Maria Bassil

Artificial muscular microfibers: hydrogel with high speed tunable electroactivity

The advancement in polymer muscle-like actuator technologies is of immense importance in the development of biologically inspired designs for tissue substitutes where the mechanical robustness is combined with fast physico-chemical responsiveness, biocompatibility and electroactivity. The multiformability (films, fibres, tubules,…) and the multifunctionality (response to temperature, pH, electromagnetic excitation,…) of hydrogels make them a great candidate for electro-bio-active artificial implantable muscular fibers and as soft actuators for gentle micro-scale manipulations. With an end objective to conceive and fabricate a system with instantaneous response to external stimuli, we present the results of an experimental method used to prepare long thin self-assembled hydrogel fibers with aspect ratio greater than 105 (length/diameter). We show for the first time that these fibers are electroactive and dynamically tunable under low applied electric field (as low as 500 V m−1) with high potential in instantaneous sensing of pH and ionic strength variations in their surrounding medium.

Electrochemical and electromechanical properties of fully hydrolyzed polyacrylamide for applications in biomimetics

This paper focuses on the development of fully hydrolyzed polyacrylamide (PAAM) hydrogel for applications in biomimetics. We present an analysis of the motion of actuators based on PAAM hydrogel in order to obtain the elementary background needed for the design of actuating devices based on this material, which has a high compatibility with living tissues. The gel properties are investigated, the electroactivity of the hydrogel is shown and a qualitative–quantitative study demonstrating the basics of motion of such actuators is presented.

A Closer Look at the Polyacrylamide Fibers for Natural-Like Artificial Muscle Fabrication

Polyacrylamide (PAAM) gels suits better the artificial muscle fabrication despite their response time which stays low compared to natural human muscle. This main problem is due to their bulky form where the ions exchange takes a long time compared to the microsecond scale in human muscle. Thus a successful artificial muscle will need to replicate the small scales of the muscle fibers that can achieve fast response. In this study we develop a technique for PAAM gel fibers fabrication with micrometric diameter, 1D structure, aiming to convert isotropic swelling into a directional one and we propose an electrical activation mode for a linear actuation mechanism.

Photovoltaic Properties of Polyaniline-Titania Composite for Hybrid Solar Cells Applications

Solar energy harvesting has been extensively studied in the last three decades to provide a green energy source. Hybrid photovoltaics (HPV) based on titania (TiO 2 ) are researched for their easiness of production and low cost. Nanostructured mesoporous titania films and conductive polymers were used recently to form hybrid solar cells [1]. TiO 2 , mainly an n-type semiconductor with a band gap of 4.2 eV, is employed in several applications from which paints form the highest world use of titania making it an attractive material to use in HPV industry. On the other side, our targeted conductive polymer is polyaniline (PANI), a hole conductor polymer, which is used in such HPV cells due to its high charge-carriers mobility, absorption coefficient in the visible range and environmental stability. PANI and nanocrystalline TiO 2 films fabricated using spin coating or layer by layer assembly techniques behave as a p-n heterojunction diode and can be used as solar cells [2-4]. Precursor solutions are prepared by polymerizing aniline-HCl inside an aqueous solution of titania. To study the effect of the precursor concentration on the PANI-TiO 2 composite, polymerization of aniline is held in diverse TiO 2 concentrations in water. Industrial grade TiO 2 powders with particle size ranging from 200 nm to several μm are used. PANI-TiO 2 precursor solutions are dip coated or slot dyed on various substrates such as PMMA, PET and PP, all with metal oxide conductive coatings. Bulk PANI-TiO 2 pellets are prepared for comparison. The electrical and photovoltaic properties of the obtained films and pellets are investigated to choose the optimum blend composition for HPV cell. Finally a theoretical study and an analytical model of the HPV cell are presented relating the size of TiO 2 and PANI particles and their respective geometrical distribution inside the blend to the transport characteristics of charge carriers and the overall efficiency of the HPV cell.[1] M. McGehee, MRS Bulletin, Vol. 34, No. 2, February 2009.[2] Z. Liu, W. Guo, D. Fu and W. Chen, Synthetic Metals, Vol. 156, pp. 414–416, 2006.[3] Z. Liu, J. Zhou, H. Xue, L. Shen, H. Zang and W. Chen, Synthetic Metals, Vol. 156, pp. 721–723, 2006.[4] X. Zhang, G. Yan, H. Ding and Y. Shan, Materials Chemistry and Physics, Vol. 102, pp. 249–254, 2007.

Synthesis and characterization of a low-cost aerogel structure using classical drying methods for thermal insulation

Purpose Lightweight insulators are of major importance for the industry, in particular for thermal insulation in buildings. The purpose of this paper is to present a low-cost method to obtain aerogels with high insulating properties. Design/methodology/approach Silica aerogel structures have been obtained by a low-cost sol-gel synthesis method. Surface modification, using dimethyldichlorosilane and trimethylchlorosilane, has been applied in order to get different thermal and optical properties. Findings The samples show very promising thermal properties as tested through an infrared camera observation. A 5-mm-thick piece of aerogel is able to withstand the temperature of a brazing flame and reduce the heat by at least 150 degrees on its opposite side. The samples have a vitreous like structure as observed by SEM, some surface cracking is observed but they stay within acceptable limits. Originality/value A very good thermal insulator is obtained with a very simple and low-cost method. The bulkiness of the supercritical drying is eliminated and the obtained structure has good properties.