Optical metasurfaces have emerged as a groundbreaking technology in photonics,offering unparalleled control over light-matter interactions at the subwavelength scale with ultrathin surface nanostructures and thereby g...Optical metasurfaces have emerged as a groundbreaking technology in photonics,offering unparalleled control over light-matter interactions at the subwavelength scale with ultrathin surface nanostructures and thereby giving birth to flat optics.While most reported optical metasurfaces are static,featuring well-defined optical responses determined by their compositions and configurations set during fabrication,dynamic optical metasurfaces with reconfigurable functionalities by applying thermal,electrical,or optical stimuli have become increasingly more in demand and moved to the forefront of research and development.Among various types of dynamically controlled metasurfaces,electrically tunable optical metasurfaces have shown great promise due to their fast response time,low power consumption,and compatibility with existing electronic control systems,offering unique possibilities for dynamic tunability of light–matter interactions via electrical modulation.Here we provide a comprehensive overview of the state-of-the-art design methodologies and technologies explored in this rapidly evolving field.Our work delves into the fundamental principles of electrical modulation,various materials and mechanisms enabling tunability,and representative applications for active light-field manipulation,including optical amplitude and phase modulators,tunable polarization optics and wavelength filters,and dynamic waveshaping optics,including holograms and displays.The review terminates with our perspectives on the future development of electrically triggered optical metasurfaces.展开更多
This study describes a novel micro proton exchange membrane fuel cell(PEMFC)(active area,2.5 cm2).The flow field plate is manufactured by applying micro-electromechanical systems(MEMS) technology to silicon substrates...This study describes a novel micro proton exchange membrane fuel cell(PEMFC)(active area,2.5 cm2).The flow field plate is manufactured by applying micro-electromechanical systems(MEMS) technology to silicon substrates to etch flow channels without a gold-coating.Therefore,this investigation used MEMS technology for fabrication of a flow field plate and presents a novel fabrication procedure.Various operating parameters,such as fuel temperature and fuel stoichiometric flow rate,are tested to optimize micro PEMFC performance.A single micro PEMFC using MEMS technology reveals the ideal performance of the proposed fuel cell.The optimal power density approaches 232.75 mW·cm-1 when the fuel cell is operated at ambient condition with humidified,heated fuel.展开更多
The simultaneous control of residual stress and resistivity of polysilicon thin films by adjusting the deposition parameters and annealing conditions is studied. In situ boron doped polysilicon thin films deposited at...The simultaneous control of residual stress and resistivity of polysilicon thin films by adjusting the deposition parameters and annealing conditions is studied. In situ boron doped polysilicon thin films deposited at 520 ℃ by low pressure chemical vapor deposition （LPCVD） are amorphous with relatively large compressive residual stress and high resistivity. Annealing the amorphous films in a temperature range of 600-800 ℃ gives polysilicon films nearly zero-stress and relatively low resistivity. The low residual stress and low resistivity make the polysilicon films attractive for potential applications in micro-electro-mechanical-systems （MEMS） devices, especially in high resonance frequency （high-f） and high quality factor （high-Q） MEMS resonators. In addition, polysilicon thin films deposited at 570 ℃ and those without the post annealing process have low resistivities of 2-5 mΩ·cm. These reported approaches avoid the high temperature annealing process （〉 1000 ℃）, and the promising properties of these films make them suitable for high-Q and high-f MEMS devices.展开更多
We aimed to develop a process technology for constructing a carbon-based micro-electromechanical system that does not require a high-temperature and high-energy process. A HOPG （highly oriented pyrolytic graphite） c...We aimed to develop a process technology for constructing a carbon-based micro-electromechanical system that does not require a high-temperature and high-energy process. A HOPG （highly oriented pyrolytic graphite） crystal microsheet was prepared by exfoliation. Cantilevers and doubly clamped beams were patterned using a photoresist. The HOPG microsheet was attached by using a tantalum layer. We fabricated cantilevers and a doubly clamped beam by controlling the thickness of the HOPG microsheet and then measured the first resonance frequency. The measurements suggest a need to improve the stiffness of the beam.展开更多
Initially studied and developed by students in universities, the very small pico satellites （with a mass lower than 1 kg） are more and more considered for science applications. In particular, there are plans to use ...Initially studied and developed by students in universities, the very small pico satellites （with a mass lower than 1 kg） are more and more considered for science applications. In particular, there are plans to use them in constellations of small spacecraft for remote sensing of various regions of the magnetosphere. They require a payload with specific size, weight and power consumption. In order to respond to this demand, new instruments have to be developed. Those instruments should exhibit at least the same performances as those used in larger satellites while fulfilling the specific requirements imposed by the satellites size. For this reason, the authors currently develop a xylophone bar magnetometer （XBM） based on micro-electromechanical systems （MEMS） with integrated detector electronics. The principle of this magnetometer is based on a classical resonating xylophone bar. A sinnsoidal current oscillating at the fundamental bending resonant frequency of the bar is applied through the device, and when an external magnetic field is present, the resulting Lorentz force yields the bar to vibrate at its fundamental mode with a displacement directly proportional to the amplitude in one direction of the ambient magnetic field. When designing a MEMS XBM, the detection method is a crucial aspect. The measurement method largely influences the geometry of the magnetometer as well as the manufacturing technology. Due to the constraints in terms of size, weight and power consumption, the two most promising measurement methods are capacitive and piezoelectric ones. Several designs including these measurement techniques are presented and simulated under realistic conditions. First, designs including lateral electrodes for capacitive measurement are tackled based on Silicon-On-Insulator （SOI） process. For the piezoelectric detection, a new configuration based on Lead Zirconate Titanate （PZT）/Pt structure is introduced and leads to much better sensitivity than the traditional Pt/PZT/Pt sandwich structure展开更多
基金supported by the Independent Research Fund Denmark(No.1134-00010B)Villum Fonden(award in Technical and Natural Sciences 2019,Nos.37372 and 50343).
文摘Optical metasurfaces have emerged as a groundbreaking technology in photonics,offering unparalleled control over light-matter interactions at the subwavelength scale with ultrathin surface nanostructures and thereby giving birth to flat optics.While most reported optical metasurfaces are static,featuring well-defined optical responses determined by their compositions and configurations set during fabrication,dynamic optical metasurfaces with reconfigurable functionalities by applying thermal,electrical,or optical stimuli have become increasingly more in demand and moved to the forefront of research and development.Among various types of dynamically controlled metasurfaces,electrically tunable optical metasurfaces have shown great promise due to their fast response time,low power consumption,and compatibility with existing electronic control systems,offering unique possibilities for dynamic tunability of light–matter interactions via electrical modulation.Here we provide a comprehensive overview of the state-of-the-art design methodologies and technologies explored in this rapidly evolving field.Our work delves into the fundamental principles of electrical modulation,various materials and mechanisms enabling tunability,and representative applications for active light-field manipulation,including optical amplitude and phase modulators,tunable polarization optics and wavelength filters,and dynamic waveshaping optics,including holograms and displays.The review terminates with our perspectives on the future development of electrically triggered optical metasurfaces.
基金Supported by the National Science Council (NSC 97-2221-E-009-067)
文摘This study describes a novel micro proton exchange membrane fuel cell(PEMFC)(active area,2.5 cm2).The flow field plate is manufactured by applying micro-electromechanical systems(MEMS) technology to silicon substrates to etch flow channels without a gold-coating.Therefore,this investigation used MEMS technology for fabrication of a flow field plate and presents a novel fabrication procedure.Various operating parameters,such as fuel temperature and fuel stoichiometric flow rate,are tested to optimize micro PEMFC performance.A single micro PEMFC using MEMS technology reveals the ideal performance of the proposed fuel cell.The optimal power density approaches 232.75 mW·cm-1 when the fuel cell is operated at ambient condition with humidified,heated fuel.
基金supported by the National High Technology Research and Development Program of China(No.2007AA04Z322)the State Key Development Program for Basic Research of China (No.2009CB320305)the Chinese Academy of Sciences
文摘The simultaneous control of residual stress and resistivity of polysilicon thin films by adjusting the deposition parameters and annealing conditions is studied. In situ boron doped polysilicon thin films deposited at 520 ℃ by low pressure chemical vapor deposition （LPCVD） are amorphous with relatively large compressive residual stress and high resistivity. Annealing the amorphous films in a temperature range of 600-800 ℃ gives polysilicon films nearly zero-stress and relatively low resistivity. The low residual stress and low resistivity make the polysilicon films attractive for potential applications in micro-electro-mechanical-systems （MEMS） devices, especially in high resonance frequency （high-f） and high quality factor （high-Q） MEMS resonators. In addition, polysilicon thin films deposited at 570 ℃ and those without the post annealing process have low resistivities of 2-5 mΩ·cm. These reported approaches avoid the high temperature annealing process （〉 1000 ℃）, and the promising properties of these films make them suitable for high-Q and high-f MEMS devices.
文摘We aimed to develop a process technology for constructing a carbon-based micro-electromechanical system that does not require a high-temperature and high-energy process. A HOPG （highly oriented pyrolytic graphite） crystal microsheet was prepared by exfoliation. Cantilevers and doubly clamped beams were patterned using a photoresist. The HOPG microsheet was attached by using a tantalum layer. We fabricated cantilevers and a doubly clamped beam by controlling the thickness of the HOPG microsheet and then measured the first resonance frequency. The measurements suggest a need to improve the stiffness of the beam.
文摘Initially studied and developed by students in universities, the very small pico satellites （with a mass lower than 1 kg） are more and more considered for science applications. In particular, there are plans to use them in constellations of small spacecraft for remote sensing of various regions of the magnetosphere. They require a payload with specific size, weight and power consumption. In order to respond to this demand, new instruments have to be developed. Those instruments should exhibit at least the same performances as those used in larger satellites while fulfilling the specific requirements imposed by the satellites size. For this reason, the authors currently develop a xylophone bar magnetometer （XBM） based on micro-electromechanical systems （MEMS） with integrated detector electronics. The principle of this magnetometer is based on a classical resonating xylophone bar. A sinnsoidal current oscillating at the fundamental bending resonant frequency of the bar is applied through the device, and when an external magnetic field is present, the resulting Lorentz force yields the bar to vibrate at its fundamental mode with a displacement directly proportional to the amplitude in one direction of the ambient magnetic field. When designing a MEMS XBM, the detection method is a crucial aspect. The measurement method largely influences the geometry of the magnetometer as well as the manufacturing technology. Due to the constraints in terms of size, weight and power consumption, the two most promising measurement methods are capacitive and piezoelectric ones. Several designs including these measurement techniques are presented and simulated under realistic conditions. First, designs including lateral electrodes for capacitive measurement are tackled based on Silicon-On-Insulator （SOI） process. For the piezoelectric detection, a new configuration based on Lead Zirconate Titanate （PZT）/Pt structure is introduced and leads to much better sensitivity than the traditional Pt/PZT/Pt sandwich structure
