ABSTRACT
Actuators play a crucial role in microelectromechanical systems (MEMS) and hold substantial potential for applications in various domains, including reconfigurable metamaterials. This research aims to design, fabricate, and characterize structures for the actuation of the EMA. The electromagnetic actuator overcomes the lack of high drive voltage required by other actuators. The proposed actuator configuration comprises supporting cantilever beams with fixed ends, an integrated coil positioned above the cantilever's movable plate, and a permanent magnet located beneath the cantilever's movable plate to generate a static magnetic field. Utilizing flexible polyimide, the fabrication process of the EMA is simplified, overcoming limitations associated with silicon-based micromachining techniques. Furthermore, this approach potentially enables large-scale production of EMA, with displacement reaching up to 250 µm under a 100 mA current, thereby expanding their scope of applications in manufacturing. To demonstrate the function of the EMA, we integrated it with a metamaterial structure to form a compact, tunable terahertz absorber, demonstrating a potential for reconfigurable electromagnetic space.
ABSTRACT
Apoptosis alteration is responsible for tumorigenesis and tumor resistance to therapies. The natural product Tanshinone IIA (Tan IIA) exhibits potent inhibitory effects against various tumors. However, the effect of Tan IIA on apoptosis and its underlying mechanism remains elusive in oral squamous cell carcinoma (OSCC). Here, we demonstrated that Tan IIA dose-dependently suppressed cell viability and colony formation in CAL27, SCC4, and SCC25 cells. Moreover, Tan IIA inhibited Akt activation from inducing Foxo3a dephosphorylation and PUMA-mediated apoptosis. PUMA or Foxo3a knockdown compromised the inhibitory effect of Tan IIA on OSCC cells. Tan IIA administration inhibited CAL27-deprived xenograft tumor growth and increased PUMA expression in vivo. Tan IIA synergistically intensified the efficacy of CDDP/5-FU-based chemotherapy on OSCC cells. Overall, our results revealed that Tan IIA exerted potent antitumor effects via promoting PUMA-mediated apoptosis in OSCC cells.
ABSTRACT
Cascaded metasurfaces can exhibit powerful dynamic light manipulation by mechanically tuning the far-field interactions in the layers. However, in most current designs, the metasurfaces are separated by gaps smaller than a wavelength to form a total phase profile, representing the direct accumulation of the phase profiles of each layer. Such small gap sizes may not only conflict with the far-field conditions but also pose great difficulties for practical implementations. To overcome this limitation, a design paradigm taking advantage of a ray-tracing scheme that allows the cascaded metasurfaces to operate optimally at easily achievable gap sizes is proposed. Enabled by the relative lateral translation of two cascaded metasurfaces, a continuous two-dimensional (2D) beam-steering device for 1064 nm light is designed as a proof of concept. Simulation results demonstrate tuning ranges of ±45° for biaxial deflection angles within ±3.5 mm biaxial translations, while keeping the divergence of deflected light less than 0.007°. The experimental results agree well with theoretical predictions, and a uniform optical efficiency is observed. The generializeddesign paradigm can pave a way towards myriad tunable cascaded metasurface devices for various applications, including but not limited to light detection and ranging (LiDAR) and free space optical communication.
ABSTRACT
Spatial light modulators based on metasurfaces have attracted great attention due to their abilities of amplitude and phase modulation. However, the traditional one degree of freedom (1-DOF) tunable metasurfaces are limited by incomplete phase coverage and coupled amplitude and phase modulation. Here, we propose an optimization method for 2-DOF tunable metasurfaces within the framework of temporal coupled mode theory. As a validation of the proposed method, we present a germanium antimony tellurium (GST)-alloy-based 2-DOF tunable reflective metasurface. Full-wave simulation shows that independent modulation of amplitude and phase is realized with full phase coverage and amplitude range from 0 to 0.55. Our proposed design scheme for a 2-DOF tunable metasurface may facilitate the development of high-performance metasurface devices.
