PhD student, University of Tartu, Institute of Technology
Biofriendly moving materials that can be used as sensors, medical applications and much more.
Bioinspired technology with biocompatibility is of great interest in modern science. Potential materials to make aforementioned biomimetic devices are electrochemically active polymers (EAP). Good performance is not the only thing in this field to take into account. The structure itself has to be made out of biocompatible materials. An actuator made out of biocompatible materials has not been reached yet. My project’s objective is to produce a biofriendly moving actuator. This three layered material consists of conductive polymer electrodes with an ion permeable biopolymer membrane in between. The electrolyte in this structure is a non-toxic ionic liquid (IL) or an IL mixture. The conductive polymer for the actuator’s electrodes was chosen to be polypyrrole (PPy). It’s biofriendly, proven in experiments concerning doping it with a bioactive compounds to be released later, and cell growth. The membrane separating the electrodes was chosen to be made out of gelatin. Using ILs as electrolytes, actuators can be used in open air without worrying the electrolyte solution (the IL) evaporating or having to use encapsulation to prevent it from happening. Despite there being a large variety of ILs, only a few are used for ionic EAP materials, and all of them are toxic. In this study non-toxic ILs based on the choline cation were synthesised, some of them novel. Choline is a substance found in different places in nature. It's a water soluble vitamin; it appears in cell membranes; and it's a precursor to a neurotransmitter called acetycholine. Potential applications for this material include: wearable electronics, soft haptic devices, implantable or disposable biomedical devices, and smart prosthesis.
Abstract: The application of deep eutectic solvents based on choline chloride or lithium chloride with ethylene glycol and glycerol as low-cost, recyclable and green electrolytes for electrochromic devices is reported. Reversible electrochromic devices incorporating DESs as alternative electrolytes and bipyridinium electrochromic probes have been tested and compared to conventional systems.
Pub.: 10 Feb '17, Pinned: 31 Jul '17
Abstract: Herein we report a facile method for the scalable production of Fe3O4/Fe doped graphene nanosheets (Fe3O4/Fe–GN) from a naturally abundant seaweed resource. The granules that remained after the recovery of liquid juice from a fresh brown seaweed, Sargassum tenerrimum, were utilized as a raw material and a deep eutectic solvent (DES) generated by the complexation of choline chloride and FeCl3 (ChoCl–FeCl3) was employed as a template as well as a catalyst for the production of graphene nanosheets. Pyrolysis of a mixture of seaweed granules and DES at 700–900 °C under a 95% N2 and 5% H2 atmosphere resulted in the formation of Fe3O4/Fe–GN with a high surface area (220 m2 g−1) and high electrical conductivity (2384.6 mS m−1). The synthesized nanosheets were then tested for their electrocatalytic activity in the oxygen reduction reaction (ORR) in an alkaline fuel cell. The electrocatalyst demonstrated a positive onset potential, high cathodic current density, low hydrogen peroxide formation (<5%) and ideal 4-electron transfer for the whole potential range in alkaline media. The present study successfully demonstrates the highly stable ORR activity of the electrocatalyst even after 30000 cycles with a retention of >80% activity of the catalyst, making the functionalized graphene sheets derived from Sargassum tenerrimum a sustainable replacement for existing precious metal-based ORR catalysts.
Pub.: 26 Jan '16, Pinned: 31 Jul '17
Abstract: In continuation of investigation for environmentally benign protocol for new solvents termed deep eutectic solvents (DESs), it is herein reported results concerning the toxicity and cytotoxicity of choline chloride (ChCl) based DESs with four hydrogen bond donors including glycerine, ethylene glycol, triethylene glycol and urea. The toxicity was investigated using two Gram positive bacteria Bacillus subtilis and Staphylococcus aureus, and two Gram negative bacteria Escherichia coli and Pseudomonas aeruginosa. The cytotoxicity effect was tested using the Artemia salina leach. It was found that there was no toxic effect for the tested DESs on all of the studied bacteria confirming their benign effects on these bacteria. Nevertheless, it was found that the cytotoxicity of DESs was much higher than their individual components (e.g. glycerine, ChCl) indicating that their toxicological behavior is different. For our best knowledge this is the first time that toxicity and cytotoxicity of DESs were studied. The toxicity and cytotoxicity of DESs varied depending on the structure of components. Careful usage of the terms non-toxicity and biodegradability must be considered. More investigation on this matter is required.
Pub.: 04 Dec '12, Pinned: 31 Jul '17
Abstract: Utilization of natural polymers has attracted increasing attention because of the consumption and over-exploitation of non-renewable resources, such as coal and oil. The development of green processing of cellulose, the most abundant biorenewable material on Earth, is urgent from the viewpoints of both sustainability and environmental protection. The discovery of the dissolution of cellulose in ionic liquids (ILs, salts which melt below 100 °C) provides new opportunities for the processing of this biopolymer, however, many fundamental and practical questions need to be answered in order to determine if this will ultimately be a green or sustainable strategy. In this critical review, the open fundamental questions regarding the interactions of cellulose with both the IL cations and anions in the dissolution process are discussed. Investigations have shown that the interactions between the anion and cellulose play an important role in the solvation of cellulose, however, opinions on the role of the cation are conflicting. Some researchers have concluded that the cations are hydrogen bonding to this biopolymer, while others suggest they are not. Our review of the available data has led us to urge the use of more chemical units of solubility, such as 'g cellulose per mole of IL' or 'mol IL per mol hydroxyl in cellulose' to provide more consistency in data reporting and more insight into the dissolution mechanism. This review will also assess the greenness and sustainability of IL processing of biomass, where it would seem that the choices of cation and anion are critical not only to the science of the dissolution, but to the ultimate 'greenness' of any process (142 references).
Pub.: 24 Jan '12, Pinned: 31 Jul '17