Researchers 3D Print Components That Can Modulate Light

Light-switchable material for vat photopolymerization

Researchers from Wroclaw University of Science and Technology, the Italian National Research Council's Istituto Nanoscienze, Scuola Normale Superiore and the University of Pisa have developed a photo-responsive resin for vat photopolymerization. 3D printed components made from this material can change how they transmit and polarize light on demand.

The resin incorporates azobenzene-based molecules. When exposed to polarized visible light, the molecules reorient and create a temporary difference in refractive index, called photoinduced birefringence. The team measured birefringence values up to 2.5 x 10^-4 and confirmed the effect held through 60,000 on-off cycles.

How the printing parameters affect performance

UV exposure during curing had a clear influence. Samples exposed for less than 0.5 minutes produced birefringence around 5 x 10^-5. Extending exposure to 1.7 minutes pushed the maximum response to roughly 2.5 x 10^-4. Between one and 40 minutes, birefringence stayed near 2 x 10^-4.

Raman spectroscopy showed the resin reached about 50% conversion during the first two minutes. The highest birefringence appeared early, before complete curing. Prolonged UV exposure began degrading the DR1 dye molecules. After 120 minutes, the dye's maximum absorbance dropped to about 60% of its original value.

Spacially controlled optical functions

The researchers printed uniform disks using a Sharebot Andromeda SLA system. A pump beam at 10 Hz modulated the transmitted laser intensity, and the effect remained stable across 60,000 cycles.

They then printed a segmented disk with four quadrants, thicknesses ranging from 420 to 600 micrometers. The different thicknesses produced phase retardations that varied by geometry, giving them control over the optical response in different regions of the same part. A wedge-shaped sample confirmed that transmitted intensity changed with printed thickness.

These are component-level demonstrations. They do not yet represent a working optical computer or communications device. Long-term stability, mechanical properties and integration into larger systems remain open questions. But the work extends earlier 3D printed photonic research into dynamic birefringence and multi-material optical functions.