Irish researchers developed a machine that lets users see what happens when tiny particles strike a surface, capturing particles in motion at speeds that are 3x faster than a bullet. The device is expected to provide insights that will enable improvements in materials and coatings for aircraft parts, medical implants, and help to simulate intergalactic collisions. The Laser Ablation Particle Acceleration and Observation (LAPAO) machine, built by members of Trinity College Dublin’s Science & Technology in Advanced Manufacturing (STAM) research group, uses a laser to fire particles of 10-60 μm in size at speeds of up to 1 km/s. A camera taking a billion pictures per second captures how these particles behave when they hit a surface, where they can stick, bounce, or even break. The information will help engineers understand how to make better materials and coatings. The process they’re improving is called “cold spray,” a technique for printing or repairing metal parts without melting them. Until now, engineers relied on computer models. With this machine, they can "see" what’s happening. Traditionally used in the aerospace industry, and now in nuclear, automotive and broader manufacturing sectors, cold spray technology enables the formation of coatings, typically metallic, over a substrate material. With this technique, engineers do not need to reach the melting temperature of materials to combine the coatings and substrate. Plastic deformation is key in this process; each tiny particle deforms on impact and triggers a complex bonding process that results in substrate adhesion and in particle-particle adhesion after a first deposition layer is formed. Additionally, cold spray has undergone improvements recently. The methods of laser-assisted and electromagnetism-assisted cold spray both improve the microstructure and performance of deposited materials. “With this machine, we can visualize real material interactions for a wide range of particle and substrate materials in minutes, which will aid us in understanding and optimizing the cold spray process for specific materials," said research team member Leo Delvin. "To date the machine has been used to find the critical velocity for a range of materials such as aluminum, Ti64, and high entropy alloy, which are used in the electrical and automotive industries as coatings which can lead to lightweight parts with more desirable material properties such as high wear and corrosion resistance,” LAPAO can be used to simulate high-velocity microscale impact events, which will help applications in/for a wide range of industries; any particle impact can be studied using LAPAO, which gives the technology a wide-ranging research potential. The machine is currently being used in an EU-funded project called MadeCold, under which scientists are developing a type of cold spray based upon electrostatic acceleration of single particles. In the project, LAPAO is providing clear indications about the precise velocity needed for bonding and providing information about the relationship between particle material and morphology.