3D Printed Multimaterial Hydrogels for Color Blindness Correction

HAIDER BUTT, MUHAMMED HISHAM

Department of Mechanical Engineering

Khalifa University

Abu Dhabi, UAE

Abstract: - Multimaterial 3D printing is a novel technology with exciting potential. This study explores the use

of vat photopolymerization-based 3D printing to build multimaterial hydrogel disks and lenses with increased

multiband optical filtering. Such hydrogel devices can be useful for treating ocular diseases including color

blindness. The printed multimaterial disks were examined for their optical characteristics and swelling behavior.

The optical qualities of the contact lenses were found to be unaffected by the multi-material printing technique.

Due to the two dyes that were utilized, the printed multimaterial hydrogels provided a combined multi-band color

blindness correction. The obtained optical spectrum closely matched the color blindness correcting glasses that

are readily available on the market.

Key-Words: - 3D Printing; Multimaterial Printing; Hydrogels; Color Blindness Correction.

Received: July 8, 2022. Revised: October 21, 2023. Accepted: November 22, 2023. Published: December 31, 2023.

1 Introduction

Multimaterial 3D printing is a promising

technique that has lately attracted a wide range of

research interests. Several 3D printing techniques,

including fused deposition modeling, material

extrusion, and vat photopolymerization, enable

multi-material printing. However, for optical

applications, the Digital Light Processing (DLP)

technique is the most suited process [1]. DLP is a sub-

variety of vat photopolymerization that uses an

appropriate light projection technology for projecting

UV light in 2D patterns on the vat. It has excellent

resolution, clean surface quality, and minimal

scattering losses. There have only been a few studies

on the use of multi-material 3D printing for

producing optical applications, including

multipurpose contact lenses. Joralmon et al. [2]

created liquid crystals whose optical characteristics

vary with temperature using multimaterial DLP

printing. Bilayer hydrogels that alter color,

brightness, and form in response to pH were printed

by Li et al. [3]. Multimaterial 1D photonic crystals

were manufactured using an e-jet printer by Iezzi et

al. [4].

In this study, we investigate the possibility of 3D

printing multi-material disks and contact lenses

composed of two distinct dyes, each of which may be

used to treat specific forms of color blindness. The

investigation explores how printing with two

different materials affects the optical characteristics

of these printed hydrogels. The optical

transmission/absorption, swelling, and dye leakage

characteristics are studied for this purpose. The

produced multimaterial hydrogels are finally

compared with commercial glasses available for

color vision deficiency.

2 Material and methods

2.1 Resin preparation

For preparing the resin, polyethylene glycol

diacrylate (PEGDA) and hydroxyethyl methacrylate

(HEMA) were mixed in a ratio of 1:1 by volume and

the photoinitiator trimethyl benzoyl

diphenylphosphine oxide (TPO) was added at 5% by

weight. Two fluorescent dyes, Atto565 and Atto488,

were used to color the hydrogel. The dyes were

dissolved in the resin using dimethyl sulfoxide

(DMSO). Three different dye concentrations were

used for the dyes: 1.25%, 2.5%, and 5% by volume.

2.2 CAD modeling and 3D printing

For 3D printing, disk-shaped CAD models were used

with dimensions of 14mm in diameter and

1mm/0.5mm in thickness. Contact lens models were

also used to print certain samples. Wanhao D8 DLP-

based 3D printer was utilized for printing. For

printing samples of multiple materials, the print was

paused at required points, and the resin in the vat was

changed before the print was resumed (Fig. 1).

DESIGN, CONSTRUCTION, MAINTENANCE

DOI: 10.37394/232022.2023.3.25

Haider Butt, Muhammed Hisham

E-ISSN: 2732-9984

260

Volume 3, 2023

Fig. 1. Multimaterial DLP printing process used

in this study.

2.2 Characterization

An Ocean Optics UV-vis spectrophotometer was

used to evaluate the transmission/absorption spectra

of the liquid resin and 3D-printed samples. To

visualize the material change occurring inside the

sample, cross-sections of the sample were

photographed. By submerging the samples in DI

water for lengthy periods, water absorption and dye

leakage were examined.

3 Results and discussion

The resins mixed with dyes were found to be quite

stable and the dyes did not separate from the resin

after the initial mixing. Optical transmission results

indicate dips in transmission at 572 nm for Atto565

and 513 nm for Atto488. In addition, a second

significant dip appears between 370 and 420 nm

because of TPO, which is included in the resin as a

photoinitiator and absorbs UV light in this range.

Given that both transparent resin and resin with the

dye have the same TPO content, they both exhibit the

same dip at 370–420 nm. As the dye's concentration

rises (from 1.25% to 5%), the transmission dip

intensity also rises. The multi-material 3D-printed

samples exhibited the same behavior but with two

simultaneous dips, one from each Atto565 and

Atto488. It was also observed that the transmission

was the same whether the two dyes were mixed

directly or printed in separate layers as multi-material

samples. This similarity in optical transmission

demonstrates that the multi-material printing process

does not have any negative effects on the optical

properties of the printed samples. Even though a

small interface was visible on the external surface of

multi-material prints, the internal cross-sections did

not show an interface, and there was no loss in

transmission due to it.

Three combinations, clear resin, clear:Atto565 dyed

resins, and clear:Atto565:Atto488 dyed resin

combinations were used to print contact lenses. The

different dyes were deposited as rings on the curved

portion of the lens. These printed samples show that

multimaterial contact lenses for optical filtering and

other functional purposes can be produced in a wide

range of combinations. Comparing the transmission

and absorption spectra of multimaterial disks with

those of color blindness corrective eyewear that is

commercially available reveals a very similar

spectral behavior. A considerably closer agreement

was obtained than was previously attainable when

employing individual dyes [5]. Transmission dips in

Enchroma glasses occur at about 486 nm and 575 nm,

with corresponding intensities of 0% and 5%. The

spectra for Atto565:Atto488 (5%, 2 mm thick),

which include transmission dips around 513 nm (7%)

and 572 nm (7%), and full-width-at-half-maxima

(FWHM) 468-596 nm, are similar to that of

Enchroma glasses. BJ-5149 glasses exhibit dips at

513 and 546 nm with intensities of 50% and 55%,

respectively, and with an FWHM of 450-570 nm. The

spectra for Atto565:Atto488 (2.5%, 1 mm thick) that

have dips at 513 nm (57%, FWHM 489-539 nm) and

572 nm (57%, FWHM 550-593 nm) are similar to

that obtained for BJ-5149 glasses.

Swelling studies show that all samples have a water

absorption capacity of about 10%, with only an

approximate 1-2% deviation from this average.

These samples took around 24 hours to swell fully

from a state of being dry. Samples made of a single

substance and those made of multiple materials did

not significantly differ in this swelling behavior.

Multimaterial printing technique therefore has no

impact on the hydrogel’s capacity to absorb water.

Studies on dye leakage show that there is no evidence

of any dye leaking from the two Atto dyes inside the

printed sample. The optical spectrum from

multimaterial samples revealed that the absorption

peak intensity did not change with immersion in DI

water.

4 Conclusion

A previously unachieved milestone was reached with

the successful 3D printing of multi-material disks and

contact lenses incorporating Atto565 and Atto488,

which provided optical performance extremely

similar to the currently available color blindness

correction glasses. The multi-material 3D printing

caused no decrease in optical transmission or

absorption. Also, even after prolonged immersion in

DI water, the color of the multi-material samples

stayed the same and they showed no leakage. The

study demonstrates that multimaterial printing offers

an alternative method to incorporate various colors

within a single hydrogel sample.

DESIGN, CONSTRUCTION, MAINTENANCE

DOI: 10.37394/232022.2023.3.25

Haider Butt, Muhammed Hisham

E-ISSN: 2732-9984

261

Volume 3, 2023

Fig. 2. (a) Transmission spectra from multimaterial

disks of different concentrations. (b) Comparison of

transmission spectra of commercial glasses and

multimaterial disks. (c) 3D printed multimaterial

contact.

Acknowledgement:

This work was supported by research funding from

KU-KAIST Joint Research Center, Sandooq Al

Watan LLC, and Aldar Properties.

References:

[1] F. Alam, A. E. Salih, and H. Butt, Development

of 3D-Printed Glasses for Color Vision Deficiency,

Adv Eng Mater, Oct. 2022.

[2] D. Joralmon, K. Jin, and X. Li, Three-

Dimensional Printing of Liquid Crystals with

Thermal Sensing Capability, ACS Appl Polym

Mater, 2022, vol. 4, no. 4, pp. 2951–2959.

[3] Z. Li, P. Liu, X. Ji, and B. Tang, Bioinspired

Simultaneous Changes in Fluorescence Color,

Brightness, and Shape of Hydrogels Enabled by

AIEgens, Advanced Materials, 2020, vol. 32, no. 11.

[4] B. Iezzi, Z. Afkhami, and M. Shtein,

Electrohydrodynamic Jet Printing of 1D Photonic

Crystals, Adv Mater Technol, 2020, vol. 5, no. 10.

[5] F. Alam, A. E. Salih, and H. Butt, 3D printed

contact lenses for the management of color blindness,

Addit Manuf, 2022, vol. 49.

Contribution of Individual Authors to the

Creation of a Scientific Article (Ghostwriting

Policy)

Muhammed Hisham carried out the experiments and

wrote the paper.

Haider Butt has organized and supervised the project.

Creative Commons Attribution License 4.0

(Attribution 4.0 International, CC BY 4.0)

This article is published under the terms of the

Creative Commons Attribution License 4.0

https://creativecommons.org/licenses/by/4.0/deed.en

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Sources of Funding for Research Presented in a

Scientific Article or Scientific Article Itself

Conflict of Interest

The authors have no conflicts of interest to declare

that are relevant to the content of this article.

DESIGN, CONSTRUCTION, MAINTENANCE

DOI: 10.37394/232022.2023.3.25

Haider Butt, Muhammed Hisham

E-ISSN: 2732-9984

262

Volume 3, 2023

This work was supported by research funding from

KU-KAIST Joint Research Center, Sandooq Al

Watan LLC, and Aldar Properties.