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Silicon Corrosion in Neutral Media: The Influence of Confined Geometries and Crevice Corrosion in Simulated Physiological Solutions
摘要： Silicon (Si) based implantable components are widely used to restore functionalities in the human body. However, there have been reported instances of Si corroding after only a few years of implantation. A key parameter often overlooked when assessing Si stability in-vitro, is the added constricting geometries introduced through in-vivo implantation. The influence of crevices and confined solutions on the stability of Si is presented in this study, considering two simulated physiological solutions: 0.01 M phosphate buffered saline (PBS) and HyClone Wear Test Fluid (WTF). It was found that Si is highly vulnerable to corrosion in confined/crevice conditions. High pitting corrosion susceptibility is found in a crevice, whereas a dissolution rate of ca. 3.6 nm/h at body temperature occurred due to local alkalization within a confined cathodic area. The corrosion rates could be increased by elevating the temperature and yielded linear Arrhenius relations, with activation energies of 106 KJ/mol in 0.01 M PBS and 109 KJ/mol in HyClone WTF, corresponding to a phosphorous-silicon interaction mechanism. Phosphorous species favored corrosion and contributed to enhanced Si dissolution, while chlorides were not so influential, and applied anodic potential induced pseudo-passivation. These results highlight the importance geometrical configurations can have on a material’s surface stability.
关键词： Silicon,Confined geometries,Corrosion,Physiological solutions,Implantable devices,Phosphorous-silicon interaction,Crevice
更新于2025-11-14 15:19:41
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Wirelessly Operated, Implantable Optoelectronic Probes for Optogenetics in Freely Moving Animals
摘要： Recording and interrogating brain activities using optical methods have become emerging technologies in neuroscience. Traditional tools for optogenetic stimulation in the deep brain are mostly based on implantable fibers, imposing constraints on the animal movement. Recently developed microscale light-emitting diodes (micro-LEDs), which can be wirelessly operated, serve as injectable light sources that directly interact with neural systems. Here, we exploit a wirelessly controlled, implantable system for optogenetic studies in behaving animals. Thin-film indium gallium nitride (InGaN)-based blue micro-LEDs transferred onto flexible probes are injected into the animal brain and optically activate channelrhodopsin-2 expressing neurons. A customized circuit module with a battery is employed to modulate the micro-LED, which is remotely controlled at a distance up to 50 m via 2.4-GHz radio frequency communications. The systems are implemented on freely moving mice, and demonstrate optogenetic modulation of locomotive behaviors in vivo. Moreover, independent and synchronous control of multiple animals is accomplished with the communication unit in the design circuit. The proposed system provides the potential for advanced optical neural interfaces and offers solutions to study complicated animal behaviors in neuroscience research.
关键词： optogenetics,Implantable devices,micro-light-emitting diodes (LEDs),wireless operation
更新于2025-09-09 09:28:46