Biomaterials for MEMS

82 References

will alleviate the tissue reaction. Surface modification of electrodes with anti-

inflammatory compounds

102

appears to lessen the glial encapsulation, but some

gliosis is still present, so research in electrode surface modification remains an

important topic for the realization of successful chronic neural electrodes.

The insertion of probes into the brain can be done quickly or slowly. Faster in-

sertion speeds and sharper needles result in less strain to the surrounding tissue.

103

This reduced strain may minimize tissue damage due to insertion, because pro-

cesses and cells near the electrode remain relatively undisturbed while those in

the electrode’s path are completely severed.

92

However, some investigators insist

that slower insertions lead to greater longevity in chronic recordings.

104

This may

be because slow insertions allow cells and their processes time to be displaced and

moved, rather than impaled, by microelectrodes.

92

Insertion technique is far from

standardized in the neural interfacing fields, and no one technique may be best for

all MEMs devices, so insertion method will probably continue to be chosen on a

device-by-device basis.

4.4 CONCLUDING REMARKS

MEMs devices hold immense promise for future neuroprosthetics and inves-

tigative biological studies. In vitro devices allow the observation of individual

cell types and their reactions to environmental stimuli; the small volumes used,

inexpensive materials, and ability to batch fabricate devices reduces the cost to

perform such studies. In vivo microdevices are less damaging to neural tissues

than larger devices, some can be batch fabricated, and most are electrically or

chemically active. Such devices may one day allow patients who have lost normal

neural function to regain it.

Neuronal interfacing technology is far from completely optimized, but new

developments are always refining existing processes and opening new frontiers.

The implications for improved understanding of the nervous system and the

ability to improve patient quality of life are some of the strongest factors driving

thefieldtoday,andbecausethepromiseisevident,wecanexpecttoseeimportant

strides being made towards seamless integration of sensor and actuator technol-

ogy with the human nervous system in the future.

References

1

Nisch, W., et al., A thin-film microelectrode array for monitoring extracellular neuronal-

activity in vitro. Biosensors & Bioelectronics, 1994, 9(9–10): 737–741.

2

Wagenaar, D. A., J. Pine, and S. M. Potter, An extremely rich repertoire of bursting

patterns during the development of cortical cultures. BMC Neuroscience, 2006, 7: p.17.

3

Hammerle, H., et al., Extracellular recording in neuronal networks with substrate

integrated microelectrode arrays. Biosensors & Bioelectronics, 1994, 9(9–10): 691–696.

4

Meister, M., J. Pine, and D. A. Baylor, Multi-neuronal signals from the retina: Acquisi-

tion and analysis. Journal of Neuroscience Methods, 1994. 51: 95–106.

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