The Department of Mechanical and Industrial Engineering, Faculty of Engineering and the Built Environment, invites you to a webinar by Prof C.W. Lim entitled:

‘Voltage Controlled Topologically Protected Wave Propagation in Dielectric Membrane-type Acoustic Metamaterials’

Department of Architecture and Civil Engineering, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong SAR, P.R. China


Topological acoustic metamaterials have attracted enormous research attention in recent years.  A significant hallmark of these structures is that they can support interface modes that are robust to structural disturbance and protected by topology.  However, most of the studies are often limited to the passive structures that manifest wave propagation at fixed frequency ranges.  In view of the shortage of non-passive topological acoustic metamaterials, this work has a primary motive to study the active control of topologically protected wave propagation in soft dielectric membrane-type metamaterials (MAM) based on quantum spin Hall effect (QSHE).  The unit cell of the periodic structure is designed with  symmetry.  Then, the plane wave expansion method is adopted to analytically capture the system dispersion properties.  A finite element model is further developed and excellent convergence with the analytical result is presented.  By adjusting locations of spraying discs in the honeycomb unit cell, mode shape inversion is observed, separating the topologically trivial state from the nontrivial counterpart.  Consequently, the topologically protected interface modes (TPIMs) are observed.  Additionally, an electrical voltage that lies within the locking-up limit is applied to MAM to actively control the working frequency of the TPIM.  Further, several waveguide paths are designed to control the robust wave propagation in the structure.  Conclusively, a voltage-controlled topological metamaterial is designed to actively tune the working frequency range of the device.

About the speaker

Ir Professor C.W. Lim (FASME, FASCE, F.EMI, FHKIE, RPE, 2020 JN Reddy Medalist)

Department of Architecture and Civil Engineering, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong SAR, P.R. China

Currently a fellow of ASME, ASCE, EMI and HKIE, Ir Professor Lim received a B.Eng. from University of Technology of Malaysia, M.Eng. and PhD from National University of Singapore and Nanyang Technological University, respectively.  Prior to joining City University of Hong Kong, he was a post-doctoral research fellow at The University of Queensland and The University of Hong Kong.  He is also a visiting professor at various universities worldwide.  He has expertise in theory of plates and shells, dynamics of smart piezoelectric structures, nanomechanics, metamaterials and symplectic elasticity.  He is currently the subject editor for Journal of Sound and Vibration, joint-editor for Journal of Mechanics of Material and Structures, subject editor for Applied Mathematical Modelling, Managing Editor (Asia-Pacific Region) for Journal of Vibration Engineering & Technologies, Associate Editor for International Journal of Bifurcation and Chaos, etc. and also on the editorial board of some other top-ranked international journals.  He has published one very well-selling title entitled “Symplectic Elasticity”, co-authored with W.A. Yao and W.X. Zhong from Dalian University of Technology, as recorded by the publisher, World Scientific, in Engineering Mechanics and Mechanical Engineering.  He has published more than 350 international journal papers and have more than 12,000 citations.  Recently Professor Lim was awarded the prestigious 2020 JN Reddy Medal as a recognition “for significant and original contributions to vibration of plates and shells, smart piezoelectric structures, nanomechanics, and symplectic elasticity”.  He will deliver a plenary lecture and chair another plenary lecture at WCCM-APACM 2022, the largest biennial meet for computational scientists worldwide.  He was also previously awarded Top Referees in 2009, Proceedings A, The Royal Society.  Professor Lim is a registered professional engineer in Hong Kong.

Keywords: metamaterials; nanomechanics; piezoelectric structures; plates and shells; symplectic elasticity


Date : 14 October 2022

Time: 11:00 am – 12:30 pm

Link : Join conversation (

October 14, 2022

Disclaimer: The University of Johannesburg encourages academic debate and discussion that are conducted in a manner that upholds respectful interaction, safety of all involved, and freedom of association as enshrined in the law, the Constitution, and within the boundaries of the University policies. The views expressed during events are expressed in a personal capacity and do not necessarily reflect the views of the University of Johannesburg.


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