Servo - January 2016

Forever Frying

This month’s nominee for the Least Likely Design for Practical Implementation award is Thermobot, designed by Takeru Nemoto and Akio Yamamoto of the University of Tokyo ( www.u-tokyo.ac.jp). The device operates purely on the basis of temperature differential using bimetal deformation for propulsion. In earlier studies, the professors noted that thermal deformation of a bimetal eccentric cylinder caused it to oscillate incessantly.

Thermobot is based on that phenomenon, with the top half of the cylinder removed and the remaining semicircle split vertically into two swinging We could find no serious suggestions for practical applications, but we’ll go out on a limb and propose that it might be used in a frying pan to stir gravy ... if you can figure out a way to steer it ... and if the gravy doesn’t thicken much.

Operation of Thermobot, turning heat into motion.

Attack of the Killer COTSBots

One of the nastiest creatures in the sea is the crown-of-thorns sea star (COTSS) — a multiple-armed starfish with tube feet and highly toxic spines that can poke into your skin, break off, and require surgical removal. These guys range in size from about 10 to 14 inches ( 25 to 35 cm) and can have up to 21 prehensile arms. Their danger to humans is overshadowed, however, by the damage they are doing to coral reefs.

The COTSS can extrude its huge stomach out through its mouth and spread it to an area almost equal to its own diameter. It then secretes digestive enzymes and sucks out the liquefied coral. Observers have reported as many as 100,000 of them per square kilometer, so it’s not surprising that recent population explosions of COTSS have devastated large reefs; most commonly in Australia but also in the Indian and Pacific Oceans. In the past, divers have attempted to control the population by manually injecting them with poison, but they can inject only about 120 of them per hour.

To improve the kill rate, a group of researchers at Australia’s Queensland University of Technology ( www.qut.edu.au) have developed the completely autonomous COTSBot, designed specifically to “seek out and murder crown-of-thorns sea stars as mercilessly and efficiently as possible.” The killer bot is basically a 30 kg yellow torpedo with a maximum speed of over two meters per second and an endurance of over six hours.

It injects each starfish with a recently developed poison that kills it within 24 hours, causing “discolored and necrotic skin, ulcerations, loss of body turgor, accumulation of colorless mucus, loss of spines [and] large, open sores that expose the internal organs.” Yum!

Researchers envision a fleet of the subs that can “murderize” most of the starfish on a reef within days or weeks. COTSBots are said to pose no threat to humans but — just to be safe — you probably should avoid swim trunks with a picture of a COTSS on them.