Construction is one of the world's largest carbon emitters, but innovative research from MIT suggests a transformative solution could be on the horizon. A team of engineers has developed a robotic assembly system using modular building blocks called "voxels" that could dramatically reduce the environmental footprint of construction while cutting both costs and build times.
Researchers at the Massachusetts Institute of Technology have published a feasibility study in the journal Automation in Construction that evaluates whether voxel-based robotic assembly could revolutionize how we build structures. Voxels are modular 3D subunits featuring lattice structures that can be assembled into complex, highly durable formations.
The research team conducted comprehensive assessments of multiple voxel designs and created three new optimized configurations specifically engineered for robotic assembly. They also developed a custom robotic assembler and an intuitive software interface capable of generating voxel-based building layouts and translating them into robot-executable instructions.
Their findings reveal remarkable potential: this voxel-based robotic assembly system could reduce embodied carbon—the total carbon emissions generated throughout a building material's lifecycle—by as much as 82% compared to conventional methods like 3D concrete printing, precast modular concrete, and steel framing.
Beyond environmental benefits, the system demonstrates competitive advantages in both cost and construction speed. However, researchers note that material selection for manufacturing voxels significantly impacts their overall carbon footprint and production expenses.
"I'm particularly excited about how the robotic assembly of discrete lattices can enable a practical way to apply digital fabrication to the built environment in a way that can let us build much more efficiently and sustainably," explains Miana Smith, a graduate student in MIT's Center for Bits and Atoms and the study's lead author.
Smith collaborated on the research with Paul Richard, a graduate student at École Polytechnique Fédérale de Lausanne in Switzerland and former visiting researcher at MIT; Alfonso Parra Rubio, a CBA graduate student; and senior author Neil Gershenfeld, an MIT professor and director of the Center for Bits and Atoms.
Engineering Better Building Blocks
For several years, scientists at the Center for Bits and Atoms have been pioneering voxel technology—lattice-structured construction units capable of forming objects with exceptional strength and stiffness, including aircraft wings, wind turbine blades, and space structures.
"Here, we are taking aerospace principles and applying them to buildings. Why don't we make buildings as efficiently as we make airplanes?" Gershenfeld asks, referencing his laboratory's prior collaborative work on voxel assembly with NASA, Airbus, and Boeing.
To assess voxel-based assembly viability for construction applications, the researchers first analyzed the mechanical performance and sustainability characteristics of eight existing voxel designs. These included a cuboctahedron constructed from glass-reinforced nylon and a Kelvin lattice made from steel.
Drawing from these evaluations, the team engineered three new voxel designs utilizing innovative geometry optimized for robotic assembly into larger structures. Their new configuration, based on a high-strength high-stiffness octet lattice, achieves mechanical self-alignment to form rigid structures.
"The interlocking nature of these voxels means we can get nice mechanical properties without needing to have a lot of connectors in the system, so the construction process can run a lot faster," Smith notes.
To accelerate on-site construction, the researchers designed a robotic assembly system featuring inchworm-inspired robots that navigate across voxel structures by anchoring and extending their bodies. These Modular Inchworm Lattice Assembler robots, dubbed MILAbots, employ grippers at each end to position voxel building blocks and engage snap-fit connections.
"The robots can assemble the voxels by dropping them into place and then stepping on them to have the pieces interlock. We can do precise maneuvers based on the mechanical relationship between the robots and the voxels," Smith explains.
The team analyzed the embodied carbon required to fabricate their new voxel designs using three different materials: plastic, plywood, and steel. They then evaluated the throughput and projected costs of using the robotic assembly system to construct a simple single-story building. These estimates were compared against performance metrics from other construction methodologies.
Environmental Impact and Practical Benefits
The research revealed that most existing voxel designs, particularly those manufactured from plastics, performed poorly compared to established methods in sustainability metrics. However, the steel and plywood voxels developed by the team delivered substantial environmental advantages.
For example, using their steel voxels would generate only 36% of the embodied carbon required by 3D concrete printing and just 52% of the embodied carbon associated with precast concrete. The plywood voxels demonstrated the lowest carbon footprint, requiring approximately 17% and 24% of the embodied carbon needed by those respective methods.
"There is still a potential viable option for a plastics-based voxel approach, we just have to be a bit more strategic about which types of plastics, infills, and geometries we use," Smith observes.
Additionally, projected on-site assembly times for the steel and wood voxel approaches averaged 99 hours, compared to 155 hours for existing construction methods.
These speed advantages stem from the distributed nature of voxel-based assembly. While a single MILAbot working independently is considerably slower than traditional techniques, deploying a team of 20 robots operating in parallel allows the system to match or exceed existing automation methods at a reduced cost.
"One benefit of this method is how incremental it is. You can start building, and if it turns out you need a new room, you can just add onto the structure. It is also reversible, so if your use changes, you can disassemble the voxels and change the structure," Gershenfeld explains.
The research team also developed a user interface enabling architects and builders to input or hand-design voxelized structures. The automated system calculates the optimal paths MILAbots should follow during construction and transmits commands to the robotic assemblers.
While important considerations including scalability, durability, long-term robustness, and fire resistance require further investigation before widespread deployment, these initial results demonstrate significant potential for automated on-site construction applications.
The next phase of this project will involve a larger testbed in Bhutan, utilizing the "super fab lab" that the Center for Bits and Atoms helped establish there. Researchers will replicate the robots to test construction for a planned sustainable city development.
Future research priorities include studying voxel structural stability under lateral loads, enhancing the design tools to account for system physics, improving MILAbot capabilities, and evaluating voxels with integrated sheeting, insulation, or electrical and plumbing routing.
"Our work helps support why doing this type of distributed robot assembly might be a practical way to bring digital fabrication into building construction," Smith concludes.
Source credit: TechXplore
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