Monotonic and fatigue testing of freestanding submicron thin beams application for MEMS

A freestanding submicron thin film specimen is designed and fabricated here to carry out a series of monotonic and fatigue testing. This freestanding beam was loaded by performing monotonic loading/unloading or closed-loop load controlled tension–tension fatigue experiments on it. Loading was applied using a piezoelectric actuator with 0.1 μm resolution connected to the test specimen. Loads were measured by connected a capacitor load cell with a resolution of less than 0.1 mN. The modulus, yield stress and maximum stress of tested submicron thin films at room temperature were found from monotonic loading/unloading tests. The results of 300 nm copper thin films fatigue experiments demonstrated a trend of decreasing cycles to failure with increasing loading amplitude and increasing mean stress.     

Comparative analysis of the NS 1 gene sequences of dengue-1 viruses prototype Hawaii strain and Thai isolate TH-Sman, and determination of the intratypic variation of NS 1 protein among dengue-1 viruses

In view of a previous report on significant antigenic and biophysical differences between the purified soluble complement-fixing antigens of dengue-1 virus strains Hawaii and TH-Sman, the NS 1 genes of both virus isolates were cloned, sequenced, and compared in an attempt to define the genetic basis for the observed differences. Sequence comparison revealed ten encoded amino acid differences between the NS 1 genes of both viruses. Three of these amino acid differences, which are associated with a change in charge distribution, are clustered within the major antigenic region previously defined by studies of recombinant dengue-1 NS 1 protein expressed in E. coli. In parallel, the NS 1 sequences of both Hawaii and TH-Sman isolates were also aligned and compared with two other published dengue-1 NS 1 protein sequences to determine the intratypic variation of dengue-1 NS 1 antigen. Pairwise comparisons between the encoded amino acid sequences revealed a variability of 1.1% to 3.1% difference in the NS 1 protein among dengue-1 strains, which is comparable to that reported for dengue-1 envelope protein (0.2% to 3.6% difference) but less than that of dengue-2 NS 1 protein (0.6% to 7.4% difference).     

Enhanced CMOS performances using substrate strained-SiGe and mechanical strained-Si technology

We developed a novel CMOS architecture that uses mechanical tensile stress, induced by the Si nitride-capping layer, together with the pseudomorphic compressive stress in SiGe layer to improve the drive current of both n- and pMOSFETs simultaneously. The unique advantage of this process flow is that on the same wafer, individual MOSFET performance can be adjusted independently to their optimum due to the separation process for two type devices. It is found that n- and pMOSFETs in the novel CMOS architecture behaved better in performance, not only a higher drain-to-source saturation current but also higher transconductance with wide gate voltage swing, than the Si-control devices, thus making this flow to show a great flexibility for developing next-generation high-performance CMOS.     

Intraperitoneal hyperthermic treatment of implanted peritoneal cancer in rats

The feasibility and efficacy of treating peritoneal cancer implants by applying heat to the peritoneal surfaces were studied in inbred Buffalo A rats given i.p. injections of Morris hepatoma 5123TC tumor cells. Heat was delivered to the peritoneum by contact with a heated physiological salt solution (Normosol-R) in the peritoneal cavity. A treatment temperature of 43.3 +/- 0.3 degrees was maintained for 30 min by an immersed stainless steel coil through which hot liquid circulated. Rats implanted with 0.5 to 1.0 x 10(8) tumor cells were treated at 1 to 4 hr (Group I), 4 to 5 days (Group II), and 22 to 24 days (Group III) after tumor implantation to simulate treatment for the clinical conditions of surgically spilled cancer cells, established microscopic cancer implants, and macroscopic cancer implants, respectively. A statistically significant improvement in survival was observed in Groups I and II compared with sham-treated control animals; 58% of the heat-treated animals were cured. Only a slight but statistically insignificant improvement was noted in Group III. These observations indicate that i.p. surface heat treatment of peritoneal implanted cancer is feasible and effective.     

Morphological control of CuPc and its application in organic solar cells

We have prepared organic photovoltaic (OPV) cells possessing an ideal bulk heterojunction (BHJ) structure using the self-assembly of copper phthalocyanine (CuPc) as the donor material and fullerene (C(60)) as the acceptor. The variable self-assembly behavior of CuPc on a diverse range of substrates (surface energies) allowed us to control the morphology of the interface and the degree of carrier transportation within the active layer. We observed rod-like CuPc structures on indium-tin oxide (ITO), poly(3,4-ethylenedioxythiophene)-poly(4-styrenesulfonate) (PEDOT:PSS) and Au substrates. Accordingly, the interfaces and continuing transport path between CuPc and fullerene domains could be greatly improved due to the ideal BHJ structure. In this paper, we discuss the mechanisms of producing CuPc rod-like films on ITO, PEDOT:PSS and Au. The OPV cell performance was greatly enhanced when a mixture of horizontal and vertical CuPc rods was present on the PEDOT:PSS surfaces, i.e.?the power conversion efficiency was 50 times greater than that of the corresponding device featuring a planar CuPc structure.     

Investigations of surface structure for thermally evaporated silicon on a Cu(111) surface

The surface structure and composition of semiconductor/Cu(111) films prepared by thermal evaporation in an ultrahigh vacuum condition have been investigated. As Si atoms were deposited on a Cu(111) surface, diffused spots were observed up to 2 monolayers while 1 × 1 spots become dimmer as revealed using low-energy electron diffraction technique. Because of a larger electron affinity of Si than that of Cu, the Cu L₃M₄₅M₄₅ Auger line shifts to a lower kinetic energy. Annealing treatments at 425 K causes a splitting of the Cu L₃M₄₅M₄₅ line. This shows the interdiffusion at the Si/Cu interface and the formation of a Cu-rich surface layer. After annealing treatments, the domains grow and aggregate to form larger domains as revealed by the decreasing full-width at half maximum of diffraction spots. Ge/Cu(111) shows 1 × 1 structure as annealing up to 500 K. Lack of a dominant structure and a large valence diameter of Ge result in different structures as compared to Si/Cu(111).     

Theory and application of a combined feedback–feedforward control and disturbance observer in linear motor drive wire-EDM machines

This paper presents a combined two-degree-of-freedom controller and disturbance observer design for a direct drive motion control system actuated by permanent-magnet linear synchronous motors (PMLSM). A feedback controller based on pole-placement design method is proposed to achieve desired tracking performance as well as stabilize the closed-loop system. A newly designed feedforward controller is proposed to reduce tracking errors based on an inverse model of the direct drive system. A digital disturbance observer is implemented to be included in the proposed feedback–feedforward control structure to compensate for nonlinear friction, cogging effects, and external load disturbance. Furthermore, the proposed control scheme has been verified as being internally stable. Experimental results indicate that the proposed controller can achieve a high contouring accuracy of ±0.3 μm as well as provide disturbance rejection and robustness. The maximum contour error of circular trajectory was reduced from 8.5 to 3.2 μm in comparison with proportional-integral-derivative (PID) controller.