1. Introduction about Soft Matter
Soft nanotechnology is the study of how to control soft nanoscale structures and designing of new materials and devices with novel and valuable properties (Case and Alexandridis, 2004; Jones, 2004). Atoms and molecules are the basic building blocks of all matter. The length scale of Angstrom is used for the size of these building blocks. In case of common systems like water, sodium chloride, etc., a microscope with tens of nanometre resolution cannot detect these structures, but in case of latex particles, like a mixture of oil, surfactant molecules and water, the structure of these molecules is visible even at a resolution of micrometers (Gompper and Schick, 2006). These materials are soft because they do not posses long range molecular scale order and they can also be induced to flow because their movement energy barriers are often accessible (Case and Alexandridis, 2004).
Thermodynamically, soft matter is always a complex one, whether it is in solid or liquid state, such that the solid is not crystalline or the liquid is extremely viscous (Jones, 2002). For example, colloidal gels, liquid crystals, and polymers, generally in which conformation of molecules is not fixed. The solids are dynamically slower than the liquid ones (Bittner, A. M., 2006).
The classical systems, which have been studied since the 19th century, mainly include three largely independent systems namely dispersion colloids, polymers and systems of small amphiphiles (Gompper and Schick, 2006). Over the last two decades, it has been realised that many phenomena in these systems have the same underlying physical and chemical mechanisms. These three research areas have been combined together into a single filed of soft matter (Case and Alexandridis, 2004; Gompper and Schick, 2006). The following sub-sections briefly describe these three independent molecular systems which led to today’s soft matter. Read more at: http://www.essaywriter.co.uk/generic-methodologies-for-nanotechnology.aspx?id=DfTM9dBNUkett
Colloids are rigid particles between the size range of 1nm and 10µm, which are usually dispersed in fluid for the purpose of avoiding the colloidal system to behave as powder. Such depression is also termed as suspension, as the colloidal particles are small enough to exhibit Brownian or thermal motion by acting as large molecules. In some aspects, the colloidal dispersion behaves much like ordinary condensed matter and can therefore provide interesting model system (Gompper and Schick, 2006). Such model systems can help to gain fundamental information on processes that apply to molecular system, such as crystallisation and glass formation (Papen-Botterhuis, 2008).
Self-assembling amphiphilic molecules usually contain hydrophilic head group and a hydrophobic tail. The hydrophobic tail typically consists of several hydrocarbon chains which can be partially unsaturated with one or more double bonds or it can also be totally saturated. The hydrophilic head group part consists of a polar group, containing dipole moments which interact strongly with water (Gompper and Schick, 2006; Kelsall et al., 2005). The hydrophilic head group part may also consist of ionizable group, e.g. COOH, which leaves a residual charge that interacts strongly with solvent dipoles. Such molecular structures have been given several names in the literature, the most common of which is the Greek name “amphiphilic”, which means “loving both”. In the biological community, this is termed as “amphipathic”. Sometimes a more favoured name used is “surfactant” which is contraction of “surface-active”, because these molecular structures absorb preferentially at interfaces of water with oil or with air, which causes reduced surface tension (Gompper and Schick, 2006).
Polymers are ubiquitous and are essentially giant molecules, or sometimes macromolecules which consist of a very large number of basic units which are chemically joined to form one entity (Gompper and Schick, 2006) (Papen-Botterhuis, 2008). Polymers show reptation, i.e. transition of the polymer chain within the approachable voids between the nearest chains, above the glass transition temperature (Bittner, A. M., 2006; Papen-Botterhuis, 2008).
Integrating dispersion colloids, polymers and systems of small amphiphiles into a single field of soft matter provided larger interdisciplinary research opportunities by avoiding the similar effects to be rediscovered in each sub field. Furthermore, combination of basic elements exhibit new properties which are not found in either sub system separately (Gompper and Schick, 2006; Jones, 2004).
3. Strong Argument
This section presents a few instances as arguments where the research in literature has found soft matter to be an ideal building material at the Nanoscale.
Research in nanotechnology and industry is exploiting property changes of materials at nanoscale in order to create new products and new markets. The behaviour of the particles at nanoscale is different as compared to the macro-scale particles of the same material (ETC Group Report, 2004). For instance, with only reducing the size and making no other changes to a substance, materials may become stronger or lighter, better conductors or more heat resistant or more water soluble. A substance which is red at a meter wide scale may be green when its width is a few nano meters. Similarly, something that is malleable and soft on a macro scale may be stronger than steel at the nanoscale. One gram of catalyst material, made up of particles 10 nano meters in diameter is about hundred times more reactive as compared to one gram of the same catalyst material made of particles one micro meter in diameter (ETC Group Report, 2004; Bittner, A. M., 2006).
The intermolecular interaction of hard matter is larger as compared to the intermolecular interaction of soft matter. For example, we can assemble and disassemble soft nano structured materials without large energy requirements and at room temperature. This is because the structural changes need an amount of intermolecular energy of only a few kT (Case and Alexandridis, 2004).
Many phenomena of soft matter do not depend on the particular chemical structure of the molecular building blocks. For example, there is a universality of phase behaviour among different classes of soft material as compared to hard material. Various types of soft matter such as colloids, and copolymers self- assemble into ordered phases, which is due to the effective interactions that are repulsive at short distances and are attractive at long distances (Gompper and Schick, 2006; Stein, 2002). Read more at: http://www.essaywriter.co.uk/generic-methodologies-for-nanotechnology.aspx?id=ugt1iUXXslnvU
One of the essences of the soft matter is its flexibility, which means that atoms can move or fluctuate between some location inside the layer and certain maximum extension (Bittner, A. M., 2006). The fundamental nature of the soft matter’s (solid or gas) structure is flexibility. Polymers can be considered as an example, above the glass transition temperature. They show “Reptation” i.e., movement of a polymer between neighbouring chains (Jones, R.A.L., 2002).
4. Comparison of Soft and Hard Matter
This section highlights a few examples in the applications of soft matter where soft matter has been proven to be ideal at the nanoscale. Following are a few such examples that compare and contrast soft matter with hard matter:
An interesting recent development in the soft nanotechnology is the introduction of new techniques to pattern surfaces. These techniques are known as soft lithography. These techniques are based on advances in surface chemistry and are several orders of magnitudes cheaper than the conventional lithography typically based on hard matter. These techniques allow creation of well-ordered layers a single molecule thick on easily available substrates, such as evaporated layers of gold (Wood et al, (2003) (Papen-Botterhuis, 2008). Soft elastomers-based simple printing techniques enable surfaces to be patterned with these molecules on a sub micron scale by using cheap and easily available equipment (Stein, 2002). These developments in soft nanotechnology have offered cheap manufacturing routes for the product development in various branches of science and technology, including tissue engineering and biomedical engineering concerned with development of new skin and organs (Wood et a.l, 2003; Kelsall et a., 2005). Fig.1. presents the soft lithography process.
Cosmetics and Pharmaceutical Products:
Molecules of soap like materials such as shampoos, hair gels cosmetics and various pharmaceutical products having two more sections exhibit different chemical characters such as those of amphiphiles, can form complex nanostructured phases by self assembly (Wood et al., (2003). These complex molecular structures are also called surfactant mesophases. Fig. 2 presents an example of soap bubble cluster. Recent research in the study of the relationship of such nanoscale structures and their properties has shown a higher degree of rational design. The nanoscale structures of this soap like molecules are soft and can be used as layout for the creation of hard materials which will exhibit more precise-controlled nanoscale porosity. These materials can be used as efficient catalyst materials and can readily improve variety of chemical engineering processes (Wood et al., 2003).
Soft magnetic materials:
A large class of magnetic applications require minimum hysteresis losses per cycle. This is typically achieved by the use of soft magnetic materials having the following attributes:
b). Soft magnetic materials also allow low hysteresis loss which is the energy used in cycling the material between magnetic fields, H and -H, and back again (as described in fig. 3), while this is difficult to achieve in hard magnetic materials.
c). Large saturation is required by both soft and hard magnetic applications and is a strong feature of soft magnetic materials.
Polymers show reptation, i.e. transition of the polymer chain within the approachable voids between the nearest chains, above the glass transition temperature (Bittner, A. M., 2006; Papen-Botterhuis, 2008). In case of surface change due to chemical reactions come parts of polymer chains are modified and the modified parts can move back into the bulk. Consequently, a fresh surface is formed, while in case of hard matter surfaces negligible movement is shown.
Liposomes or Vesicles:
Nanotechnology has brought much more sophisticated and accurately targeted means of drug molecules to specific human body parts in the field of medicine. Hard matter compounds can sometimes lead to some degree of insolubility (Kaparissides et al., 2006; Wood et al., 2003). Extremely insoluble compounds, when prepared with soft nanoscale particles can be considered for the purpose of protecting the environment from undesirable side effects of the molecules. Liposomes or Vesicles are the soft nanostructures that can be used to achieve this task.
5. Latest Conclusion
Research in soft matter is going on all around the world. This section briefly summarises the very recent discoveries in this respect. Wagner (2008) has described that colloidal glass can be melted by a shear force which can result in a flow of a highly nonlinear fashion. Latest innovation in this field has found a way to put the more formal theoretical description to such type of flow. Abkarian and Viallat (2008) have described the similarities and specialities of the characteristics of individual soft particles. These include drops, red blood cells, and lipid vesicles subjected to shear flow. Their research has highlighted that such motion depends on non trivial way the particle mechanical characteristics. White et al. (2008) have devised a high frequency and large amplitude photo driven polymer oscillator made from a photo sensitive liquid crystal polymer
Soft nanotechnology has been widely agreed to be the research focus that will lead to the upcoming generation of breakthrough in all fields of science and engineering. The application of soft nanotechnology has been compared to hard matter in the fields of lithography, cosmetics and pharmaceutical products, and magnetic materials. The chemical characteristics, energy scales, universality and flexibility of soft matter present strong argument that soft matter generally exhibit better performance at nanoscale as opposed to soft matter.