3D printing fluorescent material with tunable optical properties

Abstract

The 3D printing of fluorescent materials could help develop, validate, and translate imaging technologies, including systems for fluorescence-guided surgery. Despite advances in 3D printing techniques for optical targets, no comprehensive method has been demonstrated for the simultaneous incorporation of fluorophores and fine-tuning of absorption and scattering properties. Here, we introduce a photopolymer-based 3D printing method for manufacturing fluorescent material with tunable optical properties. The results demonstrate the ability to 3D print various individual fluorophores at reasonably high fluorescence yields, including IR-125, quantum dots, methylene blue, and rhodamine 590. Furthermore, tuning of the absorption and reduced scattering coefficients is demonstrated within the relevant mamalian soft tissue coefficient ranges of 0.005-0.05 mm^-1 and 0.2-1.5 mm^-1, respectively. Fabrication of fluorophore-doped biomimicking and complex geometric structures validated the ability to print feature sizes less than 200 μm. The presented methods and optical characterization techniques provide the foundation for the manufacturing of solid 3D printed fluorescent structures, with direct relevance to biomedical optics and the broad adoption of fast manufacturing methods in fluorescence imaging.

Figure 1

Preparation and 3D printing of fluorescent material with tunable optical properties using LCD-based masked stereolithography printing. (a) Tuning of application-specific fluorescence, absorbance, and scattering properties was achieved through the addition of pre-dispersed solutions of fluorescent dyes, absorbers, and scatterers. (b) 3D model of a coronary artery created from an MRI scan. This model was prepared for printing by adding mechanical supports, defining printing settings for the specific resin and 3D model, and generating a layer-by-layer printing file. (c) The masked stereolithography 3D printing mechanism was used where the LCD screen selectively exposes the resin vat, layer-by-layer, as per the printing file generated in (b) resulting in a 3DP structure.

Figure 2

3D printed ICG-equivalent material with tuned optical properties. (a–c) White-light and 800 nm channel fluorescence images of (a) MRI-scanned coronary artery tree structure, (b) complex geometrical lattice cube, and (c) resolution calibration cube with sub-200 μm feature sizes. (d) Fluorescence emission and excitation spectra of 3DP fluorescent material and ICG-in plasma showing close overlap in spectral features. (e) Linearity of fluorescent intensity output for increasing laser-dye concentrations in 3DP material. (f, g) Measured absorption and reduced scattering coefficient spectra of the 3DP material. Error bars indicate ± one standard deviation from the mean.

Figure 3

Optical transmission and autofluorescence measurements of 3D printed photocurable resins. Measurements are performed on 3DP solid cuvettes (12 × 12 × 40 mm³) of four commercially available clear resins that were post-cured for 1 h and 48 h. (a–d) Transmission images and spectra. (e) Relative autofluorescence measurements.

Figure 4

Spectral shifts (i–iii) and relative fluorescence yield change (iv) for 3D printed fluorescent materials compared to in-solvent fluorophores. (a) IR-125 laser dye shows significant spectra shift and broadening with a 0.24 × relative fluorescence yield. (b) 800 nm quantum dots show small shifts in spectra with a 6.7 × relative fluorescence yield. (c) Methylene blue shows a significant shift in spectra with a 0.18 × relative fluorescence yield. (d) Rhodamine 590 laser dye shows small spectra shifts and no significant change in the fluorescence yield. (e) Disodium fluorescein dye is inactivated in the 3D printing process, showing no detectable absorbance or emission spectra.

Figure 5

Visualization and measurement of absorption and reduced scattering properties. (a) Image of a side-illuminated middle phalanx. (b) Side-illuminated method for visualization of optical properties of 3DP 50 × 50 × 20 mm³ blocks. (c) Top-down and side-illuminated images of four 3DP blocks with varying nigrosin and TiO₂ concentrations. Measured absorption (d) and reduced scatter (e) coefficients spectra for the four 3DP blocks. Error bars indicate ± one standard deviation from the mean.