A patient’s own vessels are the best conduits for small diameter applications (coronary bypass or peripheral bypass) and in applications with increased infection risks (dialysis access grafts or infected revisions). These are very common life- or limb-saving procedures. For example, in France, there are ˜18 000 coronary bypass performed yearly (=160 000 in Europe, ˜397 000 in USA) and ˜40 000 patients whose life depend on a functional hemodialysis access graft (˜309 000 in Europe, =1.9 million world wide). When native vessels are no longer available, synthetic vascular graft can be used but provide much worse outcome and are only acceptable for distal bypass and dialysis access. Thus there is a clear clinical need for a small diameter vascular graft that can provide outcomes similar to that of native vessels. We have developed a method to produce robust sheets of extracellular matrix synthesized in vitro by normal, adult, human skin fibroblasts. In previous studies, these sheets of cell-assembled matrix (CAM) have been rolled into the first tissue-engineered blood vessels (TEBV) to resist arterial pressure in humans. However, the sheet-based tissue assembly can be prohibitively costly and time-consuming. Indeed, the mechanical integrity of the TEBV depends on the fusion of sheet layers during a lengthy maturation process (8-12 weeks) and this cell-driven process can be variable. In addition, the sheet rolling approach has a limited capacity to control the geometry and mechanical properties of the TEBV. In this project, we propose 3 tasks that will both advance our basic scientific knowledge of the CAM and develop an innovative textile-inspired assembly method that will reduce TEBV production time by 3X and allow fine-tuning of its mechanical properties. Task#1 aims at producing yarns from CAM sheets and characterizing their composition, organization, and mechanical properties. The first step is to use a series of analytical tools to describe the structure of the sheet (mass spectroscopy, histology, immunolabeling, scanning and transmission? electron microscopy, and second generation harmonic microscopy). In a second step, thin strips are cut from the sheets and processed to form yarns. Yarns are then analyzed using the same analytical tools to see how the various processing steps affected the morphology of the CAM. Their mechanical properties (ultimate tensile strength, Young’s modulus) will also be assessed to check whether they were affected by the processing steps. This task will determine how we can control the mechanical properties of the yarn so that we can produce the yarns that best fit our needs for TEBV production. Task#2 aims at characterizing the in vivo remodeling of the material in nude rats. In this task, we will determine how the processing steps of yarn production can affect the biological response of the host. We hypothesize that if the CAM is significantly damaged by the processing, the non-specific immune system of the host will degrade it. The host response will be evaluated on a histological level but also at the mechanical level by comparing the mechanical properties of the yarn before and after implantation. Task#3 aims at weaving a clinically relevant TEBV. We will use our knowledge from Task#1 and #2 to build a TEBV that has clinically relevant mechanical properties and is built with yarns that will not trigger a degradative host’s response. The key mechanical properties to optimize will be burst pressure, suture retention strength, compliance, transmural permeability, and kinking?. The main assembly variables will be the yarn diameter and yarn count in the longitudinal and circumferential directions. At the end of this project we will have: 1) a comprehensive knowledge base that will contribute to the development of all CAM-based products, 2) a new textile-based assembly process for CAM that is 3X faster than the sheet-based approach, and 3) a woven TEBV ready for in vivo testing.

In the framework of the transition toward condition-based maintenance, connected objects deployment is reinventing monitoring processes. This is extremely relevant with respect to corrosion which represents a significant issue in aeronautics. In 2016 the annual corrosion cost for commercial aircraft fleet operated by European airlines was estimated to 2.2 B$. Anticipating corrosive conditions ahead of time is estimated to generate between 15% and 35% of cost savings. Specific coatings are used to prevent corrosion but remain limited in their ability to completely avoid structural corrosion specially in harsh operational environment. To detect such damages, nondestructive testing methodologies for corrosion consist in “on ground” regular visual inspection which does not allow detection of the corrosion damage premises, precise quantification of corrosion damage size, and prediction of the remaining useful life of associated parts. Adding on board native connectivity to aircraft metallic parts appears as the key technology to safely face this issue while minimizing costs and environmental impact. This goes through embedding ultrasonic sensors into aeronautic airframe parts and providing them with on board structural health monitoring algorithms and digital twins able to improve operational availability without compromising safety. COQTEL is the joint multidisciplinary effort of French experts in structural health monitoring (PIMM lab), ultrasonic hardware designing (CTEC SME), aerospace metallic parts coating (RESCOLL SME), and corrosion and fatigue modelling (I2M lab) to face this challenge. It proposes to move from classical “on ground” non-destructive testing to “on board” condition-based maintenance by embedding ultrasonic sensors in aircraft metallic parts and by developing and validating dedicated hardware, digital twins, and algorithms endowing airframe parts with built-in corrosion monitoring functionalities. The ambition of COQTEL is to detect the premises of corrosion, to quantify the size of in situ corrosion damages, and to be able to predict associated remaining useful life in order to participate in the revival of the aeronautical industry and the SMEs accompanying it by providing them with a proof of concept of the use of intelligent aeronautical structures for predictive maintenance.

The ARCHITEC – Antireflective Reinforced nanostruCtures by HybrId TEChnologies – aims to improve antireflective (AR) optical coatings elaborated by Oblique Angle Deposition (OAD). This project follows Florian Maudet's PhD thesis work where ultra-high performance coatings were developed using gradient index multilayer stacks for applications in both the visible-SWIR [400-1800]nm and MWIR [3.5-5]µm spectral bands. The various solutions identified, although very efficient from an optical point of view (in terms of transmission) suffer from robustness problems. Thus, the main limitations of the current process are: (i) the poor mechanical strength of nanostructured layers for vis-SWIR applications, where layer degradation is noticed during handling or cleaning steps, (ii) chemical pollution within the nanostructured layers for MWIR applications, including oxidation of the semiconductors used, which leads to a decrease in optical transmission. The ARCHITEC project proposes to address these issues through hybrid technologies by bringing together three partners whose core expertise are linked to innovations in the fields of materials science and optics, namely: - the Ppna team at the Pprime Institute, - the R&T team at SAFRAN Electronics and Defense, - the SME RESCOLL. The solutions considered in this project to overcome the problems identified involve the deployment of new deposition tools and post-deposition encapsulation processes. The new deposition tools will allow samples to rotate and tilt in situ during OAD runs. Consequently, the development of complete stacks can be achieved in a single step, at constant temperature and without returning to atmospheric pressure, possibly improving the mechanical resistance of the treatments and significantly reducing pollution problems. Moreover, the in situ control of inclination and rotation means that numerous and complex architectures can be obtained. The modification of the morphology of the columns towards chevrons is a solid approach to the mechanical reinforcement of the nanostructured layers. Hybrid solutions for improving the mechanical resistance of deposits for visible-SWIR applications consist in reinforcing an AR stack structured by OAD via a Sol-Gel post-deposition, with high optical performance. This post-deposition, whether or not penetrating into the nanostructured layers, must be taken into account when developing the optical design. The Sol-Gel or aerogel solutions considered consist of: (i) fill the pores of the porous structure to reinforce it without significantly altering the optical index of the structure, (ii) apply a very thin surface layer to improve the resistance properties to mechanical aggression. In addition, it is also planned to bring new functionalities to AR stacks through Sol-Gel layers such as anti-fouling, hydrophobicity and so on. The improvement of the chemical robustness of nanostructured layers for MWIR applications consists in the addition of a dense surface layer via PVD included in the optical design. Another avenue explored will be the addition of an ultra-fine conformal and penetrating layer within structures even with a very high aspect ratio using Atomic Layer Deposition (ALD) technology. The economic and societal benefits associated with the industrialization of the solutions developed under this project are significant from both a civil and military point of view.

The overall objective of this collaborative project is to develop, from chemistry to the device, a tissue-engineered vascular conduit that remains in-situ physiologically functional on the long term, containing the core elements of a vascular tissue. Such development will be carried out from in vitro building to in vivo evaluation in small animals. In our project, 5 partners from hospital department or academic research and 2 companies bring together their knowledge, know-how and expertise from macromolecular science, physico-chemistry of the elaboration of natural polymer systems, cellular and tissue biology, to in vivo implantation and evaluation. The material study and device design is the starting point of the project. The investigated systems result from the association of different chitosan-based hydrogels. Chitosan is a natural bioresorbable and biocompatible polysaccharide well suited for tissue engineering. Such hydrogel associations (the ChitoArts) will bring the combined mechanical and biological properties required for the application. The chitoart architectures are specifically designed as templates for tissue engineering, and in a second step will be bio-functionalized with the pertinent cell types to rebuild in a combined in vitro and in vivo approach, multilayered vascular conduits with a resulting tissue organization inspired from natural blood vessels. The methodology used here will rely on the optimization of each component of the ChitoArt architectures, in relation with coordinated in vitro and in vivo evaluations of their mechanical and biological properties.