Biofuel cells are often limited by the current density produced by the cathode; this is especially true when such fuel cells are scaled down to fit a desired application. Herein, we created a computational model to examine the effects of carbon nanotube (CNT) connectivity and surface activity on the current density of a biofuel cell cathode. The model was motivated by the creation of a novel contact lens biofuel cell that, although more stable and biocompatible than previously reported designs, was cathode limited.The device produced a maximum current density of 22 ± 4 µA cm -2 , and a maximum power density of 2.4 ± 0.9 µW cm -2 (at 0.163 V) with an open-circuit voltage of 0.44 ± 0.08 V. Computational results showed that in a Nafion film containing 1.6% CNTs by volume, less than 20% of the CNT fibers were connected to the electrode, assuming a planar electrode. The simulations predicted that a three-fold increase in CNT loading would lead to a roughly two-fold increase in total CNT connectivity. The simulations further estimated that for the CNTs connected to the electrode, only 21% of their sidewalls were contributing to cathodic current, meaning that the remaining surfaces were not electrochemically active. Given the low bilirubin oxidase (BOD) enzyme surface concentration, which was experimentally found to be 1.24 x 10 -13 mol cm -2 , it is likely that large portions of the CNT surfaces are not connected to enzymes. This result validates the push by the research community to increase BOD and laccase adsorption/orientation to CNT surfaces.

In exploiting the unique capabilities of smart actuators for applications in vehicle systems, even in unmanned or micro aerial vehicles, the power issues for smart actuators and devices have not been well addressed. This is due to the fact that the driving power for smart materials has not reached the level of the power specifications for conventional devices and systems. To answer the power issue, we have developed a wireless power transmission technology using a flexible rectenna system and implemented it for a microwave-powered aerial vehicle (MPAV) system. For this application, two flexible dipole rectennas were designed, manufactured and characterized over a frequency range of 9-12 GHz. These flexible dipole rectennas were attached and tested on the complex structure of small MPAVs. The maximum converted power output of a flexible dipole rectenna array was about 300 mA at 80 V DC . The power output from this rectenna was sufficient to run the propellers of the MPAV. Each electrically driven propeller requires approximately 2 W for operation.

The concept of power transmission by a microwave is envisioned as the best option for alleviating the complexity associated with hard-wired control circuitry in controlling smart actuators and robots such as micro-aerial vehicles, biomimetic robots and space vehicles to produce remotely maneuverable capability. A flexible dipole rectenna array is conformably adaptable on the complex structure of vehicles used for practical applications of wireless power. For these applications, various flexible dipole rectennas and arrays were designed, fabricated and characterized over a frequency range of 9-12 GHz with 20 W and 200 W amplifiers through laboratory testing. The irradiance of the microwave power was measured. Also the irradiated power, the output power and the efficiency of the rectenna arrays were evaluated along with the microwave power and frequency. The maximum voltage of 65 V DC was observed from a series connected dipole rectenna array and the maximum current of 2.50 mA was obtained from a parallel connected rectenna array. The efficiency of dipole rectenna arrays ranges from 20% to 50% depending on the input power and the pole configuration. It was also demonstrated that the voltage, current and power output from a dipole rectenna array can be tailored by configuring the dipole rectenna elements in serial and parallel mode connections.

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In this paper we report on the experimentally measured dynamics exhibited by a system comprised of two coupled circuits whose input–output relation follow the logistic-map function. The circuit takes in two external voltages that control the initial conditions, and we employ this capability to examine the phenomenon of symmetry breaking and to submit theoretical/numerical results on this dynamical system to experimental test. We demonstrate that symmetry-broken solutions manifest in this circuit for appropriately chosen initial conditions, and proceed to investigate experimentally the basins of attraction of these solutions, as well as their dependence on the coupling strength, ϵ. We illustrate the full power of this circuit by investigating the chaotic regime and by constructing experimental bifurcation diagrams. One intriguing phenomenon captured here involves the transition from synchronized chaos to decoherent chaos as the coupling is increased. Finally, we experimentally implement uni-directional coupling and explore the dynamics of a driven logistic map.