Fig. 4: Soft materials to improve long-term stability.

a Elastic modulus of brain tissues and commonly used materials for implantable neural probes. b Neural probes with commonly used plastic polymer substrates, including polyimide, Parylene C, and SU-8 (Reproduced with permission from refs. ^68,126,127). c Neural probes with elastomer-based substrates, including PDMS, Ecoflex, and PFPE-DMA (Reproduced with permission from refs. ^74,75,78,79). d Neural probes with hydrogel-based substrates (Reproduced with permission from ref. ⁸³). e Neural probes with liquid metal electrodes (Reproduced with permission from ref. ⁹⁴). f Neural probes with conductive polymer electrodes (Reproduced with permission from ref. ⁸⁵).