Biomedical Engineering Reference
In-Depth Information
(
Figure 8.19c
), its respiratory CO
2
output was monitored in a chamber where it was allowed to
lap its wings (i.e., “ly” without moving). he neurotoxins (l-glutamic acid, L-aspartate acid
[LLA], or γ-aminobutyric acid) were loaded in a reservoir capped by a gold membrane that could
be dissolved electrochemically on command by application of a small voltage, which caused the
release of the chemicals into the thorax of the insect and the (reversible) wing paralysis within
90 seconds (
Figure 8.19d
and
e
).
Erickson's remarkable achievement, however, has the obvious shortcoming that the moth
is not free to go, so it is not practical for ield applications. A team led by Tom Daniel at the
University of Washington (Seattle) and a team led by Joel Voldman at the Massachusetts Institute
of Technology (Cambridge) have accomplished what only a few years ago was the subject of sci-
ence iction talk: to be able to remote control a moth in free light (
Figure 8.20
). he clever
design of the electrodes, which clamp circumferentially around the nerve cord in a spoke-like
manner, plays an important role in the success of the design (
Figure 8.20a
and
b
). Implantation,
as with Erickson's system, is performed at the pupal stage (2 days before eclosion) to mini-
mize rejection. Stimulation of the adult elicits abdominal motions (presumably by activating
motoneurons or interganglionic neurons) that are used to bias the light path. here is a design
trade-of that occurs when more electrode tips are introduced to provide for more stimulation
points: the spokes cannot penetrate as deep into the tissue. (Four tips did not provide enough
stimulation points, and eight tips were too small, so a compromise design was reached with six
electrodes.)
a
c
100 µm
d
Force
Split-ring
Pl
Site
Au
2 mm
Protruding tip
Pl
Force
e
f
Insert onto nerve cord
b
Electrode
500 µm
g
FSE
Nerve cord
Wireless
communication link
Tissue
FIGURE 8.20
Moth.light.control.with.a.wireless.neural.microstimulation.system..(From.Wei.Mong.
Tsang,. Alice. L.. Stone,. Zane. N.. Aldworth,. John. G.. Hildebrand,. Tom. L.. Daniel,. Akintunde. Ibitayo.
Akinwande,. and. Joel. Voldman,. “Flexible. split-ring. electrode. for. insect. light. biasing. using. multi-
site. neural. stimulation,”.
IEEE Trans. Biomed. Eng
.,. 57,. 1757,. 2010.. Figure. contributed. by. Joel.
Voldman.)
