Smart Dust Sensor Research Articles

New Insights in the Development of 3D Metal-Air Microbatteries

An increasingly number of studies is dedicated to the development of miniaturized sensors (“smartdust”), either for industrial purposes or for health monitoring. The requested power to get autonomous such miniaturized sensors led researchers to design efficient power sources. Microbatteries and microsupercapacitors have to be combined to fulfill such requirements. Our approach aims at miniaturizing metal-air batteries which can drastically boost the energy density available for smartdust sensors. In the frame of this study, the common thread is to design and to produce a full 3D microdevice in which energy is stored in the same way as in a metal-air battery. To address this task, the fabrication and characterization of miniaturized 3D metal anode and 3D macro-porous air cathode are proposed, each of those electrodes having a footprint area close to several mm2. First, a strategy for designing a 3D metal anode has been drawn, using CMOS compatible process. 3D zinc electrode (Zn micropillars) has already been electroplated through a porous membrane [1]. Despite an interesting technology, the 3D zinc scaffold is totally consumed after the first discharge (primary battery). The aim of our project is to produce a secondary metal-air microbattery by keeping safe the 3D template after the first discharge. A 3D metal electrode is then electroplated onto an inert 3D scaffold. To reach this goal, a 3D silicon template, consisting in an array of microtubes (Φ = 3 µm / depth = 50 µm) is fabricated. The lateral surface providing by the 3D scaffold allows the enhancement of the material mass loading while keeping constant the footprint area [2]. Once the geometry has been optimized by pushing back the limits of the silicon etching, the 3D scaffold is coated with a conformal deposit of metals. Zinc electroplated thin films has been deposited from an aqueous bath, and a similar approach for the electrodeposition of aluminum thin films was carried out from ionic liquids. Then, a micro-structured air cathode has been engineered using similar microelectronics processes. Air cathodes are composed of a conductive mesh, a catalyst and carbon material [3]. The project aims at reproducing the behavior of such air cathodes but at the millimeter scale: silicon wafer is double side etched with a tuned porosity. The top side of this topology acts as gas diffusion layer allowing the diffusion of oxygen into the miniaturized device. The bottom side of this electrode is composed of a large cavity, allowing the contact between the aqueous electrolyte, the catalytic sites and the oxygen. Conformal deposition of a platinum thin film is achieved by atomic layer deposition (ALD) to add the conductive contribution to the porous silicon scaffold. This platinum layer acts as the current collector and as the seed layer for catalysts electrodeposition process. These two electrodes have been separately characterized. Concerning the 3D metallic anode, various Zn-air prototypes have been assembled in KOH electrolyte using a homemade electrochemical cell with a commercially available air cathode. In the best configuration tested so far, this 3D Zn electrode can deliver a discharge capacity close to 1 mAh.cm-² with a flat discharge plateau at 1.2 V (fig. 1C). This value is three times higher than the one reported for state-of-art 3D Li-ion microbattery capacity using material thickness in the same order of magnitude [4]. Similarly, various Zn-air prototypes have been assembled using a Zn foil and the silicon micromachined air cathode in KOH electrolyte. A discharge plateau around 1.3V has been observed (fig. 1D). Finally, both components have been assembled to demonstrate the feasibility of a 3D metal-air primary microbattery with improved performance which will be reported in this communication. Acknowledgment: The RS2E and the DGA financially support this work. The French RENATECH network is greatly acknowledged for the microfabrication facilities.

Radio Frequency Identification in Supporting Traffic Safety

Due to the increased demands of traffic safety applicationsmany parameters of the traffic flow have to be measured bydifferent kind of techniques. The sensors of vehicle sensing anddetection are to be inexpensive, currently available and easy todeploy. Therefore, the state-of-the-art safety applications areusually based on mature technologies, such as video cameras,smart dust sensors, and wireless communication technologies.This paper discusses the application of RFID technology fortransportation applications. RFID is widely used for differentpurposes (e.g. cargo logistics, storage management), but isstill considered as new technology in the field of safety-relatedapplications.The paper gives an overview about the technology anddescribes scenarios of using RFID as infrastructure as well asvehicle sensor. The capabilities and limitations of RFID technologyis demonstrated through the ghost driver (wrong waydriving) detection, which is discussed in detail. In this particularapplication RFID is used as an infrastructure sensor, multiplereaders are connected in a network, thus able to monitorthe traffic flow directions in a particular road segment (e.g.in a motorway junction). Additional applications, such as flowclassification, road toll control and emergency monitoring arealso discussed in the paper.

Review and Comparison of Spatial Localization Methods for Low-Power Wireless Sensor Networks

Spatial localization (colocation) of nodes in wireless sensor networks (WSNs) is an active area of research, with many applications in sensing from distributed systems, such as microaerial vehicles, smart dust sensors, and mobile robotics. This paper provides a comprehensive review and comparison of recent implementations (commercial and academic) of physical measurement techniques used in sensor localization, and of the localization algorithms that use these measurement techniques. Physical methods for measuring distances and angles between WSN nodes are reviewed, followed by a comprehensive comparison of localization accuracy, applicable ranges, node dimensions, and power consumption of the different implementations. A summary of advantages and disadvantages of each measurement technique is provided, along with a comparison of colocalization methods in WSNs across multiple algorithms and distance ranges. A discussion of possible improvements to accuracy, range, and power consumption of selected self-localization methods is included in the concluding discussion. Although the preferred implementation depends on the application, required accuracy, and range, passive optical triangulation is reported as the most energy efficient localization method for low-cost/low-power miniature sensor nodes. It is capable of providing micrometer-level resolution, however, the applicable range (internode distance) is limited to single centimeters.

MOBILE NETWORKING FOR “SMART DUST” WITH RFID SENSOR NETWORKS

Large-scale networks of wireless sensors are becoming an active topic of research.. We review the key elements of the emergent technology of “Smart Dust” and outline the research challenges they present to the mobile networking and systems community, which must provide coherent connectivity to large numbers of mobile network nodes co-located within a small volume. Smart Dust sensor networks – consisting of cubic millimeter scale sensor nodes capable of limited computation, sensing, and passive optical communication with a base station – are envisioned to fulfil complex large scale monitoring tasks in a wide variety of application areas. RFID technology can realize “smart-dust” applications for the sensor network community. RFID sensor networks (RSNs), which consist of RFID readers and RFID sensor nodes (WISPs), extend RFID to include sensing and bring the advantages of small, inexpensive and long-lived RFID tags to wireless sensor networks. In many potential Smart Dust applications such as object detection and tracking, fine-grained node localization plays a key role.

QoS routing in wireless sensor networks—a survey

A wireless sensor network (WSN) is a one made up of small sensing devices equipped with processors, memory, and short-range wireless communication. Sensor nodes, are autonomous nodes, which include smart dust sensors, motes and so on. They co-operatively monitor physical or environmental conditions and send the sensed data to the sink node. They differ from traditional computer networks due to resource constraints, unbalanced mixture traffic, data redundancy, network dynamics, and energy balance. These kinds of networks support a wide range of applications that have strong requirements to reduce end-to-end delay and losses during data transmissions. When large numbers of sensors are deployed in a sensor field and are active in transmitting the data, there is a possibility of congestion. Congestion may occur due to buffer overflow, channel contention, packet collision, a high data rate, many to one nature, and so on. This leads to packet loss which causes a decrease in throughput and lifetime. Maximum throughput, energy efficiency and minimum error rate can be achieved by minimizing the congestion. A number of quality of service (QoS) techniques has been developed to improve the quality of the network. This article gives an overview of existing QoS techniques and a parametric comparison made with recent developments. This article mainly concentrates on network congestion in WSN environment.

Key Infection, Secrecy Transfer, and Key Evolution for Sensor Networks

Sensor networks are composed of a large number of low power sensor devices. For secure communication among sensors, secret keys are required to be established between them. Considering the strict resource constraints of sensors, key infection has been proposed by Anderson, Chan, and Perrig. However, because the communication keys are broadcasted in plaintext in key infection, some of them may be eavesdropped by an adversary. To address this security issue, secrecy transfer is presented, which utilizes pre-loaded secret keying material to enhance the security performance of key infection. To thwart on-going cryptanalytic attacks, a key evolution scheme is proposed to continuously refresh shared keys. Key evolution forces the adversary to keep monitoring traffic all the time after compromising a key; even if the adversary has compromised a key, it cannot catch up with the key evolution process, and may lose control of the compromised key quickly in a noisy communication environment. Analysis results show that key infection, secrecy transfer, and key evolution present viable trade-offs between security and resource consumption for smart dust sensor networks.

Smart dust sensor network with piezoelectric energy harvesting

Piezoelectric materials can be used to convert mechanical energy, such as vibration into electrical energy which can be used to power up devices in a smart dust sensing network. This piezoelectric mechanism exhibits great potentials to resolve many energy supply problems in sensor network to supply energy to radio frequency (RF) circuits, microcontroller, microelectromechanical systems (MEMS) and sensors placed in remote locations. This paper presents the detailed development work of a self-powered wireless sensor node which harvests the power energy from surrounding machinery vibration by the piezoelectric generator. The detailed design on a temperature sensing system is described in this paper. This approach is very useful in application in real-time remote monitoring of the machine temperature by sensor network in industries.