Researchers use 3D printing to create octopus and gecko patterns

In the molecular engineering laboratory of Heidelberg University, researchers use 3D laser printing technology to create miniature gecko and octopus patterns. This research will open up new opportunities for micro robots or biomedical fields.

Intelligent polymers with "life" characteristics: due to dynamic chemical bonds, the micro scale 3D structure can grow 8 times and harden in just a few hours. Scale: 20 microns（ μ m).

The printed microstructure is made of a new material called intelligent polymer, and its size and mechanical properties can be adjusted with high precision as required. These "lifelike" 3D microstructures were developed under the framework of the "3D Material Customization" (3DMM2O) excellence cluster, which was jointly completed by Ruperto Carola and Karlsruhe Institute of Technology (KIT).

In this study, researchers reported a new way to generate this covalent adaptive microstructure (CAM), which can precisely adjust the mechanical properties of the structure through post printing modification after manufacturing. To achieve this goal, the researchers combined 2PLP, which provides the highest 3D manufacturing accuracy, with a simple ink system that provides covalent dynamic bonds by integrating the alkoxylamine function into the printed 3D microstructure (Figure a below). Taking advantage of the dynamic and active characteristics of this bond type, the 3D micro print structure is modified by using additional nitrate oxide molecules (TEMPO) through NER and styrene as extended additional monomers through NMP (Figure b below). The combination of 2PLP technology and alkoxylamine chemistry will provide a fully adaptable 3D microstructure. In addition to precise manufacturing on molecular and micro scales, it can also adjust its mechanical properties for customized applications.

a) Schematic diagram of 3D laser printing process of alkoxylamine containing covalent adaptive microstructure (CAM); b) CAM was modified after printing by nitrogen oxide exchange reaction (left, CAM-NER) and nitrogen oxide mediated polymerization (right, CAM-NMP).

Dr. Eva Blasco, head of the Institute of Organic Chemistry and the Institute of Molecular Systems Engineering and Advanced Materials at Heidelberg University in Germany, said: "It is very necessary to manufacture programmable materials with mechanical properties that can be adjusted according to needs in many applications." This concept is called 4D printing. A prominent example of 4D printing materials is shape memory polymers - intelligent materials that can be restored to their original shape from a deformed state under the action of external stimuli such as temperature.

The team led by Professor Blasco recently introduced the first example of 3D printing shape memory polymer in microscale. In collaboration with a team of biophysicist Professor Joachim Spatz, researchers have developed a new shape memory material that can provide high-resolution 3D printing at both macro and micro scales. The production structure includes a box shaped micro building whose lid is closed when heated and can then be reopened. Christoph Spiegel, doctoral researcher of Eva Blasco's working group, explained: "These tiny structures show unusual shape memory characteristics at low activation temperatures, which is very interesting for biological applications."

a) FTIR spectra of ink, reference microstructure, CAM and CAM ner. b) Schematic diagram of nitrogen oxide exchange reaction between CAM and CAM ner. c) PEG specific (C2H5O+) signal regions refer to the ToF SIMS spectra of microstructure (Ref), CAM and CAM ner. d) ToF SIMS spectra of Ref, CAM and CAM ner in the alkoxylamine specific (C3H8NO+) signal region.

Using adaptive materials, researchers successfully produced more complex 3D microstructures in subsequent studies, such as geckos, octopuses, and even sunflowers with "life" characteristics. These materials are based on dynamic chemical bonds. Researchers at the University of Heidelberg report that alkoxyamines are particularly suitable for this purpose. At the end of the printing process, these dynamic keys make the complex microstructure grow 8 times in just a few hours, and harden while maintaining the shape. Professor Blasco stressed that "traditional inks do not have these characteristics. Adaptive materials with dynamic keys have a bright future in 3D printing."

a) FTIR spectra of CAM and CAM - NMP. The characteristic absorption peak of polystyrene highlights (purple dotted line) the FTIR spectra of b) CAM and CAM - NMP. The characteristic absorption peak of polystyrene is highlighted (purple dotted line) c) Schematic diagram of nitrogen oxide mediated CAM CAM NMP polymerization; d) ToF SIMS spectra of C7H7+ion species.

Materials scientists from Karlsruhe Institute of Technology (KIT) also participated in the research of adaptive materials with "life" characteristics. This work was funded by the German Research Foundation and the Carl Zeiss Foundation, and was carried out within the framework of the 3DMM2O excellence cluster. The research results were published in two papers in the journal Advanced Functional Materials.

Source:Covalent Adaptable Microstructures via Combining Two-Photon Laser Printing and Alkoxyamine Chemistry: Toward Living 3D Microstructures, Advanced Functional Materials, 10.1002/adfm.202207826