148,254 research outputs found
Nanocellulose Fragmentation Mechanisms and Inversion of Chirality from the Single Particle to the Cholesteric Phase
Understanding how nanostructure and nanomechanics influence physical material
properties on the micro- and macroscale is an essential goal in soft condensed
matter research. Mechanisms governing fragmentation and chirality inversion of
filamentous colloids are of specific interest because of their critical role in
load-bearing and self-organizing functionalities of soft nanomaterials. Here we
provide a fundamental insight into the self-organization across several length
scales of nanocellulose, an important bio-colloid system with wide-ranging
applications as structural, insulating and functional material. Through a
combined microscopic and statistical analysis of nanocellulose fibrils at the
single particle level, we show how mechanically and chemically induced
fragmentation proceed in this system. Moreover, by studying the bottom-up
self-assembly of fragmented carboxylated cellulose nanofibrils into cholesteric
liquid crystals, we show via direct microscopic observations, that the
chirality is inverted from right-handed at the nanofibril level to left-handed
at the level of the liquid crystal phase. These results improve our fundamental
understanding of nanocellulose and provide an important rationale for their
application in colloidal systems, liquid crystals and nanomaterials
Agent and cyber-physical system based self-organizing and self-adaptive intelligent shopfloor
The increasing demand of customized production results in huge challenges to the traditional manufacturing systems. In order to allocate resources timely according to the production requirements and to reduce disturbances, a framework for the future intelligent shopfloor is proposed in this paper. The framework consists of three primary models, namely the model of smart machine agent, the self-organizing model, and the self-adaptive model. A cyber-physical system for manufacturing shopfloor based on the multiagent technology is developed to realize the above-mentioned function models. Gray relational analysis and the hierarchy conflict resolution methods were applied to achieve the self-organizing and self-adaptive capabilities, thereby improving the reconfigurability and responsiveness of the shopfloor. A prototype system is developed, which has the adequate flexibility and robustness to configure resources and to deal with disturbances effectively. This research provides a feasible method for designing an autonomous factory with exception-handling capabilities
On the Nature and Shape of Tubulin Trails: Implications on Microtubule Self-Organization
Microtubules, major elements of the cell skeleton are, most of the time, well
organized in vivo, but they can also show self-organizing behaviors in time
and/or space in purified solutions in vitro. Theoretical studies and models
based on the concepts of collective dynamics in complex systems,
reaction-diffusion processes and emergent phenomena were proposed to explain
some of these behaviors. In the particular case of microtubule spatial
self-organization, it has been advanced that microtubules could behave like
ants, self-organizing by 'talking to each other' by way of hypothetic (because
never observed) concentrated chemical trails of tubulin that are expected to be
released by their disassembling ends. Deterministic models based on this idea
yielded indeed like-looking spatio-temporal self-organizing behaviors.
Nevertheless the question remains of whether microscopic tubulin trails
produced by individual or bundles of several microtubules are intense enough to
allow microtubule self-organization at a macroscopic level. In the present
work, by simulating the diffusion of tubulin in microtubule solutions at the
microscopic scale, we measure the shape and intensity of tubulin trails and
discuss about the assumption of microtubule self-organization due to the
production of chemical trails by disassembling microtubules. We show that the
tubulin trails produced by individual microtubules or small microtubule arrays
are very weak and not elongated even at very high reactive rates. Although the
variations of concentration due to such trails are not significant compared to
natural fluctuations of the concentration of tubuline in the chemical
environment, the study shows that heterogeneities of biochemical composition
can form due to microtubule disassembly. They could become significant when
produced by numerous microtubule ends located in the same place. Their possible
formation could play a role in certain conditions of reaction. In particular,
it gives a mesoscopic basis to explain the collective dynamics observed in
excitable microtubule solutions showing the propagation of concentration waves
of microtubules at the millimeter scale, although we doubt that individual
microtubules or bundles can behave like molecular ants
Integrating self-assembly and biofabrication for the development of structures with enhanced complexity and hierarchical control
Nature has evolved to grow and regenerate tissues and organs using self-assembling processes capable of organizing a wide variety of molecular building-blocks at multiple size scales. As the field of biofabrication progresses, it is essential to develop innovative ways that can enhance our capacity to build more complex macroscopic structures using molecular and nanoscale components in a rational manner. In this review, we highlight the emerging opportunities, advantages, and challenges of incorporating self-assembly with biofabrication for the development of more biologically relevant, active, and functional structures. The review is organized in four sections. First, to better appreciate the benefits of this integrated approach, we summarize recent advances in self-assembly and biofabrication aimed at improving hierarchical control. Then, we discuss work focused on combining self-assembly with biofabrication in three areas including a) conventional bioprinting techniques using self-assembling bioinks; b) new methods where self-assembly drives the fabrication process, and c) techniques based on cellular self-assembly. The ultimate goal of this review is to emphasize the importance of structural hierarchy in biological systems and to highlight the potential behind the integration of biofabrication and self-assembly towards the development of more functional structures for tissue engineering and regenerative medicine
Modular Self-Reconfigurable Robot Systems
The field of modular self-reconfigurable robotic systems addresses the design, fabrication, motion planning, and control of autonomous kinematic machines with variable morphology. Modular self-reconfigurable systems have the promise of making significant technological advances to the field of robotics in general. Their promise of high versatility, high value, and high robustness may lead to a radical change in automation. Currently, a number of researchers have been addressing many of the challenges. While some progress has been made, it is clear that many challenges still exist. By illustrating several of the outstanding issues as grand challenges that have been collaboratively written by a large number of researchers in this field, this article has shown several of the key directions for the future of this growing fiel
Towards adaptive multi-robot systems: self-organization and self-adaptation
Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.The development of complex systems ensembles that operate in uncertain environments is a major challenge. The reason for this is that system designers are not able to fully specify the system during specification and development and before it is being deployed. Natural swarm systems enjoy similar characteristics, yet, being self-adaptive and being able to self-organize, these systems show beneficial emergent behaviour. Similar concepts can be extremely helpful for artificial systems, especially when it comes to multi-robot scenarios, which require such solution in order to be applicable to highly uncertain real world application. In this article, we present a comprehensive overview over state-of-the-art solutions in emergent systems, self-organization, self-adaptation, and robotics. We discuss these approaches in the light of a framework for multi-robot systems and identify similarities, differences missing links and open gaps that have to be addressed in order to make this framework possible
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