BCMaterials Fortnightly Seminars #45

SARA DEL HOYO

(UPV/EHU)

PREPARATION OF POLYMER MULTILAYER SYSTEMS TO OPTIMIZE BIOMEDICAL DEVICES

There is an increasing demand of new processable biomaterials, capable of controlling cell adhesion and meeting the broad range of specific requirements needed in the development of tailored surfaces for biomedical applications. Polyethylene terephthalate (PET), a hydrophobic polymer used in traditional biomedical devices and as substrate for in vitro studies, is proposed to be modified by layer by layer assembly of polysaccharides in order to inhibit polymer–bacteria interaction and improve biological properties. This research deals with the development of a polymeric multilayer that strategically combines adhesion resistance, bacterial contact killing properties and biocides modulated releasing in order to get multiply enhanced antibacterial surfaces for biomedical applications.

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ANABEL PEREZ

(BCMaterials)

HIGH TEMPERATURE FERROMAGNETIC SHAPE MEMORY ALLOYS

Magnetically driven effects in Ni-Mn-Ga have been extensively studying during past decades. This alloys exhibit a coupling between magnetic order and crystallographic twin structure which allows the magnetic shape memory effect (MSM). It is shown that the mechanism of this effect is based on the field-induced rearrangement of twin variants in the martensitic state realized by the twin boundary motion. Up to now, Ni–Mn–Ga alloys exhibit the highest MSM effect up to 10%, which make them suitable materials for practical application as sensors and actuators. However, there are still some issues and challenges, as the improvement of mechanical properties, the reduce of twinning stress and actuation field as well as the increase of operational temperature range. Ni-Mn-Ga alloys properties have been shown to be very sensitive to composition and to additives. Previous studies have shown that the effect of doping with a fourth or/and fifth element such as Cu, Co and Fe, drastically change the martensitic transformation temperatures, T_M and magnetic properties of the alloy as curie temperature, T_C. These temperatures are fundamental parameters in terms of application, as MSM effect only takes places in the ferromagnetic martensitic state. Although if some works have been focused on increase T_M and T_C by simultaneously doping with Co and Cu or Fe and Co, any value above 80ºC for T_M and T_C in the same alloy have been achieve. Our goal is to study the influence of the simultaneous addition of the 3 elements in the Ni_50-xCo_xMn_25-yFe_yGa_25-zCu_z system in order to achieve values of T_M > 100ºC and T_C >150ºC.