The transdermal and controlled release of active substances, or the sampling of biological fluids for analysis by carried systems, requires the availability of patches of microneedles approximately 1 mm in height, in order to limit the invasiveness of medical devices. These microneedles are conventionally manufactured by casting in silicone moulds, but other processes are being studied in order to improve the design of these MDs (e.g. hollow shapes) or to increase production rates. For example, sheets of PLA, a biosourced, biocompatible and bioabsorbable thermoplastic material, can be used to manufacture microneedles by the thermoforming process. Nevertheless, the mechanical properties and bioresorption kinetics of these microneedles need to be optimized, in order to easily cross biological tissues and modulate biodegradability. To this end, the PhD student will work on the development of PLA formulations allowing (i) to optimize the stress crystallization properties of the material, in order to stiffen the material during thermoforming, and to modulate (ii) the biodegradability kinetics of the material in a biological medium, and (iii) the porosity of the microneedles. In parallel, the PhD student will focus on post-processing processes to locally modify the surface energy of the PLA.