ORCID Profile
0000-0002-9826-7138
Current Organisations
ZJU-Hangzhou Global Scientific and Technological Innovation Center
,
Zhejiang University
,
Imperial College
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Publisher: Wiley
Date: 26-08-2021
Abstract: Temperature‐dependent transport measurements are performed on the same set of chemical vapor deposition (CVD)‐grown WS 2 single‐ and bilayer devices before and after atomic layer deposition (ALD) of HfO 2 . This isolates the influence of HfO 2 deposition on low‐temperature carrier transport and shows that carrier mobility is not charge impurity limited as commonly thought, but due to another important but commonly overlooked factor: interface roughness. This finding is corroborated by circular dichroic photoluminescence spectroscopy, X‐ray photoemission spectroscopy, cross‐sectional scanning transmission electron microscopy, carrier‐transport modeling, and density functional modeling. Finally, electrostatic gate‐defined quantum confinement is demonstrated using a scalable approach of large‐area CVD‐grown bilayer WS 2 and ALD‐grown HfO 2 . The high dielectric constant and low leakage current enabled by HfO 2 allows an estimated quantum dot size as small as 58 nm. The ability to lithographically define increasingly smaller devices is especially important for transition metal dichalcogenides due to their large effective masses, and should pave the way toward their use in quantum information processing applications.
Publisher: Proceedings of the National Academy of Sciences
Date: 19-01-2016
Abstract: How adhesive forces can be scaled up from microscopic to macroscopic levels is a central problem for biological and bio-inspired adhesives. Here, we elucidate how animals with sticky footpads cope with large body sizes. We find an extreme positive allometry of footpad area across all 225 species studied, implying a 200-fold increase of relative pad area from mites to geckos. Within groups, however, pads were almost isometric, but their adhesive strength increased with size, inconsistent with existing models. Extrapolating the observed scaling, we show that to support a human’s body weight, an unrealistic 40% of the body surface would have to be covered with adhesive pads, suggesting that anatomical constraints may prohibit the evolution of adhesion-based climbers larger than geckos.
Publisher: The Royal Society
Date: 04-2023
Abstract: Many climbing animals use direction-dependent adhesives to attach to vertical or inclined surfaces. These structures adhere when activated via a pull but detach when pushed. Therefore, a challenge arises when a change in climbing direction causes external forces such as gravity to change its acting orientation upon the lizard. To investigate how specialized climbers adjust, we studied kinematics and dynamics of six Hemidactylus frenatus geckos climbing head-up and head-down a vertical racetrack. We found that limbs functionally swap their adhesive role: feet above the centre of mass (COM) generated adhesive forces, feet below the COM compressive forces, both equal in magnitude across directions. To investigate how lizards perform this swap, despite the constraint of their direction-dependent adhesives, we analysed kinematic adjustments across multiple smaller levels of hierarchy: limbs, feet and toes. All levels contributed: the hindfoot angle was reoriented realigning the adhesive structure, the hindlimb centre range of motion was further protracted and the hindfoot toe spreading was reduced. Notably, all three variables were adjustments of hindlimbs, suggesting that they make a more flexible contribution in upward versus downward climbing, while forelimbs may be anatomically or functionally constrained. The relevance of multilevel dynamic adjustments might inform the development of performant gaits for legged climbing robots.
Location: No location found
Location: China
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Tianqi Deng.