Consultant engineer Dr Jon Spratley has won the
IMechE
MediMaton 'best recent PhD thesis' prize for a multi-contact brain
probe that can be injected through a needle.
The 1.3mm diameter probe would be inserted into the motor cortex
of motor neurone disease sufferers to allow them, in principle, to
operate a computer, speech synthesiser or wheelchair.
"I built a prototype of part of the sensor: the contact spikes
were micromachined from epoxy, and I built the mechanical structure
that would support the probe, " Spratley told Electronics
Weekly.
In Spratley's concept, the probe is injected with a needle into
the brain through a standard 16mm medical access hole drilled into
the skull.
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Up to 50 15x15um spikes 1-2mm long (Spratley prototyped 16)
project from the tip of the probe and connect with neurons.
At the back of the probe, on the surface of the brain, four
wings unfurl as the needle is removed to support four 1mm diameter
coil antennas.
In operation, the probe is effectively a passive
magnetically-coupled tag.
Its base station is 16mm in diameter, and is permanently
inserted into the skull hole instead of a bone plug.
Why not use wires between the probe and the basestation?
"With a wireless link, the dura - the brain's protective sheath
- can be completely sealed," said Spratley," and the brain moves
around inside the skull."
The flexable microsensor design maximises the inductive
antenna area
No electronics were actually built. "I did some analysis of the
likely electronics layout using a passive tag to gauge the size for
the inductor coils," said Spratley. "The majority of research was
into the spikes, to determine how we could make them so they
couldn't fail during the process."
The square spikes were actually made on their sides: wet etched
from a patterned epoxy layer. Each array of spikes included a
snap-off handling tag.
The silicon wafer was etched away, then the spikes were erected
on the probe tip using a hand-controlled micromanipulator, said
Spratley. After which the handling tags were removed.
For ethical reasons, the spikes have only been tested on brain
slices, but in a final system they would be positioned in the
sufferer's brain to pick up the signals that are generated when
someone uses muscles, a left bicep, for example.
Spratley points out that only seven or so unique signals have to
be extracted to provide computer mouse-like commands to a PC.
The microsensor wing prototype folded ready for
injection within a 1.3 mm internal diameter cannula
During his three year research programme at the University of
Birmingham, has anything been uncovered that could prevent the
probe from one day being part of a thought-controlled
interface?
"There was no major stumbling block uncovered," he said.
Pictured (very top): Dr Jon Spratley receiving his
certificate and a cheque for £750 from Dr Patrick Finlay, MD of
category sponsor MediMaton.
Spratley now works for Cambridgeshire-based consultancy
42 Technology.