Novel varistor materials based on ALD surface modified metal particles embedded in a polymeric binder were found to display exceptional non-ohmic electrical properties. Sub- nanosecond transient response times with negligible overshoot and low capacitance, leakage current, and insertion loss were repeatedly observed. These properties enable these novel devices capable of suppressing fast rise-time transients induced by electromagnetic pulse (EMP) and high-power magnetic weapons (HPM).

This paper investigates the fundamental operation of and mechanism of conduction occurring within metal-insulator varistors (MIVs). MIVs based on micron-sized spherical metal particles coated with nanometer-thick Al2O3, SiO2, and BN films are investigated and discussed. MIV functionality is found to be dependent on the non-Ohmic operation of the thin electrically insulating films separating adjacent conductive metal particles within the high-density varistor particle matrix. Several experimental results suggest that the breakdown and conduction behavior are strongly dominated by Fowler–Nordheim tunneling and can be accurately modeled by a simple tunneling expression. The exceptional electrical properties exhibited by MIVs suggest a strong potential for use in the suppression of fast rise-time transients.

Ultrafast metal-insulator varistors have been fabricated using atomic layer deposition. A high-density matrix of micron-sized spherical Ni particles conformally coated with ∼7.5–22nm Al2O3 films exhibited transient response times (∼0.3ns), capacitances (∼45pF), leakage currents (∼33pA), and nonlinearities (α∼380) which were all markedly improved over conventional metal oxide varistors. These characteristics result from the Fowler–Nordheim tunneling of electrons through uniform Al2O3 tunnel junctions separating adjacent particles within the matrix.

A growing demand for deployment of autonomous sensors and sensor networks is leading to a subsequent increase in the demand for localized, independent energy harvesting capabilities for each node. In this paper, a method of remote area wind energy harvesting is presented, with a focus on an anemometer-based solution. By utilizing the motion of the anemometer shaft to turn a compact alternator, small amounts of power can be harvested from otherwise unavailable sources. Energy harvested is converted to battery potential via a pulsed buck-boost converter operating in discontinuous conduction mode (DCM). It is found that maintaining a constant input resistance at the input port of the converter biases the alternator to operate at its peak power point over a wide range of wind speeds. Results show that power harvesting capability using the discussed alternator and power converter solution are in the range of tens to hundreds of microwatts up to approximately one milliwatt. This power is passed to the central system batteries, providing a trickle-charge. As a result, sensor nodes incorporating this harvesting solution have an increased field lifetime. High overall efficiency is maintained over a wide range of potential wind speeds, with little impact on anemometer measurement accuracy.