ME researchers co-authored a paper in Science again

Alloys that have high strengths at high temperatures are crucial for a variety of important industries including aerospace. Long-range ordered superlattice alloys with strong chemical binding and associated low atomic mobility are attractive for this purpose. However, most conventional ordered alloys with ultrahigh strengths (gigapascal levels) are found to be extremely brittle during tensile deformation, which severely limits their potential use in structural applications. A recent paper on a new class of high-strength and ductile superlattice alloys, co-authored by Mr Lei Fan, PhD student, and Dr Zengbao Jiao, Assistant Professor of the PolyU Department of Mechanical Engineering, was recently published in Science. In collaboration with Prof. CT Liu from the CityU and other colleagues, the researchers designed nanoscale disordered interfaces from the multi-element co-segregation, which act as a sustainable ductilizing source and prevent brittle intergranular fractures by enhancing dislocation mobilities. The newly developed multicomponent superlattice materials exhibit ultrahigh strengths of 1.6 gigapascals with tensile ductilities of 25% at ambient temperature. Moreover, these materials achieve negligible grain coarsening with exceptional softening resistance at elevated temperatures, demonstrating high thermal stability. These superlattice materials will be of great interest for a broad range of aerospace, automotive, nuclear power, chemical engineering, and other applications. In addition, the fundamental strategy of composite architecture can be utilized to design high-strength, ductile and stable materials in many other metallic systems. Read more at: T. Yang, Y.L. Zhao, W.P. Li, C.Y. Yu, J.H. Luan, D.Y. Lin, L. Fan, Z.B. Jiao, W.H. Liu, X.J. Liu, J.J. Kai, J.C. Huang, C.T. Liu. Ultrahigh-strength and ductile superlattice alloys with nanoscale disordered interfaces. Science, 2020; 369 (6502): 427.

Success in securing GRF 2020/21

In the 2020/2021 results of grants from the Research Grants Council’s General Research Fund (GRF) announced in June 2020, ME’s success rate for the GRF was 36% in 2020/21 exercise. Eight of our GRF proposals were funded. Congratulations to the following colleagues who were successful in securing a GRF grant in this round. Principal Investigator Project Title Prof. CHENG Li Enhanced Acoustic Black Hole Effects through Intentional Mechanical/Electromechanical Coupling and Nonlinearities Dr CHOY Yat Sze Acoustics behavior of orifice with shallow backing cavity under grazing flow for development of perforated panel type metamaterial for fan noise control Prof. FU Ming-wang Size effect affected anisotropy and asymmetry in multi-scaled deformation of metallic materials Dr LEUNG Chi Kin Randolph Passive Control of Cavity Aeroacoustic Resonance Using Localized Surface Compliance Prof. SU Zhongqing Non-invasive Ultrasound Monitoring of Blood Viscosity Using A Stretchable, Conformal, and Wearable Nanocomposite Sensing Array: Fundamental Research & Proof of Concept Prof. WEN Chihyung Richtmyer–Meshkov Instability in a Multilayer Cylinder Configuration Dr WONG Wai-on Design of a tunable hybrid vibration damper with Coulomb and electromagnetic shunt damping Dr ZHANG Peng Towards Quantitatively Predictive Modelling of Droplet Collision in Spray Simulation: Headon Collision of Equal-size Droplets

ME Staff Honoured for Loyal Service

Colleagues of the PolyU Department of Mechanical Engineering (ME) has always been devoting themselves to the development of ME. This year, the Department Head, on behalf of the University, paid tribute to long-serving staff members for their loyal and committed service over the years. Prof. TL Chan received the Long Service Award for his 30 years of service in PolyU. Ms Lily Tam, Leader of Administrative Staff, received the Award for 25 years. Mrs Michelle Lai, Clerical Officer II, for 35 years. Mr KK Tang, Technician, for 30 years. Congratulations to the awardees and heartfelt thanks for their years of dedication and devotion which have marked the achievements of the Department.

ME PHD student received Young Research Award in CNERC Annual Technical Symposium 2020

Bingchen Zhou, a PolyU ME PhD student, won the Young Research Award in the Chinese National Engineering Research Centre for Steel Construction (CNERC) Annual Technical Symposium 2020 held on 12 June 2020 at PolyU. She presented her research on “Effects of Cu on the nanostructure and mechanical properties of high strength steels” at the symposium. The CNERC Annual Technical Symposium 2020 is a technical symposium organized by the CNERC aiming at promoting technological development, sharing and exhibiting the findings and accomplishments among researchers of CNERC projects. Through applied engineering research on steel construction, the CNERC aims to capitalize on huge potentials offered by construction professionals in Hong Kong to further enhance socio-economic development through technological advancement in sustainable infrastructure development. The CNERC receives strong support from the Development Bureau of the Government of Hong Kong SAR and also from the Construction Industry Council. Bingchen Zhou is under the supervision of Dr Zengbao Jiao in the ME department. Her research interest focuses on the development and characterization of advanced high-strength steels strengthened by nanoscale co-precipitates.

Transferring nanofiber technology to develop highly protective facemasks for railroad operators

Avalon Nano-Biotech (HK) Limited has provided a donation to the ME department of 3 million Hong Kong dollars to support Prof. Wallace Leung in further developing and commercializing advanced air filtration nanofiber technologies to capture airborne pollutants and viruses (e.g., COVID-19 virus). Alongside with new technology development, Prof. Leung together with Avalon has transferred a nanofiber technology, which has been licensed earlier to Avalon, for the immediate need of developing a highly protective facemask for professionals working in railroad environment. This is especially vital during the current COVID-19 pandemic. A new clean room for class 8 under ISO 14644-1 has been built in MTR Siu Ho Wan Depot in 3 months to accommodate several facemask production lines that have incorporated nanofibers into the facemasks. The produced facemasks are provided to over 17,000 MTR employees in Hong Kong. Protecting the health of MTR employees is very important as they serve nearly 6 million Hong Kong passengers riding the rail daily. This is also the first clean room ever built by the railroad service provider in the world to produce facemasks for their employees. The technology adopted by MTR is based on the nanofiber filter technology developed by Prof. Leung’s R&D group in ME since 2006. The nanofiber facemask has been certified for the ASTM level II standard with PFE (particulate filtration efficiency) and BFE (bacterial filtration efficiency) both exceeding 98% by certifying agency. In fact, the PFE and BFE of the nanofiber facemask are above 99% in the certification testing. Further, the nanofiber facemask can also capture 20-60 nm nanoaerosols with filter efficiency of 95-98%. Also, the facemask can be used in dirty environment with high aerosol loading. Not only the facemasks offer high protection against tiny invisible aerosols and airborne viruses, the pressure drop for the facemasks are relatively low providing comfort to wearers. All these merits are extremely beneficial for railroad operators and professionals. Prof. Leung has also helped to set up quality assurance and quality control to ensure all the produced facemasks in the MTR Siu Ho Wan Depot clean room meet the stringent requirements per ASTM level II certification. This ensures the nanofiber technology is well transferred into a sound and useful product that benefit the Hong Kong community.

Prof. Li Cheng awarded the Second Prize of the Science and Technology Progress Award 2019

Prof. Li Cheng, Chair Professor of Mechanical Engineering of ME Department was awarded the 2019 Second Prize of the Science and Technology Progress Award by the People’s Government of Guangdong Province, China. The prestigious prize is the fruit of long-term collaboration that Prof. Cheng and his team have been undertaking with Midea Ltd, the largest domestic product company in China. During the last two years, Prof. Cheng’s research team has been closely collaborating with Midea through a number of research and consultancy projects, targeting some bottle-necking noise and vibration problems that the company was facing. The project on which the award was granted concerns the development of a complete set of design, analysis and optimization tools on the use of Micro-Perforated Panels (MPP) for sound absorption and their application in a wide range of key products that Media is manufacturing. According to the company’s report, the MPP-based technology has been successfully implemented in a total of 1.6 million Midea’s domestic products, which has up to now secured a net additional income amounting to 1.93 billion RMB.

ME receives donation from Philip K. H. Wong Foundation to support PAED Co-op initiative

The PolyU Department of Mechanical Engineering (ME) received a generous donation from Philip K. H. Wong Foundation for the enhancement of the BEng (Hons) in Product Analysis and Engineering Design programme (PAED) engaging in real industrial learning. The perspective of the PAED programme is to train up our mechanical engineering students on product development and analytical skills. It involves a lot of hands-on and project-based trainings to get our students ready for real industrial participation. In 2019/20 academic year, PAED has launched the “Cooperative Education” (Co-op) option for students to grip the pragmatic knowledge through real-world experiential learning in professional and industrial setting. While we are having more co-op relationships with industrial entities and engaging in more product development trial projects for the students, we are in need of resources to gear up our students before setting off on the Co-op working. That involves an establishment of a product development workshop, where hardware and software facilities are the requisites. Special training on product design and development will be emphasized. Furthermore, students will have the opportunities to practice and elevate their skills through an innovative PAED contest. The department expressed sincere gratitude to Philip K. H. Wong Foundation for donating a funding of HK$1.5 million to sponsor the above Co-op initiative, which will benefit the PAED students in the coming two years.

ME researchers revealed important physical phenomenon in Nature Physics

When we press and pluck the strings of a guitar, it generates different types of acoustic waves. How those waves sound is decided by how we pick those strings and the strings’ nature properties such as length and thickness. The principle here is that wave radiation depends on both the intrinsic properties of the source and the eigenstates of its surrounding environment. This has laid the foundation to explore and exploit various physical phenomena in a wide range of wave systems. The evolving understanding of this paradigm has inspired countless breakthroughs in wave-matter interaction related fields ranging from mechanics and acoustics to optics and photonics. A long-held belief of wave-matter interaction is that an emitter always radiates into and interacts with the eigenstates that exclusively define the surrounding environment. Even in non-Hermitian systems featuring exceptional point(s) where two or more eigenstates coalesce leading to an incomplete eigen-basis in the Hilbert space, this was still deemed to be valid previously as the wave function associated with the missing dimension of the Hilbert space has not been observed in any physical system. Research team led by Dr Jie Zhu, Associate Professor of the PolyU Department of Mechanical Engineering, conducted collaboration with Prof. Ren-min Ma’s team from Peking University, Prof. Li Ge’s team from City University of New York and other colleagues. They show that the above-mentioned century-old tenet can surprisingly break down at an exceptional point. With investigation on difference classic wave systems, the researchers experimentally demonstrated a chirality-reversal phenomenon in a whispering gallery mode cavity where the excited unidirectional wave circulation exhibits opposite handedness to the coalesced eigenstate. This striking yet extensively existed phenomenon were confirmed in both acoustic and electromagnetic wave systems. Their finding, for the first time, reveals that the radiation field of an emitter can become fully decoupled from the eigenstates of its environment. Such counter-intuitive phenomenon transforms the fundamental understanding of wave-matter interaction and enriches the intriguing physics of exceptional points hidden behind source-eigenstate interplay. In acoustics, it could contribute to a board range of research fields, including non-Hermitian acoustics, noise control and abatement. This work has been recently published online on Nature Physics [ “Revealing the missing dimension at an exceptional point”, https://www.nature.com/articles/s41567-020-0807-y ]. Dr Tuo Liu, Postdoctoral Fellow of the PolyU Department of Mechanical Engineering (also a PolyU ME PhD graduate) is the co-first author. Read the full text of paper at https://rdcu.be/b2JlC.

ME MPhil student awarded IEEE MTT-S Undergraduate/Pre-graduate Scholarship 2020

PolyU ME MPhil student Man Ho TSOI was elected to be the awardee of IEEE MTT-S Undergraduate/Pre-graduate Scholarship 2020. Man Ho, under the mentorship of an IEEE MTT-S member Dr Steve Wai Yin MUNG, submitted a research proposal topic titled “Design and Implementation of Surface Acoustic Wave (SAW) device in wireless circuit” which showed high potential for a productive career in RF (Radio Frequency)/Microwave Engineering. IEEE (Institute of Electrical and Electronics Engineers) is the world’s largest professional organization devoted to the innovation and advancement of technology across disciplines. MTT-S (Microwaves and Theory and Techniques Society) is one of the technical societies within IEEE. Undergraduate/Pre-graduate Scholarship Programme is held twice a year with a maximum of ten awardees around the world in each cycle. The scholarship programme encourages students to pursue study and job related to its field. In 2020 Cycle 1, six students from universities in USA, Russia, Spain and China were awarded the scholarship, Man Ho was one of them. 2020 Cycle 1 Awardees (October 2019 Competition) Man Ho is currently pursuing the part-time MPhil degree under the supervision of Dr Yat Sze CHOY in the Department of Mechanical Engineering, the Hong Kong Polytechnic University.

Protecting personal health from impending flu season and Novel Coronavirus

The breakout of the Wuhan virus and serious influenza during the winter months in Hong Kong has raised concerns from the general public. Face masks are worn generally for the prevention of spread of virus and bacteria that cause sickness. Yet, misconceptions about the proper usage of face masks are very common in the community. Ir. Professor Wallace Leung Woon-Fong, Chair Professor of Innovative Products and Technologies of the Department of Mechanical Engineering, who has been studying the science behind masks and developing various combating technologies, suggested a user-friendly way to wear a proper mask. Leung pointed out that face masks are worn by general public and professionals for protection from airborne viruses spread through spit and mucous. Therefore, the outer layer of the mask is hydrophobic (i.e. hate water) so that ‘germs’ carried with water in the spit from others around would not come in contact with the user wearing the mask. On the other hand, the inside layer is hydrophilic (i.e. like water) which absorbs moisture, keeping the user comfortable. Based on the above understanding, he introduced a scientific method to distinguish the inside or outside layer of a face mask for the general public. His method is to simply add water droplets onto the surface of the mask and observe if the droplet ‘rolls up’ similar to that on a waxed surface (moisture prevention layer), or the water droplet soaks into the mask surface (moisture absorbing surface). The moisture prevention layer should be worn outside while the moisture absorbing layer should be worn inside in contact with the wearer. It is also important to test both sides in pursuit of the functionality of the mask. If both surfaces have been tested to have the same property, there is no inside or outside layer to speak of. Therefore wearing the mask with either side is fine, but it is preferred to purchase a better functional face mask. On the other hand, if the two surfaces are different, wearing the mask inside out lead to trapping of viruses and bacteria in the mask, this increases the risk of contact viruses and bacteria. Professor Leung had developed electrostatically charged nanofiber filter with multiple separator layers. The novel PVDF nanofiber filter can capture pollutant particles that are below 100 nm in diameter. It demonstrates much better performance in breathability and filtration efficiency, compared with existing technologies and products, and has a longer shelf life in high humidity up to 90 days. The filter or face mask applying the innovation would be an ideal defense against virus, such as measles, SARS, and other unknown health-threatening viruses during an outbreak. This is because most viruses are negatively charged and the PVDF nanofiber mask is positively charged making virus capture more effective. Media interview by Ming Pao 底層吸水 面層防水 戴錯口罩 病菌有「隙」可乘