Multimaterial Stereolithography by Crosslinking through Luminescence Excitation

Lead Research Organisation: Heriot-Watt University
Department Name: Sch of Engineering and Physical Science


Additive manufacturing, rapid prototyping or 3D printing refer to a myriad of manufacturing techniques that build an object in a layer-by-layer approach. It represents a revolution in manufacturing because it is non-specific for an industry and many companies from different sectors benefit from being able to produce customised samples in-house at high speed and with a lower amount of residues and CO2 footprint. For this reason, the 3D printing market is in expansion, and its global value is projected to increase at a CAGR of 21.8% from 2019 to 2025
There are many 3D printing techniques, all of which present advantages and disadvantages. Only a few techniques are low-cost, which is crucial for enabling their use by a high number of users and having a higher societal impact. This is the case of FFF (Fused Filament Fabrication) and some photopolymer techniques such as Stereolithography (SLA), Digital Light Processing (DLP) and Liquid Crystal Display printing (LCD).
A second limitation is the achievable resolution that determines whether an object is "smooth-to-eye" or if the layers are visible. Thirdly, few technologies are able to print with more than one colour in the same object, or with different materials integrated in the same piece, let alone mixing conductive and non-conductive materials in a sample. Currently, there is no technique that can overcome these three limitations at the same time.
The vision underpinning this project is to develop a new 3D printing technology capable of producing multimaterial/multicolour objects for the first time, while maintaining both high resolution and low cost.
For this ambitious target, MUSCLE aims to develop a new platform for photopolymer 3D printing that will enable the sequential printing of 3D pieces with different resins. The method will be applicable to cost-efficient photopolymer printers with minor modifications. It will be based on the use of engineered optical materials and printing at different wavelengths.

Planned Impact

This project is expected to have an impact from a scientific, technological and commercial point of view.
Scientifically, new crosslinking mechanisms that relay on unexploited non-linear optical phenomena will be developed. This is an important advancement, because current photopolymer technology is limited by the short penetration depth of the exposition light beam. This is of great interest for different scientific communities working on manufacturing and optical materials.
Technologically, the knowledge developed through this project will for the first time allow the provision of a high-resolution and multimaterial 3D printing technique at a low cost. The generated knowledge on photocrosslinking with enhanced penetration depth will also be relevant to the fields of curing composites and optical adhesives.
Commercially, the link with an industrial partner from the very beginning of the research assures that market-oriented considerations will be regarded during the development of the technique, paving the way towards commercialisation potential. The industrial partner will also benefit from the interaction with the academic environment that can lead to further innovative collaborations.
The UK skills base will directly benefit from the training of the PDRA, as well as two PhD students whose PhD projects will be enhanced through interaction with the project.
The general public and society will also benefit as a whole, since this new process will allow companies to reduce their manufacturing costs, delivery time, CO2 footprint and industrial waste. As a low-cost technique, it will also allow its use by small companies and particular users.
Description INRS Canada - Prof. Fiorenzo Vetrone 
Organisation National Institute of Scientific Research (INRS)
Country Canada 
Sector Academic/University 
PI Contribution Our group measured and did the optical characterisation of the nanoparticles provided by the collaborators. Remarkably, we did the photoluminescent quantum yield measurements, which provide a value for the efficiency of the optical conversion process.
Collaborator Contribution The group of Prof. Vetrone, pioneer in the thermal decomposition method for UC NPs, synthesized a new kind of upconverting nanoparticle useful for the project (these are doped LiYbF nanoparticles).
Impact Main results are reported at the manuscript with DOI: 10.1039/D0NR04357E (Nanoscale, 2020,12, 17545-17554). This collaboration is multidisciplinary, since Prof. Vetrone's group works on Inorganic Chemistry Synthesis, and where we provide the optical engineering and characterisation.
Start Year 2020
Description Nanjing University of Posts and Telecommunications - Prof. Xiangfu Wang 
Organisation Nanjing University of Posts and Telecommunications
Country China 
Sector Academic/University 
PI Contribution We studied the optical properties of Erbium doped Y2O3 microtubes and their behaviour as upconverting system, also in relation to their concentration and scattering characteristics.
Collaborator Contribution Prof. Xiangfu Wang synthesized the erbium doped Y2O3 microtubes.
Impact This work has been recently presented at OSA (Imaging and Applied Optics Congress), with proceedings under DOI: 10.1364/3D.2020.JW5C.4
Start Year 2020
Description University of Ottawa - Dr. Eva Hemmer 
Organisation University of Ottawa
Country Canada 
Sector Academic/University 
PI Contribution We performed a study about the propagation of light in scattering media. For this, we analysed the optical properties of nanoparticle suspensions provided by the collaborator. This included a wide range of concentrations, which helped to evaluate the effect of the scattering. This is important in order to evaluate how a laser beam can propagate through a turbid media with upconversion nanoparticles.
Collaborator Contribution The group of Dr. Eva Hemmer provided NaYF4:20%Yb3+, 2%Er3+ nanophosphors in the range of 30 nm size.
Impact Part of this work has been reported in the paper with DOI: 10.1364/OE.398353.
Start Year 2020