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Inspired by the brain, neuromorphic computing seeks to improve data‐centric applications in terms of power consumption and device footprint. The processing efficiency can be attributed to reconfigurable connections coupled with complex dynamics and efficient data sensing and signal processing. With field‐effect tunability, the three‐terminal thin‐film transistor is initially explored as a switch. Recently, transistors with added gates and modes have been fashioned as multi‐terminal devices capable of interconnecting complex networks and transducing multiple inputs. Here, the advances in both the semiconducting channel material and the configurational design of multi‐terminal devices are reviewed. The use of strong coupling and dynamical material properties in novel ion‐based capacitors, mixed‐ionic‐electronic semiconductors, low‐dimensional confined systems, stimuli‐responsive materials and redox‐active semiconductors has enabled new neuromorphic functionalities. These include improving reconfigurability using the regulatory ability of homeostasis, dendritic integration of sensory signals and the synaptic competition of resources. The transistor devices are also highly relevant in circuits that improve the efficiency of sensory transduction and signal processing; stimuli‐responsive semiconductors that adapt to the sensory inputs can be employed in the transistors and highly efficient sensorimotor connections between sensors and actuators can be emulated. These highly efficient, low‐complexity analog devices are crucial design elements for next‐generation neuromorphic systems. [ABSTRACT FROM AUTHOR]

Abstract Inspired by the brain, neuromorphic computing seeks to improve data‐centric applications in terms of power consumption and device footprint. The processing efficiency can be attributed to reconfigurable connections coupled with complex dynamics and efficient data sensing and signal processing. With field‐effect tunability, the three‐terminal thin‐film transistor is initially explored as a switch. Recently, transistors with added gates and modes have been fashioned as multi‐terminal devices capable of interconnecting complex networks and transducing multiple inputs. Here, the advances in both the semiconducting channel material and the configurational design of multi‐terminal devices are reviewed. The use of strong coupling and dynamical material properties in novel ion‐based capacitors, mixed‐ionic‐electronic semiconductors, low‐dimensional confined systems, stimuli‐responsive materials and redox‐active semiconductors has enabled new neuromorphic functionalities. These include improving reconfigurability using the regulatory ability of homeostasis, dendritic integration of sensory signals and the synaptic competition of resources. The transistor devices are also highly relevant in circuits that improve the efficiency of sensory transduction and signal processing; stimuli‐responsive semiconductors that adapt to the sensory inputs can be employed in the transistors and highly efficient sensorimotor connections between sensors and actuators can be emulated. These highly efficient, low‐complexity analog devices are crucial design elements for next‐generation neuromorphic systems.

The high-altitude platform station (HAPS) concept has recently received notable attention from both industry and academia to support future wireless networks. A HAPS can be equipped with fifth-generation (5G) and beyond technologies such as massive multiple-input multiple-output (MIMO) and reconfigurable intelligent surface (RIS). Hence, it is expected that HAPS will support numerous applications in both rural and urban areas. However, this comes at the expense of high energy consumption and thus shorter loitering time. To tackle this issue, we envision the use of a multimode HAPS that can adaptively switch among different modes so as to reduce energy consumption and extend the HAPS loitering time. These modes comprise a HAPS super macro base station (HAPS-SMBS) mode for enhanced computing, caching, and communication services; a HAPS relay station (HAPS-RS) mode for active communication; and a HAPS-RIS mode for passive communication. This multimode HAPS ensures that operations rely mostly on the passive communication payload, while switching to an energy-greedy active mode only when necessary. In this article, we begin with a brief review of HAPS features compared with other nonterrestrial systems, followed by an exposition of the different HAPS modes proposed. Subsequently, we illustrate the envisioned multimode HAPS and discuss its benefits and challenges. Finally, we validate the multimode efficiency through a case study. [ABSTRACT FROM AUTHOR]

Reconfigurable intelligent surfaces (RISs) have tremendous potential for both communication and localization. While communication benefits are now well understood, the breakthrough nature of the technology may well lie in its capability to provide and support localization capabilities. We present an overview of RIS-enabled localization scenarios, considering various numbers of RISs, single- or multi-antenna base stations, narrowband or wideband transmissions, and near- and far-field operations. Based on this overview, we also highlight key research directions and open challenges specific to RIS-enabled localization and sensing. [ABSTRACT FROM AUTHOR]

A novel architecture of reconfigurable, flat metalens is proposed with an electrically tunable focal length for applications in wireless communication systems working at the frequencies of millimeter waves (i.e., 60 GHz). In this approach, a reflective metalens made of silicon bricks is distributed on a grounded multilayer hosting films of a phase-transition material, namely, vanadium dioxide. The multilayer, acting as a ground plane with a controllable position, provides different phase profiles in the same metalens and, therefore, different focal lengths. Our numerical investigation of thermal and electromagnetic effects shows that the metasurface can reversibly tune the focal length at 27, 31, and 33 mm. In addition, in the operating frequency range between 58 and 62 GHz, the tunability of the metalens remains unaltered. Dynamically controlling the focal point of millimeter waves is highly desirable in wireless communications, especially for 5G and 6G cellular systems applications.

We present an Internet-of-Things (IoT) software-defined radio platform based on an ultra low-power microcontroller. Whereas conventional wireless IoT radios often implement a single protocol, we demonstrate that general-purpose microcontrollers running software implementations of wireless physical layers are a promising solution to increase interoperability of IoT devices. Yet, since IoT devices are often energy-constrained, the underlying challenge is to implement the digital signal processing of the radio in software while maintaining an overall very low power consumption. To overcome this problem, we propose an ultra low-power microcontroller architecture with an ARM Cortex-M4 processor for the protocol-specific computations and a hardware digital front-end for the generic signal processing. The proposed architecture has been prototyped in 28nm FDSOI and the physical layers of the well-known LoRa and Sigfox protocols have been implemented in software. Thanks to the efficient hardware/software partitioning and an ultra-low power digital implementation, experimental evaluations of the microcontroller prototype show sub-mW power consumptions (32 – $332~\mu \text{W}$ ) for the digital signal processing of the software-defined radios.

The proliferation of devices for the Internet of Things (IoT) and their implication in many activities of our lives have led to a considerable increase in concern about the security of these devices, posing a double challenge for designers and developers of products. On the one hand, the design of new security primitives, suitable for resource-limited devices, can facilitate the inclusion of mechanisms and protocols to ensure the integrity and privacy of the data exchanged over the Internet. On the other hand, the development of techniques and tools to evaluate the quality of the proposed solutions as a step prior to their deployment, as well as to monitor their behavior once in operation against possible changes in operating conditions arising naturally or as a consequence of a stress situation forced by an attacker. To address these challenges, this paper first describes the design of a security primitive that plays an important role as a component of a hardware-based root of trust, as it can act as a source of entropy for True Random Number Generation (TRNG) or as a Physical Unclonable Function (PUF) to facilitate the generation of identifiers linked to the device on which it is implemented. The work also illustrates different software components that allow carrying out a self-assessment strategy to characterize and validate the performance of this primitive in its dual functionality, as well as to monitor possible changes in security levels that may occur during operation as a result of device aging and variations in power supply or operating temperature. The designed PUF/TRNG is provided as a configurable IP module, which takes advantage of the internal architecture of the Xilinx Series-7 and Zynq-7000 programmable devices and incorporates an AXI4-based standard interface to facilitate its interaction with soft- and hard-core processing systems. Several test systems that contain different instances of the IP have been implemented and subjected to an exhaustive set of on-line tests to obtain the metrics that determine its quality in terms of uniqueness, reliability, and entropy characteristics. The results obtained prove that the proposed module is a suitable candidate for various security applications. As an example, an implementation that uses less than 5% of the resources of a low-cost programmable device is capable of obfuscating and recovering 512-bit cryptographic keys with virtually zero error rate. [ABSTRACT FROM AUTHOR]

The generation of unique identifiers extracted from the physical characteristics of the underlying hardware ensures the protection of electronic devices against counterfeiting and provides security to the data they store and process. This work describes the design of an efficient Physical Unclonable Function (PUF) based on the differences in the frequency of Ring Oscillators (ROs) with identical layout due to variations in the technological processes involved in the manufacture of the integrated circuit. The logic resources available in the Xilinx Series-7 programmable devices are exploited in the design to make it more compact and achieve an optimal bit-per-area rate. On the other hand, the design parameters can also be adjusted to provide a high bit-per-time rate for a particular target device. The PUF has been encapsulated as a configurable Intellectual Property (IP) module, providing it with an AXI4-Lite interface to ease its incorporation into embedded systems in combination with soft- or hard-core implementations of general-purpose processors. The capability of the proposed RO-PUF to generate implementation-dependent identifiers has been extensively tested, using a series of metrics to evaluate its reliability and robustness for different configuration options. Finally, in order to demonstrate its utility to improve system security, the identifiers provided by RO-PUFs implemented on different devices have been used in a Helper Data Algorithm (HDA) to obfuscate and retrieve a secret key. [ABSTRACT FROM AUTHOR]

Metamaterials are artificial electromagnetic media structured on the subwavelength scale for controlling the propagation of waves by means of transformation optics. The research activity is now focusing on attaining active metamaterial functionalities, including tunability, and the shaping and modulation of electromagnetic waves. Among all the different architectures, soft‐matter‐based active metamaterials, or hybrid composites, have gained special importance as they allow a variety of tuning strategies to be used, including those based on temperature, application of external electric or magnetic fields, and all‐optical methods that benefit of the strongly nonlinear responses of materials. This review aims to summarize recent and ongoing progress on active metamaterials exploiting resonances in plasmonic and dielectric materials hybridized with soft‐matter assemblies including liquid crystals, colloids, polymers, and granular matter. The theoretical background of these hybrid systems is outlined, experimental realizations are overviewed, and state‐of‐the‐art applications in multifunctional platforms for light–matter interactions are presented. Finally, up to date challenges in the field that still remain open for further research are discussed. [ABSTRACT FROM AUTHOR]

The demands for highly miniaturized and multifunctional electronics are rapidly increasing. As scaling-down processes of transistors are restricted by physical limits, reconfigurable electronics with switchable operation functions for different tasks are developed for higher function integration based on split- or vertical-dual-gate structures. To promote the present reconfigurable electronics and exceed the function integration limit, the critical issue is to integrate complex operations into simple circuit forms by establishing more control dimensions. This work proposes a multibarrier collaborative (MBC) modulation architecture to increase the control dimension by multiple forms of potential barriers and achieves combinational and reconfigurable logic operations by a single MBC device. The MBC architecture exhibits ultrahigh logic operation density, including 58.8% area reduction for multiplexer operations and 71.4% area reduction for 4-logic reconfigurable operations. Besides, a hardware security module composed of 4 MBC devices implementing 8 types of logic operations is demonstrated. This work reveals an effective design of function integration for next-generation electronics.

The proliferation of devices for the Internet of Things (IoT) and their implication in many activities of our lives have led to a considerable increase in concern about the security of these devices, posing a double challenge for designers and developers of products. On the one hand, the design of new security primitives, suitable for resource-limited devices, can facilitate the inclusion of mechanisms and protocols to ensure the integrity and privacy of the data exchanged over the Internet. On the other hand, the development of techniques and tools to evaluate the quality of the proposed solutions as a step prior to their deployment, as well as to monitor their behavior once in operation against possible changes in operating conditions arising naturally or as a consequence of a stress situation forced by an attacker. To address these challenges, this paper first describes the design of a security primitive that plays an important role as a component of a hardware-based root of trust, as it can act as a source of entropy for True Random Number Generation (TRNG) or as a Physical Unclonable Function (PUF) to facilitate the generation of identifiers linked to the device on which it is implemented. The work also illustrates different software components that allow carrying out a self-assessment strategy to characterize and validate the performance of this primitive in its dual functionality, as well as to monitor possible changes in security levels that may occur during operation as a result of device aging and variations in power supply or operating temperature. The designed PUF/TRNG is provided as a configurable IP module, which takes advantage of the internal architecture of the Xilinx Series-7 and Zynq-7000 programmable devices and incorporates an AXI4-based standard interface to facilitate its interaction with soft- and hard-core processing systems. Several test systems that contain different instances of the IP have been implemented and subjected to an exhaustive set of on-line tests to obtain the metrics that determine its quality in terms of uniqueness, reliability, and entropy characteristics. The results obtained prove that the proposed module is a suitable candidate for various security applications. As an example, an implementation that uses less than 5% of the resources of a low-cost programmable device is capable of obfuscating and recovering 512-bit cryptographic keys with virtually zero error rate.

Contemporary digital infrastructures and systems use and trust Public-Key Cryptography to exchange keys over insecure communication channels. With the development and progress in the research field of quantum computers, well established schemes like RSA and ECC are more and more threatened. The urgent demand to find and standardize new schemes – which are secure in a post-quantum world – was also realized by the National Institute of Standards and Technology which announced a Post-Quantum Cryptography Standardization Project in 2017. Recently, the round three candidates were announced and one of the alternate candidates is the Key Encapsulation Mechanism scheme BIKE. In this article, we investigate different strategies to efficiently implement the BIKE algorithm on Field-Programmable Gate Arrays (FPGAs). To this extend, we improve already existing polynomial multipliers, propose efficient strategies to realize polynomial inversions, and implement the Black-Gray-Flip decoder for the first time. Additionally, our implementation is designed to be scalable and generic with the BIKE specific parameters. All together, the fastest designs achieve latencies of 2.69 ms for the key generation, 0.1 ms for the encapsulation, and 1.89 ms for the decapsulation considering the lowest security level. [ABSTRACT FROM AUTHOR]

This article presents an efficient method to compute the dispersion diagram of periodic and uniform structures with generic anisotropic media. The method takes advantage of the ability of full-wave commercial simulators to deal with finite structures having anisotropic media. In particular, the proposed method extends the possibilities of commercial eigenmode solvers in the following ways: 1) anisotropic materials with nondiagonal permittivity and permeability tensors can be analyzed; 2) the attenuation constant can easily be computed in both propagating and stopband regions, and lossy materials can be included in the simulation; and 3) unbounded and radiating structures, such as leaky-wave antennas (LWAs), can be treated. The latter feature may be considered the most remarkable since the structures must be forcefully bounded with electric/magnetic walls in the eigensolvers of most commercial simulators. In this work, the proposed method is particularized for the study of liquid crystals (LCs) in microwave and antenna devices. Thus, the dispersion properties of a great variety of LC-based configurations are analyzed, from canonical structures, such as waveguide and microstrip, to complex reconfigurable phase shifters in ridge gap-waveguide technology and LWAs. Our results have been validated with previously reported works in the literature and with commercial software CST and HFSS. [ABSTRACT FROM AUTHOR]

Devices based on photoconductive materials are promising solutions for future reconfigurable millimeter-wave communication systems. So far, there are several examples of photoconductive radio-frequency switches in the literature, however, their operating frequency and performance are low compared to other radio-frequency switching techniques. In this paper, we propose different photoconductive switch topologies based on the coplanar waveguide, which is more suitable for millimeter-wave applications than the published solutions. The utilization of germanium as the photoconductive element is also evaluated. The main advantages of germanium are its high carrier mobility and lifetime, which facilitates the creation of efficient devices, uniform carrier concentration in thick layers, which enhances interaction with the electromagnetic field in transmission line as well as sensitivity in 1.5 µm spectral region, which simplifies the integration of radio-frequency equipment based on photoconductive devices with existing telecommunication networks. The construction of the switch was evaluated using full-wave electromagnetic simulations based on the finite-difference time-domain method. The influence of the photoconductive substrate conductivity changes on the transmission and reflection characteristics of the coplanar waveguide was investigated. Additionally, the feasibility of the utilization of thin-film photoconductive materials in the proposed switch was examined. [ABSTRACT FROM AUTHOR]

The recent developments in mmWave and Internet of Things (IoT) technologies have dramatically increased the interest and demand for radio frequency (RF) devices that can be used for applications such as smart cities, energy harvesting, and ubiquitous wireless sensor networks. Additive manufacturing technologies (AMT) plays an important role to support these applications, as they allows to significantly reduce fabrication costs and times while enabling the achievement of devices with more complex geometries and the possibility of using a wide variety of materials. This publication reviews recent developments of state-of-the-art wireless devices including reconfigurable antennas, frequency-selective surfaces and highly scalable phased arrays enabled by AMT capabilities. It also discusses the benefits of AMT in the fabrication of interconnects that are suitable for packaging of fully-integrated antennas. [ABSTRACT FROM AUTHOR]

Reconfigurable Matching Networks (RMN) have found a wide range of applications, such as antenna impedance matching (Antenna Tuning Units -ATU-), the design of reconfigurable power amplifiers, applications in Magnetic Resonance Imaging (MRI), adjustable low noise amplifier design, etc. In this paper, we propose the experimental design and verification of a reconfigurable impedance synthesis network that can simultaneously work in three different bands and is completely independent so that the impedance variations in a frequency band are approximately transparent to the rest. The variable elements used in this paper are varactors. To verify its operation, it is applied to a process of matching a laser modulator in three different frequency bands for C-RAN (Cloud Radio Access Networks) applications. Experimental results demonstrate, as expected, that losses may depend on the state in which they are driven. Consequently, a state that can guarantee a good match could also imply greater losses, leading to a certain trade-off. The application of genetic algorithms in this context points out that it may be convenient to optimize the insertion losses of the complete chain instead of the return losses.

Kirigami technique, a method to reconfigure structures via mechanical approaches, has received much attention in material science, due to its versatile and unconventional structural transformations. The counterparts in the electromagnetic metamaterial field has recently allowed for the tunable control of electromagnetic responses. However, they are limited to global tuning of absorption, chirality, etc., leaving much potential of controlling spatially varying distribution and therefore the optical wavefront unexploited. Here, the authors propose a class of kirigami‐based reconfigurable gradient metasurfaces through which the electromagnetic wavefront can be tuned over continuous‐state ranges by changing the meta‐structures from folded (compact) to unfolded (large surface) configurations. As the proof‐of‐concept, meta‐devices including switchable anomalous refractor and reconfigurable metalens are demonstrated both in simulations and experiments. Moreover, a new paradigm to mitigate chromatic dispersion is also realized by the kirigami‐based reconfigurable metalens, which is able to keep the focal length unchanged over a continuous frequency band by setting metalens with various folding states. Their approach provides a new alternative for designing reconfigurable gradient metasurface with additional mechanical properties and may have potential applications in advanced devices such as reconfigurable optical components and imaging system. [ABSTRACT FROM AUTHOR]

Reconfigurable neuromorphic computing holds promise for advancing energy-efficient neural network implementation and functional versatility. Previous work has focused on emulating specific neural functions rather than an integrated approach. We propose an all two-dimensional (2D) material-based heterostructure capable of performing multiple neuromorphic operations by reconfiguring output terminals in response to stimuli. Specifically, our device can synergistically emulate the key neural elements of the synapse, neuron, and dendrite, which play important and interrelated roles in information processing. Dendrites, the branches that receive and transmit presynaptic action potentials, possess the ability to nonlinearly integrate and filter incoming signals. The proposed heterostructure allows reconfiguration between different operation modes, demonstrating its potential for diverse computing tasks. As a proof of concept, we show that the device can perform basic Boolean logic functions. This highlights its applicability to complex neural-network-based information processing problems. Our integrated neuromorphic approach may advance the development of versatile, low-power neuromorphic hardware.

Ambipolar field‐effect transistors allowing both holes and electrons transport can work in different states, which are attractive for simplifying the manufacture of circuits and endowing the circuits with reconfigurable multi‐functionalities. However, conventional ambipolar transistors intrinsically suffer from poor switching‐off capability because the gate electrode is not able to simultaneously deplete holes and electrons across the entire transport channel, which hurdles the practical applications. This study shows that the switching‐off capability of polymer ambipolar transistor is significantly improved by up to three orders by introducing non‐uniformly distributed compensation potentials along the channel to synchronically tune the charge transport at different channel locations. The non‐uniform compensation potential is experimentally generated by the non‐uniformly distributed electret charges, which are pre‐injected into the insulators from source and drain electrodes. By this method, both n‐type and p‐type operations with high mobility (2.2 and 0.8 cm2s−1V−1 respectively) and high on/off ratio (105) are obtained in the same device, and the different states are reversibly switchable. Moreover, this method endows the device with diverse device characteristics and reconfigurable multi‐functionalities, which promotes the application of ambipolar transistors in complementary metal‐oxide semiconductors‐like circuits and some emerging electronics, including reconfigurable devices, multi‐level memories, and artificial synapses. [ABSTRACT FROM AUTHOR]

Small‐scale wireless magnetic robots and devices offer an effective solution to operations in hard‐to‐reach and high‐risk enclosed places, such as inside the human body, nuclear plants, and vehicle infrastructure. In order to obtain functionalities beyond the capability of magnetic forces and torques exerted on magnetic materials used in these robotic devices, electronics need to be also integrated into them. However, their capabilities and power sources are still very limited compared to their larger‐scale counterparts due to their much smaller sizes. Here, groups of milli/centimeter‐scale wireless magnetic modules are shown to enable on‐site electronic circuit construction and operation of highly demanding wireless electrical devices with no batteries, that is, with wireless power. Moreover, the mobility of the modular components brings remote modification and reconfiguration capabilities. When these small‐scale robotic modules are remotely assembled into specific geometries, they can achieve, if not impossible, challenging electrical tasks for individual modules. Using such a method, several wireless and battery‐free robotic devices are demonstrated using milli/centimeter‐scale robotic modules, such as a wireless circuit to power light‐emitting diodes with lower external fields, a device to actuate relatively high force‐output shape memory alloy actuators, and a wireless force sensor, all of which can be modified on‐site. [ABSTRACT FROM AUTHOR]

BIKE is a Key Encapsulation Mechanism selected as an alternate candidate in NIST’s PQC standardization process, in which performance plays a significant role in the third round. This paper presents FPGA implementations of BIKE with the best area-time performance reported in literature. We optimize two key arithmetic operations, which are the sparse polynomial multiplication and the polynomial inversion. Our sparse multiplier achieves time-constancy for sparse polynomials of indefinite Hamming weight used in BIKE’s encapsulation. The polynomial inversion is based on the extended Euclidean algorithm, which is unprecedented in current BIKE implementations. Our optimized design results in a 5.5 times faster key generation compared to previous implementations based on Fermat’s little theorem. Besides the arithmetic optimizations, we present a united hardware design of BIKE with shared resources and shared sub-modules among KEM functionalities. On Xilinx Artix-7 FPGAs, our light-weight implementation consumes only 3 777 slices and performs a key generation, encapsulation, and decapsulation in 3 797 μs, 443 μs, and 6 896 μs, respectively. Our high-speed design requires 7 332 slices and performs the three KEM operations in 1 672 μs, 132 μs, and 1 892 μs, respectively.

Abstract Small‐scale wireless magnetic robots and devices offer an effective solution to operations in hard‐to‐reach and high‐risk enclosed places, such as inside the human body, nuclear plants, and vehicle infrastructure. In order to obtain functionalities beyond the capability of magnetic forces and torques exerted on magnetic materials used in these robotic devices, electronics need to be also integrated into them. However, their capabilities and power sources are still very limited compared to their larger‐scale counterparts due to their much smaller sizes. Here, groups of milli/centimeter‐scale wireless magnetic modules are shown to enable on‐site electronic circuit construction and operation of highly demanding wireless electrical devices with no batteries, that is, with wireless power. Moreover, the mobility of the modular components brings remote modification and reconfiguration capabilities. When these small‐scale robotic modules are remotely assembled into specific geometries, they can achieve, if not impossible, challenging electrical tasks for individual modules. Using such a method, several wireless and battery‐free robotic devices are demonstrated using milli/centimeter‐scale robotic modules, such as a wireless circuit to power light‐emitting diodes with lower external fields, a device to actuate relatively high force‐output shape memory alloy actuators, and a wireless force sensor, all of which can be modified on‐site.

The generation of unique identifiers extracted from the physical characteristics of the underlying hardware ensures the protection of electronic devices against counterfeiting and provides security to the data they store and process. This work describes the design of an efficient Physical Unclonable Function (PUF) based on the differences in the frequency of Ring Oscillators (ROs) with identical layout due to variations in the technological processes involved in the manufacture of the integrated circuit. The logic resources available in the Xilinx Series-7 programmable devices are exploited in the design to make it more compact and achieve an optimal bit-per-area rate. On the other hand, the design parameters can also be adjusted to provide a high bit-per-time rate for a particular target device. The PUF has been encapsulated as a configurable Intellectual Property (IP) module, providing it with an AXI4-Lite interface to ease its incorporation into embedded systems in combination with soft- or hard-core implementations of general-purpose processors. The capability of the proposed RO-PUF to generate implementation-dependent identifiers has been extensively tested, using a series of metrics to evaluate its reliability and robustness for different configuration options. Finally, in order to demonstrate its utility to improve system security, the identifiers provided by RO-PUFs implemented on different devices have been used in a Helper Data Algorithm (HDA) to obfuscate and retrieve a secret key.

This letter investigates the feasibility of the combination of additive manufacturing and liquid crystal (LC) loaded dielectric waveguides (DWGs) at W-band (75–110 GHz). The waveguide is extruded such that it has a cavity in its center, used for LC hosting. Reproducible cross sections are achieved along the DWG and high agreement between differential phase shift and figure-of-merit (FoM) is obtained when the DWG is biased electrically or magnetically. Deembedding the structure shows attenuation constants between 0.12 and 0.33 dB/cm which lead to a high FoM in the range of 100°/dB to 160°/dB. According to simulations, higher values are obtainable if larger LC cavities are realized. [ABSTRACT FROM AUTHOR]

Deformation of flexible electronics can lead to reconfigurable electrical properties, controllable deployment, and tunable working modes, but approaches to actuate flexible electronics are quite limited. A promising method involves using magnetic fields to yield simple displacement of magnetic membranes. However, realization of complex multiaxial bending and rotations of magnetic membranes remains challenging. Here, flexible origami magnetic membranes with programmable magnetic polarities are used to generate complex spatial deformation through coupling with an external magnetic field and interaction among intrinsic magnetism. The membranes can work as standalone flexible actuators and serve as substrates to trigger spontaneous deformation of the carrying flexible devices such as antennas, energy harvesters, and light‐emitting diode arrays. The membranes can travel on a dry surface or in a liquid environment. They also exhibit the capability to reversibly capture and release objects traveling at 326 mm s–1. Flexible devices on the membranes can offer tunable gains and frequencies as well as novel folding and releasing mechanisms determined by the complex magnetic polarities of the underneath membranes. The origami magnetic membranes can be combined to yield more complicate patterns and magnetic polarities, leading to innovative applications in surgical robots, tunable antennas, and various reconfigurable flexible electronics. [ABSTRACT FROM AUTHOR]

This letter presents a new approach for reconfiguring substrate integrated waveguide (SIW) devices. It involves allowing or prohibiting the wave propagation by using a removable wall which is built from a series of drill holes. When the wall is required, the holes are filled with gallium-based liquid metal (LM), thus forming vias. When the wall is no longer required, the holes are emptied of LM. The method has been applied to a single-pole single-throw (SPST) SIW switch as well as a single-pole double-throw (SPDT) switch. Both switches perform well over a wide frequency bandwidth, approaching one octave. The SPST switch performs well from 2.4 to 4.3 GHz. In the ON-state (i.e., wall removed), the insertion loss (IL) is ≤0.5 dB. In the OFF-state (i.e., wall inserted), the isolation is 30 dB. The SPDT switch operates effectively from 4.7 to 7.2 GHz. The IL, between two connected ports, is 0.7 dB. The isolation between unconnected ports is 40 dB. The proposed approach will be applicable within a wide range of different reconfigurable microwave devices. [ABSTRACT FROM AUTHOR]

Origami offers a distinct approach for designing and engineering new material structures and properties. The folding and stacking of atomically thin van der Waals (vdW) materials, for example, can lead to intriguing new physical properties including bandgap tuning, Van Hove singularity, and superconductivity. On the other hand, achieving well‐controlled folding of vdW materials with high spatial precision has been extremely challenging and difficult to scale toward large areas. Here, a deterministic technique is reported to fold vdW materials at a defined position and direction using microfluidic forces. Electron beam lithography (EBL) is utilized to define the folding area, which allows precise control of the folding geometry, direction, and position beyond 100 nm resolution. Using this technique, single‐atomic‐layer vdW materials or their heterostructures can be folded without the need for any external supporting layers in the final folded structure. In addition, arrays of patterns can be folded across a large area using this technique and electronic devices that can reconfigure device functionalities through folding are also demonstrated. Such scalable formation of folded vdW material structures with high precision can lead to the creation of new atomic‐scale materials and superlattices as well as opening the door to realizing foldable and reconfigurable electronics. [ABSTRACT FROM AUTHOR]

This letter presents a closed-form integral-equation formulation that models the director tilting in nematic liquid crystals (LCs). The proposed formulation is computationally efficient compared to numerical methods and provides physical insight into the matter. Our previous work is generalized from the one-constant approach to all the possible cases that cover the elastic constants. These constants determine in great extent the electrical properties of the LC, and subsequently, the response of the reconfigurable devices that make use of it. Therefore, a more precise but still simple modeling of their influence is pursued here. Simulations show good agreement with numerical implementations. In comparison, the error in the estimation is considerably reduced when using the integral-equation formulation, especially as the polarization voltage or the dielectric anisotropy decreases. [ABSTRACT FROM AUTHOR]

The growing demand for low-profile, efficient compact antennas with reconfigurable characteristics has prompted antenna engineers to use novel materials in place of conventional dielectrics. Magnetodielectric materials combining both dielectric and magnetic properties have been widely investigated. In this article, we present a comprehensive literature study that examines the advantages and limitations of using these materials. We focus primarily on magnetodielectric materials exhibiting anisotropic behavior and tunable permeability by means of physical mechanisms (e.g., by applying an external magnetic field). This article provides theoretical background, modeling guidelines, and a step-by-step simulation procedure, and aims to be a straightforward and useful guide for the development of reconfigurable antennas using magnetic materials. We explain the reasons for selecting ferrimagnetic oxides for antenna applications and discuss their fundamental properties. The critical parameters that should be taken into consideration for the determination of the permeability of ferrimagnetic oxides in various magnetization states are reported. To demonstrate the proper use of this analysis, we have designed, simulated, and implemented a reconfigurable ferrite antenna prototype. The proposed simulated procedure is validated via measurements. [ABSTRACT FROM AUTHOR]

A decisive advantage of software-defined networking (SDN) is its support for flexible network reconfigurations. Considering that, software-defined networks require accurate and timely data-plane state information. Network monitoring mechanisms usually require considerable resources on SDN controllers as well as on the data-plane elements. In this paper, we propose an optimization of the statistic transmission to reduce costs on both control- and data-plane regardless of the used monitoring application and statistic provisioning tool. To this end, we intercept the statistic message exchange and 1) aggregate multiple requests coming from different monitoring applications/controllers, 2) filter irrelevant statistic messages with respect to their information gain before delivering them to the control applications, and 3) deploy statistic caching. The proposed system, denoted STATISTIC REQUEST RELAY, forms a logically centralized statistic relay between controllers and the managed data-plane network. Our evaluation shows that the number of statistics processed on controllers as well as statistic requests on switches is reduced significantly while the performance penalty is negligible when using statistic aggregation and filtering as proposed here. [ABSTRACT FROM AUTHOR]

Liquid crystals (LCs) technology have a well-established history of applications in visible light, particularly in the display industry. However, with the rapid growth in communication technology, LCs have become a topic of current interest for high-frequency microwave (MW) and millimeter-wave (mmWave) applications due to promising characteristics such as tunability, continuous tuning, low losses, and price compatibility. To improve the performance of future communication technology using LCs, it is not sufficient only with the perspective of radio-frequency (RF) technology. Therefore, it is imperative to understand not only the novel structural designs and optimization of MW engineering but also the perspective of materials engineering when implementing advanced RF devices with maximum performance for next-generation satellite and terrestrial communication. Herein, based on advanced nematic LCs, polymer-modified LCs, dual-frequency LCs, and photo-reactive LCs, this article summarizes and examines the modulation principles and key research directions for the design strategies of LCs for advanced smart RF devices with improved driving performance and novel functionality. Furthermore, the challenges in development of state-of-the-art smart RF devices that use LCs are discussed., (© 2023 Wiley-VCH GmbH.)

We overcome mismatch constraints of capacitor DAC design in SAR ADCs using a completely reconfigurable DAC with content addressable memory beneath groupings of unit capacitors. We demonstrate a linearity optimization technique in simulation and measurement. We achieve a nearly 2-bit repeatable ENOB improvement with a peak of 11.3 bits. [ABSTRACT FROM AUTHOR]

This paper presents a novel metasurface antenna whose radiation characteristics can be remotely controlled by optical means using PIN photodiodes. The proposed reconfigurable antenna is implemented using a single radiating element to minimize the size and complexity. The antenna is shown to exhibit a large impedance bandwidth and is capable of radiating energy in a specified direction. The proposed antenna consists of a standard rectangular patch on which is embedded an H-tree shaped fractal slot of order 3. The fractal slot is used to effectively reduce the physical size of the patch by 75 % and to enhance its impedance bandwidth. A metasurface layer is strategically placed above the patch radiator with a narrow air gap between the two. The metasurface layer is a lattice pattern of square framed rhombus ring shaped unit-cells that are interconnected by PIN photodiodes. The metasurface layer essentially acts like a superstrate when exposed to RF/microwave radiation. Placed below the patch antenna is a conductive layer that acts like a reflector to enhance the front-to-back ratio by blocking radiation from the backside of the patch radiator. The patch's main beam can be precisely controlled by photonically illuminating the metasurface layer. The antenna's performance was modelled and analyzed with a commercial 3D electromagnetic solver. The antenna was fabricated on a standard dielectric substrate FR4 and has dimensions of 0.778λ o × 0.778λ o × 0.25λ o mm3, where λ o is the wavelength of free space centered at 1.35 GHz. Measured results confirm the antenna's performance. The antenna exhibits a wide fractional band of 55.5 % from 0.978 to 1.73 GHz for reflection-coefficient (S 11) better than −10 dB. It has a maximum gain of 9 dBi at 1.35 GHz with a maximum front-to-back ratio (F/B) of 21 dBi. The main beam can be steered in the elevation plane from −24° to +24°. The advantage of the proposed antenna is it does not require any mechanical movements or complicated electronic systems. [ABSTRACT FROM AUTHOR]

Gallium-based room-temperature liquid metals possess extremely valuable properties, such as low toxicity, low vapor pressure, and high thermal and electrical conductivity enabling them to become suitable substitutes for mercury and beyond in wide range of applications. When exposed to air, a native oxide layer forms on the surface of gallium-based liquid metals which mechanically stabilizes the liquid. By removing or reconstructing the oxide skin, shape and state of liquid metal droplets and flows can be manipulated/actuated desirably. This can occur manually or in the presence/absence of a magnetic/electric field. These methods lead to numerous useful applications such as soft electronics, reconfigurable devices, and soft robots. In this mini-review, we summarize the most recent progresses achieved on liquid metal droplet generation and actuation of gallium-based liquid metals with/without an external force.

Reconfigurable logic circuits implemented by two-dimensional (2D) ambipolar semiconductors provide a prospective solution for the post-Moore era. It is still a challenge for ambipolar nanomaterials to realize reconfigurable polarity control and rectification with a simplified device structure. Here, an air-gap barristor based on an asymmetric stacking sequence of the electrode contacts was developed to resolve these issues. For the 2D ambipolar channel of WSe 2 , the barristor can not only be reconfigured as an n- or p-type unipolar transistor but also work as a switchable diode. The air gap around the bottom electrode dominates the reconfigurable behaviors by widening the Schottky barrier here, thus blocking the injection of both electrons and holes. The electrical performances can be improved by optimizing the electrode materials, which achieve an on/off ratio of 10 4 for the transistor and a rectifying ratio of 10 5 for the diode. A complementary inverter and a switchable AND/OR logic gate were constructed by using the air-gap barristors as building blocks. This work provides an efficient approach with great potential for low-dimensional reconfigurable electronics.

Touch panels based on ionic conductive hydrogels perform excellent flexibility and biocompatibility, becoming promising candidates for the next-generation human-machine interface. However, these ionic hydrogels are usually composed of cross-linked polymeric networks that are difficult to be recycled or reconfigured, resulting in environmental issues. Herein, we designed a lithium ion-triggered gelation strategy to provide a conductive molecular hydrogel with thixotropy, which can be mechanically recycled or reconfigured at room temperature. In this hydrogel, lithium ions function as ionic bridges to construct supramolecular nanoassemblies and charge carriers to impart ionic conductivity. With polymer additives, the mechanical accommodability of the hydrogel was improved to meet the requirements of the daily use of touch panels. When this molecular hydrogel was fabricated into a surface capacitive touch panel, real-time sensing and reliable touch locating abilities were achieved. Remarkably, this touch panel can be reconfigured into 1D, 2D, and 3D device structures by a simple stirring-remolding method under ambient conditions. This work brings new insight into enriching the functionalities of hydrogel-based ionotronics with a supramolecular approach.

Modern high-speed networks have evolved from relatively static networks to highly adaptive networks facilitating dynamic reconfiguration. This evolution has influenced all levels of network design and management, introducing increased programmability and configuration flexibility. This influence has extended from the lowest level of physical hardware interfaces to the highest level of network management by software. A key representative of this evolution is the emergence of software-defined networking (SDN). In this paper, we review the current state of the art in reconfigurable network systems, covering hardware reconfiguration, SDN, and the interplay between them. We take a top–down approach, starting with a tutorial on software-defined networks. We then continue to discuss programming languages as the linking element between different levels of software and hardware in the network. We review electronic switching systems, highlighting programmability and reconfiguration aspects, and describe the trends in reconfigurable network elements. Finally, we describe the state of the art in the integration of photonic transceiver and switching elements with electronic technologies, and consider the implications for SDN and reconfigurable network systems. [ABSTRACT FROM PUBLISHER]