Yi Cui, Postdoctoral Faculty Sponsor
Integrated Three-dimensional Hydrophilicity/hydrophobicity Design for Artificial Sweating Skin (i-TRANS) Mimicking Human Body Perspiration.
Advanced materials (Deerfield Beach, Fla.)
Artificial skins reproducing properties of human skin are emerging and significant for study in various areas, such as robotics, medicine, textiles, etc. Perspiration, as one of the most imperative thermoregulation functions of human skin, is gaining increasing attention, but how to realize ideal artificial skin for perspiration simulation remains challenging. Here, we propose an integrated three-dimensional hydrophilicity/hydrophobicity design for artificial sweating skin (i-TRANS). Based on normal fibrous wicking materials, the selective surface modification with gradient of Polydimethylsiloxane (PDMS) creates hydrophilicity/hydrophobicity contrast in both lateral and vertical directions. With the additional help of bottom hydrophilic Nylon 6 nanofibers, the constructed i-TRANS is able to transport "sweat" directionally without trapping undesired excess water and attain uniform "secretion" of sweat droplets on the top surface, decently mimicking human skin perspiration situation. This fairly comparable simulation not only presents new insights for replicating skin properties, but also provides proper in vitro testing platforms for perspiration-relevant research, greatly avoiding unwanted interference from the "skin" layer. In addition, the facile, fast and cost-effective fabrication approach and versatile usage of i-TRANS can further facilitate its application. This article is protected by copyright. All rights reserved.
View details for DOI 10.1002/adma.202204168
View details for PubMedID 35975584
Heat Conductor-Insulator Transition in Electrochemically Controlled Hybrid Superlattices.
Designing materials with ultralow thermal conductivity has broad technological impact, from thermal protection to energy harvesting. Low thermal conductivity is commonly observed in anharmonic and strongly disordered materials, yet a microscopic understanding of the correlation to atomic motion is often lacking. Here we report that molecular insertion into an existing two-dimensional layered lattice structure creates a hybrid superlattice with extremely low thermal conductivity. Vibrational characterization and ab initio molecular dynamics simulations reveal strong damping of transverse acoustic waves and significant softening of longitudinal vibrations. Together with spectral correlation analysis, we demonstrate that the molecular insertion creates liquid-like atomic motion in the existing lattice framework, causing a large suppression of heat conduction. The hybrid materials can be transformed into solution-processable coatings and used for thermal protection in wearable electronics. Our work provides a generic mechanism for the design of heat insulators and may further facilitate the engineering of heat conduction based on understanding atomic correlations.
View details for DOI 10.1021/acs.nanolett.2c01407
View details for PubMedID 35715219
Observation of an intermediate state during lithium intercalation of twisted bilayer MoS2.
2022; 13 (1): 3008
Lithium intercalation of MoS2 is generally believed to introduce a phase transition from H phase (semiconducting) to T phase (metallic). However, during the intercalation process, a spatially sharp boundary is usually formed between the fully intercalated T phase MoS2 and non-intercalated H phase MoS2. The intermediate state, i.e., lightly intercalated H phase MoS2 without a phase transition, is difficult to investigate by optical-microscope-based spectroscopy due to the narrow size. Here, we report the stabilization of the intermediate state across the whole flake of twisted bilayer MoS2. The twisted bilayer system allows the lithium to intercalate from the top surface and enables fast Li-ion diffusion by the reduced interlayer interaction. The E2g Raman mode of the intermediate state shows a peak splitting behavior. Our simulation results indicate that the intermediate state is stabilized by lithium-induced symmetry breaking of the H phase MoS2. Our results provide an insight into the non-uniform intercalation during battery charging and discharging, and also open a new opportunity to modulate the properties of twisted 2D systems with guest species doping in the Moire structures.
View details for DOI 10.1038/s41467-022-30516-z
View details for PubMedID 35637182
Mobility enhancement in heavily doped semiconductors via electron cloaking.
2022; 13 (1): 2482
Doping is central for solid-state devices from transistors to thermoelectric energy converters. The interaction between electrons and dopants plays a pivotal role in carrier transport. Conventional theory suggests that the Coulomb field of the ionized dopants limits the charge mobility at high carrier densities, and that either the atomic details of the dopants are unimportant or the mobility can only be further degraded, while experimental results often show that dopant choice affects mobility. In practice, the selection of dopants is still mostly a trial-and-error process. Here we demonstrate, via first-principles simulation and comparison with experiments, that a large short-range perturbation created by selected dopants can in fact counteract the long-range Coulomb field, leading to electron transport that is nearly immune to the presence of dopants. Such "cloaking" of dopants leads to enhanced mobilities at high carrier concentrations close to the intrinsic electron-phonon scattering limit. We show that the ionic radius can be used to guide dopant selection in order to achieve such an electron-cloaking effect. Our finding provides guidance to the selection of dopants for solid-state conductors to achieve high mobility for electronic, photonic, and energy conversion applications.
View details for DOI 10.1038/s41467-022-29958-2
View details for PubMedID 35523766
- Coloured low-emissivity films for building envelopes for year-round energy savings NATURE SUSTAINABILITY 2021
Integrated cooling (i-Cool) textile of heat conduction and sweat transportation for personal perspiration management.
2021; 12 (1): 6122
Perspiration evaporation plays an indispensable role in human body heat dissipation. However, conventional textiles tend to focus on sweat removal and pay little attention to the basic thermoregulation function of sweat, showing limited evaporation ability and cooling efficiency in moderate/profuse perspiration scenarios. Here, we propose an integrated cooling (i-Cool) textile with unique functional structure design for personal perspiration management. By integrating heat conductive pathways and water transport channels decently, i-Cool exhibits enhanced evaporation ability and high sweat evaporative cooling efficiency, not merely liquid sweat wicking function. In the steady-state evaporation test, compared to cotton, up to over 100% reduction in water mass gain ratio, and 3 times higher skin power density increment for every unit of sweat evaporation are demonstrated. Besides, i-Cool shows about 3°C cooling effect with greatly reduced sweat consumption than cotton in the artificial sweating skin test. The practical application feasibility of i-Cool design principles is well validated based on commercial fabrics. Owing to its exceptional personal perspiration management performance, we expect the i-Cool concept can provide promising design guidelines for next-generation perspiration management textiles.
View details for DOI 10.1038/s41467-021-26384-8
View details for PubMedID 34675199
- Stretchable Anti-Fogging Tapes for Diverse Transparent Materials ADVANCED FUNCTIONAL MATERIALS 2021