2021 EIC Choice Award | Actively logical modulation of MEMS-based terahertz metamaterial

"The design of tunable metamaterials is extremely important for many applications. Integration of micro-electro-mechanical system (MEMS) with metamaterials is very promising direction to achieve reconfigurable capabilities. In this paper, the authors propose and demonstrate with high-quality sophisticated fabrication a reconfigurable and programmable MEMS-based metadevice with multifunctional characteristics to simultaneously perform the logic operations. This study makes an important contribution to the future developments of smart and tunable metadevices."

-- Prof. Yuri Kivshar, Deputy Editor


Metamaterials have recently offered a strategy to artificially control electromagnetic waves on subwavelength scales and obtain unique optical response. Since the first experimental demonstration by Prof. J. B. Pendry in 2000, various metamaterial designs have attracted a great interest due to their extraordinary properties that cannot be found in traditional materials.


Most of current metamaterials can be passively controlled to perform a specific electromagnetic function. However, the active control for metamaterial designs has been desired to satisfy the requirements of the real-world applications. Therefore, there are more and more researchers paying attention to the active metamaterials via liquid crystal, laser pumping, phase transitions materials and so on.


However, many limitations exist among these tuning methods owing to the nonlinear properties of natural materials. By artificially exploiting the electromagnetic force at the micro- and nano-scale, reconfigurable metamaterials are developed to achieve larger tuning range. These reconfigurable metamaterials can be performed by using MEMS technology. By using MEMS technology, the unit cell of metamaterial can be directly released and manipulated, which assists MEMS-based metamaterials to become the candidates to overcome the limitations of the traditional tuning methods and provide an ideal platform for reconfigurable metamaterial.


For the reconfigurable capabilities of metamaterials, there have been many researches demonstrated the programmable metamaterial devices. The optical programmable metamaterials are based on the electromagnetic switching response. They have unlocked a new field for optical computing. However, most of these designs are only suitable for a specific application. To further increase the flexibility and applicability for the combo integration, the multifunctional characteristic is desired.


The research group led by Dr. Yu-Sheng Lin from Sun Yat-sen University, numerically and experimentally demonstrate a design of reconfigurable metamaterial using MEMS-based cantilever array to make the incident THz wave tunable. The proposed reconfigurable metamaterial is composed of cantilever metamaterial. Herein, the multilayer cantilevers are used as electrothermal actuator as well as resonator. By applying a DC bias voltage, the released cantilevers could be actuated downward to the substrate.


The mechanical, electrical, and optical properties are investigated to realize multifunctional device. For the opto-logic application, the functions of "OR" and "AND" gates are simultaneously performed by using MEMS-based cantilever metamaterial device. Meanwhile, the fabrication process of MEMS-based cantilever metamaterial device provides an ideal platform to form tunable three-dimensional metamaterial, which greatly improves the flexibility and applicability in metamaterial fields, such as multifunctional and logic computing applications.