ABSTRACT

Applications of wireless sensor nodes are evolving at a previously unimaginable rate. But current technology is limited because devices are bulky - measuring one cubic centimeter or more - and hampered by short lifetimes. This project is producing a one cubic millimeter sensor node. This ultra-miniaturized device is a complete sensing platform that includes transducers (for imaging, temperature sensing and other signal detection), wireless communication, a high accuracy timer, processor, memory, a battery and energy harvesting that provides the node with an extended lifetime.

The central challenge in reducing the form factor for sensor nodes is to reduce power consumption and
densely package discrete components (crystals, inductors, etc.). To this end, this team's innovations involve research and development of:

1. A novel processor that operates at a supply voltage near the threshold voltage of the transistors for optimal energy consumption.
2. A new ultra-low-leakage memory system.
3. An Ultra Wide-Band (UWB) transmitter and receiver that can communicate with other nodes over a distance of three meters with an integrated antenna.
4. A 100pW timer that is temperature compensated and designed for reduced jitter to allow accurate synchronization between sensor nodes and enable short, low energy radio communication windows.
5. A new CMOS imaging approach capable of ultra-low power motion detection and image-acquisition, and, reconfigurable to act as a solar energy harvesting unit.
6. An energy-aware software development environment to control the node

These PIs implemented early versions of several of these technologies in silicon, demonstrating the potential to package them as sensor nodes. The team's track record of producing ultra-low power circuits, and other sensing components, position them to deliver the needed 1000× form factor reduction. This research team will assemble and package 100 first- and second-generation of these sensor node platforms and disseminate them to the broader community for trials in a wide range of uses.

The development of cubic-millimeter sensor nodes will enable applications that have long been envisioned but were unachievable. For example, sensory skins could cover surfaces with a dense deployment of nodes that monitor the properties of the manifold itself or its surroundings. Implantable intelligence can enable deeply embedded physical and biological processes, e.g., malignant tumor growth monitoring or intra-ocular pressure sensing to determine the risk for retinal detachment. Applications such as these, and a myriad of other "Thinking and Linking" applications, can give everyday objects sensing, computing, communication, and tracking ability, allowing, for example, research ranging from the social network patterns of small insects to asset tracking in dynamic environments like hospitals. By shrinking sensor node size to one cubic millimeter, with potentially perpetual lifetime, the concept of "smart dust" can be taken from fiction to reality.

By disseminating the first generation of these sensors to members of the sensor network community, this project will dramatically accelerate the adoption of cubic-millimeter-class computing devices. This will have immediate impact on a wide array of research programs for intelligently sensing, tracking, measuring and optimizing physical processes. This research in turn will have a fundamental and long term impact on a diverse set of applications with critical societal import, ranging from energy conservation, environmental quality management, and health care.

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