23 June 2010
Source: Zee News
The biggest challenge of the XXI Century is probably the sustainable use of biomass. In this sense, Amazon Rainforest appears as a great source of technological possibilities, especially in Materials Science, where this reality is very clear due, mainly, to the various Cellulose applications. The use of biomass for new materials development can be the "key ecological alternative" in the context of Renewable Energies. Amazon Rainforest puts Brazil in the center of sustainable development and new technologies discussions: the biomass exploitation has stimulated research on the use of vegetable fibers for polymer production, especially with respect to Cellulose.
Cellulose is the most abundant natural polymer on Earth, consisting of glucose-glucose linkages chains. It is almost an infinite source of green materials for sustainable and biocompatible products, and has been utilized in many fields due to its biocompatibility and chirality. Cellulose has long been harvested as commercial fibers from the seed hairs of cotton (over 94% cellulose), as bast fibers (60-80% cellulose) from flax, hemp, sisal, jute and ramie or as wood (40-55% cellulose), which is a common building material and a source for purified cellulose. Wood represents a composite material with cellulose as a major part combined in excellent form with lignin and hemicelluloses, creating a unique high-strength and durable material, and recently came again into focus as a Renewable Energy resource. Cellulose also represents the basic materials in papermaking. Its fibers have high strength and durability. They are readily wetted by water, exhibiting considerable swelling when saturated, and are hygroscopic: they absorb appreciable amounts of water when exposed to the atmosphere. Even in the wet state, natural cellulose fibers show almost no loss in strength. It is the combination of these qualities with strength and flexibility that makes cellulose of unique value for paper manufacturing.
The Amazon Rainforest is the biggest forest in the world, the last big space covered with tropical plants and animals, and also the Earth's biggest cellulose source. Its territory is a tropical rainforest located in the north side of the South American continent and is shared by 9 countries: Brazil, Bolivia, Ecuador, Peru, Colombia, Venezuela, Suriname, French Guiana and Guiana. The largest part of Amazon Rainforest is located in Brazil (60%) and covers almost half of that country. The space covered with the forest is 5.5 million square kilometers (3.4 million square miles).
The "Rain" forest is a nickname that describes the humidity that you find in tropical and equatorial forests, but it doesn't rain all the time. Tropical rainforests are always located near the equator, and are very hot. All this heat associated with great portions of water make a lot of evaporation into the air. The forest also helps to retain water in their branches, roots and soil. All of this makes these forests very humid and there is a well defined rainy season that works towards the establishment of this nickname for tropical and equatorial forests. All this heat, rain and humidity make these forests a very rich ecosystem and a habitat for many organisms. A rainforest has trees, like any other forest, but they are very different from the temperate forest in colder places like in US, Europe and parts of Asia. There are 120 foot trees, thousands of different species of plants, and all sort of rainforest animals.
Polymeric composites with amazonic vegetal fibers
In recent years, a great worldwide interest has emerged for the development of products with less environmental impact. In this context, synthetic plastic materials have received special attention. In order to find a solution for this problem, various researches about polymeric composites have been conducted to ensure environmental preservation. Among of them, natural fibers are especially interesting. Natural fibers are those found in nature and can be used directly or after processing, being divided into animal fibers, vegetable fibers, and mineral fibers.
An emphasis must be given to vegetal fibers, due to the enormous variety of plants available on Amazon. Several natural vegetal fibers are usually referred to as lignocellulosic materials. In Brazil, especially in the Amazon Rainforest, there are plenty of vegetable fibers with different chemical, physical and mechanical properties.
Researchers at Inha University in South Korea have demonstrated that cellulose, the main ingredient in paper, can bend in response to electricity. The treated cellulose is lightweight, inexpensive, and has low power requirements, compared with similar electrically active materials. Cellulose has been discovered as a smart material that can be used as sensor and actuator devices. This smart material is called Electro-active Paper (EAPap). EAPap actuator is electrically activated due to a combination of ion migration and piezoelectric effects. Once piezoelectric effect is maximized in EAPap, then this material can be used for many applications such as sensors, microelectro-mechanical systems (MEMS), speakers, microphones, transducers, and especially in energy harvesters.
EAPap material is attractive for biomimetic actuators, flying magic papers and biodegradable MEMS sensors. However, there is a challenge for the development of thin-film electrodes and thin film transistors (TFT) on EAPap materials. Since conventional micro-patterning process and wet process are not applicable, because of EAPap's flexible nature, rough surfaces and hydrophilicity, a non-conventional micro-patterning technique, which is known as micro-transfer printing (MTP), is developed for EAPap material. The MTP technique is very similar to a rubber stamping. By making a rubber stamp that has a micro pattern and depositing a thin metal layer on it, the pattern of the metal layer can be transferred to a flexible paper substrate. This process consists of a master fabrication; PDMS stamp construction, and micro pattern transfer, as described in the Figure below:
The use of biomass can be the "key ecological alternative" for Renewable Energies. Amazon Rainforest puts Brazil in the center of sustainable development discussions, and also in the new materials development for energy harvesters. Cellulose is the most abundant natural polymer on Earth: it is almost an infinite source of green materials. Due to its piezoelectric properties, it can be used in the energy harvesting devices construction. This smart material is termed as electro-active paper (EAPap).Once piezoelectric effect is maximized in EAPap, then this material can be used for many applications such as sensors, microelectro-mechanical systems (MEMS), speakers, microphones, transducers, and in energy harvesting devices. The fundamental challenge is increasing the efficiency of these devices, transforming them in a competitive technology.