Tunable Switch Research Articles

Early Folding Dynamics of i-Motif DNA Revealed by pH-Jump Time-Resolved X-ray Solution Scattering.

The i-motif is a pH-responsive cytosine-rich oligonucleotide sequence that forms, under acidic conditions, a quadruplex structure. This tunable structural switching has made the i-motif a useful platform for designing pH-responsive nanomaterials. Despite the widespread application of i-motif DNA constructs as biomolecular switches, the mechanism of i-motif folding on the atomic scale has yet to be established. We investigate the early folding structural dynamics of i-motif oligonucleotides with laser-pulse-induced pH-jump time-resolved X-ray solution scattering. Following the pH-jump, we observe that the initial random coil ensemble converts into a contracted intermediate state within 113 ns followed by further folding on the 10 ms time scale. We reveal the representative structures of these transient species, hitherto unknown, with molecular dynamics simulations and ensemble fitting. These results pave the way for understanding metastable conformations of i-motif folding and for benchmarking emerging theoretical models for simulating noncanonical nucleic acid structures.

1D Crystalline Assemblies Exhibiting Large Second Harmonic Generation Susceptibilities and Stacking‐/Polarization‐Driven Tunability

AbstractNonlinear optical (NLO) van der Waals (vdW) crystals containing 1D building blocks exhibit large NLO coefficients and birefringence that are crucial for their applications. In this work, 21 NLO 1D building blocks with large second harmonic generation (SHG) susceptibility from the Computational 1D Materials Database (C1DB) are screened. Among them, 14 are hitherto unreported and have SHG susceptibilities approaching theoretical upper limits. Forty‐five new vdW NLO crystals are then constructed by stacking one or two of the 21 building blocks. Eighteen of them inherit the large SHG susceptibilities of their corresponding 1D building blocks. Three stable crystals exhibit large SHG susceptibilities and birefringence, while one stable crystal possesses ferroelectricity. Interestingly, the SHG susceptibilities of the newly constructed NLO crystals are inversely proportional to the third power of their bandgaps. Further calculations show that the SHG susceptibilities of the vdW NLO crystals can be tuned either by stacking order or by reversing electric polarization, providing possibilities for their application in tunable nonlinear optics and NLO switches.

The Fabrication of Polyimide-Based Tunable Charge Traps Ternary Memristors Doped with Ni-Co Coated Carbon Composite Nanofibers.

In the dynamic fields of information science and electronic technology, there is a notable trend towards leveraging carbon materials, favored for their ease of synthesis, biocompatibility, and abundance. This trend is particularly evident in the development of memristors, benefiting from the unique electronic properties of carbon to enhance device performance. This study utilizes sensitized chemical evaporation and spin-coating carbonization techniques to fabricate nickel-cobalt coated carbon composite nanofibers (SC-NCMNTs). Novel polyimide (PI) matrix composite memory devices were fabricated using in situ polymerization technology. Transmission electron microscopy (TEM) and micro-Raman spectroscopy analyses validated the presence of dual interface structures located between the Ni-Co-MWNTs, carbon composite nanofibers, and PI matrix, revealing a significant number of defects within the SC-NCMNTs/PI composite films. Consequently, this results in a tunable charge trap-based ternary resistive switching behavior of the composite memory devices, exhibiting a high ON/OFF current ratio of 104 and a retention time of 2500 s at an operating voltage of less than 3 V. The mechanism of resistive switching is thoroughly elucidated through a comprehensive charge transport model, incorporating molecular orbital energy levels. This study provides valuable insights for the rational design and fabrication of efficient memristors characterized by multilevel resistive switching states.

Design and performance study of a multiband metamaterial tunable thermal switching absorption device based on AlCuFe and VO2.

In this paper, we propose a multiband adjustable metamaterial absorption device based on a Dirac semimetal (BDS) AlCuFe and a thermally controlled phase-change material VO2. The absorption device has an axially symmetric structure, resulting in polarization-independent characteristics, and when VO2 is in a high-temperature metal state, ultra-high absorption rates and sensitives at frequencies of M1 = 2.89 THz, M2 = 7.53 THz, M3 = 7.97 THz, and M4 = 9.02 THz are achieved. Using a parameter inversion method, we calculated the impedance of the absorber, proving that it achieves impedance matching and produces perfect absorption in the resonance region. Additionally, we changed the physical and chemical parameters of the absorption device, demonstrating the device's excellent tunability and manufacturing tolerance. Furthermore, by lowering the temperature of VO2 to that of a low dielectric state, additional resonant peaks with ultra-high absorption rates at frequencies M5 = 5.62 THz, M6 = 7.16 THz, M7 = 7.64 THz, and M8 = 8.80 THz were obtained, broadening the absorption band of the device. Lastly, we investigated the detection sensitivity of the device by changing the external refractive index, resulting in a maximum sensitivity of 2229 GHz RIU-1. To sum up, the absorption device has great application potential in the fields of communication, sensing, temperature detection and photoelectric instruments.

Tunable multistate field-free switching and ratchet effect by spin-orbit torque in canted ferrimagnetic alloy

Spin-orbit torque is not only a useful probe to study manipulation of magnetic textures and magnetic states at the nanoscale but also it carries great potential for next-generation computing applications. Here we report the observation of rich spin-orbit torque switching phenomena such as field-free switching, multistate switching, memristor behavior and ratchet effect in a single shot, co-sputtered, rare earth-transition metal GdxCo100−x. Notably such effects have only been observed in antiferromagnet/ferromagnet bi-layer systems previously. We show that these effects can be traced to a large anistropic canting, that can be engineered into the GdxCo100−x system. Further, we show that the magnitude of these switching phenomena can be tuned by the canting angle and the in-plane external field. The complex spin-orbit torque switching observed in canted GdxCo100−x not only provides a platform for spintronics but also serves as a model system to study the underlying physics of complex magnetic textures and interactions.

Active dual quasi-BICs in a dielectric metasurface with VO2 for slow light and optical modulation.

We investigate the temperature tunable dual quasi-bound states in the continuum (qBICs) in a silicon/vanadium dioxide (Si/VO2) hybrid metasurface with Q-factor being as large as 9.3 × 106 and 2.8 × 107 by breaking the in-plane C2 symmetry. The far-field scattering of multipoles and near-field distributions confirm that the toroidal dipole and magnetic quadrupole dominate the dual qBICs resonance. The high performance of slow light with ultralarge group index exceeding 5.6 × 105 and the inverse quadratic law between the group index and asymmetric parameter are achieved. By temperature tuning of the VO2 thin film at the sub-10 K scale, a modulation depth of 90% and the ON/OFF ratio exceeding 12.8 dB are obtained. The proposed temperature tunable dual qBICs have potential applications in the fields of tunable slow light, temperature switches, and sensors.

Audio Signal-Stimulated Multilayered HfOx/TiOy Spiking Neuron Network for Neuromorphic Computing.

As the key hardware of a brain-like chip based on a spiking neuron network (SNN), memristor has attracted more attention due to its similarity with biological neurons and synapses to deal with the audio signal. However, designing stable artificial neurons and synapse devices with a controllable switching pathway to form a hardware network is a challenge. For the first time, we report that artificial neurons and synapses based on multilayered HfOx/TiOy memristor crossbar arrays can be used for the SNN training of audio signals, which display the tunable threshold switching and memory switching characteristics. It is found that tunable volatile and nonvolatile switching from the multilayered HfOx/TiOy memristor is induced by the size-controlled atomic oxygen vacancy pathway, which depends on the atomic sublayer in the multilayered structure. The successful emulation of the biological neuron's integrate-and-fire function can be achieved through the utilization of the tunable threshold switching characteristic. Based on the stable performance of the multilayered HfOx/TiOy neuron and synapse, we constructed a hardware SNN architecture for processing audio signals, which provides a base for the recognition of audio signals through the function of integration and firing. Our design of an atomic conductive pathway by using a multilayered TiOy/HfOx memristor supplies a new method for the construction of an artificial neuron and synapse in the same matrix, which can reduce the cost of integration in an AI chip. The implementation of synaptic functionalities by the hardware of SNNs paves the way for novel neuromorphic computing paradigms in the AI era.

Tunable Stochastic State Switching in 2D MoS2 Nanomechanical Resonators with Nonlinear Mode Coupling and Internal Resonance.

Coupled nanomechanical resonators have unveiled fascinating physical phenomena, including phonon-cavity coupling, coupled energy decay pathway, avoided crossing, and internal resonance. Despite these discoveries, the mechanisms and control techniques of nonlinear mode coupling phenomena with internal resonances require further exploration. Here, we report on the observation of stochastic switching between the two resonance states with coupled 1:1 internal resonance, for resonant two-dimensional (2D) molybdenum disulfide (MoS2) nanoelectromechanical systems (NEMS), which is directly driven to the critical coupling regime without parametric pumping. We further demonstrate that the probability of state switching is linearly tunable from ∼0% to ∼100% by varying the driving voltage. Furthermore, we gradually increase the white noise amplitude and show that the probability of obtaining the higher-energy state decreases, and the stochastic switching phenomenon eventually disappears. The results provide insights into the dynamics of coupled NEMS resonators and open up new possibilities for sensing and stochastic computing.

Tunable magnetic switching behavior in La0.7Sr0.3MnO3/PbTiO3 multilayers

Tuning magnetic switching behavior and related magnetic configuration of transition metal oxides (TMOs) is critical for realizing multifunctional materials and devices. In this study, we manipulated the magnetic switching behavior through interface engineering by introducing ferroelectric PbTiO3 (PTO) to form La0.7Sr0.3MnO3 (LSMO)/PTO multilayers. Both the normal hysteresis loop (NHL) and the inverted hysteresis loop (IHL) could be tuned by changing the PTO thickness. All multilayers displayed a transition from NHL to IHL with increasing temperature, and the transition temperature increased with the insertion of the PTO layer or increasing thickness of the PTO. In addition, it was found that the increase in the Curie temperature (Tc) and saturation magnetization (Ms), as well as the decrease in the coercive field (Hc) and exchange bias field (Heb) with a reduction in the thickness of the PTO, is possibly related to the interface phase. This study illustrates the influence of the ferroelectric PTO thickness on the magnetic switching behavior and related magnetic configuration in LSMO, which is possibly driven by the unscreened depolarization charge and oxygen octahedral tilting. This finding may benefit the application of TMOs in multifunctional memory devices.

Naphthalene-embedded spiropyran derivative-A type of conjugated expanded material with solid-state photochromic properties and tunable color switching range

Due to the limited free volume in the solid state, spiropyrans generally exhibit photochromic properties in solution or mixed thin films. However, few spiropyrans can display the photoisomerization process in the solid state. One conventional solution for solid-state photochromism is to embed the spiropyran on polymer chains or introduce bulky groups to create an efficient free volume in the solid state. In this article, we attempt to introduce large conjugated fragments on the spiropyran backbone to construct a donor-acceptor (D-A) building block that not only possesses an enlarged π-electron system with enhanced electronic delocalization capability but also exhibits an improved free volume for efficient solid-state photoisomerization. Through this strategy, we have successfully embedded the naphthalene ring on the spiropyran backbone to obtain a novel D-A type conjugated building block, SP-Naph, which exhibits excellent solid-state photochromic performance and reversibility. Furthermore, the D-A structure of SP-Naph significantly tuned its photochromic color-switching range to blue. Consequently, SP-Naph was successfully applied in optical printing and invisible inks. The excellent solid photochromic properties make it exhibit remarkable photochromic effects, indicating significant potential for optical printing and anti-counterfeiting applications.

Security enhancement of artificial neural network using physically transient form of heterogeneous memristors with tunable resistive switching behaviors

Security enhancement of artificial neural network using physically transient form of heterogeneous memristors with tunable resistive switching behaviors

Unconventional Photoswitching Behavior of a Diarylethene‐Perylenediimide Dyad in Nanoparticles Emerging from Multiple Intermolecular Energy Transfer Processes

AbstractPhotoswitchable fluorescent systems based on photochromic derivatives have various applications, including high‐resolution imaging and information processing. In this context, a key objective is to control, manipulate, and improve the fluorescence photoswitching of molecular systems. Herein, the intriguing zero‐order photokinetics properties of a photochromic‐fluorescent dyad made of one perylenediimide fluorophore (PDI) and two diarylethene photochromes (DAE) are reported, in the nanoparticles state, resulting from efficient intra‐ and intermolecular energy transfer processes from the PDI to the DAE, well‐rationalized by modified photokinetics equations for photochromism. It allowed the fine‐tuning of the photokinetics, leading to either classical or unconventional behavior, depending on the irradiation wavelength. Fluorescence photoswitching is investigated under a microscope, demonstrating a sigmoidal profile for fluorescence recovery which can be satisfyingly reproduced by a suitable mathematical model that is developed. These findings represent a significant advance in the development of enhanced photoswitchable fluorescent systems, showing high contrast, driven by few photons with tunable switching rates.

Active tunable terahertz multifunctional device switching from multiple narrowband perfect absorption to plasma-induced transparency

This paper puts forward a terahertz multifunctional device based on reversible phase transition property of VO2, which can realize active switching from multiple narrowband perfect absorption to plasma-induced transparency (PIT). By means of impedance matching theory and electric field distributions, we analyze the mechanism behind three absorption formants, and the absorption spectrum is consistent with data obtained from coupled mode theory. Three perfect absorption formants at the frequencies of 4.37 THz, 5.27 THz and 6.1 THz are extremely sensitive to the changes in external environment, which possesses a higher sensitivity up to 1.29 THz/RIU and FOM up to 9.45, indicating prominent sensing performance. By regulating the Fermi energy in a unified manner, three absorption formants can be observed within a specific frequency range. When the Fermi energy of three graphene patterns is individually manipulated, trimodal narrowband perfect absorption will transform into one bimodal and two unimodal ones. While the device is under PIT operation mode, two transmission windows are formed at 5.1 THz and 5.92 THz. It can be concluded that dual PIT arises from the mutual coupling between two bright modes and a dark mode formed by patterned graphene, when combined with the transmission spectra and the corresponding electric field distributions. Similarly, the modulation of graphene Fermi energy can realize dynamic tuning of the transmission performance, and single PIT can be achieved when graphene patterns are regulated separately. In summary, the proposed device can meet various functional requirements for multiple perfect absorption and PIT under different conditions and promote developments of terahertz technology in fields of environmental detection, electromagnetic modulation, multi-function devices and other application.

Electrical field-induced Fano resonance tunability in photonic crystal slabs

The creation of tunable Fano resonances in a photonic crystal structure with a side-coupled nanocavity and a waveguide with a partially transmitting element is investigated in this paper. In the proposed structure, the nanocavity’s central hole is made up of two cylinders with different radii that are nested inside each other. The outer and inner cylinders are made of quartz and liquid crystal, respectively. The performance of this device is analyzed using the three-dimensional finite-difference time-domain. The transmission spectrum, resonance wavelength, and quality factor of the proposed structure are calculated for various applied voltages. It is demonstrated that as the applied voltage increases, the quality factor changes and the Fano resonance wavelength shifts. Based on the findings, a tuning range of 5.2 nm is achievable with an excellent transmission contrast within this range. The presented structure is appropriate for applications such as tunable switches and filters.

Topological Phase and Tunable Quantum State Transfer of Su–Schrieffer–Heeger Chain with an Embedded Quantum Ring

AbstractAn extended Su–Schrieffer–Heeger (SSH) model consisting of an SSH chain with an embedded quantum ring (QR) is investigated. In the case of two SSH chains with a symmetric distribution with respect to QR, by calculating the real‐space winding number and energy spectrum, the hopping amplitude‐induced topological phase is discovered. The probability distributions of gap states and the relationship between energy and magnetic flux prove the existence of the Aharonov–Bohm effect in the QR. Moreover, in the case of asymmetric distribution, the model possesses a zero‐energy mode within the energy gap, and it is found that it can realize quantum state transfer. By adjusting the connection site between the right SSH chain and QR, the direction of the output port can be flexibly engineered. Furthermore, it is shown that high‐fidelity quantum state transfer can still be achieved with the increasing of the system size. The tunable quantum state transfer based on the zero‐energy mode can be equivalent to a topological tunable directional switch with properties of non‐directional transfer. This work provides an approach for studying topological phase transition and tunable topological devices in an SSH chain with an embedded QR.

An Artificial Universal Tactile Nociceptor Based on 2D Polymer Film Memristor Arrays with Tunable Resistance Switching Behaviors.

Nociceptor is an important receptor in the organism's sensory system; it can perceive harmful stimuli and send signals to the brain in order to protect the body in time. The injury degree of nociceptor can be divided into three stages: self-healing injury, treatable injury, and permanent injury. However, the current studies on nociceptor simulation are limited to the self-healing stage due to the limitation of the untunable resistance switching behavior of memristors. In this study, we constructed Al/2DPTPAK+TAPB/Ag memristor arrays with adjustable memory behaviors to emulate the nociceptor of biological neural network of all three stages. For this purpose, a PDMS/AgNWs/ITO/PET pressure sensor was assembled to mimic the tactile perception of the skin. The memristor arrays can not only simulate all the response of nociceptor, i.e., the threshold, relaxation, no adaptation, and sensitization with the self-healing injury, but can also simulate the treatable injury and the permanent injury. These behaviors are both demonstrated with a single memristor and in the form of pattern mapping of the memristor array.

Tunable Nonlinear Optical Bistability Based on the Fabry–Perot Cavity Composed of Dirac Semimetal and Two Symmetric Photonic Crystals

In this paper, we study the nonlinear optical bistability (OB) in a symmetrical multilayer structure. This multilayer structure is constructed by embedding a nonlinear three-dimensional Dirac semimetal (3D DSM) into a Fabry–Perot cavity composed of one-dimensional photonic crystals. The OB phenomenon stems from the third order nonlinear conductivity of 3D DSM. The local field of resonance mode could enhance the nonlinearity and reduce the thresholds of OB. This structure achieves the tunability of OB due to the fact that the transmittance could be modulated by the Fermi energy. It is found that the OB threshold and threshold width could be remarkably reduced by increasing the Fermi energy of the 3D DSM. Besides, we also found that the OB curve depends heavily on the angle of incidence of the incident light, the structural parameters of the Fabry–Perot cavity, and the position of the 3D DSM inside the cavity. After parameter optimization, we obtained OB with a threshold of 106 V/m. We believe this simple multilayer structure could provide a reference idea for realizing low-threshold and tunable all-optical switching devices.

Topological Quantum Switching Enabled Neuroelectronic Synaptic Modulators for Brain Computer Interface.

Aging and genetic-related disorders in the human brain lead to impairment of daily cognitive functions. Due to their neural synaptic complexity and the current limits of knowledge, reversing these disorders remains a substantial challenge for brain-computer interfaces (BCI). In this work, a solution is provided to potentially override aging and neurological disorder-related cognitive function loss in the human brain through the application of the authors' quantum synaptic device. To illustrate this point, a quantum topological insulator (QTI) Bi2Se2Te-based synaptic neuroelectronic device, where the electric field-induced tunable topological surface edge states and quantum switching properties make them a premier option for establishing artificial synaptic neuromodulation approaches, is designed and developed. Leveraging these unique quantum synaptic properties, the developed synaptic device provides the capability to neuromodulate distorted neural signals, leading to the reversal of age-related disorders via BCI. With the synaptic neuroelectronic characteristics of this device, excellent efficacy in treating cognitive neural dysfunctions through modulated neuromorphic stimuli is demonstrated. As a proof of concept, real-time neuromodulation of electroencephalogram (EEG) deduced distorted event-related potentials (ERP) is demonstrated by modulation of the synaptic device array.

Mechanically Tunable Circularly Polarized Luminescence of Liquid Crystal-Templated Chiral Perovskite Quantum Dots.

Endowing perovskite quantum dots (PQDs) with circularly polarized luminescence (CPL) offers great promise for innovative chiroptical applications, but the existing strategies are inefficient in acquiring stimuli-responsive flexible chiral perovskite films with large, tunable dissymmetry factor (glum) and long-term stability. Here, we report a strategy for the design and synthesis of luminescent cholesteric liquid crystal elastomer (Lumin-CLCE) films with mechanically tunable CPL, which is enabled by liquid crystal-templated chiral self-assembly and in situ covalent cross-linking of judiciously designed photopolymerizable CsPbX3 (X=Cl, Br, I) PQD nanomonomers into the elastic polymer networks. The resulting Lumin-CLCE films showcase circularly polarized structural color in natural light and noticeable CPL with a maximum glum value of up to 1.5 under UV light. The manipulation of CPL intensity and rotation direction is achieved by controlling the self-assembled helicoidal nanostructure and the handedness of soft helices. A significant breakthrough lies in the achievement of a reversible, mechanically tunable perovskite-based CPL switch activated by biaxial stretching, which enables flexible, dynamic anti-counterfeiting labels capable of decrypting preset information in specific polarization states. This work can provide new insights for the development of advanced chiral perovskite materials and their emerging applications in information encryption, flexible 3D displays, and beyond.

Sonogenetics-controlled synthetic designer cells for cancer therapy in tumor mouse models

Bacteria-based therapies are powerful strategies for cancer therapy, yet their clinical application is limited by a lack of tunable genetic switches to safely regulate the local expression and release of therapeutic cargoes. Rapid advances in remote-control technologies have enabled precise control of biological processes in time and space. We developed therapeutically active engineered bacteria mediated by a sono-activatable integrated gene circuit based on the thermosensitive transcriptional repressor TlpA39. Through promoter engineering and ribosome binding site screening, we achieved ultrasound (US)-induced protein expression and secretion in engineered bacteria with minimal noise and high induction efficiency. Specifically, delivered either intratumorally or intravenously, engineered bacteria colonizing tumors suppressed tumor growth through US-irradiation-induced release of the apoptotic protein azurin and an immune checkpoint inhibitor, a nanobody targeting programmed death-ligand 1, in different tumor mouse models. Beyond developing safe and high-performance designer bacteria for tumor therapy, our study illustrates a sonogenetics-controlled therapeutic platform that can be harnessed for bacteria-based precision medicine.