Structural multi-colour invisible inks with submicron 4D printing of shape memory polymers

Area of Science:

• Materials Science
• Nanotechnology
• Polymer Science

Background:

• Four-dimensional (4D) printing adds a time-responsive dimension to 3D printed objects.
• Shape memory polymers (SMPs) are key materials enabling 4D printing functionalities.
• Extending 4D printing to the submicron scale opens new avenues in nanophononics and advanced materials.

Purpose of the Study:

• To explore 4D printing of SMPs at the submicron length scale.
• To develop a novel SMP photoresist for high-resolution printing.
• To investigate the shape memory effect for tunable optical properties at the nanoscale.

Main Methods:

• Utilized two-photon polymerization lithography (TPL) for high-resolution 4D printing.
• Developed a new SMP photoresist based on Vero Clear.
• Fabricated submicron grid structures with size-tunable multi-colors.

Main Results:

• Achieved print features with a resolution of approximately 300 nm half pitch.
• Demonstrated reversible shape memory effects leading to significant visual shifts via nanoscale deformation.
• Observed rapid recovery of surface morphology and structural color upon heating above the glass transition temperature.

Conclusions:

• High-resolution 4D printing of SMPs is feasible at the submicron scale.
• The developed material and process enable reversible changes in microtopography and optical properties.
• This technology offers potential for temperature-sensitive labels, anti-counterfeiting solutions, and tunable photonic devices.