Softening SCS arrays meet the needs for research-grade devices in rats and could be developed into human devices in the future.

Softening neural interfaces are implanted stiff to enable precise insertion, and they soften in physiological conditions to minimize modulus mismatch with tissue. In this work, a high-charge-injection-capacity iridium electrode fabrication process is detailed. For the first time, this process enables integration of iridium electrodes onto softening substrates using photolithography to define all features in the device. Importantly, no electroplated layers are utilized, leading to a highly scalable method for consistent device fabrication. The iridium electrode is metallically bonded to the gold conductor layer, which is covalently bonded to the softening substrate via sulfur-based click chemistry. The resulting shape-memory polymer neural interfaces can deliver more than 2 billion symmetric biphasic pulses (100 μs/phase), with a charge of 200 μC/cm(2) and geometric surface area (GSA) of 300 μm(2). A transfer-by-polymerization method is used in combination with standard semiconductor processing techniques to fabricate functional neural probes onto a thiol-ene-based, thin film substrate. Electrical stability is tested under simulated physiological conditions in an accelerated electrical aging paradigm with periodic measurement of electrochemical impedance spectra (EIS) and charge storage capacity (CSC) at various intervals. Electrochemical characterization and both optical and scanning electron microscopy suggest significant breakdown of the 600 nm-thick parylene-C insulation, although no delamination of the conductors or of the final electrode interface was observed. Minor cracking at the edges of the thin film iridium electrodes was occasionally observed. The resulting devices will provide electrical recording and stimulation of the nervous system to better understand neural wiring and timing, to target treatments for debilitating diseases, and to give neuroscientists spatially selective and specific tools to interact with the body. This approach has uses for cochlear implants, nerve cuff electrodes, penetrating cortical probes, spinal stimulators, blanket electrodes for the gut, stomach, and visceral organs and a host of other custom nerve-interfacing devices.

more complex applications that more closely mimic the behavior and size scale of biology. To these ends, bioelectronic devices must demonstrate several critical features: be manufacturable via a repeatable fabrication processes; exhibit resistance to mechanical deformation; and demonstrate electrical reliability.Technologies based on TFTs allowed the microfabrication of large-area applications such as flat-panel displays, which were difficult to develop on flexible substrates due to their high temperature processing requirements and were difficult to develop on silicon due to the cost associated with using such a large area of silicon. After Nomura et al. presented TFTs based on indium-gallium-zinc-oxide (IGZO) semiconductors, these became the key component for the fabrication of system-on-glass applications. [9] The electrical performance of IGZO TFTs exhibited high-mobility values (>10 cm 2 V −1 s −1 ) compared with organic semiconductors (<0.1 cm 2 V −1 s −1 ) or amorphous silicon (≈1 cm 2 V −1 s −1 ). [9][10][11] More recently, IGZO has been reported with mobility values of 29 cm 2 V −1 s −1 by Jeon et al. to develop a voltage compensation circuit. [12] A transparent circuit based on IGZO TFTs with mobility of 70 cm 2 V −1 s −1 was presented by Liu et al. with frequency response on the order of megahertz. [13] In addition, Liu et al. incorporated silver nanowires into IGZO to achieve a mobility of 174 cm 2 V −1 s −1 , [14] but with limits on processing and scalability. Due to their relative low processing temperature requirements (compared with silicon technologies) and high-mobility, semiconductor devices made from IGZO allow for the development of emerging technologies such as flexible and wearable electronics: active-matrix phosphorescent organic light emitting diodes displays by O'Brien et al., [15] an amplifier by Münzenrieder et al., [16] and a full color organic light-emitting diodes (OLED)-based display [4] among others.There is a tradeoff among the various processing temperatures used during TFT fabrication, which affects electrical performance and the thermal compatibility with flexible substrates. Important performance characteristics of the electronic components include field effect mobility (μ FE ), threshold voltage (V TH ), changes in V TH (ΔV TH ), and subthreshold swing (SS). The use of elevated temperature during device processing can help improve the quality of amorphous IGZO, as well as its interface with a dielectric. According to Nomura, Flexible electronics are attracting great interest in healthcare, where devices such as thin-film transistors (TFTs) on polymer substrates facilitate biomedical applications requiring complex circuits in soft packages. Consequently, a repeatable process to fabricate reliable, stable electronic components on flexible substrates is required. Here, thermoset thiol-ene/acrylate shape memory polymer (SMP) substrates house indium-gallium-zinc-oxide (IGZO) TFTs and logic circuits: resulting devices exhibit stable behavior after thermal annealing at 250 °C. Fabr...

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