In the face of hundreds of sci-fi novels and thousands of media stories about nano-scale robots, it's easy to forget that they don't actually exist yet. Although scientists have had plenty of success in fabricating ultra-microscopic building materials, cogs, propellers and even engines, so far, nobody has created a piece of nanotechnology worthy of bearing the name 'robot'.

So how close are we to miniaturised robots? Well, they're nowhere near microscopic at the moment, but what may be the world's smallest robot is being developed by researchers at the USA's ?Sandia National Laboratories.

Weighing less than an ounce and about the same size as the top joint on an adult thumb, the Sandia machine is possibly the tiniest autonomous, un-tethered robot ever created. Powered by three watch batteries, it consists of an 8K ROM processor, temperature sensor, and two drive motors for spinning locomotion. Eventual accessories being considered include a miniature camera, microphone, communication device, and chemical micro-sensor.

Sticking to the path

“This could be the robot of the future,” says Ed Heller, one of the project’s researchers. “It may eventually be capable of performing difficult tasks that are done with much larger robots today, such as locating and disabling land mines or detecting chemical and biological weapons.”

He says the tiny robo-spy could, for example, trundle through pipes or prowl around buildings looking for chemical plumes or human movement. With the right communications gear, the robots would be capable of relaying information to a human operator or communicate with each other. They will be able to work in co-ordinated swarms, like insects. Most importantly, they will be able to go into locations too small for their larger relatives.

For any autonomous robot, “pathing” is the biggest challenge. This means the machine being able to identify obstacles and plan a route around them. It sounds easy, but what a human does unconsciously is a terrifically hard problem for an artificial intelligence to solve. For the mini-robot the dilemma is exacerbated by scale; both the size of its brain and the range of movement it can demonstrate. However, the plucky little crawler has already shown itself capable of maneuvering through a field of coins.

Its top speed is around 30 meters per hour.

Heavy heritage

The mini-bot’s family tree is full of older and bigger brothers. Back in 1996, ?Sandia’s Intelligent Systems Sensors and Controls Department unveiled a ?Mini Autonomous Robot Vehicle (MARV). It was four times the size of the current baby, but for it’s time, it was a miraculous piece of engineering. It contained all the necessary power, sensors, computers, and controls on board and was made primarily from commercial parts using conventional machining techniques. Over the next several years the department improved the original MARV, producing a succession of gradually smaller and smarter machines.

The robots bodies were made of printed circuit boards, and each had an obstacle detector sensor, radio, temperature sensor, and batteries. At 4 x 1.8 x 1.7 cm though, they were still larger than was desirable.

?Sandia roboticist Ray Byrne, who was involved in the early efforts, says about three years ago Intelligent Systems and Robotics Center teamed with ?Sandia’s Sensor Technologies Department to further miniaturise the robots. They sought out the department’s help because of its expertise in building sensors and other devices on miniature scales.

By playing with new techniques for packaging electronics, wheel design, and body material, the new team shrunk the robots to their present size of about 16 cubic centimeters (1/4 cubic inch). Heller, who developed the device’s microelectronics, says one significant innovation that permitted the shrinkage was the use of commercially available unpackaged electronic components.

“Previous small robots consisted of packaged electronic parts that were more bulky and took up valuable space. By eliminating the packaging and using electronic components in die form, we reduced the size of the robot’s electronics considerably,” Heller says. “This was a first major step.”

The unpackaged parts are assembled onto a simple multi-chip module on a glass substrate.

Making tracks

Doug Adkins, who developed the mechanical design for the new mini-robot, says the researchers further reduced its size by using a new rapid prototyping technique to form the device’s body. Called stereolithography, the method uses a laser focused into a polymer bath to build layer after layer of a pre-programmed shape. The material, which “grows” as each layer is added, is lightweight, strong, and can be formed into complex three-dimensional arrangements. The robot bodies built this way have cavities for the batteries, the electronics-embedded glass substrate, axles, tiny motors, switches, and other parts.

Adkins also redesigned the wheel structure of the device. Earlier models had standard wheels. However, the mobility was limited due to their small diameter.

“I thought of how tanks with their track wheels can maneuver over many large objects and realised the mini-robots could benefit from the same type of wheels,” Adkins says. With the addition of such tracks, the robot can now move easily on carpet.

The eyes have it

Just how small the miniature robots will ultimately get is primarily limited by the size of their power source: the three watch batteries. Whatever size the robot is intended to be, its body must be large enough to hold enough batteries to support its power requirements. This simple fact has always been the limiting factor in attempts at nano-scale machinery. We can build nearly everything we want in miniature...except power storage.

“Batteries, both their physical size and their running life, have been one of our biggest issues,” Heller says. “The batteries need to run longer and be smaller.”

Over the next few years, with additional help from other ?Sandia groups, Heller and Adkins expect to add to the mini-robots either infrared or radio wireless two-way communication capability, as well as miniature video cameras, microphones, and chemical micro-sensors.

So eventually the bots will be able to see us, but if growth trends continue, one day our naked eyes won’t be able to spot them.

Tag: Nanoscale robots