An analysis of the dynamic characteristics of pull-in for parallel-plate and torsional electrostatic actuators is presented. Traditionally, the analysis for pull-in has been done using quasi-static assumptions. However, it was recently shown experimentally that a step input can cause a decrease in the voltage required for pull-in to occur. We propose an energy-based solution for the step voltage required for pull-in that predicts the experimentally observed decrease in the pull-in voltage. We then use similar energy techniques to explore pull-in due to an actuation signal that is modulated depending on the sign of the velocity of the plate (i.e., modulated at the instantaneous mechanical resonant frequency). For this type of actuation signal, significant reductions in the pull-in voltage can theoretically be achieved without changing the stiffness of the structure. This analysis is significant to both parallel-plate and torsional electrostatic microelectromechanical systems (MEMS) switching structures where a reduced operating voltage without sacrificing stiffness is desired, as well as electrostatic MEMS oscillators where pull-in due to dynamic effects needs to be avoided.

Dynamic pull-in of parallel plate and torsional electrostatic MEMS actuators.

This paper describes and demonstrates a terahertz (THz) frequency tunable fishnet metamaterial (TFMM) using an electrically controlled polymer dispersed liquid crystal (PDLC) matrix. In contrast to other PDLC-based devices, the TFMM employs a novel method for encapsulating PDLC using a thin (1.5 μm) polyimide “skin layer” to form a uniform surface for metal electrodes while minimizing the Fabry-Perot effect of the skin layer on the TFMM measurements. The tunability was verified by measuring the frequency shift in the reflection coefficient (0.01 THz), with an observed minimum negative refractive index of −15 at 0.55 THz.

Tunable terahertz fishnet metamaterial

This paper presents a tunable artificial iris on flexible substrate for modulating light intensity through human eyes. The artificial iris consisted of eight rings of polymer-dispersed liquid crystals (PDLCs). These PDLC rings were switched between transparent and opaque states by applying a 100 V bias voltage. A control circuit with a photodiode was integrated to sequentially drive the PDLD rings in response to the ambient light. The transmittance of the fabricated artificial iris was decreased from 94% to 20.4% as the ambient light intensity increased from 0 lux to 2500 lux. When the ambient light intensity was 2500 lux, the modulated value passing through the artificial iris was reduced to 510 lux. The presented system can be potentially applied for assisting patients of aniridia or enhancing the functionality of robot vision.

Concentric polymer-dispersed liquid crystal rings for light intensity modulation

Provided is an active piezoelectric energy harvester, which can control a direct current voltage applied to an embedded variable capacitance layer to precisely adjust a resonance frequency in real time, and thus achieve a simpler structure and a smaller size compared to a conventional one that adjusts the resonance frequency using a separate variable capacitor provided outside. Further, the active piezoelectric energy harvester can precisely adjust the resonance frequency even when the frequency of vibration varies over time as in a real natural vibration environment or when it is degraded to undergo a variation in its own resonance frequency, and thus can continuously maintain optimal energy conversion characteristics.

Active piezoelectric energy harvester with embedded variable capacitance layer and method of manufacturing the same

Liquid crystals (LCs) possess some typical liquid properties, such as fluidity, the inability to support shear, and the formation and coalescence of droplets, which exhibit optical, electrical, and magnetic anisotropic properties, and give materials various physical properties. Composite films composed of LCs and polymers have provided a new field of LC science and technology and have attracted great attention over the past years due to their applications in displays, light shutters, fiber-optic communications, switchable windows, photonic crystals, and augmented reality/virtual reality devices. These composite films, such as polymer-dispersed liquid crystals (PDLCs), polymer-stabilized liquid crystals (PSLCs), and polymer-dispersed and polymer-stabilized liquid crystals (PD&PSLCs), are fabricated by phase separation methods as well as electrospinning and microfluidic techniques. The combination of LCs and polymers will yield a variety of novel characteristics such as switchable optical transmittance, broadband optical reflectivity, excellent optical diffusivity in diffusers for backlight units of liquid-crystal displays, high sensitivity to electric field, magnetic field, and chemical stimulation, and high ion transport speeds for smart windows, microlenses, sensors, actuators, and energy storage devices such as dielectric capacitors, dye-sensitized solar cells, thermoelectric devices, and solid batteries. This Review gives new insights and understanding about LC/polymer composite films that are particularly suitable for large-area electrically switchable windows and multiple related fields. 

Advancements and Applications of Liquid Crystal/Polymer Composite Films

A tunable capacitor based on polymer-dispersed liquid-crystal (PDLC) technology is presented in this paper. Its application for robust power harvesting microsystems was investigated. The power harvesting device utilized a piezoelectric microcantilever excited by ambient random vibrations to convert mechanical energy into electric power. For improving the power harvesting efficiency, the PDLC tunable capacitor was used to adjust the resonance frequency of the piezoelectric microcantilever beam to match the frequency of the ambient vibrations in real time. The fabrication process and measurement results of the PDLC tunable capacitor are detailed. The measured tuning ratio of the PDLC tunable capacitor was 63% at 300-Hz excitation frequency when a 25-V driving voltage was applied. The dielectric and optical properties of the fabricated PDLC tunable capacitor have been examined thoroughly. Based on the results of the experiment, an equivalent lumped-element model of the PDLC tunable capacitor has been developed. The simulation results showed that the impedance of the developed model agreed well with that of the fabricated tunable capacitor. This model can be incorporated into the equivalent circuit of the integrated power harvesting system for efficiency optimization.

Tunable Capacitor Based on Polymer-Dispersed Liquid Crystal for Power Harvesting Microsystems

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

Yu-Yin Chen

Author Tools

Chat about Author

Papers

Tunable Capacitor Based on Polymer-Dispersed Liquid Crystal for Power Harvesting Microsystems