Nanomaterials exhibit unique chemical and physical properties in comparison with their bulk-phase counterparts, attracting significant attention from the oil and gas industry in the hope of solving challenging issues. Current heavy oil extraction methods are costly and have unsatisfactory efficiency, and facing environmental restrictions increasingly. Our recent introduction of sodium (Na) nanofluid provides a promising method for heavy oil extraction since it shows improved oil recovery without burning carbon-containing fuels. Here, we conducted core-flooding tests to further evaluate the effect of this Na nanofluid on recovering oil from different formations, which had not been previously demonstrated, as well as to deepen our understanding of the underlying mechanisms. The Na nanofluid exhibited excellent oil-extraction efficiency for both types of heavy oil tested. The recovery mechanisms were found to be complicated. We also found that post-injection soaking and using the proper solvent to disperse the sodium nanoparticles are important for further boosting oil recovery.

The control of electron and phonon transport by manipulating dimensionality is essential for the performance of advanced electronic materials and devices, such as quantum electronics, thermoelectrics and superconductors, which may also lead to yet undiscovered, emergent electronic or thermal phenomena. In this study, we report a series of hybrid inorganic-organic superlattice structures, in which metallic TiS₂ monolayers are spatially confined between soft and insulating organic molecules of varying thicknesses. By choosing different organic molecules that increase the interlayer distance, the electrons inside the TiS₂ layers gradually become two-dimensional, with increasing density of states, as seen by their effective mass that increases from 5.3 to 8.6 m₀, where m₀ is the mass of a bare electron. In addition, density functional theory calculations confirm a transition of the electron distribution from bulk to two-dimensional, due to the suppressed interlayer coupling. This result demonstrates that the thermoelectric transport of two-dimensional electrons can be realized in a three-dimensional inorganic-organic superlattice, thus enabling access to the interesting properties of individual two-dimensional materials in the bulk form, which may provide new opportunities in flexible thermoelectrics.

Flexible electronic skin (e-skin) has been successfully utilized in diverse applications, including prosthesis sensing, body-motion monitoring and human-machine interfaces, due to its excellent mechanical properties and electrical characteristics. However, current e-skins are still relatively thick (> 10 µm) and uncomfortable for long-term usage on the human body. Herein, an ultrathin skin-integrated strain sensor with miniaturized dimensions, based on the piezoresistive effect, with excellent stability and robustness, is introduced. The fractal curve-shaped Au electrode in a serpentine format, which is the dominant component of the strain sensor, is sensitive to ambient strain variations and can turn the mechanical motion into a stable electrical signal output. With the advanced design of metallic electrodes, the device presents good operational stability and excellent mechanical tolerance towards bending, stretching and twisting. The stain sensor allows intimate mounting onto the human epidermal surface for the detection of body motion. By adopting a liquid bandage as an encapsulation layer, the device exhibits an ultrathin thickness (6.2 µm), high sensitivity towards mechanical deformations and capability for the clear detection of motion, such as walking, finger bending and the human pulse rate with identifiable electrical signals. Furthermore, the tattoo-like strain sensor is applied in robotic control by tracing finger bending motion and results in the smooth control of a robotic hand nearly without any detention. This e-skin design exhibits excellent potential for wearable electronics and human-machine interfaces.

In the conventional scenario, it is believed that hydrogels typically consist of two-phase coexisting structures based on polymer structural networks filled with water droplets and that the polymer-water interfacial layer may not be a substantial component in determining their structure and functionality. Unfortunately, it is challenging to unveil the properties of the interfacial layer, if any, owing to the multiphase nature and structural complexity of hydrogels. In this work, the morphology and microstructures of the well-known non-covalent bonding dominant polyacrylonitrile-based hydrogels are characterized and it is confirmed that the as-prepared hydrogels do consist of polymer networks and filled water droplets. The dielectric relaxation behavior in the ice hydrogel state with different water/ice contents is investigated in detail by means of dielectric relaxation spectroscopy, in order to avoid the electrode polarization effect, which is non-negligible in liquid hydrogels, particularly in the low-frequency range. The dielectric relaxation spectroscopy data demonstrate the remarkable dielectric response contributed from the polymer-ice interfacial layer, which likely accommodates a high density of polar molecules/dipoles. The temperature-dependent dielectric relaxation behavior of the ice hydrogels with different water contents is discussed and the thermal activation energy for the interfacial polar structure may be likely extracted from the dielectric loss peak data. It is found that this energy is approximately consistent with the typical bonding energy of non-covalent bonding dominant hydrogels. This study represents a substantial step towards understanding the interfacial coupling in hydrogels, an issue that has not yet been thoroughly considered.