ballpoint that detects if we are forging a signature
or a substitute in miniature for the CD-ROM are some
of the applications that can be carried out using
3 or 5 times thinner than a
human hair, these fine threads were invented in the
old Soviet Union for military purposes but, the broader
scientific community has been studying them for some
time now for other applications – including at the
University of the Basque Country (EHU).
Body and coating
Microwires have a metal body
and a glass coating. The size of the metal body is
usually about 1-20 µm radius and the glass coating
of between 5 and 20 µm thickness Being so fine,
the microthreads are totally flexible.
The main body of the microwire
made of a ferromagnetic alloy, the composition of
which varies depending on the metals used in the alloy
and on the final dimensions of the thread. As a result,
by balancing these two factors, the range of microwires
that can be obtained is very wide. But there is one
quality that they all have: they all have magnetic
properties. It is precisely these magnetic properties
and their diminutive size that make them so appreciated.
10 Gigabytes in 10 cm long
Amongst all the possible applications,
the research team at the EHU has launched a similar
project for using microwires as a system for storing
information. The microwires become diminutive substitutes
for the CD-ROM, given that information can be stored
magnetically on them, as with CDs.
To do this, researchers use
a magnetic properties present in certain microwires:
the magnetic bistability associated with a circular,
"bamboo"-type structure of domains. This
structure presents positive and negative magnetising
orientations at the surface of the microwire when
this is subjected to a magnetic field, i.e. the microwire
becomes magnetised. As a result, the two orientations
of the magnetisation at the surface can be interpreted
as the 1 and the 0 of a digital system (respectively
positive and negative).
Taking this property into account,
in order to create the replacement for the CD-ROM,
the microwire has to be divided up along its length.
Of course, the thread cannot be sectioned – the divisions
are carried out internally by means of a process of
The researchers calculate that
a 10 cm long microwire can carry out 10 million divisions
or cells and in each one of these a byte can be stored.
In order to store the byte, each one of these cells
is magnetised in one orientation or the other.
Once the information is recorded,
a system for retrieving and reading it has to be devised.
But the reading is not immediate. The initial response
of the reading is an electrical signal which has to
be amplified and processed in an appropriate manner
in order to access the real information.
These are the targets of this
project – but, of course, it is no easy task. The
greatest difficulty it seems will be with the reading
of information; i.e. the achievement of an electrical
signal sufficiently suitable to be converted subsequently
into a digital one.