Programmable Multistable Mechanisms for Safe Surgical Puncturing

We present novel medical devices for safe surgical puncturing, in particular a cannula for the treatment of retinal vein occlusion (RVO). This passive mechanical device has an adjustable stroke and exerts a puncturing force independent of operator applied displacement. The innovative feature of this tool is that puncturing stroke is decoupled from operator input thereby minimizing the possibility of overpuncturing. This is achieved using our concept of stability programming, where the user modifies the mechanism strain energy as opposed to imposing direct displacement which is the case for standard bistable mechanisms. Ultra-fast laser three-dimensional (3D) printing is used to manufacture the needle in glass. A microfluidic channel is integrated into the needle tip for drug injection. Numerical simulations and experimental measurements validate the mechanical stability behavior of the puncture mechanism and characterize its puncturing stroke and force.

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Mechanical Behavior of Hydroxyapatite-Chitosan Composite: Effect of Processing Parameters

Minerals ◽

10.3390/min11020213 ◽

2021 ◽

Vol 11 (2) ◽

pp. 213

Author(s):

Hamid Ait Said ◽

Hassan Noukrati ◽

Hicham Ben Youcef ◽

Ayoub Bayoussef ◽

Hassane Oudadesse ◽

...

Keyword(s):

Molecular Weight ◽

Compressive Strength ◽

Mechanical Strength ◽

Bone Repair ◽

Mechanical Stability ◽

Three Dimensional ◽

Processing Parameters ◽

Composite Effect ◽

Solid Liquid ◽

The Impact

Three-dimensional hydroxyapatite-chitosan (HA-CS) composites were formulated via solid-liquid technic and freeze-drying. The prepared composites had an apatitic nature, which was demonstrated by X-ray diffraction and Infrared spectroscopy analyses. The impact of the solid/liquid (S/L) ratio and the content and the molecular weight of the polymer on the composite mechanical strength was investigated. An increase in the S/L ratio from 0.5 to 1 resulted in an increase in the compressive strength for HA-CSL (CS low molecular weight: CSL) from 0.08 ± 0.02 to 1.95 ± 0.39 MPa and from 0.3 ± 0.06 to 2.40 ± 0.51 MPa for the HA-CSM (CS medium molecular weight: CSM). Moreover, the increase in the amount (1 to 5 wt%) and the molecular weight of the polymer increased the mechanical strength of the composite. The highest compressive strength value (up to 2.40 ± 0.51 MPa) was obtained for HA-CSM (5 wt% of CS) formulated at an S/L of 1. The dissolution tests of the HA-CS composites confirmed their cohesion and mechanical stability in an aqueous solution. Both polymer and apatite are assumed to work together, giving the synergism needed to make effective cylindrical composites, and could serve as a promising candidate for bone repair in the orthopedic field.

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An isotropic elasto-damage-plastic micromechanical framework of innovative pothole patching materials featuring high-toughness, low-viscosity nanomolecular resin

International Journal of Damage Mechanics ◽

10.1177/10567895211028649 ◽

2021 ◽

pp. 105678952110286

Author(s):

H Zhang ◽

J Woody Ju ◽

WL Zhu ◽

KY Yuan

Keyword(s):

Strain Energy ◽

Three Dimensional ◽

Elastic Strain Energy ◽

Companion Paper ◽

Computational Algorithms ◽

Mechanical Behaviors ◽

High Toughness ◽

Low Viscosity ◽

Innovative Materials ◽

Continuum Thermodynamic

In a recent companion paper, a three-dimensional isotropic elastic micromechanical framework was developed to predict the mechanical behaviors of the innovative asphalt patching materials reinforced with a high-toughness, low-viscosity nanomolecular resin, dicyclopentadiene (DCPD), under the splitting tension test (ASTM D6931). By taking advantage of the previously proposed isotropic elastic-damage framework and considering the plastic behaviors of asphalt mastic, a class of elasto-damage-plastic model, based on a continuum thermodynamic framework, is proposed within an initial elastic strain energy-based formulation to predict the behaviors of the innovative materials more accurately. Specifically, the governing damage evolution is characterized through the effective stress concept in conjunction with the hypothesis of strain equivalence; the plastic flow is introduced by means of an additive split of the stress tensor. Corresponding computational algorithms are implemented into three-dimensional finite elements numerical simulations, and the outcomes are systemically compared with suitably designed experimental results.

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Comparative Study of Silk Fibroin-Based Hydrogels and Their Potential as Material for 3-Dimensional (3D) Printing

Molecules ◽

10.3390/molecules26133887 ◽

2021 ◽

Vol 26 (13) ◽

pp. 3887

Author(s):

Watcharapong Pudkon ◽

Chavee Laomeephol ◽

Siriporn Damrongsakkul ◽

Sorada Kanokpanont ◽

Juthamas Ratanavaraporn

Keyword(s):

3D Printing ◽

Silk Fibroin ◽

Biomedical Applications ◽

Mechanical Stability ◽

Three Dimensional ◽

Structure Stability ◽

3 Dimensional ◽

Critical Technology ◽

Box Structure ◽

High Degree

Three-dimensional (3D) printing is regarded as a critical technology in material engineering for biomedical applications. From a previous report, silk fibroin (SF) has been used as a biomaterial for tissue engineering due to its biocompatibility, biodegradability, non-toxicity and robust mechanical properties which provide a potential as material for 3D-printing. In this study, SF-based hydrogels with different formulations and SF concentrations (1–3%wt) were prepared by natural gelation (SF/self-gelled), sodium tetradecyl sulfate-induced (SF/STS) and dimyristoyl glycerophosphorylglycerol-induced (SF/DMPG). From the results, 2%wt SF-based (2SF) hydrogels showed suitable properties for extrusion, such as storage modulus, shear-thinning behavior and degree of structure recovery. The 4-layer box structure of all 2SF-based hydrogel formulations could be printed without structural collapse. In addition, the mechanical stability of printed structures after three-step post-treatment was investigated. The printed structure of 2SF/STS and 2SF/DMPG hydrogels exhibited high stability with high degree of structure recovery as 70.4% and 53.7%, respectively, compared to 2SF/self-gelled construct as 38.9%. The 2SF/STS and 2SF/DMPG hydrogels showed a great potential to use as material for 3D-printing due to its rheological properties, printability and structure stability.

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Alternative derivation of the higher-order constitutive model for six-parameter elastic shells

Zeitschrift für angewandte Mathematik und Physik ◽

10.1007/s00033-021-01475-0 ◽

2021 ◽

Vol 72 (2) ◽

Author(s):

Mircea Bîrsan

Keyword(s):

Energy Density ◽

Constitutive Model ◽

Strain Energy Density ◽

Strain Energy ◽

Shell Theory ◽

Constitutive Relations ◽

Three Dimensional ◽

Classical Shell Theory ◽

Three Dimensional Elasticity ◽

General Method

AbstractIn this paper, we present a general method to derive the explicit constitutive relations for isotropic elastic 6-parameter shells made from a Cosserat material. The dimensional reduction procedure extends the methods of the classical shell theory to the case of Cosserat shells. Starting from the three-dimensional Cosserat parent model, we perform the integration over the thickness and obtain a consistent shell model of order $$ O(h^5) $$ O ( h 5 ) with respect to the shell thickness h. We derive the explicit form of the strain energy density for 6-parameter (Cosserat) shells, in which the constitutive coefficients are expressed in terms of the three-dimensional elasticity constants and depend on the initial curvature of the shell. The obtained form of the shell strain energy density is compared with other previous variants from the literature, and the advantages of our constitutive model are discussed.

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Surface micro and nanostructuring of three-dimensional components of micro medical devices

Procedia CIRP ◽

10.1016/j.procir.2020.01.178 ◽

2020 ◽

Vol 95 ◽

pp. 915-920

Author(s):

Francesco Biondani ◽

Lorenzo Benassi ◽

Giuliano Bissacco ◽

Leonardo Orazi ◽

Peter T. Tang

Keyword(s):

Medical Devices ◽

Three Dimensional

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Direct coherent multi-ink printing of fabric supercapacitors

Science Advances ◽

10.1126/sciadv.abd6978 ◽

2021 ◽

Vol 7 (3) ◽

pp. eabd6978 ◽

Cited By ~ 1

Author(s):

Jingxin Zhao ◽

Hongyu Lu ◽

Yan Zhang ◽

Shixiong Yu ◽

Oleksandr I. Malyi ◽

...

Keyword(s):

System Integration ◽

High Performance ◽

Mechanical Stability ◽

Three Dimensional ◽

High Mass ◽

Wearable Electronics ◽

Energy Storage Devices ◽

Fabrication Procedure ◽

Self Powered ◽

Mechanical Devices

Coaxial fiber-shaped supercapacitors with short charge carrier diffusion paths are highly desirable as high-performance energy storage devices for wearable electronics. However, the traditional approaches based on the multistep fabrication processes for constructing the fiber-shaped energy device still encounter persistent restrictions in fabrication procedure, scalability, and mechanical durability. To overcome this critical challenge, an all-in-one coaxial fiber-shaped asymmetric supercapacitor (FASC) device is realized by a direct coherent multi-ink writing three-dimensional printing technology via designing the internal structure of the coaxial needles and regulating the rheological property and the feed rates of the multi-ink. Benefitting from the compact coaxial structure, the FASC device delivers a superior areal energy/power density at a high mass loading, and outstanding mechanical stability. As a conceptual exhibition for system integration, the FASC device is integrated with mechanical units and pressure sensor to realize high-performance self-powered mechanical devices and monitoring systems, respectively.

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Effect Of Phosphorus On Ge/Si(001) Island Formation

MRS Proceedings ◽

10.1557/proc-737-f2.4 ◽

2002 ◽

Vol 737 ◽

Author(s):

Theodore I. Kamins ◽

Gilberto Medeiros-Ribeiro ◽

Douglas A. A. Ohlberg ◽

R. Stanley Williams

Keyword(s):

Deposition Rate ◽

Strain Energy ◽

Competitive Adsorption ◽

Lattice Mismatch ◽

Three Dimensional ◽

Deposition Process ◽

Thin Layers ◽

Island Size ◽

Partial Pressures ◽

Intermediate Size

ABSTRACTWhen Ge is deposited epitaxially on Si, the strain energy from the lattice mismatch causes the Ge in layers thicker than about four monolayers to form distinctive, three-dimensional islands. The shape of the islands is determined by the energies of the surface facets, facet edges, and interfaces. When phosphorus is added during the deposition, the surface energies change, modifying the island shapes and sizes, as well as the deposition process. When phosphine is introduced to the germane/hydrogen ambient during Ge deposition, the deposition rate decreases because of competitive adsorption. The steady-state deposition rate is not reached for thin layers. The deposited, doped layers contain three different island shapes, as do undoped layers; however, the island size for each shape is smaller for the doped layers than for the corresponding undoped layers. The intermediate-size islands are the most significant; the intermediate-size doped islands are of the same family as the undoped, multifaceted “dome” structures, but are considerably smaller. The largest doped islands appear to be related to the defective “superdomes” discussed for undoped islands. The distribution between the different island shapes depends on the phosphine partial pressure. At higher partial pressures, the smaller structures are absent. Phosphorus appears to act as a mild surfactant, suppressing small islands.

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Current Update of Collagen Nanomaterials—Fabrication, Characterisation and Its Applications: A Review

Pharmaceutics ◽

10.3390/pharmaceutics13030316 ◽

2021 ◽

Vol 13 (3) ◽

pp. 316

Author(s):

Samantha Lo ◽

Mh Busra Fauzi

Keyword(s):

Mechanical Stability ◽

Health Management ◽

Three Dimensional ◽

Volume Ratio ◽

Cartilage Regeneration ◽

Nerve Tissue ◽

Electrospinning Technique ◽

Engineering Technology ◽

Promising Alternative ◽

Tissue Repair And Regeneration

Tissue engineering technology is a promising alternative approach for improvement in health management. Biomaterials play a major role, acting as a provisional bioscaffold for tissue repair and regeneration. Collagen a widely studied natural component largely present in the extracellular matrix (ECM) of the human body. It provides mechanical stability with suitable elasticity and strength to various tissues, including skin, bone, tendon, cornea and others. Even though exogenous collagen is commonly used in bioscaffolds, largely in the medical and pharmaceutical fields, nano collagen is a relatively new material involved in nanotechnology with a plethora of unexplored potential. Nano collagen is a form of collagen reduced to a nanoparticulate size, which has its advantages over the common three-dimensional (3D) collagen design, primarily due to its nano-size contributing to a higher surface area-to-volume ratio, aiding in withstanding large loads with minimal tension. It can be produced through different approaches including the electrospinning technique to produce nano collagen fibres resembling natural ECM. Nano collagen can be applied in various medical fields involving bioscaffold insertion or fillers for wound healing improvement; skin, bone, vascular grafting, nerve tissue and articular cartilage regeneration as well as aiding in drug delivery and incorporation for cosmetic purposes.

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Mesh size sensitivity analysis for interlaminar fracture of the fiber-reinforced laminated composites

Journal of Engineered Fibers and Fabrics ◽

10.1177/1558925019883460 ◽

2019 ◽

Vol 14 ◽

pp. 155892501988346 ◽

Cited By ~ 1

Author(s):

Fatih Daricik

Keyword(s):

Crack Closure ◽

Strain Energy ◽

Three Dimensional ◽

Laminated Composite ◽

Mesh Size ◽

Strain Energy Release ◽

Virtual Crack Closure Technique ◽

Closure Technique ◽

Interlaminar Fracture ◽

Element Size

The virtual crack closure technique is a well-known finite element–based numerical method used to simulate fractures and it suits well to both of two-dimensional and three-dimensional interlaminar fracture analysis. In particular, strain energy release rate during a three-dimensional interlaminar fracture of laminated composite materials can successfully be computed using the virtual crack closure technique. However, the element size of a numerical model is an important concern for the success of the computation. The virtual crack closure technique analysis with a finer mesh converges the numerical results to experimental ones although such a model may need excessive modeling and computing times. Since, the finer element size through a crack path causes oscillation of the stresses at the free ends of the model, the plies in the delaminated zone may overlap. To eliminate this problem, the element size for the virtual crack closure technique should be adjusted to ascertain converged yet not oscillating results with an admissible processing time. In this study, mesh size sensitivity of the virtual crack closure technique is widely investigated for mode I and mode II interlaminar fracture analyses of laminated composite material models by considering experimental force and displacement responses of the specimens. Optimum sizes of the finite elements are determined in terms of the force, the displacement, and the strain energy release rate distribution along the width of the model.

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