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August 27, 2021 Leave a Comment

A team of researchers from the Thayer School of Engineering, Dartmouth College, has published a paper detailing their experiments into 3D printable fluorescent materials with tunable optical properties.

In particular, the research has focused on resin type printing with an LCD printer, and according to the paper the team has been successful in producing fluorescent materials with tunable absorption and scattering properties, using a selection of commercially available resins as a base.

Why is this useful? Read on to know more.

Indocyanine Green Fluorescence

The specimens were printed with off-the-shelf resin bases and were mixed with a variety of additive solutions which included fluorophores, absorbers, and scatterers, to vary the fluorescent properties.

IR-125 laser dye was used as the fluorophore, hemin for the absorber, and TiO2 for the scatterer.

The solutions were made via a process of sonification before being stirred into the base resins, ensuring a homogenous resin for printing.

The printing itself was achieved with the Phrozen Sonic Mini LCD MSLA 3D printer and with the Chitubox open-source slicer software.

After the printing process, the parts underwent a cleaning process in isopropyl alcohol, and were allowed to dry. They were then bathed in 405 nm light to finalize any curing remaining from the print, much as you might do with a home resin printer.

The printed samples were manufactured to mimic indocyanine green (ICG) fluorescence, as this is the most common contrast dye technique used in medical imaging. Fluorophores absorb light energy of a specific wavelength and re-emit light at a longer wavelength. When put inside the body, they fluoresce and the resulting glow can be imaged.

One specimen was printed in the form of an artery tree (blood vessels), and was placed inside an MRI scanner. This demonstrated that the resins could be used to make self supporting structures at a reasonable resolution, and could fluoresce in the MRI scanner.

3D printed fluorescent structures 3D printed fluorescent structures (Image credit: Thayer School of Engineering)

The fluorescent images such as the MRI artery, combined with spectra measurements of the material showed a correlation to the spectra and fluorescence emission of traditional ICG in plasma. The graph below shows the glowing 3D printed resin is comparable in emission and absorption as the ICG in plasma.

7538634 AM resin is comparable to the classic stuff in terms of fluorescence (Image credit: Thayer School of Engineering)

The researchers have concluded that these results demonstrate the ability to 3D print material that is spectrally equivalent to the most used contrast dye in fluorescence guided surgery (indocyanine green).

A variety of fluorescent additives were trialled including quantum dots, methylene blue, rhodamine 590, and the aforementioned IR-125 laser dye. The “tuning” of the properties is done by varying the additives in the solutions, and by the manufacturing process. The optical properties can therefore be changed to case-specific applications,

The 3D printing of fluorescent materials with tunable optical properties can potentially provide a means of mass producing stable fluorescent imaging targets, and optical tissue phantoms. This in turn can have direct uses in the fields of cancer margin detection.

If you’d like to read more about the research, you can read the open access paper over at the Nature website.