Tuning the twisting in helical nanowires: Assembly of inorganic nanoparticles into complex structures often requires a template. Researchers can now assemble helical nanowires out of cubic magnetite nanocrystals by tuning interactions that bind or separate them. Singh et al. floated the nanocrystals on a liquid and aligned them with a magnetic field. After the liquid evaporated, different twisted nanowires remained. The helices varied according to the concentration of nanocrystals, their shape, and the strength of the magnetic field. Competition between weak forces drives this self-assembly and can lead to arrays with the same twist direction. Science , this issue p. 1149

Magnetron‐sputtered Al₂O₃ thin films were annealed in ambient air. The phase compositions of the as‐deposited Al₂O₃ films were (i) fully amorphous, (ii) nanocrystalline γ‐Al₂O₃ in an amorphous Al₂O₃ matrix, and (iii) fully crystalline γ. For all samples, annealing to 1 100–1 150 °C resulted in a transformation to α‐alumina. The transformation paths depend on the phase fraction of γ in the as‐deposited films. For amorphous films and films with low initial γ fraction, the intermediate phase θ‐Al₂O₃ appeared in the range of 1 000–1 100 °C. For predominantly crystalline γ‐Al₂O₃ as‐deposited films no intermediate Al₂O₃ phases were observed, indicating a direct γ‐to‐α phase transformation at ∼1 100 °C.

Significant progress in nanotechnology has enormously contributed to the design and development of innovative products that have transformed societal challenges related to energy, information technology, the environment, and health. A large portion of the nanomaterials developed for such applications is currently highly dependent on energy-intensive manufacturing processes and non-renewable resources. In addition, there is a considerable lag between the rapid growth in the innovation/discovery of such unsustainable nanomaterials and their effects on the environment, human health, and climate in the long term. Therefore, there is an urgent need to design nanomaterials sustainably using renewable and natural resources with minimal impact on society. Integrating sustainability with nanotechnology can support the manufacturing of sustainable nanomaterials with optimized performance. This short review discusses challenges and a framework for designing high-performance sustainable nanomaterials. We briefly summarize the recent advances in producing sustainable nanomaterials from sustainable and natural resources and their use for various biomedical applications such as biosensing, bioimaging, drug delivery, and tissue engineering. Additionally, we provide future perspectives into the design guidelines for fabricating high-performance sustainable nanomaterials for medical applications.