Compared to conventional manufacturing processes, 3D printing has proved
its capability of building various structures with high accuracy and
material economy. 4D printing adds the fourth dimension, time, to 3D
printing technology. Changing through time is a key property of products
built by 4D printing. This research focused on bio-based responsive
materials, as a means of initiating change and transforming 3D printing
to 4D printing. A number of studies have been done to develop the
performance of responsive materials or to explore geometric structures
for these materials in order to configure products that can benefit from
this transformation. Precedents in medical field show great potential
for combining bio-based materials with 4D printing in manufacturing
highly customised products that adapt to the shape, movement and
physiological requirements of a human body. This research project was
initiated by the development of printable and responsive bio-based
polymers through the National Science Challenge (NSC) Portfolio 5
Spearhead Project “Additive manufacturing and 3D or 4D printing of
bio-composites”. The research is inspired by the adaptability and
biocompatibility of the medical precedents and explores the possibility
of engaging 4D printing in building wearable devices; exemplified by an
adaptive wrist splint for progressive rehabilitation. This included
researching wound healing processes and related rehabilitation methods
to determine the required functionality of the splint and exploring
relevant biological structures as inspiration for the design geometry.
Working alongside materials scientists, the design was developed along
two paths. Firstly, using the new experimental polymers and testing
their responsiveness to configure a printable shape- shifting layer of
the splint that adapts to changes in the wrist during the healing
process. Secondly, integrating these experiments into 3D models for an
adaptive splint, comprised of three layers, that responds to the
requirements of progressive rehabilitation. The research challenges the
properties of the new materials and the associated printing processes,
and more research will need to be done to improve both printability and
responsive performance. However, the design of the splint provides a
case study for potential applications in the broader field of wearable
devices that incorporate multiple layers of responsive materials and
different geometries that can adapt to the needs of a human body.
3D Printing of Living Responsive Materials and Devices
