Inspired by Sharks: A Biomimetic Skeleton for the Flapping, Propulsive Tail of an Aquatic Robot

2011 ◽  
Vol 45 (4) ◽  
pp. 119-129 ◽  
Author(s):  
John H. Long ◽  
Tom Koob ◽  
Justin Schaefer ◽  
Adam Summers ◽  
Kurt Bantilan ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Viscoelastic Properties ◽  
Vertebral Column ◽  
Stride Length ◽  
Viscoelastic Behavior ◽  
The Body ◽  
Functional Importance ◽  
Kinematic Constraint ◽  
Vertical Septum ◽  
Cartilaginous Fishes

AbstractThe vertebral column is the primary stiffening element of the body of fish. This serially jointed axial support system offers mechanical control of body bending through kinematic constraint and viscoelastic behavior. Because of the functional importance of the vertebral column in the body undulations that power swimming, we targeted the vertebral column of cartilaginous fishes—sharks, skates, and rays—for biomimetic replication. We examined the anatomy and mechanical properties of shark vertebral columns. Based on the vertebral anatomy, we built two classes of biomimetic vertebral column (BVC): (1) one in which the shape of the vertebrae varied and all else was held constant and (2) one in which the axial length of the invertebral joint varied and all else was held constant. Viscoelastic properties of the BVCs were compared to those of sharks at physiological bending frequencies. The BVCs with variable joint lengths were then used to build a propulsive tail, consisting of the BVC, a vertical septum, and a rigid caudal fin. The tail, in turn, was used as the propeller in a surface-swimming robot that was itself modeled after a biological system. As the BVC becomes stiffer, swimming speed of the robot increases, all else being equal. In addition, stiffer BVCs give the robot a longer stride length, the distance traveled in one cycle of the flapping tail.

The Mechanical Properties of Human Dentin: a Critical Review and Re-evaluation of the Dental Literature

2003 ◽  
Vol 14 (1) ◽  
pp. 13-29 ◽  
Author(s):  
J.H. Kinney ◽  
S.J. Marshall ◽  
G.W. Marshall
Keyword(s):  
Mechanical Properties ◽  
Viscoelastic Behavior ◽  
Apparent Size ◽  
The Body ◽  
Shear Moduli ◽  
Strength Data ◽  
Physiological Relevance ◽  
Coefficients Of Variation ◽  
Human Dentin ◽  
Composite Mechanics

The past 50 years of research on the mechanical properties of human dentin are reviewed. Since the body of work in this field is highly inconsistent, it was often necessary to re-analyze prior studies, when possible, and to re-assess them within the framework of composite mechanics and dentin structure. A critical re-evaluation of the literature indicates that the magnitudes of the elastic constants of dentin must be revised considerably upward. The Young’s and shear moduli lie between 20-25 GPa and 7-10 GPa, respectively. Viscoelastic behavior (time-dependent stress relaxation) measurably reduces these values at strain rates of physiological relevance; the reduced modulus (infinite relaxation time) is about 12 GPa. Furthermore, it appears as if the elastic properties are anisotropic (not the same in all directions); sonic methods detect hexagonal anisotropy, although its magnitude appears to be small. Strength data are re-interpreted within the framework of the Weibull distribution function. The large coefficients of variation cited in all strength studies can then be understood in terms of a distribution of flaws within the dentin specimens. The apparent size-effect in the tensile and shear strength data has its origins in this flaw distribution, and can be quantified by the Weibull analysis. Finally, the relatively few fracture mechanics and fatigue studies are discussed. Dentin has a fatigue limit. For stresses smaller than the normal stresses of mastication, ∼ 30 MPa, a flaw-free dentin specimen apparently will not fail. However, a more conservative approach based on fatigue crack growth rates indicates that if there is a pre-existing flaw of sufficient size (∼ 0.3-1.0 mm), it can grow to catastrophic proportion with cyclic loading at stresses below 30 MPa.

Nanoindentation Measurements of Bone Viscoelasticity as a Function of Hydration State

2005 ◽  
Vol 898 ◽  
Author(s):  
Amanpreet Kaur Bembey ◽  
Michelle Oyen ◽  
Andrew Bushby ◽  
Alan Boyde
Keyword(s):  
Mechanical Properties ◽  
Shear Modulus ◽  
Anisotropic Material ◽  
Viscoelastic Properties ◽  
Viscoelastic Behavior ◽  
Maximum Load ◽  
Dimensional Structure ◽  
Two Dimensional ◽  
Dehydration Process ◽  
Hydration State

AbstractBone is an anisotropic material, and its mechanical properties are determined by its microstructure as well as its composition. Mechanical properties of bone are a consequence of the proportions of, and the interactions between, mineral, collagen and water. Water plays an important role in maintaining the mechanical integrity of the composite, but the manner in which water interacts within the ultrastructure is unclear. Dentine being an isotropic two-dimensional structure presents a homogenous composite to examine the dehydration effects. Nanoindentation methods for determining the viscoelastic properties have recently been developed and are a subject of great interest. Here, one method based on elastic-viscoelastic correspondence for ‘ramp and hold’ creep testing (Oyen, J. Mater. Res., 2005) has been used to analyze viscoelastic behavior of polymeric and biological materials. The method of ‘ramp and hold’ allows the shear modulus at time zero to be determined from fitting of the displacement during the maximum load hold. Changes in the viscoelastic properties of bone and dentine were examined as the material was systematically dehydrated in a series of water:solvent mixes. Samples of equine dentine were sectioned and cryo-polished. Shear modulus was obtained by nanoindentation using spherical indenters with a maximum load hold of 120s. Samples were tested in different solvent concentrations sequentially, 70% ethanol to 50% ethanol, 70 % ethanol to 100% ethanol, 70% ethanol to 70% methanol to 100% methanol, and 70% ethanol to 100% acetone, after storage in each condition for 24h. By selectively removing and then replacing water from the composite, insights in to the ultrastructure of the tissue can be gained from the corresponding changes in the experimentally determined moduli, as well as an understanding of the complete reversibility of the dehydration process.

scholarly journals Age-dependent and radial sectional differences in the dynamic viscoelastic properties of bamboo culms and their possible relationship with the lignin structures

2020 ◽  
Vol 66 (1) ◽  
Author(s):  
Yoko Okahisa ◽  
Keisuke Kojiro ◽  
Hatsuki Ashiya ◽  
Takeru Tomita ◽  
Yuzo Furuta ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Viscoelastic Properties ◽  
Structural Variation ◽  
Thermal Softening ◽  
Peak Temperature ◽  
Outer Side ◽  
Phyllostachys Pubescens ◽  
Age Dependence ◽  
Age Dependent ◽  
S Peak

Abstract Age is an important factor that dictates bamboo’s mechanical properties. In Japan, bamboo plants aged 3–5 years are selected for use as materials because of their robustness and decorative or craft-friendly characteristics. In this study, the age-dependent and radial sectional differences in bamboo’s dynamic viscoelastic properties in relation to lignin structural variation, were evaluated. We used Phyllostachys pubescens samples at the current year and at 1.5, 3.5, 6.5, 9.5, 12.5, and 15.5 years of age. There was a clear age dependence in the peak temperature of tan δ and in the yield of thioacidolysis products derived from β-O-4 lignin structures. The highest peak temperature tan δ value was detected in 3.5-year-old bamboo, which contained the highest amount of the thioacidolysis products. Moreover, tan δ’s peak temperature was always higher on the outer side, and the ratio of S/G thioacidolysis products was always higher on the inner side of bamboo plants of all ages. These results suggest that changes in bamboo’s thermal softening properties from aging are caused by the maturation and degradation of lignin in bamboo.

scholarly journals Novel Hydrogels of Chitosan and Poly (vinyl alcohol) Reinforced with Inorganic Particles of Bioactive Glass

Polymers ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 691
Author(s):  
O. Sánchez-Aguinagalde ◽  
Ainhoa Lejardi ◽  
Emilio Meaurio ◽  
Rebeca Hernández ◽  
Carmen Mijangos ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Drug Release ◽  
Bioactive Glass ◽  
Vinyl Alcohol ◽  
Release Kinetics ◽  
The Body ◽  
Poly Vinyl Alcohol ◽  
X Ray Diffraction ◽  
Inorganic Particles ◽  
Release Studies

Chitosan (CS) and poly (vinyl alcohol) (PVA) hydrogels, a polymeric system that shows a broad potential in biomedical applications, were developed. Despite the advantages they present, their mechanical properties are insufficient to support the loads that appear on the body. Thus, it was proposed to reinforce these gels with inorganic glass particles (BG) in order to improve mechanical properties and bioactivity and to see how this reinforcement affects levofloxacin drug release kinetics. Scanning electron microscopy (SEM), X-ray diffraction (XRD), swelling tests, rheology and drug release studies characterized the resulting hydrogels. The experimental results verified the bioactivity of these gels, showed an improvement of the mechanical properties and proved that the added bioactive glass does affect the release kinetics.

scholarly journals Evolution of the viscoelastic properties of painting stratigraphies: a moisture weathering and nanoindentation approach

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Mathilde Tiennot ◽  
Davide Iannuzzi ◽  
Erma Hermens
Keyword(s):  
Mechanical Properties ◽  
Relative Humidity ◽  
Cultural Heritage ◽  
Mechanical Behaviour ◽  
Viscoelastic Properties ◽  
Viscoelastic Behaviour ◽  
Storage And Loss Moduli ◽  
Heritage Studies ◽  
Paint Films ◽  
The Impact

AbstractIn this investigation on the mechanical behaviour of paint films, we use a new ferrule-top nanoindentation protocol developed for cultural heritage studies to examine the impact of repeated relative humidity variations on the viscoelastic behaviour of paint films and their mechanical properties in different paint stratigraphies through the changes in their storage and loss moduli. We show that the moisture weathering impact on the micromechanics varies for each of these pigment-oil systems. Data from the nanoindentation protocol provide new insights into the evolution of the viscoelastic properties dsue to the impact of moisture weathering on paint films.

Influence of the mechanical stretch property of fabrics on the wear comfort of men’s suit pants

2021 ◽  
pp. 004051752110191
Author(s):  
Hiroyuki Kanai ◽  
Kentaro Ogawa ◽  
Tetsu Sasagawa ◽  
Kiyohiro Shibata
Keyword(s):  
Mechanical Properties ◽  
Pressure Measurement ◽  
Mechanical Stretch ◽  
The Body ◽  
Weft Yarn ◽  
Elongation Ratio ◽  
Weft Direction ◽  
Wear Comfort ◽  
Finishing Process ◽  
Elastic Thread

The stretch property of fabrics is one of the most important factors that provide comfort to wearers. It is expected that tension building up in the fabric can be relaxed and the garment pressure on the body can be reduced by appropriately exploiting its stretch property. Currently, the stretch property is predominantly realized using spandex. However, weaving or knitting elastic threads cannot be employed for the worsted fabric used to design men’s suits because of their effects on the mechanical properties of the fabric (e.g., embrittlement), which deteriorate with time. In this study, worsted fabric with a graded mechanical stretch property was produced, and the effect of the mechanical stretch property on comfort was verified. The mechanical stretch property is developed from the tension relaxation and fabric shrinkage along the weft yarn during the crabbing, scouring, and drying stages of the finishing process. Then, the form of the fabric is set by heating. In this study, the worsted fabric had an elongation ratio varying from 5.9% to 16.1% along the weft direction that was produced without using elastic thread. Furthermore, men’s suit pants were made from the fabrics. The effect of the stretch property on the garment comfort was verified through sensory evaluation and garment pressure measurement. The contribution of the mechanical stretch property in improving the garment comfort of men’s suit pants is discussed.

scholarly journals Injectable non-leaching tissue-mimetic bottlebrush elastomers as an advanced platform for reconstructive surgery

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Erfan Dashtimoghadam ◽  
Farahnaz Fahimipour ◽  
Andrew N. Keith ◽  
Foad Vashahi ◽  
Pavel Popryadukhin ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Reconstructive Surgery ◽  
Biomedical Applications ◽  
The Body ◽  
Surrounding Tissue ◽  
Curing Time ◽  
Materials Used ◽  
Significant Health

AbstractCurrent materials used in biomedical devices do not match tissue’s mechanical properties and leach various chemicals into the body. These deficiencies pose significant health risks that are further exacerbated by invasive implantation procedures. Herein, we leverage the brush-like polymer architecture to design and administer minimally invasive injectable elastomers that cure in vivo into leachable-free implants with mechanical properties matching the surrounding tissue. This strategy allows tuning curing time from minutes to hours, which empowers a broad range of biomedical applications from rapid wound sealing to time-intensive reconstructive surgery. These injectable elastomers support in vitro cell proliferation, while also demonstrating in vivo implant integrity with a mild inflammatory response and minimal fibrotic encapsulation.

scholarly journals 3D Plotting of Silica/Collagen Xerogel Granules in an Alginate Matrix for Tissue-Engineered Bone Implants

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 830
Author(s):  
Sina Rößler ◽  
Andreas Brückner ◽  
Iris Kruppke ◽  
Hans-Peter Wiesmann ◽  
Thomas Hanke ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Bone Regeneration ◽  
Material Properties ◽  
Viscoelastic Properties ◽  
Viscoelastic Behavior ◽  
Matrix Phase ◽  
Patient Specific ◽  
Active Player ◽  
Alginate Concentration ◽  
Alginate Matrix

Today, materials designed for bone regeneration are requested to be degradable and resorbable, bioactive, porous, and osteoconductive, as well as to be an active player in the bone-remodeling process. Multiphasic silica/collagen Xerogels were shown, earlier, to meet these requirements. The aim of the present study was to use these excellent material properties of silica/collagen Xerogels and to process them by additive manufacturing, in this case 3D plotting, to generate implants matching patient specific shapes of fractures or lesions. The concept is to have Xerogel granules as active major components embedded, to a large proportion, in a matrix that binds the granules in the scaffold. By using viscoelastic alginate as matrix, pastes of Xerogel granules were processed via 3D plotting. Moreover, alginate concentration was shown to be the key to a high content of irregularly shaped Xerogel granules embedded in a minimum of matrix phase. Both the alginate matrix and Xerogel granules were also shown to influence viscoelastic behavior of the paste, as well as the dimensionally stability of the scaffolds. In conclusion, 3D plotting of Xerogel granules was successfully established by using viscoelastic properties of alginate as matrix phase.

scholarly journals Viscoelastic properties of nanocellulose based inks for 3D printing and mechanical properties of CNF/alginate biocomposite gels

Cellulose ◽  
2018 ◽  
Vol 26 (1) ◽  
pp. 581-595 ◽  
Author(s):  
Ellinor B. Heggset ◽  
Berit L. Strand ◽  
Kristin W. Sundby ◽  
Sébastien Simon ◽  
Gary Chinga-Carrasco ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
3D Printing ◽  
Viscoelastic Properties

scholarly journals Functional Electrical Stimulation Changes Dynamic Resources in Children With Spastic Cerebral Palsy

2006 ◽  
Vol 86 (7) ◽  
pp. 987-1000 ◽  
Author(s):  
Chia-Ling Ho ◽  
Kenneth G Holt ◽  
Elliot Saltzman ◽  
Robert C Wagenaar
Keyword(s):  
Cerebral Palsy ◽  
Electrical Stimulation ◽  
Functional Electrical Stimulation ◽  
Stride Length ◽  
The Body ◽  
Stride Frequency ◽  
Spastic Cerebral Palsy ◽  
Significant Difference ◽  
Muscle Complex ◽  
Spring System

Abstract Background and Purpose. Children with cerebral palsy (CP) often are faced with difficulty in walking. The purpose of this experiment was to determine the effects of functional electrical stimulation (FES) applied to the gastrocnemius-soleus muscle complex on the ability to produce appropriately timed force and reduce stiffness (elastic property of the body) and on stride length and stride frequency during walking. Subjects and Methods. Thirteen children with spastic CP (including 4 children who were dropped from the study due to their inability to cooperate) and 6 children who were developing typically participated in the study. A crossover study design was implemented. The children with spastic CP were randomly assigned to either a group that received FES for 15 trials followed by no FES for 15 trials or a group that received no FES for 15 trials followed by FES for 15 trials. The children who were having typical development walked without FES. Kinematic data were collected for the children with CP in each walking condition and for the children who were developing typically. Impulse (force-producing ability) and stiffness were estimated from an escapement-driven pendulum and spring system model of human walking. Stride length and stride frequency also were measured. To compare between walking conditions and between the children with CP and the children who were developing typically, dimensional analysis and speed normalization procedures were used. Results. Nonparametric statistics showed that there was no significant difference between the children with CP in the no-FES condition and the children who were developing typically on speed-normalized dimensionless impulse. In contrast, the children with CP in the FES condition had a significantly higher median value than the children who were developing typically. The FES significantly increased speed-normalized dimensionless impulse from 10.02 to 16.32 when comparing walking conditions for the children with CP. No significant differences were found between walking conditions for stiffness, stride length, and stride frequency. Discussion and Conclusion. The results suggest that FES is effective in increasing impulse during walking but not in decreasing stiffness. The effect on increasing impulse does not result in more typical spatiotemporal gait parameters. [Ho CL, Holt KG, Saltzman E, Wagenaar RC. Functional electrical stimulation changes dynamic resources in children with spastic cerebral palsy. Phys Ther. 2006;86:987–1000.]

Sign in / Sign up

Export Citation Format

Share Document