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Neural implants, which include integrated circuits (ICs), are essential tools in advancing our understanding of the brain and treating neurological disorders. Constructed primarily from silicon, these implants must be compact and flexible to function effectively within the human body. However, the corrosive environment inside the body presents a significant challenge to the durability of these silicon-based devices. To address this issue, a research team from the Bioelectronics Section, led by Dr. Vasiliki (Vasso) Giagka, is investigating the degradation processes of silicon ICs within the body. Their approach involves coating these chips with soft polydimethylsiloxane (PDMS) elastomers, which act as barriers against bodily fluids, thereby enhancing the longevity of these implantable devices. The team’s findings mark a substantial advancement in the biomedical field and have been detailed in a study published in Nature Communications.
Importance of Neural Implants in Healthcare
Neural implants play a vital role in both the research and treatment of various brain conditions, including Parkinson’s disease and clinical depression. These devices can stimulate, block, or record neuronal activity, making them critical for both therapeutic applications and research purposes. For long-term use, the resilience of these neural implants is essential.
“The potential of miniaturized neural implants to revolutionize healthcare is immense; however, their stability over extended periods in the body poses a significant challenge,” says Vasso Giagka, a researcher at the Technical University Delft. “This study not only pinpointed the primary obstacles but also provided actionable strategies to improve the reliability of these devices, edging us closer to implementing safe and enduring clinical applications.”
The research team conducted rigorous evaluations of the electrical and material performance of silicon chips from two different manufacturers over a year, employing accelerated in vitro and in vivo tests. The investigation involved combining bare silicon ICs with soft PDMS elastomers to create protective barriers against body fluids. The chips were examined in configurations featuring a ‘bare die’ section and a ‘PDMS-coated’ section. During the accelerated in vitro tests, chips were immersed in heated saltwater and subjected to electrical biasing. Continuous monitoring indicated that these chips maintained stable electrical performance, demonstrating their functionality even in environments mimicking bodily fluids.
Further analysis revealed that while the bare sections of the chips experienced some degradation, the PDMS-coated areas showed only minimal deterioration. This result highlights PDMS’s effectiveness as a long-term encapsulation material, suggesting its potential for years of reliable implantation. The research concluded with proposals for design guidelines that could enhance the durability and broaden the practical applications of these chips in the biomedical sector.
Unexpected Findings
“We were all taken aback,” shares Kambiz Nanbakhsh, a PhD student and the lead author of the study. “I didn’t anticipate that microchips would remain so stable under conditions of prolonged soaking and electrical biasing.”
Dr. Giagka also expressed her enthusiasm regarding the outcome of their research, stating, “Our results indicate that silicon chips can function reliably within the body for several months, provided they are meticulously designed. By overcoming the challenges associated with long-term reliability, we are paving the way for advancements in miniaturized neural implants as well as next-generation bioelectronic devices for clinical uses.”
She further underscores the significance of PDMS in this context: “This research highlights the essential protective function of silicone encapsulation against the degradation of integrated circuits. By maximizing the lifespan of neural implants, our findings create opportunities for more effective technologies in brain-computer interfaces and medical therapies.” Kambiz echoes her sentiments, expressing hope that their findings will yield useful innovations for various medical applications.
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