Another reason previous attempts have not been entirely successful was because the impedance of the electrodes did not match that of the insect's tissue. This probe is made of a polyimide polymer coated with gold and carbon nanotubes, and its impedance is much closer to that of nerve tissue. One end of the probe is a ring that clamps around the VNC. The inside of the ring has five electrodes which stimulate distinct nerve bundles within the VNC.
Attached to the probe is a wireless stimulator, which contains a radio receiver, as well as a battery and a device to generate electrical pulses. The team implanted the device in the abdomen of a tobacco hawkmoth (Manduca sexta). As it weighs less than half a gram, it is easy for the moth to carry. "Their wingspan is the width of your hand," says Voldman. "These are big guys."
i-MAVs and FNP implantation. (a) Schematic of the FNP insertion process, showing how the split-ring can be opened to fit around the VNC. (b) Illustration of i-MAV including moth, FNP and wireless stimulator.
Journal of Neuroscience Methods - Insect-machine interface: A carbon nanotube-enhanced flexible neural probe