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Environmental sensing based on a network of small and inexpensive wireless sensors (motes) scattered over a very large area and able to detect tiny amounts of chemicals in air, water and soil has gained vast popularity among the scientific community and even in the popular press as a first line of defense to prevent terrorist attacks or environmental disasters [1]. Wireless sensor networks are also of interest for issues related to production and storage in the agro-food industry or other industrial processes requiring atmosphere control, air quality mapping in metropolitan area and large infrastructures, microclimatic condition monitoring for improved preservation of cultural heritage sites [2].
In pervasive sensing the information is extracted from the sensor network as a whole, Inhibitors,Modulators,Libraries in the form of a space distribution of a certain variable (temperature Inhibitors,Modulators,Libraries gradients, distribution of chemicals, wind velocity vector Inhibitors,Modulators,Libraries field, etc.) which can in principle be mapped and correlated with topological information such as for example, building distributions, the structure of main traffic-jammed roads, the presence of parks and rivers, industrial or dumping sites, etc. This requires that each node of the sensing network be characterized by the coexistence on the same unit of sensing capabilities, dedicated electronics, power supply and a wireless communication system [3].Miniaturization is a key factor assuring limited power consumption, easiness of field installation and low cost.
During the last two decades, silicon micromachining techniques have been applied to the fabrication of chemical Inhibitors,Modulators,Libraries and physical sensor microdevices, Dacomitinib through the development of platforms with different structures and geometries (see, for example [4�C8]). Micromachining techniques allow the integration on the same platform of different transducers for sensing, up to the electronics for signal processing (see for example [9,10]).One of the most popular micromachined platform for gas sensors is the so-called micro-hotplate [11�C13]. It consists of a multi-layer suspended membrane, having micrometric thickness and surrounded by a silicon rim, micromachined from a silicon wafer.
The multi-layer membrane is typically composed by metallizations and several insulating layers, alternating each other, with various shapes. Metallic electrodes on the surface selleck chemical of the platform allow the readout of the chemoresistive signal from the metal-oxide sensing layer deposited on the top. Integrated heating elements provide sensor operation temperatures up to 500 ��C. Due to its small mass and surface, as well as reduced thermal contact at border, the micro-hotplate requires very low heating power compared to traditional sensor platforms.