Julius Georgiou

• PhD
• Professor (Associate) at University of Cyprus

A multifunctional and reconfigurable programmable metasurface (PMSF) enabled by an application-specific integrated circuit (ASIC) is presented in this work, that targets smart wireless environment applications. In the accompanying paper, in Part 1, the PMSF design experimentally demonstrated the ability to control independently the magnitude and ph...

A multifunctional and reconfigurable programmable metasurface (PMSF) is presented in this work that is enabled by an application-specific integrated circuit (ASIC). The enabling ASIC integrates control, digital-to-analog converters and loading elements to programmatically alter the response of the PMSF unit cells, while minimizing power consumption...

The pressure on agricultural efficiency is nowadays greater than ever, hence there has been an abrupt technological involvement in this sector in the last decade. In this article, a stand-alone, in situ, soil quality sensing system is presented for the first time, capable of monitoring chemical parameters in the soil without any human intervention....

In this tutorial, we discuss trade-offs in sensor system design. With examples from engineered systems in our laboratories, we address design considerations at the different system levels, from the choice of a particular sensor to the signal conditioning circuits, the choice of data converter, and data communication physical interfaces. Fundamental...

The Sensors industry has seen extraordinary growth in the last 20 years. It is currently projected that the sensors market size will triple from 2020 to 2030. The most prevalent reason for this exponential growth is the technological trend towards hyper-intelligent systems. Future technologies are expected to dive into the Internet of Senses, Indus...

Reconfigurable metasurfaces are man-made surfaces, which consist of sub-wavelength periodic elements—meta-atoms—that can be reconfigured to manipulate incoming electromagnetic waves. However, reconfigurable metasurfaces developed to-date, have limitations in terms of loading impedance range, reconfiguration delay and power consumption. Also, these...

italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Goal: Uterine contractility is known to play significant role in women's health. Ultrasonography and magnetic resonance imaging have been used for assessing uterine peristalsis, however they lack practicality, objectivity, and cost-effectiveness. In th...

In this paper, the architecture of an application-specific integrated circuit for adaptive metasurfaces is presented. The architecture allows scalable networking over large metasurfaces and reconfiguration of each unit-cell with unique complex impedance settings, for adjusting metasurface electromagnetic performance. The one-chip-design metasurface...

This paper presents the design of a fully-custom integrated circuit (IC) suitable for adjusting the complex impedance of individual meta-atoms to enable programmability of metasurface systems. Implemented in a 0.18 μm mixed-signal CMOS process, the circuit utilizes four integrated complex impedance elements, each one with 2 <sup xmlns:mml="http://w...

As Technology advances in the 21st century, the inclusion of intelligence in any kind of system is becoming a necessity. First stage of intelligence, similarly to humans, is to observe and obtain information from the environment, which can only be achieved through the use of sensors. However, due to the wide diversity of the information to be obtai...

An improved approach for comparative study of plant cells for long term and continuous monitoring using electrical impedance spectroscopy is demonstrated for tomato and tobacco plant cells (MSK8 and BY2) in suspensions. This approach is based on the locations and magnitudes of defining features in the impedance spectra of the recently reported unif...

This Special Issue of the IEEE Journal on Emerging and Selected Topics in Circuits and Systems (JETCAS) is dedicated to circuits and systems applied to innovative products for the agriculture and food value chain.

A metasurface design is presented, where its meta-atoms are populated with programmable integrated circuits. The programmable integrated circuit loads the meta-atom with four complex impedance loading elements. This grants the meta-atom the capability to programmatically set its reflection amplitude and phase for both transverse electric and transv...

The concept of Precision Agriculture has been conceived several decades ago however, it has never been fully implemented due to several technological constraints, such as the high cost of automated systems. In this paper, a versatile, low-cost and stand-alone sensing node with unique capabilities is presented, suitable for direct soil quality monit...

The concept of Precision Agriculture has been conceived several decades ago however, it has never been fully implemented due to several technological constraints, such as the high cost of automated systems. In this paper, a versatile, low-cost and stand-alone sensing node with unique capabilities is presented, suitable for direct soil quality monit...

Reconfigurable metasurfaces are man-made surfaces, which consist of sub-wavelength periodic elements - meta-atoms - that can be reconfigured to manipulate incoming electromagnetic waves. However, reconfigurable metasurfaces developed to-date, have limitations in terms of impedance range, reconfiguration delay and power consumption. Also, these syst...

Electrical impedance spectroscopy was performed on suspensions of plant cells in aqueous buffer media over a wide frequency range of 4 Hz to 20 GHz. Custom probes were designed, manufactured, and used for these investigations. Experiments were performed with a custom-made parallel plate probe and impedance analysers in the low-frequency range (4 Hz...

Organic electrochemical transistors (OECTs) have been recognized as a major emerging technology in the area of flexible electronics in the last decade. Although they have yet to be incorporated in common electronic fabrication technologies, they have considerably advanced as an emerging platform for biosensing applications. The paper provides a com...

In this paper we present the theoretical considerations and the design evolution of a proof-of-concept reconfigurable metasurface, primarily used as a tunable microwave absorber, but also as a wavefront manipulation and polarization conversion device in reflection. We outline the design evolution and all considerations taken into account, from the...

A simple, ultra-wide frequency range, equivalent circuit for plant cell suspensions is presented. The model incorporates both the interfacial interactions of the suspension with the electrode, dominant at low frequencies, and the molecule and cell polarization mechanisms dominant at higher frequencies. Such model is useful for plant cell characteri...

Metasurfaces, the ultrathin, 2D version of metamaterials, have recently attracted a surge of attention for their capability to manipulate electromagnetic waves. Recent advances in reconfigurable and programmable metasurfaces have greatly extended their scope and reach into practical applications. Such functional sheet materials can have enormous im...

In this letter, preliminary results showing the memristive behavior of tantalum/tantalum oxide/platinum devices on glass substrates are reported. The ultra-thin (d < 10 nm) tantalum oxide films were obtained using solution-based anodic oxidation (anodization) of Ta in citric acid. The devices were tested using standard ReRAM characterization tests...

In this paper we present the theoretical considerations and the design evolution of a proof-of-concept intelligent metasurface, which can be used as a tunable microwave absorber, as well as a wavefront manipulation and polarization conversion device in reflection. We outline the design evolution and all considerations taken into account, from the s...

This Special Issue of the IEEE Journal on Emerging and Selected Topics in Circuits and Systems (JETCAS) is dedicated to novel contributions to the field of programmable metamaterials. Recent years have witnessed the emergence of this paradigm, whereby the electromagnetic response of the metamaterial can be encoded into a string of bits. This allows...

Recent years have seen the emergence of programmable metasurfaces, where the user can modify the EM response of the device via software. Adding reconfigurability to the already powerful EM capabilities of metasurfaces opens the door to novel cyber-physical systems with exciting applications in domains such as holography, cloaking, or wireless commu...

Metamaterials and their two-dimensional analogues, metasurfaces, have recently attracted enormous attention for their powerful control over electromagnetic (EM) waves from microwave to visible range. Moreover, by introducing explicit control within its sub-wavelength unit cells, a metamaterial can become programmable. Programmable metamaterials may...

Recent years have seen the emergence of programmable metasurfaces, where the user can modify the electromagnetic (EM) response of the device via software. Adding reconfigurability to the already powerful EM capabilities of metasurfaces opens the door to novel cyber-physical systems with exciting applications in domains such as holography, cloaking,...

HyperSurfaces (HSFs) comprise structurally reconfigurable metasurfaces whose electromagnetic properties can be changed via a software interface, using an embedded miniaturized network of controllers, enabling novel capabilities in wireless communications, including 5G applications. Resource constraints associated with a hardware testbed of this bre...

This paper provides an overview of the electronic instrumentation most commonly used for electrical and/or electrochemical impedance spectroscopy. The system is broken down to its most significant functional blocks and the most common approaches are explained. The paper further discusses the ability of these circuits to be used for soil impedance m...

This paper compares the simulated performance of three different screen-printed probe geometries for Electrochemical Impedance Spectroscopy probes for use in harsh environments. The best performing probe, which is equipped with guarding electrodes that are proven to help with the electric field uniformity, shows a linear response with the medium’s...

Food safety has attracted an exponentially growing attention in the current decade, hence the food and agricultural industries and regulation authorities require specialized tools that can define health threatening indicators and quantify them without the need of laborious and time-consuming tests. Soil water content, soil salinity, soil structural...

Metasurfaces (MS) constitute effective media for manipulating and transforming impinging EM waves. Related studies have explored a series of impactful MS capabilities and applications in areas such as wireless communications, medical imaging and energy harvesting. A key-gap in the existing body of work is that the attributes of the EM waves to-be-c...

Software-defined metasurfaces are electromagnetically ultra-thin, artificial components that can provide engineered and externally controllable functionalities. The control over these functionalities is enabled by the metasurface tunability, which is implemented by embedded electronic circuits that modify locally the surface resistance and reactanc...

We present the concept and electromagnetic aspects of HyperSurFaces (HSFs), artificial, ultrathin structures with software controlled electromagnetic properties. The HSFs key unit is the metasurface, a plane with designed subwavelength features whose electromagnetic response can be tuned via voltage-controlled continuously-tunable electrical elemen...

Metasurfaces constitute effective media for manipulating and transforming impinging EM waves. Related studies have explored a series of impactful MS capabilities and applications in sectors such as wireless communications, medical imaging and energy harvesting. A key-gap in the existing body of work is that the attributes of the EM waves to-be-cont...

Software-defined metasurfaces are electromagnetically ultra-thin, artificial components that can provide engineered and externally controllable functionalities. The control over these functionalities is enabled by the metasurface tunability, which is implemented by embedded electronic circuits that modify locally the surface resistance and reactanc...

Chua's mem-components are ideal for creating adaptive metasurfaces for manipulating EM waves given that they hold their state without external biases. In this paper, we propose a generic adaptive reactive element that is in fact a memcapacitor/meminductor. This element makes use of a polymer that demonstrates reversible trans-cis photochemical isom...

A tunable metasurface absorber is presented in this work using an optically-programmable capacitor as the tuning element. The tuning element does not employ conventional semiconductor technologies to operate but rather a bases its tuning by changing the optomechanical properties of its dielectric, poly disperse red 1 acrylate (PDR1A). Doing so ther...

Metamaterials and metasurfaces have given possibilities for manipulating electromagnetic (EM) waves that in the past would have seemed impossible. The majority of metasurface designs are suitable for a particular frequency and angle of incidence. One long-sought objective is the design of programmable metasurfaces to dynamically manipulate a variet...

The radiation tolerance of subthreshold reference circuits for space microelectronics is presented. The assessment is supported by measured results of total ionization dose and single event transient radiation-induced effects under γ-rays, X-rays, protons and heavy ions (silicon, krypton and xenon). A high total irradiation dose with different radi...

In this study, lead-free, piezoelectric devices were fabricated by vacuum radiofrequency (RF) sputtering of Ga–doped, ZnO (GZO) nanocoatings at different deposition modes on silicon substrates. Several deposition rates were varied (2 to 16 nm/min) by tuning the sputtering voltage and pressure, in order to control the microstructure and surface morp...

In this paper, the experimental study and confirmation of the memristive behavior demonstrated by nanowires made of a smart alloy, namely NiTi, are presented. Further contribution to the characterization of the proposed novel NiTi memristor, included measurements in the ac domain, confirming the memristive nature of these NiTi wires/devices. These...

We thoroughly investigate the electromagnetic response of intelligent functional metasurfaces. We study two distinct designs operating at different frequency regimes, namely, a switch-fabric-based design for GHz frequencies and a graphene-based approach for THz band, and discuss the respective practical design considerations. The performance for tu...

Metasurfaces, the two-dimensional counterpart of metamaterials, have caught great attention thanks to their powerful control over electromagnetic waves. Recent times have seen the emergence of a variety of metasurfaces exhibiting not only countless functionalities, but also a reconfigurable or even programmable response. Reconfigurability, however,...

HyperSurfaces (HSFs) are devices whose electromagnetic (EM) behavior is software-driven, i.e., it can be defined programmatically. The key components of this emerging technology are the metasurfaces, artificial layered materials whose EM properties depend on their internal subwavelength structuring. HSFs merge metasurfaces with a network of miniatu...

This article shows initial experimental results on the utilization of a durable, low-cost, screen-printed resistivity sensor in concrete for real-time measurements, with the aim of correlating concrete's electrical resistivity with moisture content. The sensor was tested in two different concrete mixtures, i. e., one with highly-absorptive aggregat...

HyperSurfaces are a merge of structurally reconfigurable metasurfaces whose electromagnetic properties can be changed via a software interface, using an embedded miniaturized network of controllers, thus enabling novel capabilities in wireless communications. Resource constraints associated with the development of a hardware testbed of this breakth...

This paper shows initial experimental results on the utilization of a durable, low-cost, screen-printed resistivity sensor in concrete for real-time measurements, with the aim of correlating concrete's electrical resistivity with moisture content. The sensor was tested in two different concrete mixtures, one with highly-absorptive aggregates (5.1%)...

A metasurface is a surface that consists of artificial material, called metamaterial, with configurable electromagnetic properties. This paper presents work in progress on the design and formal verification of a programmable metasurface, the Hypersurface, as part of the requirements of the VISORSURF research program (HORIZON 2020 FET-OPEN). The Hyp...

HyperSurfaces (HSFs) are devices whose electromagnetic (EM) behavior is software-driven, i.e., it can be defined programmatically. The key components of this emerging technology are the metasurfaces, artificial layered materials whose EM properties depend on their internal subwavelength structuring. HSFs merge metasurfaces with a network of miniatu...

We thoroughly investigate the electromagnetic response of intelligent functional metasurfaces. We study two distinct designs operating at different frequency regimes, namely, a switch-fabric-based design for GHz frequencies and a graphene-based approach for THz band, and discuss the respective practical design considerations. The performance for tu...

A metasurface is a surface that consists of artificial material, called metamaterial, with configurable electromagnetic properties. This paper presents work in progress on the design and formal verification of a programmable metasurface, the Hypersurface, as part of the requirements of the VISORSURF research program (HORIZON 2020 FET-OPEN). The Hyp...

Early micro-cancer detection in the small intestine can be realized using infrared fluorescence endoscopy (IRFE) in conjunction with an infrared fluorescence biomarker. In this paper, we present a third-generation capsule that detects weak fluorescence signals emitted by low concentrations of indocyanine green (ICG). An applicationspecific integrat...

This paper describes a novel technique to quantify and identify bacterial cultures of Bacillus Subtilis (2.10–1.30 × 10⁹ CFU mL⁻¹) and Escherichia Coli (1.60–1.00 × 10⁹ CFU mL⁻¹), in corn oil using dielectric spectroscopy at elevated frequencies of 0.0100–20.0 GHz. This technique is using the electrophysiological/biophysical differences (e.g. gram...

Purpose of review: The aim of this study was to summarize the role of recently developed diagnostic techniques in the diagnosis and management of patients with small bowel tumours (SBTs). Recent findings: Recent studies show that the overall SBT incidence is increasing. The introduction of small bowel dedicated diagnostic tools [i.e. capsule end...

The incidence of small bowel tumors is increasing over time. Until recently, their diagnosis was delayed and it was often reached only at the time of surgery. New diagnostic tools, such as capsule endoscopy, device-assisted enteroscopy, and dedicated small bowel cross-sectional imaging techniques, have been introduced recently in clinical practice....

An all-CMOS, low-power, wide-temperature-range, curvature-compensated voltage reference is presented. The proposed topology achieves a measured temperature coefficient of 12.9 ppm/°C for a wide temperature range of 180°C ( − 60 to 120°C) at a bias voltage of 0.7 V while consuming a mere 2.7 μW. The high-order curvature compensation, which leads to...

Sand-scorpions and many other arachnids perceive their environment by using their feet to sense ground waves. They are able to determine amplitudes the size of an atom and locate the acoustic stimuli with an accuracy of within 13° based on their neuronal anatomy. We present here a prototype sound source localization system, inspired from this impre...

An architectural performance comparison of bandgap voltage reference variants, designed in a 0.18 m CMOS process, is performed with respect to single event transients. These are commonly induced in microelectronics in the space radiation environment. Heavy ion tests (Silicon, Krypton, Xenon) are used to explore the analog single-event transients an...

This paper describes the design and development of a unique, body-worn vitals monitor that is able to acquire ECG, blood oxygen, body temperature and up to eight custom designed electronic stethoscopes for highly synchronized heart and lung sound auscultation. The proposed platform is a key component required for developing a Field Accident and Eme...

In this Letter, the authors describe the characterisation design and development ofthe authors’ wearable, multimodal vitals acquisition unit for intelligent field triage. The unit is able to record the standard electrocardiogram, blood oxygen and body temperature parameters and also has the unique capability to record up to eight custom designed ac...

Infrared fluorescence endoscopy (IRFE), in conjunction with an infrared fluorescent-labelling contrast agent, is a well known technique used for efficient early-stage cancer detection. In this paper we present a cost-effective ( $500) screening capsule prototype, which is able to detect infrared (IR) fluorescence emitted by indocyanine green (ICG)...

A low-voltage, low-power, low-area, wide-temperature-range CMOS voltage reference is presented. The proposed reference circuit achieves a measured temperature drift of 15 ppm/°C for an extremely wide temperature range of 190 °C (−60 to 130 °C) while consuming only 4 μW at 0.75 V. It performs a high-order curvature correction of the reference voltag...

Asymptomatic, early-stage, cancer detection is a problem in the small intestine, that is largely inaccessible. This paper presents a cost-effective screening capsule prototype, which is able to detect infrared (IR) fluorescence emitted by indocyanine green (ICG) fluorophore dye. The presented mixed-signal system has a small size, consumes little po...

Efficient microcancer detection in the small intestine can be realised by infrared fluorescence endoscopy (IRFE), in conjunction with an infrared fluorescent-labeling contrast agent that is designed to be selectively uptaken by cancerous cells. In this paper we present a second generation screening capsule, which is able to measure IR fluorescence...

A low-power, wide temperature range, radiation tolerant CMOS voltage reference is presented. The proposed reference circuit exhibits a voltage deviation of 0.8mV for 3-MeV protons total ionization dose of 2Mrad and a voltage deviation of 3.8mV for 10-keV X-rays total ionization dose of 4Mrad while being biased at the nominal supply voltage of 0.75V...

The dynamic brain networks forming during wakefulness and anesthetic-induced unconsciousness are investigated using time-delayed correlation and graph theoretical measures. Electrical brain activity (EEG) from 10 patients under propofol anesthesia during routine surgery is characterized using the shortest path length, λ, and clustering, c, extracte...

Objective A number of studies provide supporting evidence for changes in synchronization during anesthetic-induced unconsciousness. This study investigates how anesthetic administration affects the widespread patterns of phase synchrony. Methods The recently introduced method of Spatial Analytic Phase Difference (SAPD) was used to measure changes...

SUMMARYA relaxation oscillator using a memristor is hereby presented. The memristor is used to substitute the function of a capacitor in an equivalent RC oscillator. The voltage across the memristor changes according to the quantity and polarity of the current passing through, thus substituting the changing voltage across a capacitor in the equival...

Introduction Intra-operative awareness has a reported incidence of approximately 0.1-0.8%. Anesthetic-induced changes in the patient electrical brain activity (EEG) can be monitored in order to avoid intra-operative awareness cases. In this work we investigate the effect of anesthetic administration on the observed patterns of nonlinear dynamic cou...

Efficient microcancer detection in the small intestine can be realised by infrared fluorescence en-doscopy (IRFE). The affected areas can be visualised through that technique in conjunction with an infrared fluorescent-labeling contrast agent, which is selectively uptaken by cancerous cells. In this paper we present a screening capsule prototype th...

This paper presents an alternative approach for angular-rate sensing based on the way that the natural vestibular semicircular canals operate, whereby the inertial mass of a fluid is used to deform a sensing structure upon rotation. The presented gyro has been fabricated in a commercially available MEMS process, which allows for microfluidic channe...

A multichannel vestibular prosthesis includes a sensor system and a microcontroller configured to communicate with the sensor system to receive sensor signals from the sensor system while in operation. The microcontroller is configured to provide control signals in response to the sensor signals. The multichannel vestibular prosthesis also includes...

An audio-visual experiment using moving sound sources was designed to investigate whether the analysis of auditory scenes is modulated by synchronous presentation of visual information. Listeners were presented with an alternating sequence of two pure tones delivered by two separate sound sources. In different conditions, the two sound sources were...

A micro-fluidic gyroscope that mimics the natural vestibular semicircular canals (SCC) is presented. This gyro takes advantage of a hybrid MEMS process that combines micro-fluidic channels on micro-machined glass wafers with active components realized in silicon wafers. The proposed gyro offers significant advantages in terms of power consumption a...

/st>Anaesthetic agents may disrupt consciousness by inhibiting long-range synchronization of brain activity. In the current study, the patterns of widespread and spatially localized synchrony during anaesthesia are investigated using a measure called global field synchrony (GFS). /st>The EEG obtained during routine surgery in 29 patients was analys...

The ability to recognize the behavior of individuals is of great interest in the general field of safety (e.g. building security, crowd control, transport analysis, independent living for the elderly). Here we report a new real-time acoustic system for human action and behavior recognition that integrates passive audio and active micro-Doppler sona...

This paper investigates the non-linear dynamic relationship between electroencephalogram (EEG) and electrocardiogram (ECG) signals during sleep. These relationships were studied with Cross-Recurrence Rate (CRR), a non-linear measure that studies the recurrence of the phase space trajectories of dynamical systems. Data from 10 subjects during sleep...

This paper investigates the use of autoregressive (AR) model order estimation criteria for monitoring awareness during anaesthesia. The Bayesian Information Criterion (BIC) and the Akaike Information Criterion (AIC) were applied to electroencephalogram (EEG) data from 29 patients, obtained during surgery, to estimate the optimum multivariate AR mod...

This article investigates the signal processing part of a future system for monitoring awareness during surgery. The system uses features from the patients' electrical brain activity (EEG) to discriminate between "anesthesia" and "awareness." We investigate the use of a neural network classifier and Granger causality (GC) features for this purpose....

We present a design framework for neuromorphic architectures in the nano-CMOS era. Our approach to the design of spiking neurons and STDP learning circuits relies on parallel computational structures where neurons are abstracted as digital arithmetic logic units and communication processors. Using this approach, we have developed arrays of silicon...

The human auditory system is capable of grouping sounds originating from different sound sources into coherent auditory streams, a process termed auditory stream segregation. Several cues can infl uence auditory stream segregation, but the full set of cues and the way in which they are integrated is still unknown. In the current study, we tested wh...

An all-subthreshold CMOS Voltage Reference architecture is presented, which achieves 3rd order curvature compensation over a wide temperature range. The simulated performance of the proposed architecture with a supply voltage of 0.75V is 2 ppm/°C, over a temperature range of 190 °C (-45 °C to 145 °C). The high order curvature compensation is perfor...