O/T Bio-sensor puts slime mould at its heart

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Bio-sensor puts slime mould at its heart

17:32 17 May 2007

NewScientist.com news service

Will Knight

http://www.newscientisttech.com/article.ns?id=dn11875 & feedId=online-

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Inside the new chip, the slime mould is surrounded by several

electrodes that monitor conductivity

Andy Adamatzky, University of the West of England

A sensor chip controlled not by wires and transistors, but by a

living slime mould marks an important step towards more widespread

use of biologically-driven components and devices, researchers say.

The unusual chip was created by graduate student Ferran Revilla,

working with Hywel and Zauner at the University of

Southampton in the UK. At the heart of the chip is a living Physarum

polycephalum, or slime mould – a yellow, single-celled organism more

commonly found gobbling up bacteria and microbes in damp areas of

forest. The chip plugs into a computer via a normal USB interface.

Inside the new chip, the mould is surrounded by several electrodes.

These monitor conductivity at different points, to reveal the

movement of its internal fluids. This provides a way to experiment

with the organism as a tool for sensing and computation. Currently,

a mould can survive inside the chip for about a week, although the

researchers hope to extend its lifespan.

Slime mould is interesting to researchers because, although it is

primitive – it lacks even a central nervous system – it can respond

instinctively to stimuli. For example, it will gradually crawl

towards food and humidity, but shy away from light and poisonous

substances. The organism responds using fluid oscillations in

intracellular protoplasmic veins.

Storable slime

Electrode readings are fed to a separate electronic chip which can

be hooked up to a normal computer. Furthermore, since slime mould

can survive in a dormant state for months at a time, the device

could conceivably be vacuum-packed, stored and shipped, then

reactivated with moisture and nourishment.

Several tubes lead to microfluidic channels that connect to the

chamber in which the mould itself lives. Water and food can be fed

though these tubes to sustain the mould.

The research team tried passing different chemicals through the

tubes and measured the electrode readings to analyse the organism's

reaction. They were able to use the chip to detect the presence of

the organic chemicals in liquids in just a few seconds.

" We wanted to check it out as a sensor, " Zauner told New Scientist.

He says using biological organisms in this way is attractive because

they can be specialised for the task and can maintain all the

necessary chemicals and reactions. " All these points are taken care

of by the living cell, " Zauner says.

Andy Adamatzky, who researchers unconventional computer

architectures at the University of the West of England, UK, says the

new chip seems promising. " The guys have done cool stuff towards

integrating conventional electronics with amorphous biological

substrates, " he told New Scientist.

The chip is part of a wider research effort exploring the use of

living organisms for sensing, control and computation. Working with

researchers at the Kobe University in Japan, the Southampton team

previously created a small, six-legged robot with movements

controlled by a slime mould's reaction to light (see Robot moved by

slime mould's fears).

Kobe University researchers, led by Yukio-Pegio Gunji and Soichiro

Tsuda, have also demonstrated that slime mould can be used to

perform simple calculations. They created Boolean logic gates - as

used in ordinary computers - by encouraging the mould to crawl

through a series of carefully configured tubes.

Odd sort of logic

The gates are treated to ensure that mould creeping though one or

both of two " input " tubes eventually causes mould to either emerge

from a single " output " tube or to not emerge. In an " AND " gate, for

example, mould only exits from the output tube when it is fed into

both input tubes. Connecting many such tubes together can be used to

perform more complex calculations, albeit at a very slow speeds

(slime mould's top speed is 1 centimetre per hour).

As with Zauner's research, potential applications are not very

clear. But one noteworthy benefit is that a mould-based logic gate

will naturally repair itself. So biological logic gates could

perhaps be used in certain situations as a more resilient

alternative to electronic gates.

Zauner suggests that genetically modifying (GM) slime mould might

enhance its abilities. He points out that GM bacteria is already

used in various types of environmental sensors. These sensors

respond to particular chemicals in a solution by activating

bioluminescent enzymes.

" Bio-hybrid systems are very interesting and I think it is a

technology that will come, " he told New Scientist, " It's at the

interface between animate and inanimate matter. "

Adamatzky agrees. " There are a wide range of possible applications, "

he says, " from controllers and hybrid electronics for monitoring the

environment, to soft-bodied intelligent systems. "