When most people think of 3D printing, they imagine controlled lab settings or factory floors. At Cornell University, Assistant Professor Sriramya Nair and her team are testing whether the same technology can operate several meters underwater. Their goal is to develop a method for 3D printing concrete directly on the seafloor, potentially transforming how maritime infrastructure is built and repaired.
Hu, L., Zhang, A., & Warshel, A. (2025). Exploring evolutionary trajectories of drug resistance. Proceedings of the National Academy of Sciences, 122(45). https://doi.org/10.1073/pnas.2517715122
The project began after the U.S. Defense Advanced Research Projects Agency issued a call for proposals in late 2024. The agency challenged research teams to design a 3D printable concrete mixture that could be deposited underwater at shallow depths. The constraints were significant. The material needed to function in continuous water exposure and contain mostly seafloor sediment, with only a limited amount of cement. The timeline was also tight, with just one year to demonstrate feasibility.
Assistant Professor Sriramya Nair from Cornell University stated,
“We want to be constructing without being disruptive. If you have a remotely operated underwater vehicle that shows up on site with minimal disturbance to the ocean, then there is a way to build smarter and not continue the same practices that we do on the land.”
Nair’s group had prior experience working with a large scale industrial robot capable of printing concrete structures on land. Extending that capability to underwater conditions required rethinking both material composition and fabrication control. Water introduces a range of complications, the most immediate being washout. In underwater environments, cement particles can disperse before binding, weakening the structure. Traditional anti washout chemical admixtures increase viscosity, but overly viscous mixtures are difficult to pump through a robotic extrusion system. Achieving a workable balance between pumpability, cohesion, and structural stability became central to the research.
In parallel, DARPA’s requirement to incorporate seafloor sediment introduced another layer of complexity. Transporting cement to remote marine sites is expensive and logistically challenging. If sediment already present at the site can form the bulk of the material, construction becomes more practical and potentially less carbon intensive. However, sediment characteristics vary widely, and fine particles can influence strength development and print stability.
To address these issues, Nair assembled an interdisciplinary team. The materials subgroup focused on mixture design and mechanical performance, while the fabrication subgroup developed sensing and control systems for underwater operation. Collaborators include Nils Napp from electrical and computer engineering, Greg McLaskey from civil and environmental engineering, Uli Wiesner from materials science and engineering, and Jenny Sabin from architecture. Additional researchers from the University of Michigan, Clarkson University, and the University of Arizona are contributing to the effort.
Testing has taken place in controlled laboratory settings, where the team conducts repeated underwater prints in large water tanks. These experiments allow close monitoring of layer deposition, bonding between layers, and compressive strength development. The researchers are not only evaluating whether the material holds its shape during extrusion but also whether successive layers fuse effectively to create structural integrity.
Printing underwater introduces challenges that extend beyond material chemistry. Visibility can drop quickly when sediment is disturbed, making direct visual inspection impractical. Napp’s group has been developing integrated sensing systems that attach to the robotic arm, enabling real time monitoring of deposition even in turbid water. The aim is to adjust the printing path dynamically if irregularities are detected. Achieving this level of autonomy is critical, as sending divers to manually inspect structures during construction is not always feasible.
The culmination of the DARPA challenge will involve multiple teams printing an arch underwater as part of a competitive demonstration. An arch is a deliberate choice, as it tests structural performance under compression and requires accurate geometry to maintain stability. For Nair’s team, integrating optimized material mixtures with reliable sensing and robotic control has become the immediate priority.
Beyond the competition, the implications extend to maritime infrastructure more broadly. Ports, bridge foundations, offshore energy installations, and coastal defenses often require underwater repairs. Traditional methods can be disruptive, costly, and dependent on large support vessels. A robotic system capable of depositing concrete directly at the site could reduce both operational complexity and environmental disturbance.
Underwater additive manufacturing is still in early stages, and several questions remain. Long term durability in marine environments, resistance to saltwater corrosion, and structural performance under dynamic loads all require further validation. However, the combination of locally sourced sediment, robotic fabrication, and adaptive sensing represents a shift in how engineers may approach construction below the waterline.
For now, the team continues to refine mixture proportions, sensor integration, and robotic control algorithms in preparation for field demonstrations. If successful, underwater 3D printing could move from experimental tanks to real marine environments, offering a new method for building and maintaining the infrastructure that supports global trade and coastal communities.
Adrian graduated with a Masters Degree (1st Class Honours) in Chemical Engineering from Chester University along with Harris. His master’s research aimed to develop a standardadised clean water oxygenation transfer procedure to test bubble diffusers that are currently used in the wastewater industry commercial market. He has also undergone placments in both US and China primarely focused within the R&D department and is an associate member of the Institute of Chemical Engineers (IChemE).
