Enhanced energy absorption in 3D printed copper micro-honeycombs

• First ever 3D printing of copper micro-sized honeycomb architectures. • Copper micro-honeycombs in situ tested under quasi-static and high strain rate conditions with strain rate up to 110/s. • Near perfect plastic response attributed to combination of honeycomb geometry, high relative density and microstructure. • Excellent specific energy absorption ranging from 189.9 to 314.5 MJ/m 3 at different strain rates. A honeycomb architecture exhibits a high strength-to-weight ratio and excellent energy absorption properties. At the microscale, these architectures have great potential for packaging and protection applications. However, fabrication and testing of micro-honeycomb architectures remain challenging, particularly under extreme loading conditions. Here, we report the fabrication of microscale copper honeycomb architectures using an additive manufacturing technique − localized electrodeposition in liquid. The printed micro-honeycombs were mechanically tested under both quasi-static and high strain rate conditions using a piezo-based in situ setup inside SEM. The honeycombs exhibit excellent energy absorption properties under both quasi-static and high strain rate conditions, with the specific energy absorption increasing by 65 % as the strain rate rises from 0.001 s −1 to 110 s −1 . The copper honeycombs possess an ultrafine-grained microstructure that undergoes grain refinement during both quasi-static and high strain rate testing. Our work demonstrates the feasibility and potential of employing micro-honeycomb architectures as impact protection architectures for sensitive micro/nano-electromechanical systems and microelectronics operating in extreme environments.