Smart Dust Goal: Distributed sensor networks Sensor nodes: Autonomous 1mm3 Sensor Interface Power: battery, solar, cap. Comm: LOS Optical (CCR, Laser) Challenges: 1 Joule 1 kilometer 1 piece UCB: Pister, Kahn, Boser MLB: Morris UTRC: Murray Like several other groups, we’re making networks of wireless sensors. Ours have the distinction of being smallest, and still have the longest communication range! We will need to push hard on low power analog and digital electronics, since we are shooting for a 10 microWatt mean power dissipation. We will also be pushing hard on micro-optics technology, integrating lasers and scanning mirrors for communication over distances of tens of kilometers. The team includes Steve Morris of MLBCo, makers of the worlds smallest flying video surveillance platforms (8” gas airplane with gyro stabilization!). Using these aircraft in the year 3 demo we will distribute thousands of dust motes over a (friendly) military base, then return the next day to interogate the sensors to reconstruct all vehicular traffic on the base over the previous day. Additionally, we will instrument fan and first-stage compressor blades of a jet engine and obtain real-time diagnostic information while the engine is running. United Technologies will provide $100k of testing and technician time on a developmental jet engine. UT owns Pratt&Witney, Sikorsky, Otis Elevator, ...

Smart Dust Components 1-2 mm Laser diode III-V process Passive CCR comm. MEMS/polysilicon Active beam steering laser comm. MEMS/optical quality polysilicon Analog I/O, DSP, Control COTS CMOS Sensor MEMS/bulk, surface, ... Power capacitor Multi-layer ceramic The majority of the volume of the mote will consist of power supply elements. The rechargeable thick film battery will store 1 J/mm^3, with low output resistance for sub-milliAmp current. The multi-layer ceramic power capacitor (COTS) will store only 1 microJoule, but will provide high current when needed (e.g. for laser pulses). In full sun, solar cells provide roughly 1 J/day per square millimeter. Different versions of dust may have only battery, only solar cell, or some combination. The sensor will be “research off the shelf”. The only design changes will be to optimize performance at low power. Sensors options include temperature, pressure, humidity, vibration, sound (requires several cubic millimeters), and magnetic anomoly detection. Communication will be optical, line of sight. The corner cube is used to modulate light from an external interogating laser. We have demonstrated 150 meter communication using corner cubes. 1km range in full sun should be possible. Using the on-board laser and beam steering, active optical communication should be possible over distances of tens of kilometers at least. Solar cell CMOS or III-V Thick film battery Sol/gel V2O5 1-2 mm

Dust components Thick film battery: 1mm^3, 1 J storage Power capacitor: 0.25mm^3, 1uJ storage Solar cell: 1x1x0.1mm^3, 0.1mW generation CMOS controller: 1x1x0.1mm^3 Sensor: 0.5x0.5x0.1mm^3 Passive CCR comm: 0.5x0.5x0.1mm^3, 10kbps, 1uW, 1km Active laser comm: 1x0.5x0.1mm^3, 1Mbps, 10mW, 10km Total volume: < 1.5 mm^3 Total mass: < 5 mgm Total cost of all of the (unpackaged) components in volume production would be on the order of $1. Low-cost assembly of this many components at this scale is a major challenge, and one of the focusses of the DARPA 97-43 solicitation. Massively parallel wafer-scale assembly techniques are under develeopment at Berkeley and elsewhere. This is probably the weakest link in the chain, so we’ll be spending lots of time thinking about it! Note that the entire dust mote may remain “unpackaged” after assembly. Designed to be dropped, ejected, or sprayed, these motes have a terminal velocity in air of only a few meters per second.

Airborne Dust Mapleseed solar cell 1-5 cm MEMS/Hexsil/SOI If dust mote mobility is desired it can be achieved in several ways. The simplest approach is merely to slow the descent rate to keep the sensors in the air, either as long as possible or until they see something of interest. Using a Samara or mapleseed-like approach, descent rates of well under 1 m/s are possible. With control inputs on the airfoils, and auto-rotator could direct its descent, or possibly even ride thermals. Using micromachined nozzles and combustion chambers, dust motes could lie dormant for long periods of time and then shoot into the air under rocket power. Recent results with HTPB/AP based solid fuels indicate that flights of tens of seconds and distances of hundreds of meters should be possible. Controlled auto-rotator MEMS/Hexsil/SOI Rocket dust MEMS/Hexsil/SOI