Background - Nucleus pulposus degeneration is a very common musculo-skeletal pathology, which is in part responsible for low back pain, a pandemic medical problem. Artificial hydrogels are being investigated by research group around the world for the purpose of replacing the damaged tissue and thus contributing to a healing solution for low back pain. In collaboration between the LTC and the LBO, a composite reinforced hydrogel has been developed with mechanical and swelling characteristics well suited for potentially replacing the nucleus pulposus. This hydrogel contains the photoinitiator Irgacure 2959 (maximum absorption at 280 nm). It is thus polymerizable through UV exposition. In previous work, the UV illumination was obtained using an EXFO Omnicure S2000 UV light source. Hydrogel cylinders (10mm in diameter and 5 mm in thickness) were obtained with 145 mW/cm2 for 30 minutes at room temperature in vitro. The goal of this project is to develop a technological solution to polymerize homogeneously and completely the hydrogel in situ, i.e. inside the body in the annulus pulposus. Information on the polymerization status in-situ (i.e the degree of polymerization, homogeneity) would be a very useful indicator for the purpose of ensuring proper polymerization and thus the mechanical properties sought. The “probe” device is restricted to less than 6 mm in diameter in order to allow access to the nucleus pulposus by the surgeon. Proposition –We propose the following planning: 1. Defining the technical requirement of the project (illumination homogeneity, exposure time, illumination wavelength, hydrogel volume). 2. Propose different options to bring the hydrogel in-situ, to polymerize it and measure its degree of polymerization in-situ. 3. Select best option based on technical, surgical and economical aspects. 4. Realize a prototype. 5. Test it in a laboratory environment. 6. Test it in an ex vivo animal model. References 1. Borges A. Composite hydrogels for the replacement of the nucleus pulposus. EPFL thesis #4817.