Stable, chronic in-vivo recordings from a fully wireless subdural-contained 65,536-electrode brain-computer interface device.

Minimally invasive, high-bandwidth brain-computer-interface (BCI) devices can revolutionize human applications. With orders-of-magnitude improvements in volumetric efficiency over other BCI technologies, we developed a 50-µm-thick, mechanically flexible micro-electrocorticography (µECoG) BCI, integrating 256×256 electrodes, signal processing, data telemetry, and wireless powering on a single complementary metal-oxide-semiconductor (CMOS) substrate containing 65,536 recording and 16,384 stimulation channels, from which we can simultaneously record up to 1024 channels at a given time. Fully implanted below the dura, our chip is wirelessly powered, communicating bi-directionally with an external relay station outside the body. We demonstrated chronic, reliable recordings for up to two weeks in pigs and up to two months in behaving non-human primates from somatosensory, motor, and visual cortices, decoding brain signals at high spatiotemporal resolution.

Quantitative evaluation of released nanomaterials from carbon nanotube epoxy nanocomposites during environmental exposure and mechanical treatment.

Carbon nanotubes (CNTs) are promising nanomaterials exhibiting high thermal and electrical conductivities, significant stiffness, and high tensile strength. As a result, CNTs have been utilized as additives to enhance properties of various polymeric materials in a broad range of fields. In this study, we investigated the release of CNTs from CNT epoxy nanocomposites exposed to environmental weathering and mechanical stresses. The presence and amount of CNTs released from degraded polymer nanocomposites is important because CNTs can impact physiological systems in humans and environmental organisms. The weathering experiments in this study included nanocomposite exposure to both UV and a water spray, to simulate sunlight and rain exposure, whereas mechanical stresses were induced by shaking and ultrasonication. CNT release from epoxy nanocomposites was quantified by a 14C-labeling method that enabled measurement of the CNT release rates after different weathering and mechanical treatments. In this study, a sample oxidizer was used prior to liquid scintillation counting, because it was shown to reduce interferences from the presence of polymeric materials and achieve a high recovery (95%). Polymer nanocomposite degradation was confirmed by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), and light microscopy. A continuous release of 14C-labeled nanomaterials was observed after each UV and simulated rain exposure period, with 0.23% (mass/mass) of the total embedded mass of CNTs being released from the CNT nanocomposite during the full weathering process, suggesting that the water spray induced sufficient mechanical stress to eliminate the protective effect of the surface agglomerated CNT network. Importantly, additional mechanical stresses imposed on the weathered nanocomposites by shaking and ultrasonication resulted in further release of approximately 0.27% (mass /mass).

Understanding the Interactions of CO2 with Doped and Undoped SrTiO3.

SrTiO3 and doped SrTiO3 have a wide range of applications in different fields. For example, Rh-doped SrTiO3 has been shown to have photocatalytic activity for both hydrogen production and CO2 conversion. In this study, both undoped and Rh-doped SrTiO3 were synthesized by hydrothermal and polymerizable complex methods. Different characterizations techniques including X-ray photoelectron spectroscopy (XPS), XRD, Raman, and UV/Vis spectroscopy were utilized to establish correlations between the preparation methods and the electronic/structural properties of Rh-doped SrTiO3 . The presence of dopants and oxygen vacancies substantially influenced the CO2 interactions with the surface, as revealed by the in situ infrared spectroscopic study. The presence of distinctly different adsorption sites was correlated to oxygen vacancies and oxidation states of Ti and Rh.

Development of a conceptual framework for evaluation of nanomaterials release from nanocomposites: environmental and toxicological implications.

Despite the fact that nanomaterials are considered potentially hazardous in a freely dispersed form, they are often considered safe when encapsulated into a polymer matrix. However, systematic research to confirm the abovementioned paradigm is lacking. Our data indicates that there are possible mechanisms of nanomaterial release from nanocomposites due to exposure to environmental conditions, especially UV radiation. The degradation of the polymer matrix and potential release of nanomaterials depend on the nature of the nanofillers and the polymer matrix, as well as on the nature of environmental exposure, such as the combination of UV, moisture, mechanical stress and other factors. To the best of our knowledge there is no systematic study that addresses all these effects. We present here an initial study of the stability of nanocomposites exposed to environmental conditions, where carbon nanotube (CNT) containing polymer composites were evaluated with various spectroscopic and microscopic techniques. This work discusses various degradation mechanisms of CNT polymer nanocomposites, including such factors as UV, moisture and mechanical damage. An in vivo ingestion study with Drosophila showed reduced survivorship at each dose tested with free amine-functionalized CNTs, while there was no toxicity when these CNTs were embedded in epoxy. In addition to developing new paradigms in terms of safety of nanocomposites, the outcomes of this research can lead to recommendations on safer design strategies for the next generation of CNT-containing products.