Quantum sensing of microRNAs with nitrogen-vacancy centers in diamond.

Label-free detection of nucleic acids such as microRNAs holds great potential for early diagnostics of various types of cancers. Measuring intrinsic biomolecular charge using methods based on field effect has been a promising way to accomplish label-free detection. However, the charges of biomolecules are screened by counter ions in solutions over a short distance (Debye length), thereby limiting the sensitivity of these methods. Here, we measure the intrinsic magnetic noise of paramagnetic counter ions, such as Mn2+, interacting with microRNAs using nitrogen-vacancy (NV) centers in diamond. All-atom molecular dynamics simulations show that microRNA interacts with the diamond surface resulting in excess accumulation of Mn ions and stronger magnetic noise. We confirm this prediction by observing an increase in spin relaxation contrast of the NV centers, indicating higher Mn2+ local concentration. This opens new possibilities for next-generation quantum sensing of charged biomolecules, overcoming limitations due to the Debye screening.

Simultaneously Toughening and Stiffening Elastomers with Octuple Hydrogen Bonding.

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-2 ) 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.

Reconfigurable Mechanical Anisotropy in Self-Assembled Magnetic Superstructures.

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 superferromagnetism, 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.

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

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.

An ultra-durable icephobic coating by a molecular pulley.

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.

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

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.