The current ultramodern technologies are focusing on automation and miniaturization. The decreasing computing device size, increased connectivity and enhanced interaction with the physical world have characterized computing history. Recently, the popularity of small computing devices, such as hand held computers and cell phones; rapidly flourishing internet group and the diminishing size and cost of sensors and especially transistors have accelerated these strengths. The emergence of small computing elements, with sporadic connectivity and increased interaction with the environment, provides enriched opportunities to reshape interactions between people and computers and spur ubiquitous computing researches.
Smart dust is a tiny dust size device with extra-ordinary capabilities. Smart dust combines sensing, computing, wireless communication capabilities and autonomous power supply within volume of only few millimeters and that too at low cost. These devices are proposed to be so small and light in weight that they can remain suspended in the environment like an ordinary dust particle. These properties of Smart Dust will render it useful in monitoring real world phenomenon without disturbing the original process to an observable extends. Presently the achievable size of Smart Dust is about 5mm cube, but we hope that it will eventually be as small as a speck of dust. Individual sensors of smart dust are often referred to as motes because of their small size. These devices are also known as MEMS, which stands for micro electro-mechanical sensors.
Overview of Smart Dust
This section describes smart dust, beginning with a summary of early development work at UC Berkeley. Also presented are two notable smart dust applications completed in the beginning stages of smart dust history. This is followed by a description of current smart dust offerings and expected trends for the technology.
Smart dust was conceived in 1998 by Dr. Kris Pister of the UC Berkeley (Hsu, Kahn, and Pister 1998; Eisenberg 1999). He set out to build a device with a sensor, communication device, and small computer integrated into a single package. The Defense Advanced Research Projects Agency (DARPA) funded the project, setting as a goal the demonstration “that a complete sensor/communication system can be integrated into a cubic millimeter package”
In the early stages of the project, the team gained experience by building relatively large motes using components available “off the shelf”. One such mote, named “RF Mote,” is shown in the following figure. This mote has sensors for “temperature, humidity, barometric pressure, light intensity, tilt and vibration, and magnetic field” and it is capable of communicating distances of about 60 feet using radio frequency (RF) communication. If the mote operated continuously, its battery would last up to one week.
One of the issues that the UC Berkeley team faced in building smaller motes involved powering the device. Small batteries help minimize the size of the resulting mote, but they contain less energy than traditional, larger batteries and thus, they have shorter life spans. However, long battery life is critical to applications where it would be costly, inconvenient, or impossible to retrieve a smart dust mote in order to replace its batteries. This would be true, for example, with temperature and humidity-monitoring motes placed inside the walls of a building during its construction.
Faced with the trade-off between miniaturization and long battery life, early smart dust developers leaned toward miniaturization. The Smart Dust project Web site states that “the primary constraint in the design of Smart Dust motes is volume, which puts a severe constraint on energy since we do not have much room for batteries or large solar cells”.
However, the team applied tactics to conserve...