550 research outputs found
Field-control, phase-transitions, and life's emergence
Instances of critical-like characteristics in living systems at each
organizational level as well as the spontaneous emergence of computation
(Langton), indicate the relevance of self-organized criticality (SOC). But
extrapolating complex bio-systems to life's origins, brings up a paradox: how
could simple organics--lacking the 'soft matter' response properties of today's
bio-molecules--have dissipated energy from primordial reactions in a controlled
manner for their 'ordering'? Nevertheless, a causal link of life's macroscopic
irreversible dynamics to the microscopic reversible laws of statistical
mechanics is indicated via the 'functional-takeover' of a soft magnetic
scaffold by organics (c.f. Cairns-Smith's 'crystal-scaffold'). A
field-controlled structure offers a mechanism for bootstrapping--bottom-up
assembly with top-down control: its super-paramagnetic components obey
reversible dynamics, but its dissipation of H-field energy for aggregation
breaks time-reversal symmetry. The responsive adjustments of the controlled
(host) mineral system to environmental changes would bring about mutual
coupling between random organic sets supported by it; here the generation of
long-range correlations within organic (guest) networks could include SOC-like
mechanisms. And, such cooperative adjustments enable the selection of the
functional configuration by altering the inorganic network's capacity to assist
a spontaneous process. A non-equilibrium dynamics could now drive the
kinetically-oriented system towards a series of phase-transitions with
appropriate organic replacements 'taking-over' its functions.Comment: 54 pages, pdf fil
Artificial Muscles
Course material for "Artificial Muscles" e-course
Tuning Properties of Iron Oxide Nanoparticles in Aqueous Synthesis without Ligands to Improve MRI Relaxivity and SAR.
Aqueous synthesis without ligands of iron oxide nanoparticles (IONPs) with exceptional properties still remains an open issue, because of the challenge to control simultaneously numerous properties of the IONPs in these rigorous settings. To solve this, it is necessary to correlate the synthesis process with their properties, but this correlation is until now not well understood. Here, we study and correlate the structure, crystallinity, morphology, as well as magnetic, relaxometric and heating properties of IONPs obtained for different durations of the hydrothermal treatment that correspond to the different growth stages of IONPs upon initial co-precipitation in aqueous environment without ligands. We find that their properties were different for IONPs with comparable diameters. Specifically, by controlling the growth of IONPs from primary to secondary particles firstly by colloidal and then also by magnetic interactions, we control their crystallinity from monocrystalline to polycrystalline IONPs, respectively. Surface energy minimization in the aqueous environment along with low temperature treatment is used to favor nearly defect-free IONPs featuring superior properties, such as high saturation magnetization, magnetic volume, surface crystallinity, the transversal magnetic resonance imaging (MRI) relaxivity (up to r₂ = 1189 mM(-1)·s(-1) and r₂/r₁ = 195) and specific absorption rate, SAR (up to 1225.1 W·gFe(-1))
Solid-Liquid Composites for Soft Multifunctional Materials
Soft materials with a liquid component are an emerging paradigm in materials
design. The incorporation of a liquid phase, such as water, liquid metals, or
complex fluids, into solid materials imparts unique properties and
characteristics that emerge as a result of the dramatically different
properties of the liquid and solid. Especially in recent years, this has led to
the development and study of a range of novel materials with new functional
responses, with applications in topics including soft electronics, soft
robotics, 3D printing, wet granular systems and even in cell biology. Here we
provide a review of solid-liquid composites, broadly defined as a material
system with at least one, phase-separated liquid component, and discuss their
morphology and fabrication approaches, their emergent mechanical properties and
functional response, and the broad range of their applications
Design, Construction and Validation of a New Generation of Bioreactors for Tissue Engineering Applications.
132 p.The thesis reports on the design, fabrication and validation of a new generation of bioreactors for cell culture stimulation, in order to improve cell proliferation in advanced tissue engineering strategies. Bioreactors are developed to take advantage of responsive materials allowing to mimic cell microenvironments, resembling some of the most common physical stimuli within the human body. Some stimuli can be produced by polymer-based scaffolds such as magnetoelectric, which can work as mechanical and electrical actuators.Two types of bioreactors were developed: one for bone tissue engineering through magnetoelectric stimulation (through mechanical vibration and piezoelectricity) and another for muscle tissue engineering through mechanical stretching and controlled current impulses.This project encompasses several fields of engineering such as device engineering, design, mechanics and electronics, having also into account proper material selection and the final biomedical application
Mechanical Force-Triggered Drug Delivery
Advanced drug delivery systems (DDS) enhance treatment efficacy of different therapeutics in a dosage, spatial, and/or temporal controlled manner. To date, numerous chemical- or physical-based stimuli-responsive formulations or devices for controlled drug release have been developed. Among them, the emerging mechanical force-based stimulus offers a convenient and robust controlled drug release platform and has attracted increasing attention. The relevant DDS can be activated to promote drug release by different types of mechanical stimuli, including compressive force, tensile force, and shear force as well as indirect formats, remotely triggered by ultrasound and magnetic field. In this review, we provide an overview of recent advances in mechanically activated DDS. The opportunities and challenges regarding clinical translations are also discussed
Energy transfer and -conversion by functionalized nano-bio-fibers for biomedical applications
[no abstract
Beyond Equilibrium Assemblies: Applying Light, Flow, and Confinement.
We report the flow and microstructural behavior of colloidal dispersions and surfactant assemblies away from bulk equilibrium conditions. Self-assembly methods have slow time scales and large material requirements, and are not applicable to the dynamic industrial processing conditions. By introducing light, flow, and confinement, we find a mechanism for directed assembly of colloidal crystals, a regime of near-wall velocity fluctuations of surfactant assemblies under flow, and a method for generating droplets with intrinsic mechanical properties from their internal microstructures.PhDChemical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/120722/1/youngri_1.pd
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