Development of Triple and Quadruple Shape-Morphing Actuators via Selective Photopolymerization
Chovancová, Petronela (2025)
2025
Master's Programme in Materials Science and Engineering
Tekniikan ja luonnontieteiden tiedekunta - Faculty of Engineering and Natural Sciences
Hyväksymispäivämäärä
2025-09-22
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tuni-202509229412
https://urn.fi/URN:NBN:fi:tuni-202509229412
Tiivistelmä
Shape memory polymers (SMPs) are a class of smart materials that can change shape in response to external stimuli, such as heat. These materials are widely used in 4D printing, which adds time as a fourth dimension to 3D printing. 4D-printed structures can respond to temperature changes by bending, folding, or unfolding without the need for motors or external controls. This opens exciting possibilities for applications in fields such as soft robotics, biomedical devices, and deployable systems. However, most studies focus on single or dual-shape transformations. Ac tuators that can perform three or even four shape changes remain difficult to achieve. In many cases, previous research relies on custom resin formulations or expensive printing equipment, which limits practical use.
The goal of this thesis is to develop and test triple and quadruple shape-morphing actuators using affordable, commercially available materials and desktop Digital Light Processing (DLP) printers. The key idea is to utilize selective photopolymerization to create structures with distinct regions that respond to heat at varying temperatures. By carefully adjusting UV exposure time during printing, it is possible to change the glass transition temperature (Tg) of the resin. This allows one part of the structure to soften and move at one temperature, while another part re sponds at a higher temperature.
Two photopolymer resins were tested: Phrozen Tough ABS-like Grey and Anycubic UV-sen sitive Beige. Actuator designs were created in computer-aided design (CAD) and printed using controlled exposure settings. Thermal and mechanical properties were evaluated through ther mogravimetric analysis (TGA), differential scanning calorimetry (DSC), tensile testing, and shape memory experiments. The grey resin did not show meaningful changes in Tg and did not demon strate shape memory behaviour. In contrast, the beige resin exhibited a strong response to expo sure time, with Tg values ranging from 18 °C to 56 °C. The most reliable shape-morphing perfor mance was observed in the 4–8 second exposure range, where samples showed good balance between flexibility and shape retention.
This study proves that complex shape transformations can be achieved without custom resins or industrial printers. By precisely controlling UV exposure, it is possible to create programmable, multi-shape structures using standard tools. These findings offer a practical approach for design ing low-cost 4D-printed actuators. Future research should focus on improving exposure resolution and exploring other activation methods such as light, moisture, or pH.
The goal of this thesis is to develop and test triple and quadruple shape-morphing actuators using affordable, commercially available materials and desktop Digital Light Processing (DLP) printers. The key idea is to utilize selective photopolymerization to create structures with distinct regions that respond to heat at varying temperatures. By carefully adjusting UV exposure time during printing, it is possible to change the glass transition temperature (Tg) of the resin. This allows one part of the structure to soften and move at one temperature, while another part re sponds at a higher temperature.
Two photopolymer resins were tested: Phrozen Tough ABS-like Grey and Anycubic UV-sen sitive Beige. Actuator designs were created in computer-aided design (CAD) and printed using controlled exposure settings. Thermal and mechanical properties were evaluated through ther mogravimetric analysis (TGA), differential scanning calorimetry (DSC), tensile testing, and shape memory experiments. The grey resin did not show meaningful changes in Tg and did not demon strate shape memory behaviour. In contrast, the beige resin exhibited a strong response to expo sure time, with Tg values ranging from 18 °C to 56 °C. The most reliable shape-morphing perfor mance was observed in the 4–8 second exposure range, where samples showed good balance between flexibility and shape retention.
This study proves that complex shape transformations can be achieved without custom resins or industrial printers. By precisely controlling UV exposure, it is possible to create programmable, multi-shape structures using standard tools. These findings offer a practical approach for design ing low-cost 4D-printed actuators. Future research should focus on improving exposure resolution and exploring other activation methods such as light, moisture, or pH.