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A Feedback Control Strategy for Energy-Harvesting in Diffusion-Based Molecular Communication Systems

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Abstract

Piezoelectric nanogenerators recently emerged as a turning point in the design of energy-aware and energy harvesting transmission scheme at the nanoscale. This work considers their adoption in diffusion-based molecular communications, proposing a power control strategy based on feedback control theory. In particular, the transmission power of an electrochemical nanodevice fed by a piezoelectric nanogenerator is dynamically set proportionally to the available energy budget, by using a closed-loop control scheme. The resulting system is analytically modeled with a discrete-time nonlinear state equation. The range of acceptable values of the proportional gain is theoretically derived by studying technological constraints and global asymptotic stability. The impact of the proportional gain on both output variance and time constant of the linearized system around the equilibrium point is also investigated. Computer simulations validate the theoretical analysis under different parameter settings. The comparison against state of the art transmission scheme also demonstrates the unique ability of the conceived approach to ensure, at the equilibrium, the targeted performance level.

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A number of techniques have been recently proposed to implement molecular communication, a novel method which aims to implement communication networks at the nanoscale, known as nanonetworks. A common characteristic of these techniques is that their main resource consists of molecules, which are inherently discrete. This paper presents DIRECT, a novel networking model which differs from conventional models by the way of treating resources as discrete entities; therefore, it is particularly aimed to the analysis of molecular communication techniques. Resources can be involved in different tasks in a network, such as message encoding, they do not attenuate in physical terms and they are considered 100% reusable. The essential properties of DIRECT are explored and the key parameters are investigated throughout this paper.
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Harvesting ambient mechanical energy at the nanometer scale holds great promises for powering small electronics and achieving self-powered electronic devices. The self-powering capability allows electronic device packages to exclude bulky energy storage components and makes possible forgoing the inclusion of bulky battery components. Recent development of nanogenerators (NGs) has demonstrated a possible solution for the design of self-sufficient power source that directly draws energy from ambient mechanical resources. Piezoelectric nanowires (NWs) are the building blocks of NGs. In this review paper, theoretical calculations and experimental characterization methods for predicting or determining the piezoelectric potential output of NWs are reviewed first. Representative models of NGs are then discussed for harvesting mechanical energy from high-frequency acoustic waves and low-frequency vibrations/frictions. A numerical calculation is also presented to estimate the energy output from NW-based NGs. A potential practical application of NGs for harvesting energy from respiration is shown using piezoelectric polymer thin films. At the end, perspectives of the NG concept are discussed. The nanometer-scale piezoelectric and mechanical properties, the piezotronic effect, and large-scale manufacturing capability are suggested to be the essential aspects that would eventually lead the promising NG concept to a practical power source.
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No sweat, no gain: Flexible biofuel cells functionalized with lactate oxidase (LOx) and platinum as anode and cathode materials harvested biochemical energy from human perspiration. Substantial power was generated from human sweat in real-life scenarios.
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Harvesting energy from irregular/random mechanical actions in variable and uncontrollable environments is an effective approach for powering wireless mobile electronics to meet a wide range of applications in our daily life. Piezoelectric nanowires are robust and can be stimulated by tiny physical motions/disturbances over a range of frequencies. Here, we demonstrate the first chemical epitaxial growth of PbZr(x)Ti(1-x)O(3) (PZT) nanowire arrays at 230 °C and their application as high-output energy converters. The nanogenerators fabricated using a single array of PZT nanowires produce a peak output voltage of ~0.7 V, current density of 4 μA cm(-2) and an average power density of 2.8 mW cm(-3). The alternating current output of the nanogenerator is rectified, and the harvested energy is stored and later used to light up a commercial laser diode. This work demonstrates the feasibility of using nanogenerators for powering mobile and even personal microelectronics.