At the Advanced System Technology branch (AST) of Fraunhofer Institute for Optronics, System Technologies, and Image Exploitation (IOSB) in Ilmenau, the underwater robotics department knows that even a single air bubble could theoretically cost millions if one of their valuable autonomous underwater vehicles (AUVs), developed for various clients, failed due to faulty electronic components. To prevent this, the electronics are encapsulated in silicone gel and completely degassed in the Memmert Vacuum Oven VO101. During an enlightening day at the institute, we were introduced to the fascinating challenges of underwater research by the AUV team.
Around 25 years ago, Professor Dr.-Ing. habil. Thomas Rauschenbach, Director of Fraunhofer IOSB-AST, and his team began underwater research, establishing himself in this specialized field. "The surface of the moon is better explored than the ocean," he remarked during our visit, noting that even space requires less durability and robustness from materials.
The vast, unexplored regions of the deep sea have intrigued scientists worldwide over recent decades, spurring the development of autonomous underwater vehicles (AUVs) at Fraunhofer IOSB-AST. These AUVs can now dive as deep as 6,000 meters, withstanding water pressure that would crush a conventional vehicle.
At a depth of 10 meters, underwater pressure reaches 1 bar, while at the Mariana Trench, the deepest point on Earth, pressure is a staggering 1000 bars. In earlier designs, underwater vehicles were built with pressure-resistant exteriors. However, the DEDAVE vehicles (Deep Diving AUV for Exploration) from Ilmenau are designed to be pressure neutral. This means the internal pressure, including that of all components, matches the external pressure. Thanks to their smaller, lighter construction, these vehicles achieve greater dive depths, longer deployment times, more efficient deep-sea data collection, and enhanced manoeuvrability. Outfitted with advanced lithium-ion batteries, efficient electric drives, and state-of-the-art sensors, cameras, and communication systems, they ensure precise data collection and real-time transmission. Each electronic component is carefully encapsulated to withstand the harsh ocean environment, including cold and high salinity.
The smaller “siblings” of these AUVs, remotely operated vehicles (ROVs), are also developed in Ilmenau for specific clients or research purposes. They communicate with a control computer via an 800-meter fiber optic cable, whereas the AUV stores collected data onboard and only transmits its location to the base via an underwater acoustic modem.
Each vehicle’s application is tailored to client needs or research objectives. Commercial uses include seafloor mapping, inspections of sheet pile walls, dams, locks, offshore wind farms, and pipelines, or research into underwater welding, joining, and repair.
With vacuum encapsulation in the Memmert VO101, Professor Rauschenbach’s team ensures that electronics are fully and bubble-free encapsulated in silicone gel—an essential step for the reliability and longevity of pressure-neutral underwater systems. The process runs at 5 mbar and room temperature for 2-5 minutes without requiring heat. Degassing is crucial for several reasons:
Before acquiring the Memmert Vacuum Oven VO101, components at the Ilmenau lab were encapsulated using a vacuum bell and pump. After thorough research, they chose this model for its spacious interior within a compact design, broad pressure range, stable pressure control, user-friendly interface, and low maintenance.
Professor Dr.-Ing. habil. Thomas Rauschenbach noted, “The Memmert Vacuum Oven was the largest model available with an integrated vacuum pump and pump control. Its vacuum range between 5 and 1100 mbar ensures precise pressure conditions and reproducibility.”
“We have come to know Memmert as a reliable and flexible partner, and we look forward to discussing specific features and configurations with them in the future,” he concluded.
Memmert extends its deepest gratitude to the Fraunhofer IOSB-AST team, especially Dr. Thomas Rauschenbach, Sebastian Matz, and Martin Käßler, for their invaluable insights and kind support in creating this article.