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  • The analysis shown in Figs and suggests

    2018-10-26

    The analysis shown in Figs. 8 and 9 suggests that the influence of small shifts in the flexor angle may be mitigated through design. Specifically, switches designed with a larger flexor angle will show smaller variation with small changes in leg angle. Therefore, we recommend that future device designs consider minimizing force variation with small changes in flexor angle. The cooling of the tin during molding is an important source of induced stress in the molded design. As the tin cools, the outside frame of the system shrinks, inducing compressive strain in the thin beams. To model this effect, an additional horizontal strain was added to the model, and the force required for switching was calculated for the geometry of the molded design. The strain may be estimated by finding the thermal strain due to cooling of the tin. With a tin linear thermal expansion coefficient of 22×10K, and cooling of 200K from the melting point, the estimated compressive strain is 0.044%. The results are shown in Fig. 10. Note that noise in the data is due to the numerical solution used. Fig. 10 shows that at the estimated induced strain, the percent change in switching force relative to a switch with no induced strain is almost 15%. Hence, while this effect is smaller than the variation due to small changes in the beam angle, it may also be a significant contributor to the variation seen in Fig. 7. To minimize these effects, selecting flexors and bodies made from either the same metal or from metals with similar expansion coefficients would be preferable.
    Conclusions This paper presents the results of design, fabrication, and testing for two acceleration switch designs both based on the deformation of steel flexors. The use of steel minimizes the influence of stress relaxation, resulting in acceleration switches with very small drift over time. One design, which is amenable to stamping from stainless steel sheets, showed a threshold variation of 2.8%. The other design, based on tin molding around steel flexors, showed a variation of 14.9%. In both cases, switches were tested over a buprenorphine hydrochloride of 2–3weeks. By comparison, previous plastic switches have exhibited average drift of 54% over a period of only 72h [13]. The acceleration switches demonstrated here could be used in a variety of applications requiring power-free measurement of threshold acceleration, including shipping or infrastructure monitoring. The switches are also easily adapted to use wireless readout using RFID technology [10].
    Introduction Abiotic fuel cells represent a promising technology for the conversion of organic fuel, such as glucose into electricity for powering bio-implantable devices that require ultra-low power sources [1–3]. Abiotically catalyzed glucose fuel cells employ abiotic catalysts such as noble metals, activated carbon, and zinc oxide to electrochemically catalyze the oxidation of glucose fuel and reduction of oxygen, thereby converting the chemical energy stored in the glucose fuel into electricity [3–9]. Although abiotic fuel cells use catalysts that do not denature and/or desorb from the electrode surface as observed with enzymes used in enzymatic based glucose biofuel cells, they usually operate at extremely low power (μW) compared to enzymatic based fuel cells. This key disadvantage has resulted in the development of an alternative energy generator for powering bio-implantable devices. Al/phosphate hybrid cell systems have been proven as an attractive strategy to generate energy from the activation of Al via ZnO nanocrystal in neutral phosphate buffer solution and physiological saline buffer [10]. However, the generated power from a single Al/phosphate cell is not sufficient for operating any device. Several research groups have used power management systems to enhance the voltages produce in electrochemical power cells through the use of capacitors to store the energy from fuel cells and then deliver it in large power burst [11–13]. While an enhanced performance of the fuel cells have been demonstrated in terms of increased voltages, this typically involves a series of manually charging and discharging a capacitor using different capacitor values and charging and discharging potentials by connecting/disconnecting it to the fuel cell. However, this approach alone is not practical when considering fuel cells or Al/phosphate cell application in bio-implantable devices. Here, we present the construction of capacitor circuit via a switched capacitor regulator to automatically charge and discharge the capacitor and provide sufficient power to drive a light-emitting diode (LED).