3D‐Printed High‐Entropy Alloy Nanoarchitectures

System miniaturization is a key driver in developing nanoelectromechanical systems, sensors, and microchips. To enhance reliability and extend operational lifetimes, high-entropy alloys (HEAs) have emerged as promising materials due to their exceptional mechanical robustness and thermal stability. These advantageous properties are predominantly demonstrated in bulk HEA forms; however, research on small-dimensional HEAs is largely confined to nanoparticles, nanopillars, and thin films, limiting their broader applications in nanodevice systems. This study introduces nanoarchitectured HEAs that exhibit remarkable mechanical and thermal properties. Using a custom-designed 3D nanoprinter, HEA nanoparticles are printed in situ into complex nanoarchitectures, enabling flexible elemental combinations and freeform 3D geometries. Structural dimensions and grain size are precisely controlled as design parameters to synergistically leverage the benefits of alloying, size scaling, and architectural design. The resulting 3D-printed HEA nanoarchitectures demonstrate ultrahigh strength (≈4 GPa), outstanding toughness, and exceptional thermal stability. These properties position nano-architectured HEAs as a novel class of materials suitable for high-stress, high-toughness applications in small-dimensional devices. By combining the versatility of 3D nanoprinting with the expansive alloy design space of HEAs, this approach paves the way for their potential integration into future nanodevices.