The first step of our innovation process consisted in an immersion phase. For a better understanding of our subject, we had to:
-come up with a state of the art, recording and analyzing existing or inspiring initiatives, actors, and institutions;
-meet diverse experts, from associations (ADEPA, Figure 1) to industries (I.CERAM, Figure 2), going through national institutes (CERAH, Figure 3), or hospitals (Georges Pompidou hospital, Figure 4);
-identify specific literature and technical documents regarding existing prosthesis;

This step led us to understand amputees daily lives (behaviors, psychology, life environments, healthcare system, economic resources, etc.) and to specify the main issues (such as bacterial infections) and challenges to address in order to propose them relevant and effective innovations. These contents (data, testimonies, etc.) have been collected thanks to humans and social tools (semi-directive interview grids), design tools (mood boards), and documentation tools (photography, video, sound recording).

After identifying knowledge, references, issues and constraints, we started a problem solving process by sketching first ideas, thanks to design tools, such as:
-brainstorming and post-it sessions (Figure 1), to write down the first ideas;
-cartographic and mind-mapping tools, to structure ideas;
-sketching, user journey and roadmaps, to give form to the first concepts.

Thanks to the previous step and to our network of experts, we filtered generated ideas in order to keep only the more adapted and relevant solutions regarding amputee’s behaviors, habits, psychology, life environments, economic resources, etc.

To make the step from the first ideas to tangible solutions, we designed a complete system (hardware and software solutions) including:
- an implantation stem featuring our engineered biofilm;
- a device making the bridge between the stump and a bionic prosthesis, to collect and process the signal from nerves;
- a charging station, to recharge the device and synchronize data with a distant server;
- an app / website, to monitor informations, such as device’s battery level, health status, etc.

In order to design these solutions in a relevant, feasible and comfortable way, we payed strong attention to the device dimensions, ergonomics, assemblies, materials, colors, look and feel, electronic parts, production process and cost. The following devices have been conceived and developed thanks to design and engineering knowledge, skills and tools (McNeel Rhino 3D (Figure 1) as 3D modeling tool, Luxion Keyshot as 3D rendering tool), as well as scientific and industrial advice from experts. Colors, materials and finishes have been chosen regarding our devices constraints and thanks to material databases and color charts.

We designed a fully functional stem (Figure 2 and 3) composed of:
- a biocompatible tube made of titanium, to mechanically assemble the device to the user’s stump (1.). This material have been chosen instead of stainless steel 316L thanks to the mechanical modeling of the 3D representation of a humerus bone with a prosthesis (Download the mechanical modeling here);
- a porous ceramic part (2.), surrounding the metallic tube inside the amputee’s bone (3.) to durably and safely link the tube to the bone;
- our engineered biofilm (4.), surrounding the metallic tube inside the amputee’s stump flesh;
- a nanoporous membrane made of PEDOT: PSS (5.), to confine the biofilm within our system, to fixate nerves on it, and to allow the ionic current from nerves to be transformed into an electrical current, that would be processed and used to actuate a bionic prosthesis;
- a thin structure (6.) that supports the nanoporous membrane and transmits electric current from nerves to the stem (7., 8.).

We designed an ergonomic and functional device (Figure 4) to link the stump to a bionic prosthesis, composed of:
- a three parts plastic case made of light-weight, heat and shock resistant injection moldable plastic (ABS - Acrylonitrile-Butadiene-Styrene), to safely enclose technical parts. Injection molding is a reliable process that permits a low cost mass production. Two removable shells (1.) surround the main structure (2.) to facilitate maintenance. An elastomer seal (3.) is placed between these parts and make the device waterproof. Moreover, plastic have been textured to make user’s daily interactions with his device easier;
- a antibacterial ceramic shell (4.), placed between the stump and the device, to improve hygiene and to protect the user from friction;
- electronic parts, to amplify and process the signal (5.), to charge the device (6., 7., 8.), to store (9.) and to send data (10.).

We designed an easy to use charging / synchronization station (Figure 5), composed of:
- a plastic case (1., 2.) made of ABS, to safely enclose technical parts;
- electronic parts, to charge the device thanks to induction (3.) and a USB-C plug (4.), to send and receive data via wifi and bluetooth connection (5.), to save data via a micro SD card (6.), to demonstrate the charging and synchronization process via a LED ring (7.);
- an elastic strip (8.) placed at the back of the charging station, to store cables during transportation.

We designed an efficient system to allow our device to securely exchange data with the digital world. Thanks to integrated electronic parts and to the designed digital architecture, data from nerves signals, bionic prosthesis movements, and user’s health status can be recorded, stored and exchanged. An online algorithme would learn from the user on a daily basis, and improve future interactions. To do so, our communication system (Figure 6) is composed of:
- Bluetooth Low Energy, a very energy-efficient technology enabling heavy data transfer on short distance, to share daily stored data from the device to the charging station, and vice versa;
- Wifi connection, to exchange those data with the distant secure NeuronArch server, and vice versa.

Figure 6: Communication network

Figure 7: Diagram of the app principle screens