Metal may be the Velcro of the future
Researchers at Texas A&M and Sandia National Laboratories have demonstrated a class of 3D-printed shape-memory alloy connections that snap together like building blocks yet carry structural loads far beyond conventional fasteners, adhesives, Velcro or plastic joints.
Like these interlocking bricks, a new 3D-printed metal connector from Texas A&M and Sandia National Laboratories locks into place, holds under load and pulls apart on command.
Researchers at Texas A&M University and Sandia National Laboratories have built a 3D-printed shape-memory alloy connector that locks together like a Lego brick. This connection point will have heavy-load capabilities while maintaining the ability to return to its initial shape after use. This technology is targeted toward industry, where traditional bolts are used for assembly in machinery.
The connections allow for continued engaging and disengaging without the loss of grip and wear on the material. This technology opens possibilities in satellite panels being locked into place after launch and drone arms being swapped out in seconds, all without the added weight of fasteners.
“For generations, engineers have relied on bolts, welds and adhesives to hold structures together,” said Dr. Ibrahim Karaman, Chevron Professor and head of the Department of Materials Science and Engineering. “This work suggests a different path where materials themselves provide the ability to connect, disconnect and reconnect while carrying significant loads. That capacity could enable a new class of adaptive structures that can be assembled, repaired and reconfigured in ways that are difficult to achieve today.”
A metal that bounces back
The trick to this is in the metal itself, nickel-titanium, often called Nitinol. The metal has superelastic ability, which means it can stretch much further than any ordinary metal with the ability to return to its original shape. Most metals recover only a small amount after being stretched until they are no longer usable, but Nitinol has a higher percentage of recovery.
That ability in Nitinol is what helps the team’s design work. It allows a passive metal tube that is pushed into an active metal lock. As the tube enters, the lock opens, then snaps back while grabbing it without the need for any adhesive, welds or fasteners. The shape is what provides the strength based on how they are pressed together. The researchers have called it a tube-lock interlocking metasurface.
Traditional bolts or screws work because they are separate hardware that bring two parts together. If the bolts are removed, the two parts will not hold. The team’s design combats this by allowing two surfaces to directly grip each other, resulting in a more efficient assembly time and reducing any additional weight from fasteners.
“The Lego analogy works because the joint is geometry-driven” said Dr. Abdelrahman Elsayed, an assistant research scientist in Karaman’s group. “But the difference is a metallic snap-fit powered by a reversable phase transformation inside the metal.”
This builds on work the team published in 2024, when they first presented these joints. The team shared how they could lock and unlock materials as the metal is heated and cooled. Now they have pushed further by engineering joints that snap back instantly under stress alone, without requiring heat.
Printing the part, layer by layer
The parts are made with a laser powder bed fusion, a form of metal 3D-printing. The laser isn’t just melting the powder; it is also shaping the internal structure and chemistry at the same time. Not enough energy will result in a partly fused powder, as too much energy creates cracks and pores in the final part.
“We’re not just 3D printing a shape” Elsayed said. “We’re trying to print the right chemistry, microstructure, texture and functional response into the metal.”
This requires the printed part to come out nearly flawless. The geometry must maintain the stretch range the metal could fully recover from. The team aimed for a 3% range in stretch. This was targeted for a more reliable final product. Pushing past that would result in the metal holding to a slight permanent bend each time, slowly reducing the ability to maintain the grip strength.
To test this, the team repeated the process of snapping in and snapping out eight times. In this test, the researchers reported that the initial cycle took the most force. As they continued, the material settled into the range they were hoping for, resulting in the part never failing. They used computer models to predict where the metal would stretch along the process and by how much. These predictions matched the real parts. This resulted in a near-zero deformation with each cycle.
Where it could go
The researchers are slow to call these products, but possibilities. The lab work has proven the concept, but they are far from getting to a spacecraft or even a human body. There is more testing that needs to be conducted; testing for fatigue, vibrations and consistency when it comes to aerospace. Human application, biocompatibility, sterilization and many other medical approvals will be needed.
With the locks being able to engage, release and reengage while still carrying a load, this points to what the team is calling an adaptive structure: hardware that does not need to stay in a fixed shape.
“The long-term vision is load-bearing hardware that can be assembled, released and reconfigured without bolts, welds, adhesives or external heating,” Elsayed said.
Karaman sees the significance reaching well beyond any single connection. While the technology is still in the research stage, he believes it shows how shape-memory alloys can do what conventional materials and fasteners cannot. The two-year collaboration paired Sandia expertise in interlocking metasurfaces design with Texas A&M’s work in shape memory alloys, additive manufacturing and materials testing. Alongside Elsayed and Karaman, contributors include Dr. Alaa Elwany of the Wm Michael Barnes ’64 Department of Industrial and Systems Engineering, Dr. Raymundo Arroyave of the Department of Materials Science and Engineering, doctoral student Taresh Guleria, and Sandia’s Dr. Brad Boyce, one of the inventors of the original metasurface concept. Funding is administered by the Texas A&M Engineering Experiment Station (TEES).
