Tailoring bombyx mori silk as multifuctional material for advanced applications.

Abstract

Materials support human development. Among the available materials, polymers are nowadays essential and practically omnipresent because of their unrivalled properties. Unfortunately, polymers are synthesized from oil, and they tend to accumulate in nature, which represents a serious environmental impact.To minimize these damages, materials science suggests replacing synthetic polymers with bio-based materials. To promote the use of these more sustainable materials, the objective of the work has been to demonstrate the real applicability of bio-based materials, and more specifically Silk Fibroin (SF), a protein obtained from Bombyx mori (silkworm) cocoons. This protein displays unique physical-chemical properties that make it an interesting substrate for the development of new materials with advanced properties.Two main fields of application have been selected in this work for SF: i) electronics (active composites for sensors and actuators) and ii) porous structures for biomedicine, energy, and environment.For electronics, SF has been combined with i) carbon nanotubes (CNT) to obtain force sensors with piezoresistive responses (PR) of ~ 4 MPa-1 at pressures of 0.11 MPa; ii) with silver nanowires (SNW) to obtain PR of 26 GPa-1 when the pressure is between 0.2 and 0.4 MPa. Also, SF/SNW nanocomposites show optical transparency at SNW loads above 3%; iii) with cobalt ferrite nanoparticles (CFO) to obtain magnetic actuators with a magnetization value of ~ 10 emu·g¿1 and coercivity of almost 4 kOe, (20 wt. % CFO); and iv) with ionic liquids (IL) to obtain bending actuators with bending responses of ~ 0.5 by applying low voltages (3-5 V).SF has been processed also for the development of porous structures by i) electrospinning, to obtain scaffolds that when are combined with CFO particles, stimulate the bone cells development; ii) by salt leaching; to obtain Li-ion battery separators that lead to battery performance of 89,3 y 131,3 mAh·g¿1, for 2C and C/8 cycles respectively and iii) by gas foaming, gelation and freeze-drying, to obtain samples with porosity values above 94% and aqueous Cr adsorption capacities up to 3 mg/g.