Although just cute little creatures at first glance, the microscopic geckos and octopuses fabricated by 3D laser printing in the molecular engineering labs at Heidelberg University could open up new oppor­tunities in fields such as micro­robotics or biomedicine. The printed micro­structures are made from smart polymers whose size and mechanical properties can be tuned on demand and with high precision. These “life-like” 3D micro­structures were developed in the framework of the “3D Matter Made to Order” (3DMM2O) Cluster of Excellence, a colla­boration between Ruperto Carola and the Karlsruhe Institute of Techno­logy (KIT).

“Manu­facturing programmable materials whose mechanical properties can be adapted on demand is highly desired for many appli­cations,” states Eva Blasco, group leader at the Institute of Organic Chemistry and the Institute for Molecular Systems Engi­neering and Advanced Materials of Heidelberg University. This 4D printing refers to the ability of three-dimen­sionally printed objects to alter their properties over time. One prominent example of materials for 4D printing are shape memory polymers – smart materials that can return to their original shape from a deformed state in response to an external stimulus such as tempera­ture.

The team recently introduced one of the first examples of 3D printed shape memory polymers at the microscale. In cooperation with the working group of biophysicist Joachim Spatz, a scientist at Ruperto Carola and Director at the Max Planck Institute for Medical Research, the researchers developed a new shape memory material that can be 3D printed with high resolution both at the macro and at the microscale. The structures produced include box-shaped micro­architectures whose lids close in response to heat and can then be reopened. “These tiny structures show unusual shape memory properties at low acti­vation temperatures, which is extremely interesting for bioappli­cations,” explains Christoph Spiegel, a doctoral researcher in the working group of Eva Blasco.

Using adaptive materials, the researchers succeeded in a follow-up study in producing much more complex 3D micro­structures like geckos, octopuses, and even sunflowers with “life-like” properties. These materials are based on dynamic chemical bonds. The Heidelberg researchers report that alkoxy­amines are particularly suitable for this purpose. After the printing process, these dynamic bonds allow for the complex, micrometric structures to grow eight-fold in just a few hours and to harden, while maintaining their shape. “Conven­tional inks do not offer such features,” emphasises Blasco. “Adaptive materials containing dynamic bonds have a bright future in the field of 3D printing,” adds the chemist. (Source: U. Heidelberg)

Reference: Y. Jia et al.: Covalent Adaptable Microstructures via Combining Two-Photon Laser Printing and Alkoxyamine Chemistry: Toward Living 3D Microstructures, Adv. Func. Mat., online 22 September 2022; DOI: 10.1002/adfm.202207826

Link: Centre for Advanced Materials, Heidelberg University, Heidelberg, Germany