DNA Nanotechnologies for the Design of Bio-Inspired Soft Nanocomposites With Reversible Rigidity

2019 ◽  
Author(s):  
Theo Calais ◽  
Thileepan Stalin ◽  
Vincent S. Joseph ◽  
Pablo Valdivia y Alvarado
Keyword(s):  
Mechanical Properties ◽  
Dna Hybridization ◽  
Limited Range ◽  
Robot Locomotion ◽  
Dna Oligonucleotides ◽  
Dna Strands ◽  
Shape Memory Effects ◽  
Order Of Magnitude ◽  
Helicoidal Structure ◽  
Novel Strategy

Abstract Structures and mechanisms in soft robotics are primarily based on chemically versatile species such as hydrogels, polymers, or elastomers, thus offering great potential for the design of adaptive core properties. In particular, tunable rigidity is highly desirable to enable control of soft grippers or for advanced robot locomotion. However, most of the strategies explored so far rely on mechanisms, such as phase transitions or shape memory effects, that require heavy external hardware or have a limited range of tunable rigidity. In this work, we propose a novel strategy inspired by the sea cucumber dermis mechanism. High aspect ratio carbon nanotubes (CNTs) are reversibly interconnected by DNA oligonucleotides within a polyacrylamide (PAAm) hydrogel. The combination of the excellent mechanical properties of CNTs and the reversible hybridization of DNA strands into a stable double-helicoidal structure allowed the reversible tunability of mechanical properties over one order of magnitude (from ∼100 Pa to ∼1 kPa) within minutes by increasing the temperature beyond the melting temperature of DNA strands (∼50 °C). First, the functionalization strategy of CNTs with DNA strands is described and characterized. The aggregation of CNTs driven by the DNA hybridization is then demonstrated. The mechanical properties of hydrogels functionalized with CNTs are finally analyzed using rheology measurements.

Molecular Modeling as a Visualization Tool in Design of DNA Crosslinked Polyacrylamide

2004 ◽  
Author(s):  
Karin Rafaels ◽  
John Kerrigan ◽  
Noshir Langrana ◽  
David Lin
Keyword(s):  
Mechanical Properties ◽  
Critical Concentration ◽  
Computer Assisted ◽  
Nanoscale Structures ◽  
Dna Oligonucleotides ◽  
Dna Crosslinks ◽  
Sequence Of Events ◽  
Modified Dna ◽  
Dna Strands ◽  
Gel Composition

Polymers such as polyacrylamide form a diverse class of biomaterials in use today. The experimental research performed by our group has demonstrated how a critical concentration of crosslinking DNA strands can lead to gel formation in the polyacrylamide. The removal or addition of DNA strands can reverse or significantly increase the stiffness and strength of the gel. DNA is a versatile material for the exploration of nanoscale structures because its hybridization chemistry is very specific. DNA crosslinked gels use end-modified DNA oligonucleotides in the gels. The ability to choose the base sequence in the DNA crosslinks offers an opportunity to engineer the nanoscale structure of this material. However, it is extremely difficult to visualize the sequence of events that occurs when DNA is crosslinked with polyacrylamide. Computer modeling is a tool that enables the researchers to study the structural aspects of the newly engineered DNA crosslinkers. In this study, polyacrylamide gel crosslinked with DNA has been assayed with respect to energy and size using AMBER 7.0 software [1]. Since DNA-crosslinked gels are likely to find a range of applications it is important to know how to tailor the gel composition for a particular application. It is also of interest to know what the composition is that would induce the greatest change in stiffness. The molecular models generated in AMBER survey the mechanical properties of the gel as a function of crosslinker density, polyacrylamide density, and crosslinker length. The structure of an equilibrium state is computed using an explicitly solvated model. Visual inspection of the model determines other mechanical properties of the gel and helps predict chemical interactions. A long-term goal of this work is to use computer assisted modeling techniques to guide the experiments, to predict linker stiffness, and to examine other mechanical properties of the DNA crosslinker.

The Influence of the Addition of Ti on the Mechanical Properties of W-S-Ti Coatings

2006 ◽  
Vol 514-516 ◽  
pp. 687-691 ◽  
Author(s):  
Manuel Evaristo ◽  
Ana Nossa ◽  
Albano Cavaleiro
Keyword(s):  
Mechanical Properties ◽  
Friction Coefficient ◽  
Tribological Performance ◽  
The Self ◽  
Wear Coefficient ◽  
Gradual Loss ◽  
Order Of Magnitude ◽  
Amorphous Structures ◽  
Ti Content ◽  
Ti Films

In this work, W-S-Ti films were deposited by r.f. magnetron sputtering, using simultaneously WS2 and Ti targets. The atomic percentage of Ti in the coating was varied from 0 at.% up to 28 at.%. No significant variations in the S/W ratio with the increase of Ti content were observed. The increasing Ti contents in the films led to a gradual loss of crystallinity. Coatings with contents greater than ≈ 16 at.% only presents a broad peak characteristic of amorphous structures. Alloying the films with Ti led to significant improvements in the hardness (from 0.3 to 8.9 GPa). Also, the adhesive critical load continuously grew with the increase of the Ti content in the films. The wear coefficient of the films dropped more than one order of magnitude with the increase of Ti content whereas the friction coefficient was kept fairly constant with just a small increase in relation to single W-S film. In conclusion, to have a good tribological performance, the addition of Ti to the films should be balanced in order that the increase of the mechanical properties does not lead to severe loss of the self-lubricant properties.

scholarly journals Effect of Post-Process Curing and Washing Time on Mechanical Properties of mSLA Printouts

Materials ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 4856
Author(s):  
Bartłomiej Nowacki ◽  
Paweł Kowol ◽  
Mateusz Kozioł ◽  
Piotr Olesik ◽  
Jakub Wieczorek ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Bending Strength ◽  
Curing Time ◽  
Cross Sectional ◽  
Post Process ◽  
Order Of Magnitude ◽  
Static Tensile ◽  
High Roughness ◽  
Ambiguous Effect

The article discusses the influence of the post-process on the mechanical properties of elements produced with the use of the mask stereolithography (mSLA) method. Printed samples were subjected to the following post-process steps: Washing and post-curing, at various times. Then, static tensile and static bending tests were carried out, as well as Shore D hardness measurements for the inner and surface part of the sample, as well as profilographometric analysis of the surface. The post-curing time has been found to strongly affect the tensile and bending strength of printouts, and to improve their surface quality. Washing has an ambiguous effect on the strength of the printouts, but, in the end, it was found that extended washing slightly reduces the strength. Washing significantly affects the quality of the printout surface. A washing time that is too short results in a surface that strongly resembles the printing process, with high roughness. Increasing the washing time to 10 min lowers the roughness by one order of magnitude. Post-curing has also been shown to be beneficial for the cured sample with the application of shielding water. This approach results in an improvement in the flexural strength of the printouts. In general, the obtained research results indicate that, for printouts with cross-sectional dimensions of several mm, the optimal washing time is no more than 10 min and the post-curing time is at least 30 min.

scholarly journals Hardening of Nickel Alloys by Ion Implantation of Titanium and Carbon

1996 ◽  
Vol 444 ◽  
Author(s):  
S. M. Myers ◽  
D. M. Follstaedt ◽  
J. A. Knapp ◽  
T. R. Christenson
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Surface Layer ◽  
Ion Implantation ◽  
Finite Element Modeling ◽  
Yield Stress ◽  
Nickel Alloys ◽  
Element Modeling ◽  
Order Of Magnitude ◽  
Amorphous Surface

AbstractDual ion implantation of titanium and carbon was shown to produce an amorphous surface layer in annealed bulk nickel, in electroformed Ni, and in electroformed Ni7 5Fe 2 5. Diamond-tip nanoindentation coupled with finite-element modeling quantified the elastic and plastic mechanical properties of the implanted region. The amorphized matrix, with a thickness of about 100 nm, has a yield stress of approximately 6 GP and an intrinsic hardness near 16 GPa, exceeding by an order of magnitude the corresponding values for annealed bulk Ni. Implications for micro-electromechanical systems are discussed.

Strength and permeability evolution of andesite during benchtop acid dissolution experiments: implications for volcanic systems

2021 ◽  
Author(s):  
Jamie Farquharson ◽  
Bastien Wild ◽  
Alexandra Kushnir ◽  
Michael Heap ◽  
Patrick Baud ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Physical And Mechanical Properties ◽  
Permeability Evolution ◽  
Acid Dissolution ◽  
Crater Lakes ◽  
Glass Dissolution ◽  
Order Of Magnitude ◽  
Flow Pathways ◽  
Permeability Increase ◽  
Chemical Conditions

<p>Acidic crater lakes are common features of subaerial volcanic systems; indeed, research suggests the existence of over 700 volcanic lakes around the world. Their persistence requires a regular input of water (e.g., meteoric water) at a rate that exceeds the migration of fluid from the system—for example, due to evaporation or fluid flow through the porous edifice.  Flank aquifers and fumarole fields may similarly be strongly acidic environments.</p><p>In order to explore the evolution of the physical and mechanical properties of an andesite under these field-relevant chemical conditions, we performed batch reaction experiments over timescales from 1 day to 4 months. The experiments involved immersion of a suite of samples in a solution of sulfuric acid (0.125 M; pH ∼0.6). Periodically, samples were removed and their physical and mechanical properties measured. We observe a progressive loss of sample mass, along with a general increase in porosity. We attribute this to the dissolution of plagioclase,  accompanied by the generation of a microporous diktytaxitic groundmass due to glass dissolution.</p><p>Plagioclase phenocrysts are seen to undergo progressive pseudomorphic replacement by an amorphous phase enriched in silica and depleted in other, relatively more soluble, cations (Na, Ca, and Al). In the first phase of dissolution (i.e. between 1 and 10 days), this process appears to be confined to preexisting fractures within the plagioclase phenocrysts. Ultimately, however, these phenocrysts tend toward entire replacement by amorphous silica. We do not observe evidence of induced dissolution or alteration in the other mineral constituents of the material: pyroxene, cristobalite, and titanomagnetite, specifically.</p><p>Examining the required Klinkenberg corrections during permeability measurements, we quantitatively demonstrate that the relative aperture of flow pathways increases with progressive acid immersion, by as much as a factor of five. We propose that the dissolution process results in the widening of pore throats and the improvement of pore connectivity, with the effect of increasing permeability by over an order of magnitude relative to the initial measurements. Compressive strength of our samples was also decreased, insofar as porosity tends to increase.</p><p>We highlight broader implications of the observed permeability increase and strength reduction for volcanic systems including induced flank failure and related hazards, improved efficiency of volatile migration, and attendant eruption implications.</p>

Preparation and Electrochemical Characterization of DNA-modified Nanocrystalline Diamond Films

2002 ◽  
Vol 737 ◽  
Author(s):  
Wensha Yang ◽  
Orlando Auciello ◽  
James E. Butler ◽  
Wei Cai ◽  
John A. Carlisle ◽  
...  
Keyword(s):  
Dna Sequences ◽  
Dna Hybridization ◽  
Diamond Films ◽  
Nanocrystalline Diamond ◽  
Dna Oligonucleotides ◽  
Quantitative Studies ◽  
Boron Doped ◽  
Complementary Sequences ◽  
Nanocrystalline Diamond Films

ABSTRACTNanocrystalline diamond thin films of sub-micron thickness have been covalently modified with DNA oligonucleotides. Quantitative studies of hybridization of surface-bound oligonucleotides with fluorescently tagged complementary and non-complementary oligonucleotides were performed. The results show no detectable nonspecific adsorption, with extremely good selectivity between matched and mismatched sequences. Impedance spectroscopy measurements were made of DNA-modified boron-doped nanocrystalline diamond films. The results show that exposure to non-complementary sequences induce only small changes in impedance, while complementary DNA sequences produce a pronounced decrease in impedance. The combination of high stability, selectivity, and the ability to directly detect DNA hybridization via electrical means suggest that diamond may be an ideal substrate for continuously-monitoring biological sensors.

scholarly journals Predicting the Saturated Hydraulic Conductivity of Clayey Soils and Clayey or Silty Sands

Geosciences ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 393
Author(s):  
Stefania Bilardi ◽  
Domenico Ielo ◽  
Nicola Moraci
Keyword(s):  
Hydraulic Conductivity ◽  
Clay Content ◽  
Limited Range ◽  
Saturated Hydraulic Conductivity ◽  
Reliable Estimate ◽  
Clayey Soils ◽  
Geotechnical Parameters ◽  
Wide Range ◽  
Order Of Magnitude ◽  
Different Soils

Predictive models able to provide a reliable estimate of hydraulic conductivity can be useful in various geotechnical applications. Since most of the existing predictive methods for saturated hydraulic conductivity estimation are valid only for a limited range of soils or can be applied under certain restrictive conditions, a new method applicable to clayey soils and clayey or silty sands having a wide range of values of soil index properties is proposed in this study. For this purpose, 329 saturated hydraulic conductivity values, obtained by laboratory tests carried out on different soils, were collected in a database and used to develop five equations using a multiple regression approach. Each equation correlates the hydraulic conductivity with one or more geotechnical parameters. An equation was developed that predicts, within an order of magnitude, the saturated hydraulic conductivity in the range from 1.2 × 10−11 to 3.9 × 10−6 m/s, based on simple geotechnical parameters (i.e., clay content, void ratio, plastic limit, and silt content).

Novel Strategy of the Determination of Mechanical Properties of Human Carotid Atherosclerotic Plaques

2012 ◽  
Author(s):  
Renate W. Boekhoven ◽  
Richard G. P. Lopata ◽  
Marcel C. M. Rutten ◽  
Marc R. H. M. van Sambeek ◽  
Frans N. van de Vosse
Keyword(s):  
Mechanical Properties ◽  
Carotid Endarterectomy ◽  
Early Stage ◽  
Three Dimensions ◽  
Atherosclerotic Plaques ◽  
Ct Data ◽  
Novel Strategy ◽  
Unstable Plaques ◽  
Set Up

Carotid endarterectomy is the procedure of choice in patients with a recent symptomatic stenosis of 70–99%. Currently, the selection of candidates eligible for carotid endarterectomy is based on stenosis size only. However, the treatment is only beneficial for patients with unstable plaques, which comprises only 16% of the patient population [1]. Hence, identifying plaque stability at an early stage would permit timely intervention, while substantially reducing overtreatment of stable plaques. The objective of this study is to distinguish between stable and unstable carotid atherosclerotic plaques by determining the plaque geometry, the plaque composition and the mechanical properties of plaque components in three dimensions (3D). Mechanical properties from healthy vessels were assessed earlier by van den Broek et al. [2] using ultrasound (US) imaging. They obtained a dynamic dataset in 2D + t. When blood pressure and vessel wall movement are known, mechanical properties can be extracted from these data using a constitutive model. However, atherosclerotic plaques are mostly asymmetric, and present calcifications will cause unfavorable acoustic shadowing when using US. In this study, the focus is on the assessment of plaque geometry, from in vitro echo-CT data, overcoming the aforementioned problems. In an experimental set-up (Fig. 1) both healthy and endarterectomy specimens were mounted, and exposed to physiological intraluminal pressures. Echo-CT was used to image the arterial segments in 3D+t. Automated geometry assessment of the arterial segments will be demonstrated and validated using microCT (μCT).

Strengthened, recyclable shape memory rubber films with a rigid filler nano-capillary network

2019 ◽  
Vol 7 (12) ◽  
pp. 6901-6910 ◽  
Author(s):  
Wenchao Wu ◽  
Chuanhui Xu ◽  
Zhongjie Zheng ◽  
Baofeng Lin ◽  
Lihua Fu
Keyword(s):  
Mechanical Properties ◽  
Shape Memory ◽  
Memory Effects ◽  
Water Soluble ◽  
Capillary Network ◽  
Rigid Filler ◽  
Shape Memory Effects

Water-soluble CMCS nano-capillary network endowed XSBR films with improved mechanical properties, recyclability and shape memory effects.

scholarly journals Empirical surface gravities

1997 ◽  
Vol 189 ◽  
pp. 119-124
Author(s):  
P. F. L. Maxted
Keyword(s):  
Binary Stars ◽  
Short Review ◽  
Limited Range ◽  
Stellar Atmospheres ◽  
Fundamental Parameter ◽  
Dwarf Stars ◽  
Eclipsing Binary ◽  
White Dwarf Stars ◽  
Eclipsing Binary Stars ◽  
Order Of Magnitude

The surface gravity of a star (log g) is a fundamental parameter in models of stellar atmospheres. Given suitable spectra, log g can be determined from such models with an accuracy of 0.1dex, at best. Detached eclipsing binary stars can provide values of log g an order of magnitude more accurate than this, though for a more limited range of stars. Naturally, less accurate surface gravities can be obtained for a wider range of eclipsing binary stars.These facts are well known, so in this short review I will outline the types of stars to which the two methods have be usefully applied and might be applied in the near future. This naturally leads to the question of where the two ranges overlap and the comparison of results from the two methods. Techniques for allowing this comparison to made directly will be described. Surface gravities derived from winds in hot stars and (indirectly) from gravitational redshifts in white dwarf stars will also be covered briefly.

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