SEU Research | SEU scores new progress in these areas
Prof. Sun Litao’s team from SEU achieved significant progress in “visualized” atomic-scale manufacturing
Recently, the research result achieved by Prof. Sun Litao’s team from School of Electronic Science and Engineering and School of Microelectronics of Southeast University, titled “Tailoring atomic diffusion for in situ fabrication of different heterostructures”, was published online in Nature Communications 12, 4812 (2021) with Southeast University as the only accomplishment institute. Ph.D. student Zhang Hui and associate researcher Xu Tao are the co-first authors with Prof. Sun Litao as the corresponding author.
Heterogeneous nanostructures highlighting excellent performance are of particular importance for the development and manufacturing of new electronic devices. Diffusion is considered as the primary technical method for preparing heterogeneous nanostructures. However, it is difficult to regulate and control the atomic-scale diffusion precisely with the current methods, and also difficult to achieve controllable synthesis of single heterogeneous nanostructures, which have thus severely restricted the manufacturing precision and manufacturing level of nanodevices in the future.
Fig1.: In situ preparation process of two different heterostructures obtained by controlling the diffusion of atoms by electric field
In response to the above challenges, Prof. Sun Litao’s team developed a visualized atomic-scale manufacturing method based on in-situ electron microscopy technology. Through regulation and control of the electric field, the in-situ preparation of two different heterostructure nano-monomers (the core-shell structure and the segmented heterogeneous structure) was achieved in the same system (Fig. 1). This method used the direction of the electric field to control the direction of the directional diffusion of atoms, and the temperature change caused by Joule heat could regulate the atomic diffusion mode (the surface diffusion or the bulk diffusion), thereby preparing the nano monomers with different heterostructures. The research results have verified that regulation of atomic diffusion by the electric field can be adopted as an effective way to control the preparation of single heterogeneous nanostructures, meanwhile, it is also conducive to better understand the microscopic driving force and related mechanisms of the diffusion direction and diffusion mode of atoms between materials, enabling the manufacturing under the atomic-scale can be achieved in a more accurate and controllable manner.
“Visualized” atomic-scale manufacturing is a new method proposed by Prof. Sun Litao’s team based on in-situ electron microscopy technology, which integrates various processing approaches such as force, electricity, light, and heat, etc. to achieve precise manufacturing and real-time manifestation of materials and devices at the atomic scale. The new method can directly reveal the new principles and new mechanisms in the atomic manufacturing process, and ultimately achieve stable and controllable manufacturing. Related results achieved by the team previously were published in Adv. Mater. 30, 1705954 (2018), Adv. Science 5, 1700213 (2018), Nano Lett. 19, 519 (2019), ACS Nano 2021 (DOI: 10.1021/acsnano. 1c00209) and other significant academic journals respectively. This project was funded by the National Natural Science Foundation of China etc.
Paper’s link:
https://www.nature.com/articles/s41467-021-25194-2
Prof. Chen Zhen’s team from SEU proposed the concept of “thermal rectification” in the research paper published on Joule, a world-known journal, making the continuous utilization of solar energy possible
Recently, Prof. Chen Zhen’s team from School of Mechanical Engineering of SEU and Prof. Chris Dames’s team from University of California at Berkeley have jointly published a paper, titled “4-fold enhancement in energy scavenging from fluctuating thermal resources using a temperature-doubler circuit”, on Joule, an internationally famous journal, making it possible to incessantly utilize solar energy with the proposed concept of “thermal rectification”.
In a broad sense, human’s research on renewable resources mainly focuses on the development and utilization of solar energy, an ideal thermal source generated by the sun. However, the utilization efficiency of solar energy by people at night is limited by the cyclical activity of the sun rising in the east and setting in the west.
Inspired by the power distribution and usage schemes, researchers from both SEU of China and University of California at Berkeley of the U.S. put forward a new solution. Based on the study of the thermal diode and other nonlinear thermal devices, the Sino-US research team conceived the “thermal rectifier” according to the similarity between electricity and heat, which was verified by the theories integrated with experiments. Besides, compared to the traditional approach, this conception can increase the thermal-to-electrical energy conversion efficiency by 4 to 8 times. Furthermore, the proposed concept of “thermal rectification” provides not only a possibility for solar energy to be used around the clock, but also a theoretical basis for people to extract energies from any other temperature fields that change over time. Therefore, this research result can be applied to the construction of bases on the Moon and Mars, so as to offer continuous energy support for the mankind’s march into the space.
Meanwhile, this research also modified the expression of a common sense in thermodynamics textbooks, that is, updating “the heat engine can only be initiated by connecting a heat source and a heat sink simultaneously” as “the heat engine can be independently initiated by a heat source featuring periodic changes in temperature”.
Zhao Xiaodong, an assistant engineer from School of Mechanical Engineering of SEU, and Mitchell Westwood, a postgraduate student from Department of Mechanical Engineering of University of California at Berkeley, are the co-first authors, and Chen Zhen, a Youth Chief Professor from SEU, and Chris Dames, a Howard Penn Brown Chair Professor from Department of Mechanical Engineering of University of California at Berkeley, are the co-corresponding authors.
It is reported that Joule is the flagship journal for energy launched in 2017 by Cell, one of the world’s most authoritative academic journals, to mainly publish the latest research findings and advances in the energy field. In addition, its up-to-date impact factor in 2021 is 41.
Paper’s link:
https://www.cell.com/joule/fulltext/S2542-4351(21)00295-6
Li Quan’s team from SEU made a breakthrough in researching the covalent adaptable liquid crystal network soft robots
Recently, the team led by Li Quan, Member of the Academy of Europe from Institute of Advanced Materials of School of Chemistry and Chemical Engineering of SEU, has scored crucial progress in the research on the covalent adaptable liquid crystal network (LCN) soft robots enabled by reversible ring-opening cascades of cyclic disulfides. The relevant results, titled “Covalent Adaptable Liquid Crystal Networks Enabled by Reversible Ring-Opening Cascades of Cyclic Disulfides”, was published online on Journal of the American Chemical Society, a top international journal. The assessment experts believed that this research represents a breakthrough in the domain of LCN soft robots.
The liquid crystal actuators, with an extensive application prospect in the fields of artificial muscles, intelligent soft devices, soft robots, etc., are therefore of great concern. Nevertheless, the traditional liquid crystal networks based on the cross-linked covalent bonds are all unable to be re-processed, re-adjusted and recycled. The development of covalent adaptable liquid crystal networks (LCNs) enabled by introducing dynamic covalent bonds has endowed liquid crystal actuators with self-healing properties and reversible shape programmability, thus broadening their applications in diverse soft robotic devices. However, the finite molecular design strategy limits the recyclability and the architectural diversity of these materials.
In terms of these problems, the team first reported the strategy which fabricates photoresponsive polydisulfide-based covalent adaptable LCNs by ring-opening polymerization of cyclic dithiolane groups. Based on the disulfide metathesis, the resulting materials are self-healable, re-shapable, and reprogrammable. Besides, the equilibrium between the polymer backbones and the dithiolane-functionalized monomers enables catalytic depolymerization to recycle monomers, which could significantly minimize the shortcomings of the traditional subtractive manufacturing method of photomechanical devices. Furthermore, this research rooted in the molecular structure design of chemistry would provide an economical and environmentally-friendly strategy for the fabrication of functional soft robots with excellent programmability and renewability and beyond.
The young teacher Huang Shuai from SEU is the first author of this paper, with Li Quan and Yang Hong as the co-corresponding authors and SEU as the first corresponding institute. Moreover, this research was funded by both the National Natural Science Foundation of China and the Natural Science Foundation of Jiangsu Province.
Paper’s link:
https://pubs.acs.org/doi/10.1021/jacs.1c03661
Submitted by School of Electronic Science and Engineering and School of Microelectronics, School of Mechanical Engineering, School of Chemistry and Chemical Engineering
Revised by Shu Yuan
Proofread by Melody Zhang
Edited by Qi Yuchen