Applications In Multifunctional Devices Research Articles

(K,Na)NbO3-based lead-free ceramics with enhanced temperature-stable piezoelectricity and efficient red luminescence

There has been a surge of research interest in the promising lead-free potassium−sodium niobate (KNN)-based ceramics, applications of which could be significantly promoted by improving thermal stability of piezoelectricity. Besides, endowing the KNN-based ceramics with photoluminescence property by rare-earth-ion doping can make them more completive lead-free counterparts in potential applications such as novel multifunctional sensing devices. Herein, a novel KNN-based ceramic material doped with Eu was elaborately designed to simultaneously obtain enhanced temperature-stable piezoelectricity and good luminescence property. By the introduction of diffused phase transition and the modulation of unit cell distortion, a large piezoelectric strain coefficient (<i>d</i>^*₃₃) with a small variation (590±59 pm/V) over a wide temperature range (from room temperature to 110 ℃) was realized. The optimal composition also exhibited a considerable piezoelectric coefficient (<i>d</i>₃₃) with small fluctuation (330±33 pC/N) from 20 to 80 ℃. In addition to the enhanced temperature-stable piezoelectricity, the luminescence of these ceramics was slightly enhanced with the elevation of BaZrO₃ (BZ) doping contents, which could be attributed to the increased compositional disorder and the decreased unit cell distortion of the matrix material. Moreover, an optical characteristic was more prominent at ultra-low temperatures. This work unprecedentedly provides a novel paradigm for the design of multifunctional KNN-based ceramics with enhanced temperature-stable piezoelectricity and good luminescence property, revealing the great potential of the rare-earth-element-doped KNN material for future applications in the novel multifunctional devices.

Two‐Step Magnetic‐Pulling Chemical Vapor Deposition Growth of CdS1−xSex Lateral Nanoribbon Heterostructures for High‐Performance Photodetectors

Bandgap integration in a single semiconductor nanostructure is an important task for their applications in photonics and photoelectronics. Herein a two‐step growth of CdS x Se1−x alloy nanoribbon heterostructures along the lateral direction by an improved two‐step magnetic‐pulling chemical vapor deposition (CVD) method is reported. Microstructural characterizations further demonstrate that these ribbons are formed by two separate components along the lateral direction of the nanoribbons, including CdS0.76Se0.24 at the central region and CdS0.44Se0.56 at both lateral sides, respectively. Under a laser excitation, photoluminescence spectrum and 2D emission mapping at the junctions show two different emission bands at 555 and 603 nm, which show agreement with the structural characterization results. More importantly, under 355 nm laser illumination, room‐temperature dual‐wavelength lasing with peak center at 542.3 and 605.2 nm is realized using these sandwich‐like nanoribbons. Additionally, photodetectors based on these achieved nanoribbons are fulfilled with great performance of high responsivity (2.4 × 104 A W−1), high external quantum efficiency of 2.9 × 105%, fast response speed (rise ≈25 ms, decay ≈21 ms), and high I on/I off ratio (106). These structures may offer an interesting system for exploring new applications in multifunctional nanophotonic and optoelectronic devices, such as high‐performance detectors, miniature tunable lasers, and high‐density color displays.

Wet-spinning of continuous hyaluronic-based MXene/CNTs hybrid fibers for flexible supercapacitor applications

Carbon nanotube (CNTs) fibers with high conductivity and excellent electrochemical properties are the most promising candidate materials for flexible supercapacitor electrodes. Utilizing the high energy storage characteristics of MXene materials, this paper designed and prepared the novel MXene/CNTs/HA hybrid fibers by wet spinning methods with sodium hyaluronate (HA) as the dispersant, and MXene and CNTs powder as main materials. The volumetric capacitance of obtained MXene/CNTs/HA hybrid fibers can reach 13.95 ± 2.45 F/cm3 and the retention rate of capacitance could remain 82 % after 1000 charge–discharge cycles. These results indicate that MXene/CNTs/HA hybrid fibers have great potential application in flexible supercapacitors and multi-functional electronic devices.

Investigations of room temperature multiferroic and magneto-electric properties of (1-Φ) PZTFT-Φ CZFMO particulate composites

Multiferroic composites consisting of a single-phase multiferroic [0.6(PbZr0.53Ti0.47O3)-0.4(PbFe0.5Ta0.5)O3] as a matrix and a magnetostrictive phase (Co0.6Zn0.4Fe1.7Mn0.3O4) dispersed in the matrix are fabricated via hybrid synthesis technique. The structure and surface morphology studies using x-ray diffraction and field emission scanning electron microscopy techniques indicate the formation of 3-0 type particulate composites. Coexistence of soft-magnetic behavior and ferroelectric characteristics are confirmed for composites from magnetization vs magnetic field (M–H) and polarization vs electric field (P–E) measurements, respectively. Magneto-dielectric (MD) measurement shows significant changes in the dielectric properties with the application of a magnetic field, indicating the existence of strong MD behavior. The biquadratic nature of magneto-electric (ME) coupling is described by the Landau free energy equation arising from the strain transfer at the interfaces between the constituent phases. The direct magneto-electric voltage coefficient measurement also confirms very strong coupling between ferroelectricity and magnetism and supports the strain-mediated magneto-electric effect in composites. The Φ = 0.3 composite exhibits the maximum ME coefficient of 20.72 mV/cm Oe with MS = 24.62 emu/g, HC = 59.66 Oe, and piezoelectric coefficient value d33 = 19 pC/N. The strong magneto-electric effect along with low dielectric loss at room temperature in these composites suggests their suitability for multifunctional magneto-electric device applications such as magnetic sensors, etc.

Enhancement in the magneto-dielectric and ferroelectric properties of BaTiO3 – CoFe1.9Yb0.1O4 core-shell multiferroic nanocomposite

Herein we report the dielectric, ferroelectric, magnetocapacitance and energy storage density properties of CoYb0.1Fe1.9O4-BaTiO3 core-shell multiferroic nano-composite synthesized by the combination of co-precipitation and sol-gel method. The XRD spectra revealed that the ferroelectric BT phase is compatible with the magnetic YbCFO phase. Scanning Electron microscopy (SEM), Energy-Dispersive X-ray spectroscopy (EDS) and Transmission Electron Microscopy (TEM) confirmed the formation of core-shell like structure in the composite. The magnetic and ferroelectric phase preserves their basic individual properties in the core–shell form. The temperature dependence of dielectric permittivity showed a sharp phase transition from cubic to tetragonal structure of the core-shell composite at 312.726 K. Frequency dependent dielectric study shows an enhanced value of permittivity (36905.0218) along with low dielectric losses (1.354). It was found that the prepared composite exhibited moderate values of saturation magnetization (3.379 emu/g) and polarization (5.146 μC/cm2) along with low remnant polarization (1.777 μC/cm2) at room temperature. Moreover, we also observed enhanced energy storage efficiency (60%) and magneto-capacitance (5.853%) which are explained due to strong interfacial coupling and reduced leakage current, making this composite promising for multifunctional device applications.

Non-volatile control of topological phase transition in an asymmetric ferroelectric In2Te2S monolayer.

The coupling of topological electronic states and ferroelectricity is highly desired due to their abundant physical phenomenon and potential applications in multifunctional devices. However, it is difficult to achieve such a phenomenon in a single ferroelectric (FE) monolayer because the two polarized states are topologically equivalent. Here, we demonstrate that the symmetry of polarized states can be broken by constructing a Janus structure in a FE monolayer. We illustrate such a general idea by replacing a layer of Te atoms in the In2Te3 monolayer with S atoms. Using first-principles calculations, we show that the In2Te2S monolayer has two asymmetric polarized states, which are characterized by a metal and semiconductor, respectively. Importantly, as the spin-orbit coupling is included, a band gap (50.4 meV) is created in the metallic state, resulting in a non-trivial topological phase. Thus, it proves to be a feasible method to engineer non-volatile FE control of topological order in a single-phase system. We also demonstrate the underlying physical mechanism of topological phase transition, which is unveiled to be related to the weakened intrinsic electric field resulting from charge transfer. These interesting results provide a general way to design asymmetric FE materials and shed light on their potential application in non-volatile multifunctional devices.

Spin-orbit splitting and piezoelectric properties of Janus Ge2XY (X ≠ Y = P, As, Sb and Bi).

The coexistence of spin-orbit coupling and piezoelectricity in a single material may have potential application in multifunctional devices, including spintronics, nanorobotics and piezotronics. Spin-orbit coupling provides a new means to manipulate electron's spin without an additional external magnetic field, while piezoelectricity refers to the interplay between mechanical stresses and electric polarization. Using first-principles calculations, the structural, electronic, optical, spin, and piezoelectric properties of the Janus Ge2XY (X ≠ Y = P, As, Sb, and Bi) monolayers were systematically investigated. All the Ge2XY are energetically and dynamically stable in the α phase. At the GW level, Ge2AsSb, Ge2AsBi, and Ge2SbBi have direct fundamental band gaps of 0.65, 0.64, and 0.91 eV. At the GW + BSE level, their optical gaps are 0.42, 0.45, and 0.63 eV, and the optical absorption coefficients can reach about 10-5 cm-1 in the infrared light region, which reveals that they have potential for application in infrared photodetectors. For Ge2PBi, Ge2AsBi, and Ge2SbBi containing the heavy Bi element, the lowermost conduction band and uppermost valence band have large spin splitting along the M-K and K-Γ lines, and the bands near the Fermi level possess Rashba spin splitting at the Γ point. Ge2PBi and Ge2SbBi have both large in-plane piezoelectric coefficients d11 (-0.75 and -3.18 pm V-1) and out-of-plane piezoelectric coefficients d31 (0.37 and 0.30 pm V-1). Our findings are helpful to understand the mechanism of the spin-orbit physics and piezoelectricity of Janus Ge2XY monolayers and guide experiments in exploring novel multifunctional materials.

Recent advances in n-type and ambipolar organic semiconductors and their multi-functional applications.

Organic semiconductors have received broad attention and research interest due to their unique integration of semiconducting properties with structural tunability, intrinsic flexibiltiy and low cost. In order to meet the requirements of organic electronic devices and their integrated circuits, p-type, n-type and ambipolar organic semiconductors are all necessary. However, due to the limitation in both material synthesis and device fabrication, the development of n-type and ambipolar materials is quite behind that of p-type materials. Recent development in synthetic methods of organic semiconductors greatly enriches the range of n-type and ambipolar materials. Moreover, the newly developed materials with multiple functions also put forward multi-functional device applications, including some emerging research areas. In this review, we give a timely summary on these impressive advances in n-type and ambipolar organic semiconductors with a special focus on their synthesis methods and advanced materials with enhanced properties of charge carrier mobility, integration of high mobility and strong emission and thermoelectric properties. Finally, multi-functional device applications are further demonstrated as an example of these developed n-type and ambipolar materials.

Reconfigurable band alignment of SWSe/h-BP heterostructures for photoelectric applications.

The integration of two-dimensional (2D) materials into van der Waals heterostructures (vdWHs) is regarded as an effective strategy for fabricating multifunctional devices. Herein, the effects of the vertical electric field and biaxial strain on the electronic, optical and transport properties of SeWS (SWSe)/h-BP vdWHs are systematically investigated using density functional theory calculations. The study shows that electric fields and biaxial strain can modulate not only the band gap but also the band alignment to produce multifunctional device applications. The SWSe/h-BP vdWHs can be used as highly efficient 2D exciton solar cells with a power conversion efficiency of up to 20.68%. In addition, the SWSe/h-BP vdWHs present a significant negative differential resistance (NDR) with a peak-to-valley ratio of 1.12 (1.18). The present work may provide a direction for tunable multiple-band alignments in SWSe/h-BP vdWHs and help achieve multifunctional device applications.

Van der Waals Multilayer Heterojunction for Low-Voltage Organic RGB Area-Emitting Transistor Array.

Organic light-emitting transistors (OLETs) have garnered considerable attention from academy and industry due to their potential applications in next-generation display technologies, multifunctional devices, and organic electrically pumped lasers. However, overcoming the trade-offs among power consumption, external quantum efficiency (EQE), and uniform area emission remains a long-standing issue for OLETs. Herein, a van der Waals multilayer heterojunction methodology is proposed to enhance the layer-to-layer interfacial interaction and contact, resulting in better dipole shielding, carrier transport, exciton recombination, and current density distribution. The prepared multilayer heterojunction OLET (MLH-OLET) array shows uniform and bright RGB area emission and low operating voltage (<30V among the lowest applied voltage of reported lateral LETs). Additionally, a high brightness under area emission of 1060cd m-2 , a high EQE value of 0.85%, and a high loop stability (over 380 cycles, outperforming state-of-the-art OLETs) indicate that the proposed multilayer heterojunction is obviously superior to the reported lateral device configuration. The van der Waals multilayer heterojunction developed for the preparation of OLET arrays sufficiently meets the low-voltage, high-performance, and low-cost requirements of future display technologies.

Comparative studies of electrical, dielectric, ferroelectric, and magnetic properties of two BiFeO3-based ceramics: (BiCa)(FeTi2)O8 and (BiSr)(FeTi2)O8

In this communication, we report the comparative studies of the transport mechanism, dielectric, ferroelectric, and magnetic responses of two BiFeO3-based ceramics: (BiCa)(FeTi2)O8 and (BiSr)(FeTi2)O8, synthesized using a high-temperature mixed-oxide reaction technique. Preliminary X-rays diffraction profile exhibits the phase formation of these compounds in the orthorhombic crystal system. The scanning electron micrographs show the inhomogeneous distribution of grains of different shapes and sizes in the morphology of the compounds. A detailed study of the Nyquist plots of the resistance shows the temperature and frequency dependence of the electrical properties of the compounds, indicating a good correlation with the morphology. The conductivity spectra obey Jonscher’s double power law and reveal a typical signature of CBH-type ac conduction in both the grain and grain boundary region. The lowest value of the dielectric loss at each temperature is obtained from Sr- containing compound, which have novel applications in data storage devices. The simultaneous presence of ferroelectric P-E loops and ferromagnetic M-H loops in both the compounds finds applications in multifunctional devices and inspires the development of lead-free multiferroics.

Superhydrophobic MXene Coating with Biomimetic Structure for Self-Healing Photothermal Deicing and Photoelectric Detector.

Two-dimensional transition metal carbides (Ti3C2Tx MXene) have emerged as new candidates for applications in multifunctional devices owing to their outstanding performance. However, these electronic devices are easily disturbed by water, breakage, oxidation during use, and limited energy resources. To solve these problems, herein, inspired by nature, a novel superhydrophobic, healable photothermal deicing and photodetector (SHPP) with a "papillary structure" is successfully fabricated for the first time, by a simple layer-by-layer assembly spraying process with 0D/1D/2D nanomaterials. As a result, the superhydrophobic modified 2D MXene coating (FM coating) on the SHPP sensor exhibits outstanding self-cleaning, long-term durability (>20 days), as well as excellent photothermal deicing performances under near-infrared light. Meanwhile, the unique semiembedded nano-ZnO/1D silver nanowire supports the sensor with desirable photoelectric performance with UV light and a fast response time (∼1 s), and good cycle stability. Moreover, benefiting from the transparent self-healing substrate, the photothermal deicing and photodetector properties can be restored at room temperature. The bioinspired structures and function mechanisms offer SHPP sensors great potential for the utilization of clean light energy, sensing, self-cleaning, anti-icing, and so forth.

Tunable electronic properties and negative differential resistance effect of the intrinsic type-III ZrS[formula omitted]/WTe[formula omitted] van der Waals heterostructure

Van der Waals heterostructure (vdWH) has attracted considerable interest because of its ability to combine the excellent properties of stacked materials to suit different application requirements. The limited presence of type-III vdWH is a serious barrier for the development of two-dimensional materials in the field of tunneling field effect transistors. Herein, we propose a novel ZrS2/WTe2 vdWH with type-III band alignment and investigate its structural, electronic and quantum transport properties using first-principles calculations. The physical mechanism of type-III band alignment is analyzed. The electronic structures of this vdWH can be adjusted to enhance the band-to-band tunneling effect or achieve an interesting transition from type-III to type-II band alignment via external vertical electric field and different strains. Finally, we study the quantum transport properties and confirm again the type-III band alignment. The I–V curve shows apparent negative differential resistance (NDR) behaviors under low bias voltages, which provides substantial evidence supporting the applicability of this vdWH to low power devices. Our study not only expands the field of type-III band alignment heterostructures in 2D materials, but also provides a remarkable candidate material with tunable electronic properties and the favorable NDR effect for experimental designs and practical applications of novel multi-functional nanoelectronic devices.

Band structures and transport properties of broken-gap heterostructures: 2D C3N/MX case

Building van der Waals heterostructures (vdWHs) is an effective method to broaden two-dimensional (2D) material applications in multifunctional devices. However, few broken-gap vdWHs are realized, which limit 2D materials development in the tunnel field-effect transistors. Here, based on the density functional theory, we theoretically design the stable 2D C3N/MX(M = Ga, In; X = S, Se, Te) vdWHs, where the band-to-band tunneling (BTBT) exists due to the broken-gap band alignment. The negative electric field expands the tunneling window, while multifunctional band alignment can be realized under positive electric field. Moreover, the I–V curves present the obvious negative differential resistance behavior. This work provides the understanding of physical mechanism and possible applications for 2D broken-gap vdWHs.

Correlation between structural, luminescence, and dielectric properties of novel Sm3+ and trioxotungsten-doped NBBT ceramic system for multifunctional device applications

Correlation between structural, luminescence, and dielectric properties of novel Sm3+ and trioxotungsten-doped NBBT ceramic system for multifunctional device applications

Smart Soft Materials with Multiscale Architecture and Dynamic Surface Topographies

ConspectusSmart soft materials have one or more characteristics that can be significantly altered in convertible fashions by external stimuli, such as light, moisture, mechanical force, temperature, electric/magnetic fields, pH, and so on. These materials can lead to widespread application in multifunctional smart devices. Recently, various smart soft materials have been developed under the inspiration of the intriguing multiscale structures, adaptive mechanisms, and dynamic responses of natural life, with an aim to further design advanced material systems with novel, intriguing, and unprecedented properties.Herein, inspired by the fascinating visual display strategies and adaptive mechanisms in animals and plants, we have fabricated a series of smart soft material-based devices that can respond to external stimuli with instantaneous and reversible fashions in optical, electrical, mechanical, and/or shape deformation signals. These devices can be fabricated for widespread applications, including smart windows, encryption devices, thermal camouflage, wearable strain sensors, anticounterfeit tabs, 3D stretchable electronics, dynamic displays, rewritable media, human–machine interfaces, and so on. The key to successfully achieving those intriguing characteristics in these smart material systems lies in the function-orientated structural design, which integrates bioinspired design and surface engineering with multiscale architecture as the crucial elements. In this Account, we provide a summary, with a main focus on our own work, of the recent advances in the bioinspired smart soft materials fabricated on the basis of 2D or 3D film–substrate multilayered structures. These materials are characterized by convertible topographies like dynamic cracks, folds, stimuli-responsive wrinkles, and other analogous structures. Those topographies are responsible for the dynamic stimuli-responsive optical, electrical, and mechanical properties demonstrated in the system, such as strain-dependent light scattering effect, mechanical tunable light shielding properties, moisture/mechanically/photothermally tunable surface reflectance, moisture/mechanically responsive resistance, etc. Besides, those 2D functional materials can be further evolved into shape adaptive 3D structures via strain relaxation methods. These systems demonstrate high design flexibility, excellent reversibility, and wide applicability, which can pave new routes for designing next generation smart soft materials equipped with versatile, tunable, adaptable, and interactive stimuli-responsive properties.

Microstructure, magnetodielectric and multiferroic properties in PVDF-based sandwich-structured composites

The multiferroic thin films are promising candidates for applications in magnetic sensors, spintronics, information memory, and other multifunctional devices. In this work, BaTiO3-PVDF/CoFe2O4-PVDF/BaTiO3-PVDF sandwich-structured composites were designed and fabricated by a tape-casting method. The microstructure, dielectric, ferroelectric, magnetic and magnetodielectric properties were systematically investigated. An enhanced ferroelectricity is observed for the maximum polarization (Pmax~1.656 μC/cm2) and the high dielectric constant (εr) of 22 as well as a low dielectric loss for all BaTiO3 filler loading, much better than that of the pure PVDF matrix (εr∼8.26). A recoverable energy density of 0.648 J/cm3 is achieved at an electric field 950 kV/cm, along with a high efficiency (η∼71.0 %). The observed typical magnetic hysteresis loop reveals the presence of long-range ferromagnetic ordering in composites, accompanied by the significant magnetic properties with saturation magnetization (MS~0.507 emu/g), and coercivity (HC~2.3 kOe). Additionally, the response of the dielectric performance under the applied magnetic fields is obvious at RT, i.e., a large negative magnetodielectric coefficient of 2.85 % is obtained at a low magnetic field of 2 kOe, and is up to 6.53 % at 6 kOe for 5 vol% BaTiO3. Ultimately, it is anticipated that this work may provide an efficient method to develop flexible multiferroic composite for multifunctional devices.

Enhanced magnetic and magnetodielectric behavior in morphologically distinct BTFO and LSMO composites

In this work, sol–gel modified technique is used to synthesize the (1-x)BTFO-(x)LSMO composites (x = 0, 0.1, 0.2, 0.3, and 0.4). The composite's dual (BTFO and LSMO) phases are verified using X-ray diffraction analysis. A scanning and transmission electron microscope is used to analyze the distinct morphology of the two phases that demonstrated the plate-like grains and quasi-spherical particles of BTFO and LSMO phases in the composites, respectively. The magnetic studies reveal that the saturation magnetization (Ms ∼ 7.0 emu/g) and coercive field (Hc ∼ 1660 Oe) increased by nearly-three and 66 times for 40 % LSMO contained composite. The enhanced magnetic behavior is due to the interaction between the multiple magnetic ordering (AFM/FM) present in the prepared composites. The estimated values of squareness ratio (Mr/Ms) are lower than 0.5, illustrating the multi-domain nature of the composites. The switching field distribution (SFD) plot indicates that strong exchange coupling exists in the x = 0.4 composite compared to others. The change in dielectric permittivity at different magnetic fields is due to the magnetodielectric (MD) coupling in the composites. The field-dependent MD studies reveal that maximum MD strength (∼0.34 %) and minimum magnetoloss (ML) (∼0.02 %) are observed in x = 0.2 and 0.1 composites at 100 kHz, respectively. It is due to the non-collinear alignment of magnetic Mn ions at RT, which leads to the inverse Dzyalonskii-Moriya interaction. Additionally, the maximum MD coupling strength γ (-16.87 (emu/g)2) is observed in the x = 0.2 composite. The observed MD response in the composites is due to the dominating grain capacitive effect rather than the resistive effect, which is ascertained by the frequency-dependent magnetoresistance measurement. Hence, the composite's enhanced magnetic and magnetodielectric behavior makes it a suitable candidate for multifunctional device applications.

Advances and challenges in developing smart, multifunctional microneedles for biomedical applications.

Microneedles (MNs) have been developed as minimally invasive tools for diagnostic and therapeutic applications. However, in recent years, there has been an increasing interest in developing smart multifunctional MN devices to provide automated and closed-loop systems for body fluid extraction, biosensing, and drug delivery in a stimuli-responsive manner. Although this technology is still in its infancy and far from being translated into the clinic, preclinical trials have shown some promise for the broad applications of multifunctional MN devices. The main challenge facing the fabrication of smart MN patches is the integration of multiple modules, such as drug carriers, highly sensitive biosensors, and data analyzers in one miniaturized MN device. Researchers have shown the feasibility of creating smart MNs by integrating stimuli-responsive biomaterials and advanced microscale technologies, such as microsensors and microfluidic systems, to precisely control the transportation of biofluids and drugs throughout the system. These multifunctional MN devices can be envisioned in two distinct strategies. The first type includes individual drug delivery and biosensing MN units with a microfluidic system and a digital analyzer responsible for fluid transportation and communication between these two modules. The second type relies on smart biomaterials that can function as drug deliverers and biosensors by releasing drugs in a stimuli-responsive manner. These smart biomaterials can undergo structural changes when exposed to external stimuli, such as pH and ionic changes, mimicking the biological systems. Studies have demonstrated a high potential of hydrogel-based MN devices for a wide variety of biomedical applications, such as drug and cell delivery, as well as interstitial fluid extraction. Biodegradable hydrogels have also been advantageous for fabricating multifunctional MNs due to their high loading capacity and biocompatibility with the drug of choice. Here, we first review a set of MN devices that can be employed either for biosensing or delivery of multiple target molecules and compare them to the conventional and more simple systems, which are mainly designed for single-molecule sensing or delivery. Subsequently, we expand our insight into advanced MN systems with multiple competencies, such as body fluid extraction, biosensing, and drug delivery at the point of care. The improvement of biomaterials knowledge and biofabrication techniques will allow us to efficiently tune the next generation of smart MNs and provide a realistic platform for more effective personalized therapeutics.

Dynamic bifunctional THz metasurface via dual-mode decoupling

Metasurfaces have powerful light field manipulation capabilities and have been researched and developed extensively in various fields. With an increasing demand for diverse functionalities, terahertz (THz) metasurfaces are also expanding their domain. In particular, integrating different functionalities into a single device is a compelling domain in metasurfaces. In this work, we demonstrate a functionally decoupled THz metasurface that can incorporate any two functions into one metasurface and switch dynamically through external excitation. This proposed metasurface is formed by the combination of split-ring resonators and phase change material vanadium dioxide ( VO 2 ). It operates in the single-ring resonant mode and double-ring resonant mode with varying VO 2 in insulating and metallic states, respectively. More importantly, the phase modulation is independent in two operating modes, and both cover a 360° cross-polarized phase with efficient polarization conversion. This characteristic makes it obtain arbitrary independent phase information on the metasurface with different modes to switch dual functions dynamically. Here, we experimentally demonstrate the functions of a tunable focal length and large-angle focus deflection of a THz off-axis parabolic mirror to verify the dual-function switching characteristics of the functionally decoupled metasurface. The functionally decoupled metasurface developed in this work broadens the way for the research and application of multifunctional modulation devices in the THz band.