Long-term recording reliability of liquid crystal polymer µECoG arrays

Abstract

Objective. The clinical use of microsignals recorded over broad cortical regions is largely limited by the chronic reliability of the implanted interfaces. Approach. We evaluated the chronic reliability of novel 61-channel micro-electrocorticographic (μECoG) arrays in rats chronically implanted for over one year and using accelerated aging. Devices were encapsulated with polyimide (PI) or liquid crystal polymer (LCP), and fabricated using commercial manufacturing processes. In vitro failure modes and predicted lifetimes were determined from accelerated soak testing. Successful designs were implanted epidurally over the rodent auditory cortex. Trends in baseline signal level, evoked responses and decoding performance were reported for over one year of implantation. Main results. Devices fabricated with LCP consistently had longer in vitro lifetimes than PI encapsulation. Our accelerated aging results predicted device integrity beyond 3.4 years. Five implanted arrays showed stable performance over the entire implantation period (247–435 days). Our regression analysis showed that impedance predicted signal quality and information content only in the first 31 days of recordings and had little predictive value in the chronic phase (> 31 days). In the chronic phase, site impedances slightly decreased yet decoding performance became statistically uncorrelated with impedance. We also employed an improved statistical model of spatial variation to measure sensitivity to locally varying fields, which is typically concealed in standard signal power calculations. Significance. These findings show that μECoG arrays can reliably perform in chronic applications in vivo for over one year, which facilitates the development of a high-density, clinically viable interface.

Ultra-Long-Term Reliable Encapsulation Using an Atomic Layer Deposited HfO2/Al2O3/HfO2 Triple-Interlayer for Biomedical Implants

“…The results for the PI/ALD-3/PI film reveal that the impedance and the phase angle remain stable during exposure to PBS, indicating that the barrier was not affected by the soaking environment. (Table 1) [12,44,45]. To the best of our knowledge, the soaking results reported in this paper represent an excellent long-term encapsulation and PI/ALD-3/PI has great potential for the development of long-term implantable medical electronic devices.…”

“…Minnikanti et al, Woods et al, and Forssell et al have put effort into evaluating the lifetime of barriers Al2O3/parylene C, LCP, and parylene C/TiO2/Al2O/TiO2 at an acceleration temperature (60 °C) in PBS, respectively. These barriers performed well up to a few hundred days under similar acceleration conditions (Table 1) [12,44,45]. To the best of our knowledge, the soaking results reported In a previous paper, we showed that a 16 µm PI (HD2611) has a high WVTR of 4.3 g•m −2 •day −1 while ALD-3 coated on the same thickness polyimide resulted in a significant improvement of WVTR to less than 5 × 10 −4 g•m −2 •day −1 [4].…”

Regulation of perceptual learning by chronic chemogenetic manipulation of parvalbumin-positive interneurons

“…First, we collected longitudinal data pertaining to behavioral performance but obtained a single readout of neuronal activity. In light of recent advances in devices for chronic and reliable neurophysiological recordings (Woods et al, 2018), future studies may collect both functional and behavioral data simultaneously over the whole training period to better understand the relationship between neuronal circuit function and performance. Future studies could also help determine whether these measures are correlated with PV expression.…”

Remote-Controlled Fully Implantable Neural Stimulator for Freely Moving Small Animal

“…The long-term reliability of the LCP encapsulation, including LCP-based electrode arrays and LCP packaging of electronics, has been demonstrated in the previous studies. These studies suggested that the lifetime of LCP encapsulation, including all the possible water penetration paths, e.g., LCP-LCP adhesion, LCP-metal adhesion, and LCP surface permeation, is estimated to be at least a few years at body temperature [40][41][42][43][44][45][46]. The only interface that has not been addressed in the previous studies is the 4ch/8ch connectors sealed by dental cement.…”