The term ‘‘Internet-of-Things’’ is used as an umbrella keyword for covering various aspects related to the extension of the Internet and the Web into the physical realm, by means of the widespread deployment of spatially distributed devices with embedded identification, sensing and/or actuation capabilities. Internet-of-Things envisions a future in which digital and physical entities can be linked, by means of appropriate information and communication technologies, to enable a whole new class of applications and services. In this article, we present a survey of technologies, applications and research challenges for Internetof-Things.

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Internet of things: Vision, applications and research challenges

This paper reviews the state-of-the art in vibration energy harvesting for wireless, self-powered microsystems. Vibration-powered generators are typically, although not exclusively, inertial spring and mass systems. The characteristic equations for inertial-based generators are presented, along with the specific damping equations that relate to the three main transduction mechanisms employed to extract energy from the system. These transduction mechanisms are: piezoelectric, electromagnetic and electrostatic. Piezoelectric generators employ active materials that generate a charge when mechanically stressed. A comprehensive review of existing piezoelectric generators is presented, including impact coupled, resonant and human-based devices. Electromagnetic generators employ electromagnetic induction arising from the relative motion between a magnetic flux gradient and a conductor. Electromagnetic generators presented in the literature are reviewed including large scale discrete devices and wafer-scale integrated versions. Electrostatic generators utilize the relative movement between electrically isolated charged capacitor plates to generate energy. The work done against the electrostatic force between the plates provides the harvested energy. Electrostatic-based generators are reviewed under the classifications of in-plane overlap varying, in-plane gap closing and out-of-plane gap closing; the Coulomb force parametric generator and electret-based generators are also covered. The coupling factor of each transduction mechanism is discussed and all the devices presented in the literature are summarized in tables classified by transduction type; conclusions are drawn as to the suitability of the various techniques.

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Energy harvesting vibration sources for microsystems applications

A wireless network consisting of a large number of small sensors with low-power transceivers can be an effective tool for gathering data in a variety of environments. The data collected by each sensor is communicated through the network to a single processing center that uses all reported data to determine characteristics of the environment or detect an event. The communication or message passing process must be designed to conserve the limited energy resources of the sensors. Clustering sensors into groups, so that sensors communicate information only to clusterheads and then the clusterheads communicate the aggregated information to the processing center, may save energy. In this paper, we propose a distributed, randomized clustering algorithm to organize the sensors in a wireless sensor network into clusters. We then extend this algorithm to generate a hierarchy of clusterheads and observe that the energy savings increase with the number of levels in the hierarchy. Results in stochastic geometry are used to derive solutions for the values of parameters of our algorithm that minimize the total energy spent in the network when all sensors report data through the clusterheads to the processing center.

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An energy efficient hierarchical clustering algorithm for wireless sensor networks

The worldwide thirst for portable consumer electronics in the 1990s had an enormous impact on portable power. Lithium ion batteries, in which lithium ions shuttle between an insertion cathode (e.g., LiCoO2) and an insertion anode (e.g., carbon), emerged as the power source of choice for the highperformance rechargeable-battery market. The performance advantages were so significant that lithium ion batteries not only replaced Ni-Cd batteries but left the purported successor technology, nickel-metal hydride, in its wake.1 The thick metal plates of * To whom correspondence should be addressed. J.W.L: e-mail, jwlong@ccs.nrl.navy.mil; telephone, (+1)202-404-8697. B.D.: e-mail, bdunn@ucla.edu; telephone, (+1)310-825-1519. D.R.R.: e-mail, rolison@nrl.navy.mil; telephone, (+1)202-767-3617. H.S.W.: e-mail, white@chem.utah.edu; telephone, (+1)810-585-6256. † Naval Research Laboratory. ‡ UCLA. § University of Utah. 4463 Chem. Rev. 2004, 104, 4463−4492

Brian Liebowitz

Papers

Smart Dust: Communicating with a Cubic-Millimeter Computer