On September 24, 2018, the team of Prof. Chen Huawei published a research article entitled “Ultrafast water harvesting and transport in hierarchical micro-channels” in Nature Materials online. Focusing on the speedy water transport process on the surface of a Sarracenia trichome, the research provides a thorough description of the two-mode process, which features a water transport velocity that is about three orders of magnitude faster than that on spider silk and cactus spine. It is expected to find application in a wide range of fields.

The research article published in Nature Materials online

A Nature-Inspired and Interdisciplinary Effort

It all began with an encounter with some microscopic photos of plants on a foreign photo website. Among those photos, one capturing the surface of a Sarracenia, a kind of insect-trapping plants, deeply intrigued the team members. With the knowledge that microstructures can show special properties that are not observable from a macro perspective, they thought it might also be the case with the Sarracenia.

Closer analysis proved their speculation. The team carefully studied the microstructure of the trichome on the surface of the Sarracenia and found for the first time the two types of ribs with different heights aligned along the gradient trichome to form approximately parallel hierarchical microchannels. This particular structure enables two different and successive modes of water transport: when it is dry, fine water droplets are condensed and collected together to form a thin film of water on the microchannels, which is called Mode I. Once the film comes into being, more water droplets can be transported on it at an ultrafast speed, which is Mode II.

The hierarchical microchannels found on the surface of the Sarracenia trichome

Based on this discovery, the team further revealed how parameters of the hierarchical microchannels affect the ultrafast transport process and proposed a bio-inspired design of the microchannels. The research findings are expected to be applied in the fields where high-speed liquid collection and transport are needed, such as microfluidic chips, highly-efficient heat dissipation structure, liquid collection, seawater desalination and so on.

The liquid collection process of the Sarracenia trichome

Just like a previous research of the team published in Nature about the continuous directional water transport found in Nepenthes alata, this research also involves a multidisciplinary effort made by researchers in mechanics and chemistry. In building the theoretical framework, the team received assistance from Prof. Jiang Lei, Member of the Chinese Academy of Science, and Dr. Zhou Jiajia from his team. Their contribution made up for the disadvantage of the team of engineering students in terms of theory.

A Team with High Aspirations

Behind the research is a preserving and far-sighted team. According to Prof. Chen, considerable difficulties confronted the team during the 3-year research. For example, several months were spent solely on the microscopic observation of dynamic liquid transport, which required a large amount of work in image comparison. It was the combined effort of every team member as well as the support and encouragement from Prof. Zhang Deyuan, the leader of the team, that finally brought the research inspiration into reality against all obstacles.

The one who coordinated the work of different members in this research is Ran Tong, a doctoral student supervised by Prof. Chen and recognized by him as “a patient and steadfast doer”. Such quality is valued greatly in the team on their way to achieve the goal of building a complete system from theory to engineering practice.

“Science majors pay more attention to theoretical work, while the priority of engineering majors is to apply a technology to real life. What we want to do is to bring the two ends together and complete a path that links observation, theoretical model, engineering design and application. Of course, this ideal entails multidisciplinary cooperation and may require efforts made by several generations of teachers and students,” said Prof. Chen.

In his opinion, graduate education should also follow the principle. To be more specific, a doctoral student should work on “major research” that provides a thorough and systematic study of a question from theory to application. Prof. Chen himself always encourages his students to aim high in this direction and consider publication in Nature and Science as their goal. In a larger scale, the evaluation system of graduates at Beihang University also weighs quality over quantity, encouraging graduate students to keep exploring, mount challenges and bring about innovations.

A Step Forward

Talking about future research directions, Prof. Chen proposed several ideas, such as if the addition of nanowire between low ribs to create a third-level microstructure can further increase the transport velocity, and why 3-5 low ribs between high ribs lead to the highest transport speed. Applications of this structure are also a possibility. Witnessing the wider and wider application of the previous work about Nepenthes alata, he expected that the research into Sarracenia microchannels could also follow the precedent and find its way into various fields.

Staying true to their aspirations, the team led by Prof. Chen will carry on with their efforts to convert discoveries of natural structures to systematic research and applications. Step by step, these researchers are showing the world China’s strength in bioinspired micro- and nano-manufacturing, and it is believed that both their research findings and their idea of quality engineering research can be a source of inspiration for future researchers.

The research article:

https://www.nature.com/articles/s41563-018-0171-9

Reported by Tan Lisha, Li Xinxin and Li Mingzhu

Written by Li Xinxin

Designed by Wang Chenyan

Edited and Translated by Li Mingzhu

Special thanks to the School of Mechanical Engineering and Automation

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