No abstract

The high thermal conductivity of graphene and few-layer graphene undergoes severe degradations through contact with the substrate. Here we show experimentally that the thermal management of a micro heater is substantially improved by introducing alternative heat-escaping channels into a graphene-based film bonded to functionalized graphene oxide through amino-silane molecules. Using a resistance temperature probe for in situ monitoring we demonstrate that the hotspot temperature was lowered by ∼28 °C for a chip operating at 1,300 W cm−2. Thermal resistance probed by pulsed photothermal reflectance measurements demonstrated an improved thermal coupling due to functionalization on the graphene–graphene oxide interface. Three functionalization molecules manifest distinct interfacial thermal transport behaviour, corroborating our atomistic calculations in unveiling the role of molecular chain length and functional groups. Molecular dynamics simulations reveal that the functionalization constrains the cross-plane phonon scattering, which in turn enhances in-plane heat conduction of the bonded graphene film by recovering the long flexural phonon lifetime.

Weizheng (2020) Origamiinspired electret-based triboelectric generator for biomechanical and ocean wave energy harvesting. Nano Energy, 67. p. 104197.

No abstract

In this report, we studied the electron transport through cyclic π-conjugated molecules. The model system consists of metalloporphyrin with two thiol groups at either 9,11-substitution (P-connection) or 1,5-substitution (D-connection) which form chemical bonds with gold electrodes. We investigated 10 typical bivalent metals as the metal-molecule-metal junctions using first principle density functional theory and nonequilibrium Green's function calculations. Due to the particular electron transport paths, all models in P-connection show similar I-V curves, indicating that the electron does not pass through the metal center in this configuration. In the D-connection, the electron takes the path through the metal center, leading to considerable difference in the I-V curves between the different metalloporphyrins. This means that the D-connected metalloporphyrin is potentially applicable in chemical sensor. We also studied a prototype for chemosensing the CO molecule theoretically at the same level.

TiO x /PEI electron transport layer achieve an average power conversion efficiency of 8.72% (the champion power conversion efficiency is 9.08%), which is much better than that of the control devices based on PEI (7.00%) or TiO x (7.38%). The room-temperature TiO x /PEI layer exhibits outstanding capacities, including increased electron mobility, reduced series resistance and improved electron extraction at the cathode interface.

Shape memory polymers (SMPs), as a class of intelligent materials, have shown great potential in biomedical and robotic fields. Although efforts have been made to design and fabricate SMPs in the past decades, most of the SMPs are not suitable for use in the human body due to their unpleasant triggering conditions. Furthermore, it is of great importance to diversify the shape memory effect (SME) of SMPs to extend their applications. In this work, through thiol-ene chemistry, SMPs based on random cross-linked hydrophobic polytetrahydrofuran (PTHF) and hydrophilic poly­(ethylene glycol) (PEG) oligomers were facilely fabricated. These SMPs showed a body temperature-triggered two-way SME with a reversible strain of up to 25.2%. Besides, the SMPs exhibited a good body temperature- and water-triggered one-way triple-SME. These features bestowed the polymers with a bright future in biomedical applications. Polymer P60-G40 was applied as a new type of esophageal stent, and the in vitro assessment showed that the stent was adjustable, self-expandable, and had the ability to release drugs, which were attributed to the one-way triple-SME and two-way SME.

No abstract