PMID-23852172 A comparison of polymer substrates for photolithographic processing of flexible bioelectronics
- Describe the deployment of shape-memory polymers for a neural interface
- Thiol-ene/acrrylate network (see figures)
- Noble metals react strongly to the thiols, yielding good adhesion.
- Cr/Au thin films.
- Devices change modulus as they absorb water; clever!
- Transfer by polymerization patterning of electrodes (rather than direct sputtering).
- This + thiol adhesion still might not be sufficient to prevent micro-cracks.
- "Neural interfaces fabricated on thiol-ene/acrylate substrates demonstrate long-term fidelity through both in vitro impedance spectroscopy and the recording of driven local field potentials for 8 weeks in the auditory cortex of laboratory rats. "
- Impedance decreases from 1M @ 1kHz to ~ 100k over the course of 8 weeks. Is this acceptable? Seems like the insulator is degrading (increased capacitance; they do not show phase of impedance)
- PBS uptake @ 37C:
- PI seems to have substantial PBS uptake -- 2%
- PDMS the lowest -- 0.22%
- PEN (polyethelene napathalate) -- 0.36%
- Thiol-ene/acrylate 2.19%
- Big problem is that during photolithographic processing all the shape-memory polymers go through Tg, and become soft/rubbery, making thin metal film adhesion difficult.
- Wonder if you could pattern more flexible materials, e.g. carbon nanotubes (?)
- Good paper, many useful references!
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