Biology subjects

Donaldson, N.

Publications and source records attributed to Donaldson, N..

3 recordsLinked to original sources

bioRxiv2025

On the Stability of Silicone-Encapsulated CMOS ICs for Active Implantable Devices: 4.3 Years of Accelerated Life Testing

The reliability of polymer-encapsulated CMOS integrated circuits (ICs) is critical for the development of miniaturised active implantable medical devices (AIMDs). Traditional hermetic packaging methods become impractical as implant sizes decrease, necessitating alternative methods of protection from body fluids. This study evaluates the long-term stability of silicone-encapsulated CMOS ICs through accelerated life testing using electrical impedance spectroscopy (EIS) and visual inspection. CMOS interdigitated combs (IDCs) were encapsulated in medical grade silicone rubber, subjected to immersion in phosphate-buffered saline (PBS), and tested at elevated temperatures (47{degrees}C, 67{degrees}C, and 87{degrees}C) under both 5V DC and biphasic voltage biases for up to 4.3 years. Remarkably, no insulation failures were observed in the IDCs, with no significant water ingress detected through impedance changes. Failures at the ICs were limited to wire bond open-circuits, though there was some pad discolouration/corrosion. Other failures were elsewhere, not at the ICs. This highlights the stability of modern silicon oxide/silicon nitride bilayer passivation when encapsulated in adhesive silicone rubber. Visual analysis revealed occasional solder and aluminium pad corrosion, particularly at higher temperatures, but these changes did not correlate with EIS failures. The findings suggest that silicone encapsulation, combined with passivation and shielding strategies, enables long-term IC reliability in biofluid environments. To our knowledge, this paper presents the longest reported accelerated ageing study of test structures for implantable devices, laying the groundwork for the integration of silicone-encapsulated ICs into next-generation chip-scale bioelectronic implants.

biochemistry↗

bioRxiv2024

Longevity of Implantable Silicon-ICs for Emerging Neural Applications: Evaluation of Bare Die and PDMS-Coated ICs After Accelerated Aging and Implantation Studies

Silicon integrated circuits (ICs) are central to the next-generation miniature active neural implants, whether packaged in soft polymers for flexible bioelectronics or implanted as bare die for neural probes. These emerging applications bring the IC closer to the corrosive body environment, raising reliability concerns, particularly for long-term clinical use. Here, we evaluated the long-term electrical and material stability of silicon-ICs from two foundries, after one-year accelerated in vitro and in vivo animal studies. The ICs featured various custom-designed test structures and were partially PDMS coated, creating two regions on each chip, uncoated "bare die" and "PDMS-coated". During the accelerated in vitro study, ICs were electrically biased and periodically monitored. Results demonstrated stable electrical performance for at least a year, suggesting that bare die ICs can function in the body for months. Despite electrical stability, material analysis revealed chemical and electrically driven degradation of the IC passivation in the bare die regions. In contrast, PDMS-coated regions revealed no such degradation, making PDMS a highly suitable encapsulant for ICs intended for years-long implantation. Based on the new insights, guidelines are proposed that may enhance the longevity of implantable ICs, significantly broadening their applications in the biomedical field.

neuroscience↗

bioRxiv2024

Single cell RNA-sequencing of Ewing sarcoma tumors demonstrates transcriptional heterogeneity and clonal evolution.

Ewing sarcoma is the second most common bone cancer in children, accounting for 2% of pediatric cancer diagnoses. Patients who present with metastatic disease at the time of diagnosis have a dismal prognosis, compared to the >70% 5-year survival of those with localized disease. Here, we utilized single cell RNA-sequencing to characterize the transcriptional landscape of primary Ewing sarcoma tumors and surrounding tumor microenvironment (TME). Copy-number analysis identified subclonal evolution within patients prior to treatment. Primary tumor samples demonstrate a heterogenous transcriptional landscape with several conserved gene expression programs, including those composed of genes related to proliferation and EWS targets. Single cell RNA-sequencing and immunofluorescence of circulating tumor cells at the time of diagnosis identified TSPAN8 as a novel therapeutic target.

cancer biology↗