Improved methods for studying the mechanical properties of biological systems with random length changes

1986 ◽  
Vol 24 (3) ◽  
pp. 292-300 ◽  
Author(s):  
R. B. Stein ◽  
R. Rolf ◽  
B. Calancie
Keyword(s):  
Mechanical Properties ◽  
Biological Systems ◽  
Length Changes ◽  
Improved Methods

Automated Finite Element Analysis on Tree Branches

2016 ◽  
Author(s):  
Devon Keane ◽  
Domenick Avanzi ◽  
Lance Evans ◽  
Zahra Shahbazi
Keyword(s):  
Mechanical Properties ◽  
Finite Element Analysis ◽  
Finite Element ◽  
User Interface ◽  
Elemental Analysis ◽  
Biological Systems ◽  
Complex Geometries ◽  
Analysis Software ◽  
Element Analysis

There are many instances where creating finite element analysis (FEA) requires extensive time and effort. Such instances include finite element analysis of tree branches with complex geometries and varying mechanical properties. In this paper, we discuss the development of Immediate-TREE, a program and its associated Guided User Interface (GUI) that provides researchers a fast and efficient finite elemental analysis of tree branches. This process was discussed in which finite element analysis were automated with the use of computer generated Python files. Immediate-TREE uses tree branch’s data (geometry, mechanical properties and etc.) provided through experiment and generates Python files, which were then run in finite element analysis software (Abaqus) to complete the analysis. Immediate-TREE is approximately 240 times faster than creating the model directly in the FEA software (Abaqus). The process used to develop Immediate-TREE can be applied to other finite element analysis of biological systems such as bone and tooth.

scholarly journals The Effect of Low-Level Activation on the Mechanical Properties of Isolated Frog Muscle Fibers

1971 ◽  
Vol 58 (2) ◽  
pp. 145-162 ◽  
Author(s):  
J. Lännergren
Keyword(s):  
Mechanical Properties ◽  
Sarcomere Length ◽  
Length Change ◽  
Ringer Solution ◽  
Tension Development ◽  
Low Level ◽  
Tension Response ◽  
Resting Tension ◽  
Hypertonic Solutions ◽  
Length Changes

The mechanical properties, as revealed by minute length changes, of isolated twitch fibers of the frog have been studied at rest and during low-level activation. Resting tension is 77 ± 23 mN/cm2 (mean ± SD) at 2.2 µm sarcomere length.1 The slope of the tension curve (ΔP/ΔL) recorded during a constant-speed length change of a resting fiber is initially large. At length changes exceeding about 0.18 % of the initial length of the fiber ΔP/ΔL falls abruptly and remains close to zero during the rest of the length change. The amplitude of the tension response is reduced after a length change and returns to normal in about 3 min. Hypertonic sucrose-Ringer solutions cause a small, maintained rise in tension up to 1.4–1.6 times normal osmotic strength. Higher sucrose concentrations cause relatively large, transient tension responses. The initial ΔP/ΔL is increased in moderately hypertonic solutions; it may be reduced in more strongly hypertonic solutions. Elevated [K]o (range 10–17.5 mM) causes a marked reduction in ΔP/ΔL. In this range of [K]o the reduction is not accompanied by changes in resting tension. Addition of 1–1.5 mM caffeine to the Ringer solution affects the resting tension very little but also reduces ΔP/ΔL. The results suggest that stiffness and tension development are not related in a simple way.

Atomistic And Continuum Studies Of Flaw Tolerant Nanostructuresin Biological Systems

2004 ◽  
Vol 844 ◽  
Author(s):  
Markus J. Buehler ◽  
Haimin Yao ◽  
Baohua Ji ◽  
Huajian Gao
Keyword(s):  
Mechanical Properties ◽  
Composite Structures ◽  
Biological Systems ◽  
Critical Length ◽  
Theoretical Strength ◽  
Small Scale ◽  
Bond Rupture ◽  
Length Scale ◽  
Modes Of Failure ◽  
Superior Mechanical Properties

AbstractBone-like biological materials have achieved superior mechanical properties through hierarchical composite structures of mineral and protein. Geckos and many insects have evolved hierarchical surface structures to achieve superior adhesion capabilities. What is the underlying principle of achieving superior mechanical properties of materials? Using joint atomistic-continuum modeling, we show that the nanometer scale plays a key role in allowing these biological systems to achieve such properties, and suggest that the principle of flaw tolerance and design for robustness may have had an overarching influence on the evolution of the bulk nanostructure of bone-like materials and the surface nanostructure of gecko-like animal species. We illustrate that if the characteristic dimension of materials is below a critical length scale on the order of several nanometers, Griffith theory of fracture no longer holds. An important consequence of this finding is that materials with such nano-substructures become flaw-tolerant, as the stress concentration at crack tips disappears and failure always occurs at the theoretical strength of materials, regardless of defects. The atomistic simulations complement continuum analysis and reveal a smooth transition between Griffith modes of failure via crack propagation to uniform bond rupture at theoretical strength below a nanometer critical length. This modeling resolves a long-standing paradox of fracture theories, and these results have important consequences for understanding failure of small-scale materials. Additional investigations focus on shape optimization of adhesion systems. We illustrate that optimal adhesion can be achieved when the surface of contact elements assumes an optimal shape. The results suggest that optimal adhesion can be achieved either by length scale reduction, or by optimization of the contact shape. Whereas change in shape does not lead to robustness, reducing the dimension results in robust adhesion devices.

Mechanical Properties of Cotton Yarns Mercerized in Liquid Ammonia and Sodium Hydroxide

1976 ◽  
Vol 46 (12) ◽  
pp. 872-879 ◽  
Author(s):  
M. L. Nelson ◽  
C. B. Hassenboehler ◽  
F. R. Andrews ◽  
A. R. Markezich
Keyword(s):  
Mechanical Properties ◽  
Sodium Hydroxide ◽  
Liquid Ammonia ◽  
Breaking Strength ◽  
Continuous Process ◽  
Elongation At Break ◽  
High Tension ◽  
Initial Modulus ◽  
Cotton Yarns ◽  
Length Changes

Yarns spun from high- and low-maturity cottons were mercerized in liquid ammonia in a continuous process, and in liquid ammonia and sodium hydroxide in skein form under various tensions. Both swelling agents produced similar changes in mechanical properties (breaking strength, tenacity, elongation-at-break, and initial modulus) under comparable conditions. Mercerization under high tension increased breaking strength and tenacity and decreased elongation-at-break. Slack mercerization in caustic resulted in elongations-at-break substantially higher than did ammonia treatment. A major difference between reagents was noted during treatment. When skeins were swollen slack and then restretched, much greater force was required to restretch ammonia-swollen skeins, and they could not be stretched as much as those that were caustic-swollen. Measurements of length changes in yarns during swelling, tensioning, and deswelling gave quantitative data to substantiate this observation. Differences in mechanism of swelling are discussed in relation to these findings.

A force transducer for measuring mechanical properties of single cardiac myocytes

1999 ◽  
Vol 277 (6) ◽  
pp. H2400-H2408 ◽  
Author(s):  
C. Tasche ◽  
E. Meyhöfer ◽  
B. Brenner
Keyword(s):  
Mechanical Properties ◽  
Laser Beam ◽  
Cardiac Myocytes ◽  
Cardiac Myocyte ◽  
Isometric Force ◽  
Force Transducer ◽  
Cardiac Cells ◽  
Beam Deflection ◽  
Resonance Frequencies ◽  
Length Changes

We have described a transducer design capable of recording forces generated by single cardiac myocytes with sufficient temporal resolution to detect force responses to rapid length changes. Our force sensors were made from thin steel foils that act as cantilevers whose bending is monitored by reflection off a laser beam. Deflection of the laser beam is measured by a differential photodiode detector. A small, 50-μm-thick tungsten needle attached to the free end of the steel foil allowed us to glue single cardiac cells to the force transducer. The transducers have compliances of ∼0.02 m/N and resonance frequencies between 2 and 3 kHz. The resolution is ∼18 nN rms at a detector bandwidth of 16 kHz, so we were able to resolve 0.2% of the maximum isometric force (∼12 μN) developed by a single cardiac myocyte. We have demonstrated that the transducer is well suited to analysis of mechanical properties of single ventricular myocytes, for example, the recording of isometric forces and rate constants of force redevelopment after rapid release-restretch maneuvers.

scholarly journals Healable thermoset polymer composite embedded with stimuli-responsive fibres

2012 ◽  
Vol 9 (77) ◽  
pp. 3279-3287 ◽  
Author(s):  
Guoqiang Li ◽  
Harper Meng ◽  
Jinlian Hu
Keyword(s):  
Mechanical Properties ◽  
Human Skin ◽  
Biological Systems ◽  
Healing Process ◽  
Self Healing ◽  
Stimuli Responsive ◽  
Closed Crack ◽  
Healing Efficiency ◽  
Thermoset Polymer ◽  
Crack Interface

Severe wounds in biological systems such as human skin cannot heal themselves, unless they are first stitched together. Healing of macroscopic damage in thermoset polymer composites faces a similar challenge. Stimuli-responsive shape-changing polymeric fibres with outstanding mechanical properties embedded in polymers may be able to close macro-cracks automatically upon stimulation such as heating. Here, a stimuli-responsive fibre (SRF) with outstanding mechanical properties and supercontraction capability was fabricated for the purpose of healing macroscopic damage. The SRFs and thermoplastic particles (TPs) were incorporated into regular thermosetting epoxy for repeatedly healing macroscopic damages. The system works by mimicking self-healing of biological systems such as human skin, close (stitch) then heal, i.e. close the macroscopic crack through the thermal-induced supercontraction of the SRFs, and bond the closed crack through melting and diffusing of TPs at the crack interface. The healing efficiency determined using tapered double-cantilever beam specimens was 94 per cent. The self-healing process was reasonably repeatable.

scholarly journals Time dependent stress relaxation and recovery in mechanically strained 3D microtissues

2020 ◽  
Author(s):  
Matthew Walker ◽  
Michel Godin ◽  
James L. Harden ◽  
Andrew E. Pelling
Keyword(s):  
Mechanical Properties ◽  
Stress Relaxation ◽  
Single Cells ◽  
Collagen Matrix ◽  
Step Length ◽  
Linear Process ◽  
The Body ◽  
Time Dependent ◽  
Step Size ◽  
Length Changes

AbstractCharacterizing the time-dependent mechanical properties of cells is not only necessary to determine how they deform, but also to fully understand how external forces trigger biochemical-signaling cascades to govern their behavior. Presently mechanical properties are largely assessed by applying local shear or compressive forces on single cells in isolation grown on non-physiological 2D surfaces. In comparison, we developed the microfabricated vacuum actuated stretcher to measure tensile loading of 3D multicellular ‘microtissue’ cultures. With this approach, we assessed here the time-dependent stress relaxation and recovery responses of microtissues, and quantified the spatial remodeling that follows step length changes. Unlike previous results, stress relaxation and recovery in microtissues measured over a range of step amplitudes and pharmacological treatments followed a stretched exponential behavior describing a broad distribution of inter-related timescales. Furthermore, despite a performed compendium of experiments, all responses led to a single linear relationship between the residual elasticity and degree of stress relaxation, suggesting that these mechanical properties are coupled through interactions between structural elements and the association of cells with their matrix. Lastly, although stress relaxation could be quantitatively and spatially linked to recovery, they differed greatly in their dynamics; while stress recovery behaved as a linear process, relaxation time constants changed with an inverse power law with step size. This assessment of microtissues offers insights into how the collective behavior of cells in a 3D collagen matrix generate the dynamic mechanical properties of tissues, which is necessary to understanding how cells deform and sense mechanical forces in the body.

Sign in / Sign up

Export Citation Format

Share Document