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Advanced Laboratory Phantoms for Soft Tissues in Engineering and Medicine: ALPHA-STEM

Periodic Reporting for period 2 - ALPHA-STEM (Advanced Laboratory Phantoms for Soft Tissues in Engineering and Medicine: ALPHA-STEM)

Periodo di rendicontazione: 2020-10-01 al 2021-09-30

Research has shown that the success rate in many types of surgeries is strictly related to the experience of the surgeon. However, early in their career, trainees are not given the opportunity to operate on a sufficient number of patients nor to perform an exhaustive mix of procedures.
Training and technical tasks are usually practiced on cadavers, animals or using virtual simulators. However, all these alternatives present difficulties: limited availability, expensive handling and preservation processes (cadaveric training), costly set-up, etc. A potential solution is to promote the use of artificial synthetic models, also known as phantoms. Phantoms are reproduction of human parts and organs that allow the trainee to practice positioning of the anatomical structures as well as hand coordination. Unfortunately, they lack of reliable tactile feedback (e.g. palpation) and real tissue deformations which critically reduce the fidelity of the surgical training.

The project’s main objective is the investigation and creation of new materials that can be used to design laboratory phantoms for surgical training.
The main plan starts from the design of novel soft materials, the tuning of their mechanical capabilities (crosslinking agents, network configurations and 3D patterned structures) and finally the development of 3D phantoms of human organs and tissues.

The Objectives are:
To develop multicomponent natural and/or synthetic materials
To investigate the capabilities of the 3D structures in enhancing the nonlinear mechanical behavior of the materials
To tune the designed materials to mimic the properties of human tissues
To apply the acquired know-how in the design of life-sized phantoms for medical applications and beyond
During the the fellowship the following work has been completed:
5. Acquired knowledge on the mechanical characteristics of the human tissues from the literature: stiffness, porosity, viscoelasticity, range of deformations they are usually subjected to.
6. Acquired knowledge on single and multicomponent soft materials and their physical and chemical crosslinking capabilities.
7. Carried out the design of various polymeric networks and characterized them through mechanical testing and chemical analysis.
8. Used mathematical approaches to fit hyperelastic and viscoelastic material models to the preliminary collected data. The fitting routines were coded in Matlab and compared with related results available in the literature. Some of the implemented models included Neo-Hookean, Mooney-Rivlin, Polynomial, Gent and Prony Series formulations, in order to capture the materials’ properties.
9. Designed computer models of 3D patterned structures, including origami, kirigami, cellular materials (including rotating square patterns) chiral patterns, arabic motifs and corrugated thin sheets. Learnt how to use Periodic Boundary Conditions, User-defined subroutines developed in Fortran, material formulations fitted and instructed by experimental testing and analysis. Designed full 3D computer models of the respiratory cycle of the human lung. Learned shape optimization strategies to optimize lung airways geometries with the aim of manufacturing a more precise and reliable lung phantom.
10. Developed new manufacturing skills, like laser cutting, polymer coating and 3D printing that were employed to manufacture 3D structures and hybrid structure polymer materials.

Despite the impact of the pandemic on the project and the closure of the labs I have managed to publish 8 journal papers (1 is still under review but the preprint is available on arxiv, 1 is in press, and I am working on a couple more) on the fundamental behavior of hybrid structural-soft materials and how these can be preprogrammed to have several functions. A complete list can be found on the project's website:

The results of my fellowship have been disseminated through several channels. I participated at the European Research Night in 2019 in Milan and it was an amazing experience. I had the opportunity to disseminate my work and explain what I do to both scientists and member of the public, including younger students and kids. Unfortunately it was not possible to replicate the experience in 2020 because of COVID and travel restrictions. Therefore Politecnico of Milan in collaboration with a great EU outreaching team organized a virtual (online) MEETmeTONIGHT 2020. I agreed to participate and made a video explaining what Alpha-stem is about. I also contributed by being available online via Teams to member of the public audience that would connect to the virtual rooms and ask questions about the research. It was not the same as having the event in person but it was nevertheless enjoyable!

The results of the project have also been disseminated via conferences and several seminars. the full list is on the project website:
The progress beyond the state of the art is the creation of new materials that combine 3D structures with soft polymers. An example of these materials are the kirigami inflatables that have been designed with the future aim of simulating lung tissue, when fabricated at the micro-scale. Unfortunately the microscale fabrication and testing of the materials has not taken place during the outgoing phase of the fellowship due to the shut down of the labs and facilities cause by the pandemic.
This has impacted the full completion of the last WPs, delaying the delivery of the life-sized phantoms. However the work is propagating past the end of the fellowship and the fellow is confident that the the remaining results will be published soon.
The societal impact of the project will be the availability of phantoms that respond realistically to the touch and can reproduce the deformations of real organs (like the respiratory cycle in the lungs). These will help medical trainees to practice their surgical skills on surrogates before entering the operation room. If, due to the extraordinary circumstances, the project does not achieve this main objective, the research conducted into the material science and design will still be an extremely valuable outcome and a solid base to achieve the creation of the phantoms in the near future.
example of brain laboratory phantom previously developed by the fellow