra-high-performance liquid chromatography-electrospray ionization-quadruple time-of-flight mass spectrometry. Principal component analysis (PCA) showed that the metabolomic profiles of melioidosis patients are distinguishable from bacteremia patients and controls. Using multivariate and univariate analysis, 12 significant metabolites from four lipid classes, acylcarnitine (n = 6), lysophosphatidylethanolamine (LysoPE) (n = 3), sphingomyelins (SM) (n = 2) and phosphatidylcholine (PC) (n = 1), with significantly higher levels in melioidosis patients than bacteremia patients and controls, were identified. Ten of the 12 metabolites showed area-under-receiver operating characteristic curve (AUC) >0.80 when compared both between melioidosis and bacteremia patients, and between melioidosis patients and controls. SM(d18:2/16:0) possessed the largest AUC when compared, both between melioidosis and bacteremia patients (AUC 0.998, sensitivity 100% and specificity 91.7%), and between melioidosis patients and controls (AUC 1.000, sensitivity 96.7% and specificity 100%). Our results indicate that metabolome profiling might serve as a promising approach for diagnosis of melioidosis using patient plasma, with SM(d18:2/16:0) representing a potential biomarker. Since the 12 metabolites were related to various pathways for energy and lipid metabolism, further studies may reveal their possible role in the pathogenesis and host response in melioidosis.     

Joining of dense Si3N4 ceramics with tape cast Lu-Al-Si-O-N interlayer

Lu-Al-Si-O-N tapes with different thickness were used to join gas pressure sintered Si₃N₄ ceramics. The microstructure of the joints and the influences of the joint thickness and joining temperature on the bonding strength of the as-joined Si₃N₄ ceramics have been investigated. The highest bonding strength about ~ 300 MPa of the joined specimens was achieved by using 450 µm interlayer at 1450 °C. The existence of Si₃N₄ nanowires was beneficial for the improvement of the bonding strength by interweaving the oxynitride glass matrix in the joint region.     

The formation of the S‐shaped edge‐on lamellae on the thin porous polylactic acid membrane via phase separation induced by water microdroplets

Biodegradable polymers have received increased attention due to their potential application in the medicine and food industries; in particular, poly(lactic acid) (PLA) is a primary biopolymer because of its excellent biocompatibility and absorbability features. In this study, a porous PLA membrane was fabricated by phase separation using water microdroplets produced by an ultrasonic atomizer as a coagulation bath. The formation of S‐type clusters was attributed to the slow exchange rate between solvent and coagulant, which provided time for the movement of polymer molecules. The effect of preparation conditions on the structure of S‐type clusters, including polymer concentration in solution and ambient temperature was investigated. The PLA porous membrane prepared from water micro‐droplets with different morphology compared with the sample fabricated from distilled water has potential application in fields of tissue engineering and artificial organ generation. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43355.