More than a decade of research in the field of thermal, motion, vibration and electromagnetic radiation energy harvesting has yielded increasing power output and smaller embodiments. Power management circuits for rectification and DC-DC conversion are becoming able to efficiently convert the power from these energy harvesters. This paper summarizes recent energy harvesting results and their power management circuits.

Micropower energy harvesting

The idea of the Internet of Things (IOT) notion is that everything within the global network is accessible and interconnected. As such Wireless Sensor Networks (WSN) play a vital role in such an environment, since they cover a wide application field. Such interconnection can be seen from the aspect of a remote user who can access a single desired sensor node from the WSN without the necessity of firstly connecting with a gateway node (GWN). This paper focuses on such an environment and proposes a novel user authentication and key agreement scheme for heterogeneous ad hoc wireless sensor networks. The proposed scheme enables a remote user to securely negotiate a session key with a general sensor node, using a lightweight key agreement protocol. The proposed scheme ensures mutual authentication between the user, sensor node, and the gateway node (GWN), although the GWN is never contacted by the user. The proposed scheme has been adapted to the resource-constrained architecture of the WSN, thus it uses only simple hash and XOR computations. Our proposed scheme tackles these risks and the challenges posed by the IOT, by ensuring high security and performance features.

A novel user authentication and key agreement scheme for heterogeneous ad hoc wireless sensor networks, based on the Internet of Things notion

The concept of Internet of Things (IOT), which is already at our front doors, is that every object in the Internet infrastructure (II) is interconnected into a global dynamic expanding network. Sensors and smart objects are beside classical computing devices key parties of the IOT. We can already exploit the benefits of the IOT by using various weareables or smart phones which are full of diverse sensors and actuators and are connected to the II via GPRS or Wi-Fi. Since sensors are a key part of IOT, thus are wireless sensor networks (WSN). Researchers are already working on new techniques and efficient approaches on how to integrate WSN better into the IOT environment. One aspect of it is the security aspect of the integration. Recently, Turkanovic et?al.'s proposed a highly efficient and novel user authentication and key agreement scheme (UAKAS) for heterogeneous WSN (HWSN) which was adapted to the IOT notion. Their scheme presented a novel approach where a user from the IOT can authenticate with a specific sensor node from the HWSN without having to communicate with a gateway node. Moreover their scheme is highly efficient since it is based on a simple symmetric cryptosystem. Unfortunately we have found that Turkanovic et?al.'s scheme has some security shortcomings and is susceptible to some cryptographic attacks. This paper focuses on overcoming the security weaknesses of Turkanovic et?al.'s scheme, by proposing a new and improved UAKAS. The proposed scheme enables the same functionality but improves the security level and enables the HWSN to dynamically grow without influencing any party involved in the UAKAS. The results of security analysis by BAN-logic and AVISPA tools confirm the security properties of the proposed scheme.

An efficient user authentication and key agreement scheme for heterogeneous wireless sensor network tailored for the Internet of Things environment

Modern gas monitoring scenarios for medical diagnostics, environmental surveillance, industrial safety, and other applications demand new sensing capabilities. This Review provides analysis of development of new generation of gas sensors based on the multivariable response principles. Design criteria of these individual sensors involve a sensing material with multiresponse mechanisms to different gases and a multivariable transducer with independent outputs to recognize these different gas responses. These new sensors quantify individual components in mixtures, reject interferences, and offer more stable response over sensor arrays. Such performance is attractive when selectivity advantages of classic gas chromatography, ion mobility, and mass spectrometry instruments are canceled by requirements for no consumables, low power, low cost, and unobtrusive form factors for Internet of Things, Industrial Internet, and other applications. This Review is concluded with a perspective for future needs in fundament...

Multivariable Sensors for Ubiquitous Monitoring of Gases in the Era of Internet of Things and Industrial Internet

Breath sensors can revolutionize medical diagnostics by on-demand detection and monitoring of health parameters in a noninvasive and personalized fashion. Despite extensive research for more than two decades, however, only a few breath sensors have been translated into clinical practice. Actually, most never even left the scientific laboratories. Here, we describe key challenges that currently impede realization of breath sensors and highlight strategies to overcome them. Specifically, we start with breath marker selection (with emphasis on metabolic and inflammatory markers) and breath sampling. Next, the sensitivity, stability, and selectivity requirements for breath sensors are described. Concepts are elaborated to systematically address these requirements by material design (focusing on chemoresistive metal oxides), orthogonal arrays, and filters. Finally, aspects of portable device integration, user communication, and clinical applicability are discussed.

Breath Sensors for Health Monitoring

Wireless sensor networks (WSNs) have recently been applied in industrial monitoring applications including hazardous gases detection. As a major power consumer of a node, gas sensors may significantly constrain its lifetime. Hence, the sensing circuit must be carefully designed to optimize performance and retain accuracy. In this paper, we propose for the first time the principle of gas concentration measurement based on a single sensor in a voltage divider circuit, instead of the well-known Wheatstone bridge sensing circuit, which employs two sensors. We discuss the design of a real WSN node for gas sensing and evaluate it with respect to an identical platform that uses the Wheatstone bridge. The proposed approach ensures significant energy savings and helps to avoid zero offset issue. Besides, we employ a more efficient and secure sensor heating profile; it does not damage the sensor and does not make gas sensing dependent on environmental conditions. Experimental results show a 30% reduction in power with respect to the state-of-the-art.

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Circuit Design and Power Consumption Analysis of Wireless Gas Sensor Nodes: One-Sensor Versus Two-Sensor Approach

Fires or toxic gas leakages may have grave consequences like significant pecuniary loss or even lead to human victims. In this paper we present an autonomous wireless sensor system for early fire and gas leak detection. The system consists of two modules: a gas sensor module and a power management module. The operation of the gas sensor module is based on the pyrolysis product detection which makes it possible to detect fire before inflammation. In addition, the on board gas sensor can identify the type of leaking gas. A generic energy scavenging module, able to handle both alternating current and direct current based ambient energy sources, provides the power supply for the gas sensor module. The harvested energy is stored in two energy buffers of different kind, and is delivered to the sensor node in accordance to an efficient energy supply switching algorithm. At the end of the paper we demonstrate the experimental results on gas detection, energy consumption evaluation, and show how to ensure the system autonomous operation.

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Combustible gases and early fire detection: an autonomous system for wireless sensor networks

Wireless sensor networks (WSNs) have recently been applied for the detection of a number of hazardous gases. Gas monitoring is of significance, for gas leakage and the resultant penetration of gases into the environment can lead to grave or sometimes fatal consequences. In this work, we propose a sensor node architecture for a wireless outdoor CO monitoring unit with an emphasis on the energy efficiency of measurements and optimal power supply mechanism. To guarantee the ‘perpetual’ operation, the sensor node is supported by a hybrid power supply, which takes advantage of both wind and solar ambient energy sources to power the node and to charge the high capacity super capacitors that act as energy buffers. Using an electrochemical CO sensor, we secure the low power consumption of the node without degrading the sensing capabilities. We demonstrate our experience of operating the developed wireless sensor node in real conditions. Our solution can be applied for CO monitoring in urban areas and outdoor industrial facilities.

POCO: ‘Perpetual’ operation of CO wireless sensor node with hybrid power supply

Wireless Sensor Network (WSN) paradigm has been applied to a high number of monitoring and control applications. However, the scarcity of WSN energy resources imposes restrictions on its truly ubiquitous and long-term deployments. We address the problem of long-term autonomous operation of a wireless gas sensor by employing the far-field RF energy harvesting technology at 900 MHz in the power range from −20 dBm to 10 dBm. The node conducts regular CH4 or CO measurements and communicates the data to a wireless network coordinator at 2.4 GHz. Experimental results demonstrate that the optimized energy consumption of WSN, as well as energy harvesting of at least 1 mW (0 dBm) from ambient RF signal, ensure the ‘perpetual’ operation of WSN.

Feasibility of RF energy harvesting for wireless gas sensor nodes

Monitoring of hazardous and combustible gases at industrial premises and in the living apartments has been a topic of top priority for a number of decades. Within the last decade a great many of solutions have been proposed including the one relying on the Wireless Sensor Network (WSN) paradigm. Being an autonomous monitoring system, it is essential to guarantee a long lifetime of gas WSN. In this work, we are investigating and implementing a number of heating profiles for catalytic and semiconductor sensors used on board of the wireless sensor nodes to reduce their power consumption. After analyzing the pros and cons of these profiles, we propose the heating profile based on the Pulse Width Modulation (PWM) and the multi stage heating profile. Experimental results demonstrate that the average current consumption of the gas sensor node can be reduced up to 0.76 mA and its power consumption up to 2.54 mW thereby ensuring the autonomous operation of the sensing device for more than one year.

Denis Spirjakin

Papers

Circuit Design and Power Consumption Analysis of Wireless Gas Sensor Nodes: One-Sensor Versus Two-Sensor Approach

Combustible gases and early fire detection: an autonomous system for wireless sensor networks

POCO: ‘Perpetual’ operation of CO wireless sensor node with hybrid power supply

Feasibility of RF energy harvesting for wireless gas sensor nodes

Investigation of heating profiles and optimization of power consumption of gas sensors for wireless sensor networks