Switchable Device Research Articles

Electrochemically Switchable Double-Gate Nanofluidic Logic Device as Biomimetic Ion Pumps

Biological ion pumps with two separate gates can actively transport ions against the concentration gradient. Developing an artificial nanofluidic device with multiple responsive sites is of great importance to improve its controllability over ion transport to further explore its logic function and mimic the biological process. Here, we propose an electrochemical polymerization method to fabricate electrochemically switchable double-gate nanofluidic devices. The ion transport of the double-gate nanofluidic device can be in situ and reversibly switched among four different states. The logic function of this nanofluidic device is systematically investigated by assuming the gate state as the input and the transmembrane ionic conductance as the output. A biomimetic electrochemical ion pump is then established by alternately applying two different specific logic combinations, realizing an active ion transport under a concentration gradient. This work would inspire further studies to construct complex logical networks and explore bioinspired ion pump systems.

Fast refocusing lens based on ferroelectric liquid crystals.

Optical devices like virtual reality (VR) headsets present challenges in terms of vergence-accommodation conflict that leads to visual fatigue for the user over time. Lenses available to meet these challenges include liquid crystal (LC) lenses, which possess a response time in the millisecond range. This response time is slow, while accessing multiple focal lengths. A ferroelectric liquid crystal (FLC) has a response time in the microsecond range. In this article, we disclose a switchable lens device having a combination of the fast FLC-based polarization rotation unit and a passive polarization-dependent LC lens. A cascaded combination of three such lens units allows access to eight different focal points quite rapidly and can be a convenient device for VR applications.

Thermally switching between perfect absorber and asymmetric transmission in vanadium dioxide-assisted metamaterials.

In this paper, we propose a switchable bi-functional metamaterial device based on a hybrid gold-vanadium dioxide (VO2) nanostructure. Utilizing the property of a metal-to-insulator transition in VO2, perfect absorption and asymmetric transmission (AT) can be thermally switched for circularly polarized light in the near-infrared region. When VO2 is in the metallic state, the designed metamaterial device behaves as a chiral-selective plasmonic perfect absorber, which can result in an optical circular dichroism (CD) response with a maximum value ∼ 0.7. When VO2 is in the insulating state, the proposed metamaterial device exhibits a dual-band AT effect. The combined hybridization model and electromagnetic field distributions are presented to explain the physical mechanisms of chiral-selective perfect absorption and AT effect, respectively. The influences of structure parameters on CD response and AT effect are also discussed. Moreover, the proposed switchable bi-functional device is robust against the incident angle for obtaining perfect absorption and strong CD response as well as the AT effect. Our work may provide a promising path for the development of multifunctional optoelectronic devices, such as thermal emitters, optical modulators, CD spectroscopy, optical isolator, etc.

A metal-porphyrinic framework film as an efficient optical limiting layer in an electro-optical switchable device.

Herein we report a 2D surface-coordinated porphyrinic metal-organic framework film (SURMOF) CuTCPP prepared by a layer by layer method as an optical limiting layer in a polymer-dispersed liquid crystal (PDLC) device. The results show that the CuTCPP SURMOF/PDLC device has excellent switchable transparency and optical limiting performance, providing a new route to achieve mutilfunctional electro-optical applications.

Reflective‐Type Transparent/Colored Mirror Switchable Device Using Reversible Electrodeposition with Fabry–Perot Interferometer

AbstractReversible electrodeposition (RED) devices have been considered as the optical transmittance or reflectance switchable display for the reflective display applications. In this study, transparent/colored mirror switchable RED device is demonstrated by integrating the Fabry–Perot (FP) interferometer. Indium‐tin‐oxide (ITO)‐based FP interference effect is utilized for color filter to emit particular wavelength. Color‐switchable RED cells are researched using ITO (red, green, and blue (RGB)) films and tungsten (W) films as partially reflective layers for the cavities. The red/green/blue colored mirrors are developed according to ITO thickness as the Ag film deposit. Then, the ITO (RGB) pixelated RED devices are investigated by differential deposition process. In the 25 × 25 µm2 sized ITO (RGB) micro‐subpixels mirror, the high transparent and high reflectivity states are successfully achieved, which can be applied to reflective‐type transparent displays.

Flexible, switchable and wearable image storage device based on light responsive textiles

Materials with reversible optical properties under light irradiation have great potential application in various optoelectronic fields. Particularly, photochromic materials have received extensive attention in many fields. Herein, a novel composite photochromic fabric was fabricated via Layer-by-Layer self-assembling of phosphomolybdic acid (PMoA) and polyacrylamide (PAM). Based on the established electron transfer photochromic system, the dynamic manipulation of photochromic behavior of the cotton fabric was achieved with outstanding fine high-resolution image under the visible light irradiation. The prepared fabric can change from colorless to blue rapidly (within 5 min) under UV light and maintain excellent reusability photochromic performance after more than 20 reversible color changing cycles, implying its great potential applications in the field of intelligent devices and UV detection in sunlight. Moreover, we constructed fabric weaving and developed a Quick Response (QR) code security identification to prove the practical application of the prepared photochromic fabric in the fields of wearable, optical information storage and information security encryption.

Growth of amorphous, anatase and rutile phase TiO2 thin films on Pt/TiO2/SiO2/Si (SSTOP) substrate for resistive random access memory (ReRAM) device application

Memory structures play a basic role in providing integrated circuits of powerful processing capabilities. Even most powerful processors have nothing to offer without an accompanying memory and importantly, the development of mobile devices is dependent on the continual improvement of memory technology. Herein, we report the synthesis of TiO2 thin films on SSTOP (Pt/TiO2/SiO2/Si) substrate via physical vapour deposition process for the first time. The layers consisted of Si, SiO2, TiO2 and Pt, hence the SSTOP shorthand is used throughout the text. Three different phases of TiO2 thin films were obtained, i.e. amorphous, anatase and rutile phases, by controlling the reaction parameters which were examined by x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), atomic force microscopy (AFM) and Raman-scattering spectroscopy in order to understand the crystallographic, morphological, compositional and scattering properties. The detailed studies confirmed the formation of various crystal phases of titania. The grown thin films on SSTOP substrates were further utilized to fabricate resistive random access memory (ReRAM) devices and the initial electrical screening was performed on capacitor-like structures which were prepared using platinum top electrodes (diameter = 250 μm) on a 14 × 14 array metal contact mask. Current-Voltage (I–V) measurements were implemented employing a range of current compliances (IC). The detailed electrical characterizations revealed that the forming field for a switchable unipolar device was found to be greatest on rutile titania and lowest on the amorphous titania phase. Similarity, the resistive contrast was greatest on the rutile titania phase and lowest on the anatase titania phase.

On-chip switchable and reconfigurable optical mode exchange device using cascaded three-waveguide-coupling switches.

Data exchange between different data channels can offer more flexible and advanced functions for many optical networks. In this paper, we propose a switchable and reconfigurable data exchange device for arbitrary two optical mode channels based on three-waveguide-coupling (TWC) switches in mode-division multiplexing (MDM) networks. The working principle of the TWC switches is numerically analyzed using the coupled supermode theory. As a proof of concept, switchable data exchange between arbitrary two mode channels among the first three-order quasi-transverse electric modes is experimentally demonstrated successfully. The insertion losses of the device are less than 5.6 dB, including the coupling loss of the multiplexer and demultiplexer, while the mode crosstalk is less than -13.0 dB for all functions. The proposed device is expected to offer more flexibility to on-chip MDM networks due to its low loss, low crosstalk and good scalability.

Flexible Electrochromic Zn Mirrors Based on Zn/Viologen Hybrid Batteries

Herein, we present a strategy for a switchable electrochromic zinc mirror/battery, which acts as a battery and a switchable electrochromic device via the electrodeposition and dissolution of Zn ont...

Excitation wavelength as logic operator.

Multiple molecular logic gates were harvested on a single synthesized material, (E)-2-(2-hydroxy-3-methoxybenzylideneamino)phenol (MBAP), by combining excitation wavelength dependent multi-channel fluorescence outputs and the same chemical inputs. Interestingly, the effortless switching of logic behavior was achieved by simply tweaking the excitation wavelength and sometimes the emission wavelengths with no alteration of chemical inputs and the main device molecule, MBAP. Additionally, new generation purely optically driven memory units were designed on the same system supporting an almost infinite number of write-erase cycles since inter-conversion of memory states was completely free from chemical interferences and impurity issues. Two-way memory functions ("erase-read-write-read" and "write-read-erase-read") worked simultaneously on the same system and could be accessed by simple optical switching between two excitation and emission wavelengths. Our optically switchable device might outperform traditional multifunctional logic gates and memory devices that generally employ chemical triggers to switch functionality and memory states. These optically switchable multifunctional molecular logic gates and memory systems might drive smart devices in the near future with high energy efficiency, extended life span, structural and functional simplicity, exclusive reversibility and enhanced data storage density.

Reliable optoelectronic switchable device implementation by CdS nanowires conjugated bent-core liquid crystal matrix

Enhancing the performance of high luminescent and dielectrically capable cadmium sulfide nanowire (CdS NW) is of great importance, because of their promising ability in analyzing the dimensionality and size. The tuned physical characteristics of semiconductor CdS NWs allowed the manipulation of both electronic and optoelectronic devices at the nanoscale by dispersing a new bent core (BC) liquid crystal (LC) compound. This was derived from a 4-chlororesorcinol central core unit with two terephthalate based rod-like units carrying chiral ( S )-3, 7-dimethyloctyloxy (namely ‘CPDB’) terminal chains, which have been synthesized in a pure solvo-chemical process. The mesomorphic properties of the newly-prepared bent-core LC, exhibiting an enantiotropy ‘Sm A’ phase as a result of dispersing 0.005% of CdS NWs, were investigated by several spectroscopic investigations. In addition, the hydrothermal fabrication of CdS NWs with a high-yield was modified with a cationic agent, cetyltrimethyl ammonium bromide (CTAB), which was utilized as a compatibilizer for providing a better interaction with LC molecules and giving a homogeneous solution. This work focused on the experimental investigation and optimization, using a combinational view of bent-core liquid crystal (CPDB) compound dispersion which was achieved in a controllable manner. The product of the resulting composite matrix has a very outstanding and promising behavior, e.g. semiconductor nanostructures emission polarization that can be manipulated using an external bias modulation of the novel switchable device, which was found quite convincing in the recent trends of brand-new technologies. In particular, the electro-optic responses by POM of various mesophases were investigated from the view point of the CdS incorporated bent-core LC matrix formation and transitional phase variants of ‘ON’ and ‘OFF’ states, which were depending on the geometrical parameters of CdS NW's. Finally, the future challenges and prospects of any other nanomaterials dispersed into CPDB compound which will give rise to an increase of the mesomorphic range by preserving the mesophase type were explored in detail. • High-yield CdS nanowires (7–10 nm diameter) were successfully fabricated via hydrothermal assisted route. • Chemical systhesis of bent-core liquid crystalline compounds (CPDB). • Electro-optic responses by POM of various mesophases are investigated and analyzed. • Homogeneously diffused CdS nanowires into bent-core liquid crystalline matrix. • Various textural phase patterns reveal the modification of crystallographic configuration. • Golden opportunities of nanowires into bent-core liquid crystal mesomorphic investigations.

Thermal and visual comfort analysis of adaptive vacuum integrated switchable suspended particle device window for temperate climate

In this work, thermal and visual comfort of low heat loss switchable suspended particle device-vacuum (SPD-vacuum) glazing was investigated for less energy-hungry adaptive building’s glazing or façade integration at temperate climate. This SPD-vacuum glazing had 38% visible transmittance in the presence of 110 V applied an alternating voltage and 2% visible transmittance in the absence of electrical power. Outdoor test cell characterisation was employed to measure the thermal and daylighting parameters of this glazing. Solar heat gain or solar factor was calculated using non calorimetric methods and varied between 0.38 (Switch OFF/opaque) to 0.51 (Switch ON/transparent). Test cell indoor and ambient parameters (incident solar radiation and ambient temperature) were engaged for thermal comfort analysis by using PMV and PPD methods. Visual comfort was analysed from glare potential, useful daylight index, and colour properties. The comfortable thermal environment was attainable using both states of this glazing for a clear sunny day. Acceptable daylight throughout the day was possible for a clear sunny day for opaque state; however clear state offered allowable/comfortable correlated colour temperature (CCT) of 5786.18 K and colour rendering index (CRI) of 94.83.

Design and modeling of a transmission and reflection switchable micro-focusing Fresnel device based on phase-change materials.

In this paper, a switchable micro-focusing Fresnel device based on phase-change materials (PCMs) is proposed, which can selectively display the functions of transmission and reflection without the use of mechanical adjustment on micro scale. The switchable function is realized by combining Fresnel structure with PCM. A four-level switchable Fresnel device consisting of a typical PCM Ge3Sb2Te6 (GST-326) is designed to focus light into a focal length of 30 µm at wavelength of 3.1 µm. The optical performance of the switchable device has been analyzed by using finite-difference time-domain (FDTD) method, showing bright convergence point near pre-designed focal length with focusing efficiencies larger than 18%, depth of focus (DOF) less than 4.65 µm and the full width at half-maximum (FWHM) not larger than 1.30 µm. Furthermore, by precisely manipulating the variation of PCM thickness, we also obtain a device that possesses the characteristics of a transmission-reflection focusing beam splitter. The devices show good potential for the combination of traditional binary optical devices and PCM to produce new functions, and provides a promising innovative approach for miniature focal length switching device.

Tunable topological valley transport in two-dimensional photonic crystals

Recently, exploring the valley degree of freedom in photonic crystals has attracted considerable attentions since it opens up the possibility of extending valleytronics to optics. However, the fixed structural parameters limit the practical applications of valley photonic crystals. How to design steerable valley photonic structures becomes an important research topic. In this work, we design a tunable valley photonic crystal using an array of regular triangular metal rods embedded in liquid crystals. Electrically controlled valley-selective excitation, valley-locked beam splitting behavior and valley-projected edge transportation have been numerically demonstrated. Using these novel effects, a switchable valley filter device has also been designed. Our proposed valley-based photonic devices are beneficial for the development of robust wave manipulation.

Growth dynamics of CBD-assisted CuS nanostructured thin-film: optical, dielectric and novel switchable device applications

The microcrystal structure of copper sulfide (CuS) nano-structured ultra-thin film was prepared on glass substrate from aqueous ammonia solution and sodium hydroxide at 60 °C using a simple and cost-effective chemical bath deposition (CBD). The powder X-ray diffraction method was used to characterize the hexagonal structure of the prepared CuS thin-film. While, surface morphology and surface topology were investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The optical properties were investigated by using UV–visible absorption spectrum. The electronic properties including average energy gap (Penn gap), Fermi energy, electronic polarizability and valence electron plasma energy of CuS thin films were determined. Semiconductor characterization of CuS film was confirmed using temperature dependent conductivity analysis. To prove the positive photoconductivity of nano-structured CuS nano-structured thin film, photoconductivity measurements were performed. I–V characteristics result, and Hall Effect measurements were also evaluated. Our results showed that the prepared CuS nano-structured thin films have higher crystallinity, purity and higher content of copper (Cu: 89.6%) as confirmed by XRD and EDX elemental analysis, respectively. While, their optical band gap energy is about 2.2 eV. Polarization-dependent Raman investigations allowed sample identification by dominant peaks at 265 cm−1 and 474 cm−1, proving the formation of CuS. Moreover, stimulating energy was found to be 0.028 eV by employing DC conductivity measurements. The estimated surface roughness was about (115 nm) with an average thickness of about (16.3 nm) as obtained from AFM analysis. Finally, remarkable smooth multi-colored marble like textural patterns have been recorded confirming the novel switching as recorded by the polarizing optical microscopy.

EGOFET Gated by a Molecular Electronic Switch: A Single‐Device Memory Cell

AbstractElectrolyte‐gated organic field‐effect transistors (EGOFETs) exploit the transduction of interfacial phenomena, such as biorecognition or redox processes, into detectable changes of electrical response. Here, it is shown that, beyond sensing applications, EGOFETs may act effectively as memory devices, through the functionalization of the gate electrode with a self‐assembly monolayer comprising a switching molecule undergoing a large and persistent change of dipole moment, upon application of a small (0.6 V) programming potential. This first example of a switchable EGOFET device with memory retention is based on a tetrathiafulvalene derivative self‐assembled on gold and an aqueous buffer as electrolyte in a microfluidic assembly. Changes of the self‐assembled monolayer redox state lead to variations of the gate electrochemical potential and, as a consequence, the EGOFET's threshold voltage undergoes reversible shifts larger than 100 mV. The distinctive electrical readout upon different redox states opens the possibility of writing and erasing information, thus making the transistor behave as a single memory cell.

A switchable single-molecule electrochromic device derived from a viologen-tethered triazolium-based poly(ionic liquid)

This work demonstrates the synthesis of a switchable single-molecule electrochromic device generated by tethering a viologen onto a poly(ionic liquid) (PIL) via an alkyl linker.

Switchable Holographic Device Based on Reversible Electrodeposition

AbstractA new switchable holographic device concept using reversible electrodeposition (RED) technology is proposed. The proposed device has a structure in which the cavity structure is changed by the reversible deposition of Ag, and thus the characteristics of the reflected light are modulated. It has a high reflectance due to a mirror reflection structure and exhibits phase modulation by the reversible deposition of Ag. Because the proposed device is a current‐driven device, it is expected to overcome the limitation in the scaling down of the pitch in spatial light modulators, which is considered a limitation of liquid crystal device. A passive type switchable holographic device with a 1 µm pitch is implemented using the proposed device. The successful implementation of a switchable holographic image using the fabricated device is confirmed. The proposed device is expected to be applicable as an active metasurface and spatial light modulator device in the visible light region in the future because it has a large modulation in the visible light region.

Terahertz Switching Focuser Based on Thin Film Vanadium Dioxide Zone Plate

In this paper, we propose a switchable focuser device based on a Fresnel zone plate (FZP) structure for terahertz (THz) applications. Each FZP contains seven rings, etched in thin VO2 film with the designed focal lengths of 50 and 100 mm for 3.7-THz frequency. Temperature-induced VO2 phase transition leads to the change in dielectric susceptibility of the material, which allows one to switch on and off the focusing properties of the device. The devices were tested with radiation of 3.1 and 3.7 THz emitted by quantum cascade lasers. Experimental results were compared with numerical simulations. In this article, we compare the FZP based on VO2 films with different properties and show that a thicker VO2 film reveals higher focusing efficiency, while a thinner one reveals a higher modulation ratio for the peak intensity at the focal point of FZP. We demonstrate experimentally the near-diffraction-limited size of the beam in the focal point of the device. Switching between two phase states of the VO2 films results in up to the 38-fold change of intensity in the focal point.

2D/3D switchable displays through PDLC reverse mode parallax barrier

ABSTRACTIn this paper, we present a new type of parallax barrier, for switchable 2D/3D display vision, obtained by using a Reverse Mode Polymer Dispersed Liquid Crystal display (RV-PDLC). The parallax barrier was prepared by sandwiching the RV-PDLC film between two ITO conductive glass supports. Strips of ITO were removed from one of the supports, in order to alternate conductive to not conductive strips. In this way the RV-PDLC films could be electrically switched in a parallax barrier able to turn a 2D image in a 3D one. The RV-PDLC barrier was obtained in tree steps: (1) a nematic diacrylate monomer (NDM) was dissolved in a nematic liquid crystal (NLC) in the presence of a small quantity of radical polymerisation initiator; (2) the mixture was homeotropically aligned between the glass conductive supports, previously treated with an aligning chemical; (3) the liquid crystal monomer was polymerised by UV curing. A 2D/3D switchable device was finally obtained by coupling the parallax barrier with a 2D tablet display.