Since surfaces and interfaces of soft materials (“soft interface”) play an important role in various technological applications, precise control of soft interfaces would greatly promote the innovation of future science and technology. This study investigated the design of soft interfaces by biomimetic approach such as nano-texturing of polymer thin films, and high-density polymer brush immobilization to achieve the control of wettability and tribological characteristics. The anisotropic wetting which can preset on the desert beetle surface was designed by micropatterned fluoroalkylsilane monolayer surfaces consisting of a hydrophilic/hydrophobic area. The lotus leaf like nano-texture was fabricated on the fluoropolymer film surface by nanoimprinting technique to reveal lotus effect with an water and oil repellency based on the Cassie mode wetting. Super hydrophilic surface was fabricated on the silicon wafer by surface grafting of zwitter-type polyelectrolyte bearing phosphorylcholine groups which exist as a hydrophilic group in biomembrane. A water droplet on the polyelectrolyte brush surface showed a very low contact angle, and the air bubble and hydrocarbon liquid were hardly attached to the brush surface in the hydrated state. The phosphobetaine-type polyelectrolyte brush showed a low friction coefficient in humid air and aqueous solution because the hydrated brush formed a boundary layer for water lubrications.
In biological systems, there are several “nano machines” whose mechanical motions are triggered by ATP (adenosine-5'-triphosphate). We expected that integration of such unique biological mechanisms into materials chemistry could open a door to conceptually new bioresponsive nano devices. Chaperonin proteins are one of those, whose biological function is to assist folding of newly formed or denatured proteins by taking them inside their cylindrical nanoscopic cavity. We have developed a semibiological molecular machine by chemical modification of chaperonin GroEL, which was capable of controlling the releasing process of denatured proteins in response to ATP and light as input stimuli. Furthermore, chemical modification of engineered GroEL with spiropyran allowed for formation of 1D tubular assemblies of GroELs, which are capable of encapsulating denatured proteins into their nanoscopic cavities. On the other hand, inspired by biological molecular machines such as chaperonin, we have also developed completely synthetic molecular machines, consisting of ferrocene and photoresponsive units. These molecular machines are programmed to operate via interlocking of multiple different movable units with restricted motions via both covalent and non-covalent bonds.
The semi-terrestrial isopod, Ligia exotica, lives on the seashore among jetties and rocks. It shows poor resistance to desiccation and cannot live without seawater. When it is exposed to dry conditions, its body weight decreases to 90% of the initial weight within three hours. When subsequently presented with wet paper, legs VI- and VII-th of the animal are firmly apposed and stationed for a while. Since the body weight had increased after this behaviour, a pair of caudal legs seemed to play an important role to absorb water. Morphological observations of those caudal legs revealed that there is a series of thin cuticler protrusions, oriented in several parallel lines, which is developed on from 2nd to 5th podite of the VI-th preiopod and 6th podite of the VII-th pereiopod. When we immersed each leg from the tip, the water flows along those series of thin cuticler protrusions. The animal absorbs water along those surface structures of the caudal legs.
Living organisms produce a wide variety of materials at room temperature and atmospheric pressure. Moreover, each produced material plays a key role in each function in biological systems. “Biomimetic materials processing (BMMP)” is defined as the design and synthesis of new functional materials by refining knowledge and understanding of related biological products, structures, functions and processes. Hence the BMMP is not a simple imitation of biological materials processes, but is advanced materials processing for bionics, electronics, photonics, mechatronics and so on. By means of this BMMP we can prepare “biomimetic materials” or more widely “bioinspired materials”. We can also prepare “biomimetic surfaces” or “bioinspired surfaces” by using the BMMP concept.
Wood cell wall, consisting of polysaccharides (cellulose and hemicelluloses) and an aromatic polymer (lignin), exhibits a honeycomb-like arrangement. Our research group has been making attempts to reconstruct those wood components, isolated through a biorefinery process, to prepare a wood-cell-wall-mimicking material, aiming at better understanding of the function of each wood component, and serving a novel, functional material. This article shows a protocol to prepare honeycomb-patterned cellulose from the ones with two different polymorphisms as a basic framework of artificial cell wall structure. It also illustrates the effect of the presence of other wood cell wall components (hemicelluloses and lignin) adsorbed onto the framework on its physical property.
Cell functions are known to be regulated not only by the biochemical or physiological conditions of extracellular milieu but also by the mechanical conditions of substrate surface or extracellular matrix. The detailed understandings for the cellular responses induced by such mechanical field or mechanical stimuli, and its application for systematic design of mechanical field of cell culture substrate are expected to establish solid basis for constructing high-functional cell manipulation materials. Especially, cell manipulation by the elastic substrates has recently drawn a strong attention in relation to the stem cell manipulation technologies. In this report, to address the mechanical design of elastic interface for cell manipulation, we will focus on the mechanics of cell adhesion and the cell motility manipulation as the dynamical control of adhesion mechanics. The potential application of the systematic design of micromechanical environment of elastic substrate for cell functional regulation is discussed.