Structural DNA nanotechnology can produce a wide range of 3D nanostructures with programmable structure and size at <5 nm resolution. However, it is challenging to dry these structures without capillary force-induced damage. As a result, the applications of 3D DNA nanostructures have long been limited in aqueous environments. Ready access to free-standing 3D DNA nanostructures in the dry state could revolutionize many research areas, especially in the development of low-density, high-strength materials. Here we report a method to obtain free-standing wireframe 3D DNA tetrahedra in air on a solid substrate, such as SiO2 and mica, by absorbing uranyl acetate and lyophilization. The dried DNA tetrahedron structure, 93 ± 2 nm in height, withstands 42 ± 22 nN of loading force. The effective hardness (9.1 ± 5.1 MPa) and Young's modulus (77 ± 48 MPa) of this low-density (70.7 kg/m3) DNA-inorganic hybrid nanostructure are comparable to other reported low-density high-strength materials.
Keywords: 3D DNA nanostructure; free-standing; high strength; indentation; lyophilization; uranyl acetate.