Publications by authors named "Jianying He"

57 Publications

Simultaneously Toughening and Stiffening Elastomers with Octuple Hydrogen Bonding.

Adv Mater 2021 Jun 3;33(23):e2008523. Epub 2021 May 3.

NTNU Nanomechanical Lab, Department of Structural Engineering, Norwegian University of Science and Technology (NTNU), Trondheim, 7491, Norway.

Current synthetic elastomers suffer from the well-known trade-off between toughness and stiffness. By a combination of multiscale experiments and atomistic simulations, a transparent unfilled elastomer with simultaneously enhanced toughness and stiffness is demonstrated. The designed elastomer comprises homogeneous networks with ultrastrong, reversible, and sacrificial octuple hydrogen bonding (HB), which evenly distribute the stress to each polymer chain during loading, thus enhancing stretchability and delaying fracture. Strong HBs and corresponding nanodomains enhance the stiffness by restricting the network mobility, and at the same time improve the toughness by dissipating energy during the transformation between different configurations. In addition, the stiffness mismatch between the hard HB domain and the soft poly(dimethylsiloxane)-rich phase promotes crack deflection and branching, which can further dissipate energy and alleviate local stress. These cooperative mechanisms endow the elastomer with both high fracture toughness (17016 J m ) and high Young's modulus (14.7 MPa), circumventing the trade-off between toughness and stiffness. This work is expected to impact many fields of engineering requiring elastomers with unprecedented mechanical performance.
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http://dx.doi.org/10.1002/adma.202008523DOI Listing
June 2021

Reconfigurable Mechanical Anisotropy in Self-Assembled Magnetic Superstructures.

Adv Sci (Weinh) 2021 Apr 15;8(8):2002683. Epub 2021 Feb 15.

NTNU Nanomechanical Lab Department of Structural Engineering Norwegian University of Science and Technology (NTNU) Trondheim 7491 Norway.

Enhancement of mechanical properties in self-assembled superstructures of magnetic nanoparticles is a new emerging aspect of their remarkable collective behavior. However, how magnetic interactions modulate mechanical properties is, to date, not fully understood. Through a comprehensive Monte Carlo investigation, this study demonstrates how the mechanical properties of self-assembled magnetic nanocubes can be controlled intrinsically by the nanoparticle magnetocrystalline anisotropy (MA), as well as by the superstructure shape anisotropy, without any need for changes in structural design (i.e., nanoparticle size, shape, and packing arrangement). A low MA-to-dipolar energy ratio, as found in iron oxide and permalloy systems, favors isotropic mechanical superstructure stabilization, whereas a high ratio yields magnetically blocked nanoparticle macrospins which can give rise to metastable , as expected in cobalt ferrite simple cubic supercrystals. Such full parallel alignment of the particle moments is shown to induce mechanical anisotropy, where the superior high-strength axis can be remotely reconfigured by means of an applied magnetic field. The new concepts developed here pave the way for the experimental realization of smart magneto-micromechanical systems (based, e.g., on the permanent super-magnetostriction effect illustrated here) and inspire new design rules for applied functional materials.
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http://dx.doi.org/10.1002/advs.202002683DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8061348PMC
April 2021

Stability, deformation and rupture of Janus oligomer enabled self-emulsifying water-in-oil microemulsion droplets.

Phys Chem Chem Phys 2020 Nov 30;22(43):24907-24916. Epub 2020 Oct 30.

NTNU Nanomechanical Lab, Norwegian University of Science and Technology (NTNU), Trondheim 7491, Norway.

Microemulsions exist widely in nature, daily life and industrial manufacturing processes, including petroleum production, food processing, drug delivery, new material fabrication, sewage treatment, etc. The mechanical properties of microemulsion droplets and a correlation to their molecular structures are of vital importance to those applications. Despite studies on their physicochemical determinants, there are lots of challenges of exploring the mechanical properties of microemulsions by experimental studies. Herein, atomistic modelling was utilized to study the stability, deformation, and rupture of Janus oligomer enabled water-in-oil microemulsion droplets, aiming at revealing their intrinsic relationship with Janus oligomer based surfactants and oil structures. The self-emulsifying process from a water, oil and surfactant mixture to a single microemulsion droplet was modulated by the amphiphilicity and structure of the surfactants. Four microemulsion systems with an interfacial thickness in the range of 7.4-17.3 Å were self-assembled to explore the effect of the surfactant on the droplet morphology. By applying counter forces on the water core and the surfactant shell, the mechanical stability of the microemulsion droplets was probed at different ambient temperatures. A strengthening response and a softening regime before and after a temperature-dependent peak force were identified followed by the final rupture. This work demonstrates a practical strategy to precisely tune the mechanical properties of a single microemulsion droplet, which can be applied in the formation, de-emulsification, and design of microemulsions in oil recovery and production, drug delivery and many other applications.
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http://dx.doi.org/10.1039/d0cp03092aDOI Listing
November 2020

Vitamin K2 Modulates Vitamin D-Induced Mechanical Properties of Human 3D Bone Spheroids In Vitro.

JBMR Plus 2020 Sep 3;4(9):e10394. Epub 2020 Aug 3.

Department of Biomaterials University of Oslo Oslo Norway.

Rotational culture promotes primary human osteoblasts (hOBs) to form three-dimensional (3D) multicellular spheroids with bone tissue-like structure without any scaffolding material. Cell-based bone models enable us to investigate the effect of different agents on the mechanical strength of bone. Given that low dietary intake of both vitamin D and K is negatively associated with fracture risk, we aimed to assess the effect of these vitamins in this system. Osteospheres of hOBs were generated with menaquinone-4 (MK-4; 10μM) and 25-hydroxyvitamin D [25(OH)D; 0.01μM], alone and in combination, or without vitamins. The mechanical properties were tested by nanoindentation using a flat-punch compression method, and the mineralized extracellular bone matrix was characterized by microscopy. The in vitro response of hOBs to MK-4 and 25(OH)D was further evaluated in two-dimensional (2D) cultures and in the 3D bone constructs applying gene expression analysis and multiplex immunoassays. Mechanical testing revealed that 25(OH)D induced a stiffer and MK-4 a softer or more flexible osteosphere compared with control. Combined vitamin conditions induced the same flexibility as MK-4 alone. Enhanced levels of periostin ( < 0.001) and altered distribution of collagen type I (COL-1) were found in osteospheres supplemented with MK-4. In contrast, 25(OH)D reduced COL-1, both at the mRNA and protein levels, increased alkaline phosphatase, and stimulated mineral deposition in the osteospheres. With the two vitamins in combination, enhanced gene expression of periostin and COL-1 was seen, as well as extended osteoid formation into the central region and increased mineral deposition all over the area. Moreover, we observed enhanced levels of osteocalcin in 2D and osteopontin in 3D cultures exposed to 25(OH)D alone and combined with MK-4. In conclusion, the two vitamins seem to affect bone mechanical properties differently: vitamin D enhancing stiffness and K2 conveying flexibility to bone. These effects may translate to increased fracture resistance in vivo. © 2020 The Authors. published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.
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http://dx.doi.org/10.1002/jbm4.10394DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7507351PMC
September 2020

When Thermodynamic Properties of Adsorbed Films Depend on Size: Fundamental Theory and Case Study.

Nanomaterials (Basel) 2020 Aug 27;10(9). Epub 2020 Aug 27.

Porelab, Department of Chemistry, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway.

Small system properties are known to depend on geometric variables in ways that are insignificant for macroscopic systems. Small system considerations are therefore usually added to the conventional description as needed. This paper presents a thermodynamic analysis of adsorbed films of any size in a systematic and general way within the framework of Hill's nanothermodynamics. Hill showed how to deal with size and shape as variables in a systematic manner. By doing this, the common thermodynamic equations for adsorption are changed. We derived the governing thermodynamic relations characteristic of adsorption in small systems, and point out the important distinctions between these and the corresponding conventional relations for macroscopic systems. We present operational versions of the relations specialized for adsorption of gas on colloid particles, and we applied them to analyze molecular simulation data. As an illustration of their use, we report results for CO2 adsorbed on graphite spheres. We focus on the spreading pressure, and the entropy and enthalpy of adsorption, and show how the intensive properties are affected by the size of the surface, a feature specific to small systems. The subdivision potential of the film is presented for the first time, as a measure of the film's smallness. For the system chosen, it contributes with a substantial part to the film enthalpy. This work can be considered an extension and application of the nanothermodynamic theory developed by Hill. It provides a foundation for future thermodynamic analyses of size- and shape-dependent adsorbed film systems, alternative to that presented by Gibbs.
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http://dx.doi.org/10.3390/nano10091691DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7558047PMC
August 2020

Self-Deicing Electrolyte Hydrogel Surfaces with Pa-level Ice Adhesion and Durable Antifreezing/Antifrost Performance.

ACS Appl Mater Interfaces 2020 Aug 21;12(31):35572-35578. Epub 2020 Jul 21.

NTNU Nanomechanical Lab, Department of Structural Engineering, Norwegian University of Science and Technology (NTNU), 7491 Trondheim, Norway.

Despite the remarkable advances in mitigating ice formation and accretion, however, no engineered anti-icing surfaces today can durably prevent frost formation, droplet freezing, and ice accretion in an economical and ecofriendly way. Herein, sustainable and low-cost electrolyte hydrogel (EH) surfaces are developed by infusing salted water into a hydrogel matrix for avoiding icing. The EH surfaces can both prevent ice/frost formation for an extremely long time and reduce ice adhesion strength to ultralow value (Pa-level) at a tunable temperature window down to -48.4 °C. Furthermore, ice can self-remove from the tilted EH surface within 10 s at -10 °C by self-gravity. As demonstrated by both molecular dynamic simulations and experiments, these extreme performances are attributed to the diffusion of ions to the interface between EH and ice. The sustainable anti-icing properties of EH can be maintained by replenishing in real-time with available ion sources, indicating the promising applications in offshore platforms and ships.
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http://dx.doi.org/10.1021/acsami.0c06912DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7660571PMC
August 2020

The effects of morphology and temperature on the tensile characteristics of carbon nitride nanothreads.

Nanoscale 2020 Jun 4;12(23):12462-12475. Epub 2020 Jun 4.

NTNU Nanomechanical Lab, Norwegian University of Science and Technology (NTNU), Trondheim 7491, Norway.

Very recently synthesized carbon nitride nanothreads (CNNTs) by compressing crystalline pyridine show outperform diamond nanothreads in chemical and physical properties. Here, using first-principles-based ReaxFF molecular dynamics (MD) simulations, a comprehensive investigation on the mechanical characteristics of seven experimentally synthesized CNNTs has been performed. All CNNTs exhibit unique tensile properties that change with molecular morphology, atomic arrangement and the distribution of nitrogen in the skeleton. The CNNTs with more effective covalent bonds at cross-sections are more mechanically robust. Surprisingly, a tiny CNNT with periodic unit structures of 56-cage shows extreme ductility because of the formation of a linear polymer via 4-step dissociation-and-reformation of bonds at extremely low temperatures in the range of 1-15 K; however, it shows brittle failure at one cross-section with low ductility at higher temperatures similar to other CNNTs at different temperatures; this offers a feasible way to design a kind of lightweight material that can be used in ultra-low temperature conditions, for example, the harsh deep space environment. The results also show that temperature significantly affects the fracture stress and rupture strain but not the effective stiffness. The analysis of atomic bond orders and bond lengthening reveals that the unique nonlinear elasticity of CNNTs is attributed to the occurrence of local bond transformations. This study provides physical insights into the tensile characteristics of CNNTs for the design and application of CNNT-based nanostructures as multifunctional materials.
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http://dx.doi.org/10.1039/d0nr03206aDOI Listing
June 2020

Enhancement of Thermal Boundary Conductance of Metal-Polymer System.

Nanomaterials (Basel) 2020 Apr 2;10(4). Epub 2020 Apr 2.

NTNU Nanomechanical Lab, Department of Structural Engineering, Norwegian University of Science and Technology (NTNU), Trondheim 7491, Norway.

In organic electronics, thermal management is a challenge, as most organic materials conduct heat poorly. As these devices become smaller, thermal transport is increasingly limited by organic-inorganic interfaces, for example that between a metal and a polymer. However, the mechanisms of heat transport at these interfaces are not well understood. In this work, we compare three types of metal-polymer interfaces. Polymethyl methacrylate (PMMA) films of different thicknesses (1-15 nm) were spin-coated on silicon substrates and covered with an 80 nm gold film either directly, or over an interface layer of 2 nm of an adhesion promoting metal-either titanium or nickel. We use the frequency-domain thermoreflectance (FDTR) technique to measure the effective thermal conductivity of the polymer film and then extract the metal-polymer thermal boundary conductance (TBC) with a thermal resistance circuit model. We found that the titanium layer increased the TBC by a factor of 2, from 59 × 10 W·m·K to 115 × 10 W·m·K, while the nickel layer increased TBC to 139 × 10 W·m·K. These results shed light on possible strategies to improve heat transport in organic electronic systems.
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http://dx.doi.org/10.3390/nano10040670DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7221886PMC
April 2020

CO wetting on pillar-nanostructured substrates.

Nanotechnology 2020 Mar 3;31(24):245403. Epub 2020 Mar 3.

NTNU Nanomechanical Lab, Norwegian University of Science and Technology (NTNU), Trondheim 7491, Norway. Department of Physics, Research Institute for Biomimetics and Soft Matter, Jiujiang Research Institute and Fujian Provincial Key Laboratory for Soft Functional Materials Research, Xiamen University, Xiamen 361005, People's Republic of China.

CO capture by dropwise CO condensation on cold solid surfaces is a promising technology. Understanding the role of the nanoscale surface and topographical features of CO droplet wetting characteristics is of importance for CO capture by this technology, but this remains unexplored as of yet. Here, using large-scale molecular dynamics (MD) simulations, the contact angle and wetting behaviors of CO droplets on pillar-structured Cu-like surfaces are investigated for the first time. Dynamic wetting simulations show that, by changing the strength of the solid-liquid attraction [Formula: see text] a smooth Cu-like surface offers a transition from CO-philic to CO-phobic. By periodically pillared roughening of the Cu-like surfaces, however, a higher contact angle and a smaller spreading exponent of a liquid CO droplet are realized. Particularly, a critical crossover of CO-philic to CO-phobic can appear. The wetting of the pillared surfaces by a liquid CO droplet proceeds non-uniformly. A liquid CO droplet is capable of exhibiting a transition from the Cassie state to the Wenzel state with increasing [Formula: see text] increasing inter-pillar distance, and increasing pillar width. The wetting morphologies of the metastable Wenzel state of a CO droplet are very different from each other. The findings will inform the ongoing design of CO-phobic solid surfaces for practical dropwise condensation-based CO capture applications.
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http://dx.doi.org/10.1088/1361-6528/ab7c49DOI Listing
March 2020

Enabling phase transition of infused lubricant in porous structure for exceptional oil/water separation.

J Hazard Mater 2020 May 22;390:122176. Epub 2020 Jan 22.

NTNU Nanomechanical Lab, Department of Structural Engineering, Norwegian University of Science and Technology (NTNU), Trondheim, 7491, Norway. Electronic address:

The fundamental mechanism behind oil/water separation materials is their surface wettability that allows either oil or water to pass through. The conventional materials for oil/water separation generally have extreme wettability, namely superhydrophilic for water separation and superhydrophobic for oil separation. Using easily accessible materials that are medium hydrophobic or even relatively hydrophilic for preparing highly efficient oil/water separators have rarely been reported. In this work, a new strategy by triggering phase transition of infused lubricant from liquid to solid state in porous structure is realized in fabricating slippery lubricant infused porous structure for oil/water separations. By infusing polyester fabric with coconut oil, after phase transition, excellent water repellency and oil permeability by an absorbing-permeating mechanism are achieved, despite the low water contact angle on the new material. Although the new phase transformable slippery lubricant infused porous structure, features much milder hydrophobicity than conventional oil/water separators, it can remove diverse types of oil from water with high efficiencies. The phase transformable slippery lubricant infused porous structure is able to maintain their water repellency after immersing in high concentration salt (10 wt% NaCl), acid (25 % HCl), alkaline (25 % NH·HO) solutions for 120 h, showing remarkably functional durability in harsh environment. The lubricant phase transition mechanism proposed in this study is universally applicable to porous substrates with various chemical compositions and pore structures, such as porous sponges or even daily life breads, for creating efficient oil/water separators, which can serve as a novel accessible design principle of phase transformable slippery lubricant infused porous structure for eco-friendly oil/water separators.
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http://dx.doi.org/10.1016/j.jhazmat.2020.122176DOI Listing
May 2020

Transport of Cd through saturated porous media: Insight into the effects of low-molecular-weight organic acids.

Water Res 2020 Jan 14;168:115182. Epub 2019 Oct 14.

Henan Joint International Research Laboratory of Environmental Pollution Control Materials, College of Chemistry and Chemical Engineering, Henan University, Kaifeng, 475004, China; Ministry of Education Key Laboratory of Pollution Processes and Environmental Criteria, Nankai University, Tianjin, 300350, China. Electronic address:

Low-molecular-weight organic acids (LMWOAs) are ubiquitous in the aquatic environment and consequently may affect the heavy metal transport in aquifer systems. In this study, the influences of LMWOAs on the transport of Cd under different pH conditions in saturated porous media were evaluated. For this, three LMWOAs such as acetic acid, tartaric acid, and citric acid were employed. A two-site nonequilibrium transport model was applied to simulate the transport data. Under acidic conditions (pH 5.0), the results indicated that LMWOAs inhibited the transport of Cd even at the low concentrations of organic acids (i.e., 0.05 and 0.1 mM). The inhibition effects might be attributed to the complexation role of the sand surface-bound organic acids and also electrostatic interaction. Meanwhile, the inhibition effects of LMWOAs on Cd transport in the following order of citric acid > tartaric acid > acetic acid, which was also in agreement with the decreasing complex stability constants between Cd and LMWOAs. This order may be dependent on their molecular structures (i.e., amount and type of functional groups) and complexing strength. Interestingly, when the LMWOA concentrations 0.5 mM, tartaric acid and citric acid still inhibited Cd transport, while acetic acid slightly enhanced the Cd mobility due to its weaker complexing strength. However, under neutral conditions (pH 7.0), LMWOAs generally enhanced the transport of Cd. The transport-enhancement of LMWOAs was ascribed to the formation of stable aqueous non-adsorbing Cd-organic acid complexes. In addition, citric acid could obviously inhibit the transport of Cd under competitive transport conditions (i.e., with competing cations), which is mainly due to different complex affinities of citric acid to Pb and Cd. These findings demonstrate that LMWOAs may inhibit or facilitate Cd transport under different environmental conditions. Thus, environmental assessment concerning the transport of heavy metals should consider the roles of organic acids.
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http://dx.doi.org/10.1016/j.watres.2019.115182DOI Listing
January 2020

Highly Thermally Conductive Polymer Composite Originated from Assembly of Boron Nitride at an Oil-Water Interface.

ACS Appl Mater Interfaces 2019 Nov 31;11(45):42818-42826. Epub 2019 Oct 31.

Institute of Applied Technology, Hefei Institutes of Physical Science, Chinese Academy of Sciences , Hefei 230088 , People's Republic of China.

Thermally conductive polymer packaging material is of great significance for the thermal management of electronics. Inorganic thermally conductive fillers have been demonstrated as a convenient approach to achieve this goal by sacrificing the lightweight and processability of the polymer. To address this problem, an effective 3D boron nitride (BN) network was constructed as a heat conduction pathway in a polystyrene (PS) matrix based on an oil-water interface assembly in this work. Styrene oil droplets were stabilized by BN sheets in the water phase to form Pickering emulsions, and then in situ polymerization was trigged to synthesize PS microspheres with ultrathin BN layer-covered surfaces ([email protected] microspheres). Composite substrates were fabricated through hot-compressing the [email protected] microspheres to form BN networks based on the original microsphere template. Benefited from the network structure, the maximum thermal conductivity of the composite substrate reached 0.94 W/mK at 33.3 wt % BN, which is 626% folds of that of pure PS. It was also demonstrated that the storage modulus and thermal stability of the composite substrate were dramatically improved by the BN network. The reported composite substrate and its fabrication strategy are promising in the development of thermal management of electronics.
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http://dx.doi.org/10.1021/acsami.9b15259DOI Listing
November 2019

One-Step Fabrication of Bioinspired Lubricant-Regenerable Icephobic Slippery Liquid-Infused Porous Surfaces.

ACS Omega 2018 Aug 30;3(8):10139-10144. Epub 2018 Aug 30.

NTNU Nanomechanical Lab, Department of Structural Engineering, Norwegian University of Science and Technology (NTNU), Trondheim 7491, Norway.

Icephobic coating and surfaces are essential for protecting infrastructures such as transmission lines, transportation vehicles, and many others from severe damages of excessive icing. The slippery liquid-infused porous surfaces (SLIPS) are attracting escalating attention because of their low-ice adhesion strength. Despite all of the encouraging laboratory scale results, the SLIPS are still far from being applicable in real environments owing to the key unsolved problem, namely anti-icing durability. Inspired by the functionality of the amphibians' skin, lubricant regenerability was introduced to conventional SLIPS and realized by a facile and scalable fabrication route. A series of polydimethylsiloxane (PDMS)-based skinlike SLIPS were designed and fabricated by using a one-step method, the solvent evaporation-induced phase separation technique. The obtained skinlike SLIPS were able to regenerate surface lubricant constantly by internal residual stress because of phase separation and survive more than 15 cycles of wiping/regenerating tests. Thanks to the regenerability of the surface lubricant, the new SLIPS demonstrated durable icephobicity, showing a long-term low-ice adhesion strength below 70 kPa, which was only 43% of 160 kPa that for the pristine PDMS (Sylgard 184), even after 15 icing/deicing cycles. This work paves a new and facile way for achieving icephobic durability of SLIPS.
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http://dx.doi.org/10.1021/acsomega.8b01148DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6645152PMC
August 2018

Enabling sequential rupture for lowering atomistic ice adhesion.

Nanoscale 2019 Sep 27;11(35):16262-16269. Epub 2019 Aug 27.

Department of Structural Engineering, The Norwegian University of Science and Technology - NTNU, Trondheim, Norway.

State-of-the-art passive icephobicity relies mainly on static parameters such as surface energy, coating elastic modulus, crack sizes and so on. Low ice adhesion resulting from the dynamic de-icing process, for instance ice detaching modes from substrates, has not yet been explored. In the current study, atomistic modeling and molecular dynamics simulations were employed to identify ice rupture modes as crucial dynamic factors for surface icephobicity. A fish-scale-like icephobic surface prototype enabling low-adhesion sequential rupture of the atomistic interactions at the ice-solid interface was proposed. The novel surface has an intrinsic extended interface rupture pathway, which can lead to a ∼60% reduction in atomistic ice adhesion compared with concurrent ice rupture. This study sheds light on interface mechanical design for surface icephobicity, and could provide solutions for anti-icing, nanoscale tribology and many others. The concept of implementing interfacial rupture modes proposed in this study can also apply to interface design for tailored adhesion mechanics.
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http://dx.doi.org/10.1039/c9nr00104bDOI Listing
September 2019

Breathable Nanowood Biofilms as Guiding Layer for Green On-Skin Electronics.

Small 2019 08 4;15(31):e1901079. Epub 2019 Jun 4.

NTNU Nanomechanical Lab, Department of Structural Engineering, Norwegian University of Science and Technology (NTNU), Trondheim, 7491, Norway.

Thin-film electronics are urged to be directly laminated onto human skin for reliable, sensitive biosensing together with feedback transdermal therapy, their self-power supply using the thermoelectric and moisture-induced-electric effects also has gained great attention (skin and on-skin electronics (On-skinE) themselves are energy storehouses). However, "thin-film" On-skinE 1) cannot install "bulky" heatsinks or sweat transport channels, but the output power of thermoelectric generator and moisture-induced-electric generator relies on the temperature difference (∆T ) across generator and the ambient humidity (AH), respectively; 2) lack a routing and accumulation of sweat for biosensing, lack targeted delivery of drugs for precise transdermal therapy; and 3) need insulation between the heat-generating unit and heat-sensitive unit. Here, two breathable nanowood biofilms are demonstrated, which can help insulate between units and guide the heat and sweat to another in-plane direction. The transparent biofilms achieve record-high transport /transport (//: along cellulose nanofiber alignment direction, ⊥: perpendicular direction) of heat (925%) and sweat (338%), winning applications emphasizing on ∆T/AH-dependent output power and "reliable" biosensing. The porous biofilms are competent in applications where "sensitive" biosensing (transporting sweat up to 11.25 mm s at the 1st second), "insulating" between units, and "targeted" delivery of saline-soluble drugs are of uppermost priority.
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http://dx.doi.org/10.1002/smll.201901079DOI Listing
August 2019

Upregulation of miR-27b Facilitates Apoptosis of TNF-α-Stimulated Fibroblast-Like Synoviocytes.

Yonsei Med J 2019 Jun;60(6):585-591

Department of Orthopedics, Jiangxi Provincial People's Hospital Affiliated to Nanchang University, Nanchang, Jiangxi, China.

Purpose: The aim of this study was to explore the function of microRNA-27b (miR-27b) in fibroblast-like synoviocytes (FLSs) stimulated by tumor necrosis factor α (TNF-α).

Materials And Methods: mRNA expression of miR-27b in FLS cells (MH7A) treated with or without TNF-α was determined by q-PCR. MiR-27b mimics was transfected into MH7A cells to upregulate miR-27b expression. MTT assay and flow cytometry analysis were performed to investigate the effect of miR-27b on MH7A cell viability and apoptosis. The targets of miR-27b were predicted by TargetScan. The direct regulation of miR-27b on IL-1β expression was verified by luciferase assay. The protein expression levels of apoptosis-related proteins, IL-1β, and NF-κB signaling-related proteins were detected by Western blot.

Results: We discovered that miR-27b expression was decreased in MH7A cells stimulated by TNF-α. Upregulation of miR-27b by miR-27b mimics significantly inhibited the proliferation and promoted the apoptosis of TNF-α-stimulated MH7A cells. Consistently, upregulation of miR-27 decreased the level of Bcl-2 and increased Bax and caspase-3 expression in MH7A cells stimulated by TNF-α. Luciferase assay revealed that IL-1β was indeed a target of miR-27b. By quantitative real-time PCR and Western blot, we found that the expression of IL-1β is negatively regulated by miR-27b. Moreover, the NF-κB signaling pathway was significantly inhibited by miR-27b.

Conclusion: Taken together, our results illustrated that enhanced miR-27b expression results in the suppression of proliferation and the promotion of apoptosis in FLSs stimulated by TNF-α, partially by regulating IL-1β expression and NF-κB signaling.
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http://dx.doi.org/10.3349/ymj.2019.60.6.585DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6536399PMC
June 2019

An ultra-durable icephobic coating by a molecular pulley.

Soft Matter 2019 Apr;15(17):3607-3611

NTNU Nanomechanical Lab, Department of Structural Engineering, Norwegian University of Science and Technology (NTNU), Trondheim 7491, Norway.

Slide-ring crosslinked polydimethylsiloxane (PDMS) is designed and prepared for anti-icing/deicing applications. Compared with the covalent crosslinks, the slidable crosslinks enhance the mobility of polymer networks and endow the materials with low elastic modulus. The PDMS matrix guarantees the hydrophobicity of as-prepared coatings. These properties synergistically lead to ultra-low ice adhesion strength (13.0 ± 1.3 kPa) and excellent mechanical durability. The ice adhesion strength on the coating maintains a value of ∼12 kPa during 20 icing/deicing cycles, and increases gradually to a value of ∼22 kPa after 800 cycles of abrasions. The novel design strategy provides one-step forward to anti-icing/deicing solutions for targeted applications.
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http://dx.doi.org/10.1039/c9sm00162jDOI Listing
April 2019

Understanding the role of hollow sub-surface structures in reducing ice adhesion strength.

Soft Matter 2019 Apr 11;15(13):2905-2910. Epub 2019 Mar 11.

NTNU Nanomechanical Lab, Department of Structural Engineering, Norwegian University of Science and Technology (NTNU), Trondheim 7491, Norway.

The accretion of ice on exposed surfaces results in detrimental effects in many aspects of life and technology. Passive icephobic coatings, designed by strategies towards lowering ice adhesion to mitigate icing problems, have recently received great attention. In our previous studies, incorporation of hollow sub-surface structures which act as macro-scale crack initiators has been shown to drastically lower the ice adhesion on PDMS surfaces. In this study, the effects of hollow sub-surface structure geometry, such as the heights, shapes, and distributions, as well as the directions of the applied shear force, are experimentally investigated. Our results show that the number of potential macro-scale crack initiation sites dictates ice adhesion strength. The directions of the applied shear force also influence the ice adhesion strength when the potential crack length is dependent on the applied shear force direction. The inter-locking effect between ice and the coating, caused by the pre-deformation, needs to be considered if one of the dimensions of the hollow sub-surface structures approaches the millimeter scale. These results improve the understanding of the role of hollow sub-surface structures in reducing ice adhesion, providing new insights into the design principles for multi-scale crack initiator-promoted icephobic surfaces.
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http://dx.doi.org/10.1039/c9sm00024kDOI Listing
April 2019

P38 Mitogen-activated Protein Kinase and Parkinson's Disease.

Transl Neurosci 2018 12;9:147-153. Epub 2018 Nov 12.

School of Pharmaceutical Science and Yunnan Key Laboratory of Pharmacology for Natural Products, Kunming Medical University, Kunming, China.

Parkinson's disease, the second major neurodegenerative disease, has created a great impact on the elder people. Although the mechanisms underlying Parkinson's disease are not fully understood, considerable evidence suggests that neuro-inflammation, oxidative stress, mitochondrial dysfunction, cell proliferation, differentiation and apoptosis are involved in the disease. p38MAPK, an important member of the mitogen-activated protein family, controls several important functions in the cell, suggesting a potential pathogenic role in PD. This review provides a brief description of the role and mechanism of p38MAPK in Parkinson's disease.
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http://dx.doi.org/10.1515/tnsci-2018-0022DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6234472PMC
November 2018

Atomistic dewetting mechanics of Wenzel and monostable Cassie-Baxter states.

Phys Chem Chem Phys 2018 Oct;20(38):24759-24767

NTNU Nanomechanical Lab, Department of Structural Engineering, Norwegian University of Science and Technology (NTNU), 7491 Trondheim, Norway.

Water adhesion underlies wettabilities, and thus hydrophobicities, and defines surface properties like self-cleaning, icephobicity and many others. The nanomechanics of water adhesion, especially in the dynamic dewetting processes, has not been fully investigated. Here in this article, atomistic modeling and molecular dynamics simulations were utilized to probe the adhesion mechanics of water droplets on nanopillars and flat surfaces, covering dewetting in the Wenzel and the newly discovered monostable Cassie-Baxter states. The simulations were able to identify intermediate dewetting states on rough surfaces, and resolve the transition between wetting states under force. The results revealed characteristic features of dynamic water adhering stress underpinning dewetting on the nanoscale, which provided deeper knowledge on surface dewetting mechanics. This work complements nanoscale dewetting experiments for new fundamental insights in studies including nanoroughness design, enhanced oil recovery, anti-icing and others.
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http://dx.doi.org/10.1039/c8cp03256dDOI Listing
October 2018

Nature-inspired entwined coiled carbon mechanical metamaterials: molecular dynamics simulations.

Nanoscale 2018 Aug;10(33):15641-15653

Department of Physics, Research Institute for Biomimetics and Soft Matter, Jiujiang Research, Institute and Fujian Provincial Key Laboratory for Soft Functional Materials Research, Xiamen University, Xiamen 361005, PR China.

Entwining-induced robust natural biosystems show superior mechanical performances over their counterparts. However, the role played by topological entwinement in the mechanical properties of artificial nanohelixes remains unknown. Here, the tensile characteristics of nano-entwined carbon nanocoil (ECNC) metamaterials are explored by atomistic simulations. The simulation results show that ECNCs exhibit heterogeneous pre-stress distribution along the spiral surfaces. The predicted stretching stress-strain responses correlate with the topological nano-entwining and dimensionality. Topological analysis reveals that the collective stretching of the bond and bond angle on the inner hexagon edge of the coils characterizes both early and final elastic extensions, whereas the intermediate elasticity is exclusively attributed to the inner-edged hexagon-angular deformation. The ECNCs impart pronounced tensile stiffnesses to the native structures, surprisingly with a maximum of over 13-fold higher stiffness for one triple-helix, beyond the scalability of mechanical springs in parallel, originating from the nano-entwining mechanism and increase in bulkiness. However, the reinforcement in strengths is restricted by the elastic strain limits that are degraded in ECNCs owing to the steric hindrance effect. All metastructures show superelongation-at-break due to a successive break-vs.-arrest process. Upon plastic deformation, the localized reduction in the radii of ECNCs leads to the formation of carbyne-based networks.
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http://dx.doi.org/10.1039/c8nr04507kDOI Listing
August 2018

Adiponectin Reduces Bone Stiffness: Verified in a Three-Dimensional Artificial Human Bone Model .

Front Endocrinol (Lausanne) 2018 14;9:236. Epub 2018 May 14.

Department of Biomaterials, Institute for Clinical Dentistry, University of Oslo, Oslo, Norway.

Primary human osteoblasts and osteoclasts incubated in a rotating coculture system without any scaffolding material, form bone-like tissue that may be used to evaluate effects of various compounds on mechanical strength. Circulating adiponectin has been found to be negatively associated with BMD and strength and was therefore assessed in this system. Osteospheres of human osteoblasts and osteoclasts were generated with and without adiponectin. The osteospheres were scanned using micro-computed tomography, the mechanical properties were tested by flat punch compression using nanoindentation equipment, and the cellular morphology characterized by microscopy. The association between autologously produced adiponectin and biomechanical properties was further evaluated by quantitation of adiponectin levels using quantitative polymerase chain reaction (qPCR) and immunoassays, and identification of stiffness by bending test of rat femurs. The molecular mechanisms were examined using human bone cells. Mechanical testing revealed that adiponectin induced a more compliant osteosphere compared with control. The osteospheres had a round, lobulated appearance with morphologically different areas; inner regions containing few cells embedded in a bone-like material surrounded by an external area with a higher cell quantity. The expression of adiponectin was found to correlate positively to ultimate bending moment and ultimate energy absorption and deflection, on the other hand, it correlated negatively to bending stiffness, indicating autocrine and/or paracrine effects of adiponectin in bone. Adiponectin enhanced proliferation and expression of collagen, leptin, and tumor necrosis factor-alpha in osteoblasts and stimulated proliferation, but not the functional activity of osteoclasts. Our results indicate that both administration of adiponectin during osteosphere production and elevated levels of adiponectin in rat femurs, reduced stiffness of the bone tissues. An increase in undifferentiated cells and extracellular matrix proteins, such as collagen, may explain the reduced bone stiffness seen in the osteospheres treated with adiponectin.
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http://dx.doi.org/10.3389/fendo.2018.00236DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5960720PMC
May 2018

Design and preparation of sandwich-like polydimethylsiloxane (PDMS) sponges with super-low ice adhesion.

Soft Matter 2018 Jun;14(23):4846-4851

NTNU Nanomechanical Lab, Department of Structural Engineering, Norwegian University of Science and Technology (NTNU), Trondheim 7491, Norway.

The mitigation of ice on exposed surfaces is of great importance to many aspects of life. Ice accretion, however, is unavoidable as time elapses and temperature lowers sufficiently. One practical solution is to reduce the ice adhesion strength on a surface to as low as possible, by either decreasing the substrate elastic modulus, lowering surface energy or increasing the length of cracks at the ice-solid interface. Herein, we present a facile preparation of polydimethylsiloxane (PDMS) based sandwich-like sponges with super-low ice adhesion. The weight ratio of the PDMS prepolymer to the curing agent is tuned to a lower surface energy and elastic modulus. The introduction of PDMS sponge structures combined the advantages of both a reduced apparent elastic modulus and most importantly, the macroscopic crack initiators at the ice-solid interface, resulting in dramatic reduction of the ice adhesion strength. Our design of sandwich-like sponges achieved a low ice adhesion strength as low as 0.9 kPa for pure PDMS materials without any additives. The super-low ice adhesion strength remains constant after 25 icing and deicing cycles. We thus provide a new and low-cost approach to realize durable super-low ice adhesion surfaces.
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http://dx.doi.org/10.1039/c8sm00820eDOI Listing
June 2018

A review on wetting and water condensation - Perspectives for CO condensation.

Adv Colloid Interface Sci 2018 Jun 29;256:291-304. Epub 2018 Mar 29.

Department of Structural Engineering, Norwegian University of Science and Technology, Høgskoleringen 6, 7491 Trondheim, Norway.

Liquefaction of vapor is a necessary, but energy intensive step in several important process industries. This review identifies possible materials and surface structures for promoting dropwise condensation, known to increase efficiency of condensation heat transfer. Research on superhydrophobic and superomniphobic surfaces promoting dropwise condensation constitutes the basis of the review. In extension of this, knowledge is extrapolated to condensation of CO. Global emissions of CO need to be minimized in order to reduce global warming, and liquefaction of CO is a necessary step in some carbon capture, transport and storage (CCS) technologies. The review is divided into three main parts: 1) An overview of recent research on superhydrophobicity and promotion of dropwise condensation of water, 2) An overview of recent research on superomniphobicity and dropwise condensation of low surface tension substances, and 3) Suggested materials and surface structures for dropwise CO condensation based on the two first parts.
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http://dx.doi.org/10.1016/j.cis.2018.03.008DOI Listing
June 2018

Enhancing the Mechanical Durability of Icephobic Surfaces by Introducing Autonomous Self-Healing Function.

ACS Appl Mater Interfaces 2018 Apr 27;10(14):11972-11978. Epub 2018 Mar 27.

NTNU Nanomechanical Lab, Department of Structural Engineering , Norwegian University of Science and Technology (NTNU) , Trondheim 7491 , Norway.

Ice accretion presents a severe risk for human safety. Although great efforts have been made for developing icephobic surfaces (the surface with an ice adhesion strength below 100 kPa), expanding the lifetime of state-of-the-art icephobic surfaces still remains a critical unsolved issue. Herein, a novel icephobic material is designed by integrating an interpenetrating polymer network (IPN) into an autonomous self-healing elastomer, which is applied in anti-icing for enhancing the mechanical durability. The molecular structure, surface morphology, mechanical properties, and durable icephobicity of the material were studied. The creep behaviors of the new icephobic material, which were absent in most relevant studies on self-healing materials, were also investigated in this work. Significantly, the material showed great potentials for anti-icing applications with an ultralow ice adhesion strength of 6.0 ± 0.9 kPa, outperforming many other icephobic surfaces. The material also exhibited an extraordinary durability, showing a very low long-term ice adhesion strength of ∼12.2 kPa after 50 icing/deicing cycles. Most importantly, the material was able to exhibit a self-healing property from mechanical damages in a sufficiently short time, which shed light on the longevity of icephobic surfaces in practical applications.
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http://dx.doi.org/10.1021/acsami.8b01866DOI Listing
April 2018

Grain-Size-Controlled Mechanical Properties of Polycrystalline Monolayer MoS.

Nano Lett 2018 02 5;18(2):1543-1552. Epub 2018 Feb 5.

NTNU Nanomechanical Lab, Department of Structural Engineering, Norwegian University of Science and Technology (NTNU) , Trondheim 7491, Norway.

Pristine monocrystalline molybdenum disulfide (MoS) possesses high mechanical strength comparable to that of stainless steel. Large-area chemical-vapor-deposited monolayer MoS tends to be polycrystalline with intrinsic grain boundaries (GBs). Topological defects and grain size skillfully alter its physical properties in a variety of materials; however, the polycrystallinity and its role played in the mechanical performance of the emerging single-layer MoS remain largely unknown. Here, using large-scale atomistic simulations, GB structures and mechanical characteristics of realistic single-layered polycrystalline MoS of varying grain size prepared by confinement-quenched method are investigated. Depending on misorientation angle, structural energetics of polar-GBs in polycrystals favor diverse dislocation cores, consistent with experimental observations. Polycrystals exhibit grain-size-dependent thermally induced global out-of-plane deformation, although defective GBs in MoS show planar structures that are in contrast to the graphene. Tensile tests show that presence of cohesive GBs pronouncedly deteriorates the in-plane mechanical properties of MoS. Both stiffness and strength follow an inverse pseudo Hall-Petch relation to grain size, which is shown to be governed by the weakest link mechanism. Under uniaxial tension, transgranular crack propagates with small deflection, whereas upon biaxial stretching, the crack grows in a kinked manner with large deflection. These findings shed new light in GB-based engineering and control of mechanical properties of MoS crystals toward real-world applications in flexible electronics and nanoelectromechanical systems.
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http://dx.doi.org/10.1021/acs.nanolett.7b05433DOI Listing
February 2018

Atomistic insights into the nanofluid transport through an ultra-confined capillary.

Phys Chem Chem Phys 2018 Feb;20(7):4831-4839

NTNU Nanomechanical Lab, Department of Structural Engineering, Faculty of Engineering, Norwegian University of Science and Technology (NTNU), 7491 Trondheim, Norway.

Nanofluid or nanoparticle (NP) transport in confined channels is of great importance for many biological and industrial processes. In this study, molecular dynamics simulation has been employed to investigate the spontaneous two-phase displacement process in an ultra-confined capillary controlled by the surface wettability of NPs. The results clearly show that the presence of NPs modulates the fluid-fluid meniscus and hinders the displacement process compared with the NP-free case. From the perspective of motion behavior, hydrophilic NPs disperse in the water phase or adsorb on the capillary, while hydrophobic and mixed-wet NPs are mainly distributed in the fluid phase. The NPs dispersed into fluids tend to increase the viscosity of the fluids, while the adsorbed NPs contribute to the wettability alteration of the solid capillary. Via capillary number calculations, it is uncovered that the viscosity increase of fluids is responsible for the hindered spontaneous displacement process by hydrophobic and mixed NPs. The wettability alteration of the capillary induced by adsorbed NPs dominates the enhanced displacement in the case of hydrophilic NPs. Our findings provide guidance for modifying the rate of capillary filling and reveal the microscopic mechanism transporting NPs into porous media, which is significant to the design of NPs for target applications.
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http://dx.doi.org/10.1039/c7cp08140eDOI Listing
February 2018

Effects of long-acting GnRH: a prolonged protocol in assisted pregnancy via IVF-ET in infertile patients with PCOS.

Minerva Chir 2018 04 23;73(2):251-253. Epub 2018 Jan 23.

Reproduction Center, People's Hospital of Jinhua, Jinhua, China -

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http://dx.doi.org/10.23736/S0026-4733.18.07573-9DOI Listing
April 2018

Raman antenna effect from exciton-phonon coupling in organic semiconducting nanobelts.

Nanoscale 2017 Dec;9(48):19328-19336

NTNU Nanomechanical Lab, Department of Structural Engineering, Norwegian University of Science and Technology (NTNU), Trondheim, 7491, Norway.

The highly anisotropic interactions in organic semiconductors together with the soft character of organic materials lead to strong coupling between nuclear vibrations and exciton dynamics, which potentially results in anomalous electrical, optical and optoelectrical properties. Here, we report on the Raman antenna effect from organic semiconducting nanobelts 6,13-dichloropentacene (DCP), resulting from the coupling of molecular excitons and intramolecular phonons. The highly ordered crystalline structure in DCP nanobelts enables the precise polarization-resolved spectroscopic measurement. The angle-dependent Raman spectroscopy under resonant excitation shows that all Raman modes from the skeletal vibrations of DCP molecule act like a nearly perfect dipole antenna I ∝ cos(θ - 90), with almost zero (maximum) Raman scattering parallel (perpendicular) to the nanobelt's long-axis. The Raman antenna effect in DCP nanobelt is originated from the coupling between molecular skeletal vibrations and intramolecular exciton and the confinement of intermolecular excitons. It dramatically enhances the Raman polarization ratio (ρ = I/I > 25) and amplifies the anisotropy of the angle-dependent Raman scattering (κ = I/I > 12) of DCP nanobelts. These findings have crucial implications for fundamental understanding on the exciton-phonon coupling and its effects on the optical properties of organic semiconductors.
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http://dx.doi.org/10.1039/c7nr07212kDOI Listing
December 2017

Multiscale crack initiator promoted super-low ice adhesion surfaces.

Soft Matter 2017 Sep;13(37):6562-6568

NTNU Nanomechanical Lab, Department of Structural Engineering, Norwegian University of Science and Technology (NTNU), Trondheim 7491, Norway.

Preventing icing on exposed surfaces is important for life and technology. While suppressing ice nucleation by surface structuring and local confinement is highly desirable and yet to be achieved, a realistic roadmap of icephobicity is to live with ice, but with lowest possible ice adhesion. According to fracture mechanics, the key to lower ice adhesion is to maximize crack driving forces at the ice-substrate interface. Herein, we present a novel integrated macro-crack initiator mechanism combining nano-crack and micro-crack initiators, and demonstrate a new approach to designing super-low ice adhesion surfaces by introducing sub-structures into smooth polydimethylsiloxane coatings. Our design promotes the initiation of macro-cracks and enables the reduction of ice adhesion by at least ∼50% regardless of the curing temperature, weight ratio and size of internal holes, reaching a lowest ice adhesion of 5.7 kPa. The multiscale crack initiator mechanisms provide an unprecedented and versatile strategy towards designing super-low ice adhesion surfaces.
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http://dx.doi.org/10.1039/c7sm01511aDOI Listing
September 2017