Michromechanics in biogenic hydrated silica: hinges and interocking devices in diatoms.

Diatoms are single-celled organisms with rigid parts in relative motion at the micrometrescale and below. These biogenic hydrated silica structures have elaborate shapes, interlocking devices, and, in some cases, hinged structures. The silica shells of the diatoms experience various forces from the environment and also from the cell itself when it grows and divides, and the form of these micromechanical parts has been evolutionarily optimized during the last 150 million years or more, achieving mechanical stability. Linking structures of several diatom species such as Aulacoseira, Corethron, and Ellerbeckia are presented in high-resolution SEM images and their structure and presumed functions are correlated. Currently, the industry for micro- and nanoelectromechanical devices (MEMS and NEMS) puts great effort into investigating tribology on the micro- and nanometre scale. It is suggested that micro- and nanotribologists meet with diatomists to discuss future common research attempts regarding biomimetic ideas and approaches for novel and/or improved MEMS and NEMS with optimized tribological properties

Microfluidic simulation of a colonial diatom chain reveals oscillatory movement

Diatoms are single-celled organisms with rigid parts in relative motion at the micro- and nanometer length scales. Some diatom species form colonies comprising many cells. In this manuscript, the results of a two-dimensional finite element computer model are presented. This model was established to discover if diatom colonies start to exhibit some kind of »pumping« behaviour when subjected to water flow. To analyze this computationally, a model diatom colony with continuously repeated units of ten cells is investigated in a fluid dynamic simulation. In this first simple model, undisturbed fluid flow is allowed for between the single cells. The cells do not move actively, and are solely moved by the water. The initial fluid velocity is assumed between 0.01 m s–1 and 1 m s–1. Acomputational result that does not change anymore with time is called a steady state solution. Such a steady state solution is reached in all calculations performed. The steady state for a chain where initially all diatoms are spaced equally (equidistant spacing) has forces that encourage the formation of cell pairs with less distance between one another. These forces result from the flow of the surrounding fluid. The steady state for a chain with initially paired cells shows the opposite effect: the pairs tend to un-pair and head for the equidistant state again. The mutual change in forces between these two states, i.e., paired and unpaired formations, suggests that these two steady states lead into each other: The computer simulations suggest that a diatom colony subjected to water flow exhibits some kind of oscillatory movement. Such movement might facilitate nutrient uptake of the diatom colony

Field Emission Dark Current of Technical Metallic Electrodes

In the framework of the Low Emittance Gun (LEG) project, high gradient acceleration of a low emittance electron beam will be necessary. In order to achieve this acceleration a -500 kV, 250 ns FWHM, pulse will be applied in between two electrodes. Those electrodes should sustain the pulsed field without arcing, must not outgass and must not emit electrons. Ion back bombardment, and dark current will be damageable to the electron source as well as for the low emittance beam. Electrodes of commercially available OFE copper, aluminium, stainless steel, titanium and molybdenum were tested following different procedures including plasma glow discharge cleaning.Comment: 22 pages, 6 tables, 10 figures Vs 2 : graphics more readable, enhanced content Vs 3 : typo correcte

TRIBOLOGY IN BIOLOGY: BIOMIMETIC STUDIES ACROSS DIMENSIONS AND ACROSS FIELDS

ABSTRACT Biomimetics is a field that has the potential to drive major technical advances. It might substantially support successful mastering of current tribological challenges, i.e., friction, adhesion and wear in machines and devices from the meter to the nanometer scale. Science currently goes through a major change, with biology gaining increasing importance. Indeed, biology is becoming the new Leitwissenschaft. Tribology is omnipresent in biology. Various examples for biological tribosystems across dimensions are introduced to the reader, exemplifying the hierarchical nature of biomaterials, and concepts such as integration instead of additive construction, optimization of the whole instead of maximization of a single component feature, multifunctionality instead of mono-functionality and development via trial-and-error processes. The current state of biomimetics in tribology is reviewed, and possible biomimetic scenarios to overcome current tribological challenges are suggested (switchable adhesives, micromechanic devices, novel lubricants and adhesives)

Raw Materials Synthesis from Heavy Metal Industry Effluents with Bioremediation and Phytomining: A Biomimetic Resource Management Approach

Heavy metal wastewater poses a threat to human life and causes significant environmental problems. Bioremediation provides a sustainable waste management technique that uses organisms to remove heavy metals from contaminated water through a variety of different processes. Biosorption involves the use of biomass, such as plant extracts and microorganisms (bacteria, fungi, algae, yeast), and represents a low-cost and environmentally friendly method of bioremediation and resource management. Biosorption-based biosynthesis is proposed as a means of removing heavy metals from wastewaters and soils as it aids the development of heavy metal nanoparticles that may have an application within the technology industry. Phytomining provides a further green method of managing the metal content of wastewater. These approaches represent a viable means of removing toxic chemicals from the effluent produced during the process of manufacturing, and the bioremediation process, furthermore, has the potential to save metal resources from depletion. Biomimetic resource management comprises bioremediation, biosorption, biosynthesis, phytomining, and further methods that provide innovative ways of interpreting waste and pollutants as raw materials for research and industry, inspired by materials, structures, and processes in living nature