Passive Devices Research Articles

Conformally printed additively manufactured RF demonstrator for circuit compaction

Abstract Recently, there has been interest in applying Additive Manufacturing (AM) to RF and Microwave applications, especially in packaging of microelectronic devices. Additive packaging offers advantages of expanded functionality in restricted volume, through miniature, low-SWaP-C sensors, allowing for non-traditional form factors. In this work, design, fabrication, and characterization of a non-planar multi-material MMIC structure is presented to demonstrate significant footprint reduction and circuit compaction. Performance of a non-planar passive RF device and details of planar to non-planar AM connections for characterization of the transitions will be demonstrated. The work will present details of the design and fabrication of the non-planar structure, optimization of the process parameters for the Optomec 5-axis Aerosol Jet Printer for multi-material printing, and the results of the characterization and testing. RF measurements were conducted to demonstrate the functionality of the developed non-planar circuit and compared with simulations which showed good agreement. The results of this work show that fully additive approach is feasible for non-planar circuits, which will allow for footprint reduction, weight reduction, and achievement of novel form factors that are critical for microwave applications.

Acoustic detection rate can outperform traditional survey approaches in estimating relative densities of breeding waders

Passive acoustic devices are increasingly being used to monitor biodiversity. However, few studies have compared the accuracy of acoustic surveys and traditional surveys against ground‐truthed data. Here, we assess whether acoustic recorders used in conjunction with an artificial intelligence (AI) classifier can predict the relative breeding density of four wader species better than traditional fieldworker transect surveys. In a 27‐km2 upland study site, acoustic data were collected at 83 sampling points and analysed using the BirdNet bird‐sound classifier to estimate vocal detection rate at each location; we also carried out concurrent transect bird surveys. To ground‐truth these approaches, intensive field surveys were undertaken to identify each breeding territory of our focal species. With both the acoustic dataset and the transect dataset, we used similar analytical approaches (random forest regression trees) to predict relative territory density across the study site, and then compared these predictions with the territory density obtained from the intensive field surveys. The classifier performed well at identifying the presence of target species' vocalizations within 3‐s periods for Lapwing (accuracy = 0.911), Curlew (0.826) and Oystercatcher (0.841), but less well for Golden Plover (0.699). For Curlew and Oystercatcher, the predictions obtained from the acoustic approach were a better fit to actual territory density than the transect approach. In contrast, for Lapwing and Golden Plover, the transect predictions outperformed the acoustic predictions, with the acoustic model particularly poor for Golden Plover. We attributed these differences to the performance of the classifier, species' ecology and vocal behaviour. Data gathering for the acoustic approach was more time‐efficient than the transect surveys, requiring less than a quarter of the fieldworker days. We conclude that there is high potential for acoustic approaches to augment traditional methods, although species' ecological characteristics should be considered: species that vocalize more frequently, at higher amplitudes and hold larger territories will be better‐suited to sampling‐based acoustic methods.

Optimization and evaluation of tuned inerter-based dampers for mitigating coupled responses of offshore wind turbines

To achieve lightweight vibration control in offshore wind turbines (OWTs), this study proposes the utilization of two types of tuned inerter-based dampers (TIBDs), namely, the tuned viscous mass damper (TVMD) and tuned inerter damper (TID), to mitigate the coupled responses of an OWT induced by wind and wave loads. First, a multi-degree-of-freedom (MDOF) lumped mass model is established to represent an OWT equipped with a TIBD. Then, a novel structural control module for TIBDs is developed and seamlessly integrated into the modular numerical analysis code OpenFAST. This enables fully coupled aero-hydro-servo-elastic simulations of the OWT-TIBD system. Using the established MDOF model, a TIBD parameter optimization design method is proposed to minimize the peak of the non-dimensional displacement frequency response function. Additionally, a parametric study is performed to investigate the effect of inertance and span height on the control performance. Finally, the performance of the TIBD in attenuating both fatigue and extreme loads is evaluated through nonlinear fully coupled time-domain simulations using OpenFAST and compared to traditional tuned mass dampers (TMDs). The results showed that a lightweight and small damper displacement TIBD is capable of effectively dampening OWT vibrations, yielding a better mitigation effect than that provided by a bulky TMD. Overall, the reduced installation requirements and the commendable control efficiency of a TIBD highlight its potential as a promising candidate for passive control devices in OWT applications.

A 3D-Printed Bionic Membrane with Autonomously Passive Unidirectional Liquid Transfer Capability for Water Condensation, Collection, and Purification.

Interfacial solar vapor generation is a promising technology for alleviating the current global water crisis, and the evaporation rate and efficiency have approached the theoretical limit. In a practical interfacial evaporation water purification system, the collection rate of purified water is typically lower than the evaporation rate. Passive collection devices based on gravity are susceptible to environmental influences and exhibit low collection efficiency, while active collection devices consuming external energy suffer from complex device systems and extra energy consumption. Given that both collection devices are nonselective and unable to distinguish contaminants mixed in the vapor, bionic membranes with autonomously passive and unidirectional water transfer capacity are developed through 3D printing for efficient water collection. More importantly, the bionic membranes are capable of high-speed water transportation without the need for external energy or gravity drive and liquid-selective transportation for separating oily pollutants from the collected products. The directional transport property facilitates the modular assembly of the bionic membrane, extending its application to practical large-scale solar-driven seawater desalination systems.

Design and Optimization of a Fan-Out Wafer-Level Packaging- Based Integrated Passive Device Structure for FMCW Radar Applications

This paper presents an integrated passive device (IPD) structure based on fan-out wafer-level packaging (FOWLP) for the front end of frequency-modulated continuous wave (FMCW) radar systems, focusing on enhancing the integration efficiency and performance of large passive components like antennas. Additionally, a new metric is introduced to assess this structure’s effect on the average noise figure in FMCW systems. Using this metric as a loss function, we apply the support vector machine (SVM) for electromagnetic simulation and the genetic algorithm (GA) for optimization. The sample fitting variance is 2.42 dB, reducing computation time from 12 min to under 1 millisecond, with the entire optimization completed in less than 100 s. The optimized IPD structure is 0.7 × 0.9 × 0.014 λ03 in size and achieves over 35 dB isolation between the transmitter and receiver. Compared to the IPD model calculated by empirical formulas, the optimized device lowers the average noise figure by 15.2 dB and increases maximum gain by 4.19 dB.

Daily and seasonal use of vocalizations by nesting black‐tailed godwits

Ground‐nesting shorebirds must balance the need for acoustic communication at the nest with the constant threat posed by predators. Although it may seem likely that their calls are adapted to minimize detection by predators, little is known about how these birds communicate at the nest or whether they employ cryptic strategies to avoid predation. Using passive acoustic devices and software to analyse extensive acoustic data, we quantified and categorised the calls of black‐tailed godwits Limosa limosa limosa recorded throughout the whole incubation at eight nests at a dairy farm in the Netherlands in March–June 2021. While incubating, godwits frequently use five main call types, with distinct diurnal patterns and high variation in the number of calls between breeding pairs. Birds used two quiet calls, one for communication at the nest and a second without an easily suggested meaning. Three loud calls were presumably used for predator alert, territory establishment, and long‐range communication. Interestingly, although nests were close to each other and exposed to the same aerial predators, the involvement of incubating birds in predator alert calling consistently differed. Furthermore, we described the relationship between the number of predator alert calls and the probability of a godwit flying off the nest. Our findings show that incubating godwits predominantly use loud vocalizations during the day, with only a few calls at night, which were more frequent on nights with a full moon. These descriptive findings for a single godwit community should now be expanded to other contexts, experimental situations, and shorebird species.

Silicon-based integrated passive device stack for III-V/Si monolithic 3D circuits operating on RF band

In this study, we demonstrated a silicon (Si)-based integrated passive device (IPD) stack to support III-V/Si monolithic 3D (M3D) ICs operating on the radio frequency (RF) band. The IPD stack was fabricated based on an 8-inch CMOS process line and integrated via M3D with an InGaAs HEMT layer. A process condition for a trap rich layer and a buried oxide layer in the IPD was established to simultaneously minimizing both the RF loss and wafer bowing. Through the process condition, the RF loss of the coplanar waveguides was −0.631 dB/mm at 30 GHz, lower than that of the CMOS foundry, and the wafer bowing of the stack was as low as −5.5 μm. The maximum quality factor of the inductors showed good values when compared to those of other CMOS foundry process-based inductors operating on the RF bands reported thus far. To obtain a compressive profile for the IPD stack, which is one of the most important requirements in advancing to wafer-to-wafer-level 3D bonding with the III-V active layer, a process method for the final IMD layer of the IPD was developed, resulting in a change from a tensile profile to a compressive profile for the IPD (corresponding wafer bowing value from −12.6 to + 10.7 μm).

Response control of chimneys using tuned mass damper, multi-tuned mass damper and tuned mass inerter system

Growing industry and shifting environmental regulations have made chimneys taller and more flexible, thus making them susceptible to wind forces. Consequently, it becomes necessary to analyze the chimney for undesired wind force causing vortex induced vibration (VIV) and to enhance their performance by the implementation of appropriate countermeasures. In this study, three passive control devices, namely, tuned mass inerter system (TMIS), tuned mass damper (TMD) and multi-tuned mass damper (MTMD), are used to control the VIV of high-rise chimneys. The TMIS comprises a mass element, spring, damper, and inerter subsystem. The MTMD is distributed over the top one-third height of the chimney. The three control devices control the response of the chimneys under random vortex induced forces, and their relative performances are evaluated. The modal spectral analysis and Genetic Algorithm are employed to establish a method for optimizing the damper-structure system for VIV control. The response analysis duly considers the effect of the nonlinear aero-elastic effect. The novelty of the paper lies in the application of TMIS for chimney subjected to vortex induced vibration and comparing its results with other traditional dampers (TMD and MTMD) for the three chimneys of height 120 m, 210 m, and 360 m of varying diameter, taken as illustrative examples. In addition, the study examines the impact of different mass ratios and the mass of the inerter on chimneys. For the three chimneys considered, it is observed that the performance of the TMD is best among the three control techniques adopted. For the tallest chimney (360 m), all three control devices display an optimum mass ratio for which the response reduction is maximum. The performance of the TMIS improves with the increased height of the chimney.

Expert opinion on candidacy for bone conduction hearing implants Osia System and Baha Connect System.

<b>Introduction:</b> Bone conduction hearing implants (BCHI) are a widely used rehabilitation solution for patients with conductive hearing loss (CHL), mixed hearing loss (MHL), or single-sided deafness (SSD).<b>Aim:</b> This expert review presents candidacy criteria considerations when choosing between active transcutaneous bone-conduction hearing devices (Osia<sup></sup> System) and passive percutaneous bone-conduction hearing devices (Baha<sup></sup> Connect System) to help streamline the decision-making process in those contexts where economics have a major impact on professionals' and patients' choice.<b>Methods:</b> Eight experts participated in two online surveys and two virtual meetings to discuss real-world clinical experience to highlight treatment approaches and factors considered when counseling the patients and selecting an optimal BCHI solution. Key considerations for decision-making were recorded following consensus from all experts.<b>Conclusions:</b> Aspects in decision making include the requirement to use local <i>versus</i> general anesthesia for the implantation procedure, bone thickness, considerations for future magnetic resonance imaging (MRI) procedures, and patient preference. Increased risk of skin infections, requirements for cleaning and managing the implant site, particularly for those with limited dexterity, as well as esthetic concerns could make the Baha<sup></sup> Connect System unsuitable for some patients. In these cases, the Osia<sup></sup> System may provide clear advantages, particularly in patients for whom good hearing performance is a priority, and this would need to be discussed individually with the patient in a multidisciplinary setting. Conversely, for patients requiring minimally invasive surgery, who have contraindications for general anesthesia or require frequent head MRI scans in the future, the Baha Connect System may be more suitable.

A systematic review of hybrid passive energy dissipating devices

Once earthquakes occur, they release a considerable amount of elastic strain energy, which is measured by Peak Ground Acceleration (PGA). To reduce the impact of this energy, buildings can be fitted with dampers. These include passive energy dissipation devices, which are effective in mitigating the effects of both high and low PGA. Hybrid dampers, which combine multiple devices, enhance strengths and minimize weaknesses, significantly improving a building’s seismic resilience by reducing roof displacement, drift, inter-story, floor acceleration, and base shear. These dampers are the focus of extensive research, emphasizing their role in seismic performance enhancement. Despite numerous studies, their application in concrete structures remains underexplored, presenting a vast scope for advancement in the design, development, and implementation of hybrid damping devices. These devices are particularly valued for their superior vibration control capabilities, offering a promising avenue for bolstering structural stability.

Experimental characterisation and visualisation of a novel two-phase flexible heat transfer device

The importance of passive Flexible Heat Transfer Device (FHTD) in electronic cooling or space applications lies in their ability to provide efficient, reliable, and adaptable thermal management solutions. Heat transfer enhancement studies pertaining to FHTD developed to meet the thermal management demands of futuristic flexible electronic devices are presented in the current work. The possibility of extending the heat transport limit of FHTD beyond 24 W by limiting the maximum operating temperature to 60 °C is discussed. The superior performance of FHTD at varying heat loads from 5 W to 40 W at 45°and 90°bending angles is brought out compared with existing heat transfer devices like Flexible Heat Pipe (FHP) and copper thermal straps. The performance is reported in thermal resistance and equivalent thermal conductivity. A commercial dielectric liquid is used as a working fluid in FHTD to enhance the heat transfer limit employing phase change. The evaporator and condenser sections of the flexible section are made transparent to visualise the boiling and condensation phenomenon. Under steady-state operation at a 45°bending angle, The FHTD demonstrates a minimum thermal resistance of 0.73 K/W and a peak effective thermal conductivity of 8172 W/m K. The heat transfer coefficient ranges from 200 to 700 W/m2 K, consistent with values reported for heat pipes in the literature. Additionally, the study explores the impact of modifying the external surface texture to create more nucleation sites, thereby enhancing the performance of the FHTD. The results show that the laser-textured surface on the heat pipe condenser effectively reduces the onset of nucleate boiling for dielectric fluid by 3.5 °C and decreases the maximum temperature of the evaporator by 4.5 °C. The present work dictates the fundamental baseline for possible design choices of futuristic passive flexible heat transfer devices.

Design and Analyses of Passive Continuous Distraction Osteogenesis Device for Oral and Maxillofacial Reconstruction

Design and Analyses of Passive Continuous Distraction Osteogenesis Device for Oral and Maxillofacial Reconstruction

Pilot Randomized Clinical Trial of a Passive Non-invasive Positive End-Expiratory Pressure (PEEP) Device for Delivering Positive Pressure Therapy Compared to Standard Care in Non-critically Ill Patients With COVID-19.

During the COVID-19 pandemic, there were reports of a shortage of ventilators and oxygen supply, particularly in resource-limited settings. We report the preliminary evaluation of a non-invasive positive end-expiratory pressure (PEEP) mask in hospitalized non-critically ill patients with COVID-19. We randomly assigned hospitalized adult patients with confirmed COVID-19 infection and requiring greater than 40% supplemental oxygen to either standard care oxygen delivery (control) or via Materialise passive non-invasive PEEP device mask (intervention; Belgium). The primary outcome was a change in mean respiratory rate from baseline over the first three hours after the commencement of the intervention. Secondary outcomes included dyspnea score, need for escalation of respiratory or cardiovascular support, days alive and free of ICU, and day-28 mortality. Between April 30, 2021, and October 10, 2021, we enrolled 132 (65 control, 67 intervention) patients in the study. The mean respiratory rates at baseline were 23 ± 3 and 23 ± 3 in the control and intervention groups, with no significant differences at three hours (23 ± 2.3 vs. 23 ± 2.1, p=0.14). The control group had a higher mean dyspnea score compared to the intervention group (day 5: 5.4 ± 1.6 vs. 4.7 ± 1.4, p=0.015; day 6: 4.7 ± 1.7 vs. 4.0 ± 0.7, p=0.008). A higher proportion of patients in the control group required escalation of respiratory support (38%), as compared to intervention (12%) (p=0.0004). The two groups had no significant differences across other secondary outcomes or with respect to adverse events (barotrauma, aspiration pneumonia, need for vasopressor support). The use of the novel mask compared to standard care in hospitalized non-critically ill patients with COVID-19 was not associated with reductions in the respiratory rate but was associated with a reduction in the need for escalation of respiratory support without an increase in adverse effects. Large-scale clinical trials of this device are warranted.

Piloting a Novel Computational Framework for Identifying Prosthesis-Specific Contributions to Gait Deviations.

This paper introduces a novel computational framework for evaluating above-knee prostheses, addressing a major challenge in gait deviation studies: distinguishing between prosthesis-specific and patient-specific contributions to gait deviations. This innovative approach utilizes three separate computational models to quantify the changes in gait dynamics necessary to achieve a set of ideal gait kinematics across different prosthesis designs. The pilot study presented here employs a simple two-dimensional swing-phase model to conceptually demonstrate how the outcomes of this three-model framework can assess the extent to which prosthesis design impacts a user's ability to replicate the dynamics of able-bodied gait. Furthermore, this framework offers potential for optimizing passive prosthetic devices for individual patients, thereby reducing the need for real-life experiments, clinic visits, and overcoming rehabilitation challenges.

Monolithic integration of waveguide amplifiers and passive polymer photonic devices using photolithography

The monolithic integration of rare-earth-doped waveguide amplifiers with passive photonic devices has long been a subject of extensive research. Herein, we propose a method for active-passive monolithic integration based on polymer photonic integrated devices. The monolithic integration of passive devices with active waveguide amplifiers is achieved by spin-coating an active layer atop a passive polymer waveguide and subjecting specific regions of the active layer to selective photolithography. To validate the proposed monolithic integration scheme's impact on the performance of passive devices, performance tests were conducted on both passive and active-passive integrated 8-channel arrayed waveguide grating (AWG) devices. The crosstalk (CT) of the AWG devices before and after adding the active layer ranged from −12.04 dB to −14.72 dB and from −10.02 dB to −14.88 dB, respectively, with channel spacings of 9.29 nm and 8.80 nm, indicating consistent performance of the passive devices with the addition of the active layer. In a 0.5 cm-long active waveguide, internal net gain was achieved across all eight channels of the AWG, with a gain bandwidth ranging from 1518 nm to 1580 nm. Notably, an internal net gain of 9.5 dB was attained at 1527 nm. The successful integration of rare-earth-doped waveguide amplifiers with passive components on a monolithic chip has been achieved for the first time, requiring only two straightforward photolithography steps. This milestone not only preserves the inherent functionality of passive components but also enables effective signal amplification. This technological innovation holds the promise of fully harnessing the potential of rare-earth-doped waveguide amplifiers in the realm of photonic integrated circuits, thereby catalyzing significant breakthroughs and advancements in the field of optoelectronics.

Intelligent-Reflecting-Surface-Assisted Single-Input Single-Output Secure Transmission: A Joint Multiplicative Perturbation and Constructive Reflection Perspective.

Due to the inherent broadcasting nature and openness of wireless transmission channels, wireless communication systems are vulnerable to the eavesdropping of malicious attackers and usually encounter undesirable situations of information leakage. The problem may be more serious when a passive eavesdropping device is directly connected to the transmitter of a single-input single-output (SISO) system. To deal with this urgent situation, a novel IRS-assisted physical-layer secure transmission scheme based on joint transmitter perturbation and IRS reflection (JPR) is proposed, such that the secrecy of wireless SISO systems can be comprehensively guaranteed regardless of whether the reflection-based jamming from the IRS to the eavesdropper is blocked or not. Moreover, to develop a trade-off between the achievable performance and implementation complexity, we propose both element-wise and group-wise reflected perturbation alignment (ERPA/GRPA)-based IRS reflection strategies, respectively. In order to evaluate the achievable performance, we analyze the ergodic secrecy rate (ESR) and secrecy outage probability (SOP) of the SISO secure systems with the ERPA/GRPA-based JPRs, respectively. Finally, by characterizing the simulated and numerical ESR and SOP performance results, our proposed scheme is compared with the benchmark scheme of random phase-based reflection, which strongly demonstrates the effectiveness of our proposed scheme.

Nonlinear electronic devices on single-layer CVD graphene for thermistors

In this article, we present simple, cost-effective, passive (non-gated) electronic devices based on single-layer (SL) chemical vapor deposited (CVD) graphene that show nonlinear and asymmetric current-voltage characteristics (CVCs) at ambient temperatures. Al2O3-Ti-Au contacts to graphene results in a nonlinear resistance to achieve nonlinearity in the CVC. Upon transfer to polyethylene terephthalate, the CVD-grown SL graphene shows mobility of 6200 cm2V-1S-1. We have observed both thermoelectric effect and thermoresistive sensing in the fabricated devices such as voltage and temperature concerning change in electronic power and resistance through asymmetric and nonlinear CVC. The device is stable both at low and high voltages (±200 mV to ±4 V) and temperatures (4 K - 300 K). Graphene-based thermosensing devices can be ultra-thin, cost-effective, non-toxic/organic, flexible, and high-speed for integration into future complementary metal-oxide semiconductor (CMOS) interface, and wearable self-power electronics. A strong negative temeperature coefficent of resistance is demonstrated in the realized nonlinear graphene-integrated resistors for its application in NTC thermistors.

Transient behavior of the DYNASWIRL® phase separator during cryogenics tank-to-tank transfer operations

In order to separate gas and liquid from a two-phase mixture in space or earth applications, one can generate a strong artificial acceleration field instead of relying on gravity. This can be achieved by generating a swirl flow in a separator. The DYNASWIRL® phase separator is such a passive device, which had been demonstrated in air/water mixtures in the laboratory and on five reduced gravity NASA parabolic flights. In this work, extensive laboratory testing and numerical simulations are conducted to demonstrate the validity of the DYNASWIRL for phase separation with cryogenics. Liquid nitrogen (LN2) is used for extensive testing involving unsteady tank-to-tank transfer with quenching of separator and piping, liquid boil-off and vaporization, phase separation and recovery. This paper describes the separator and testing setups used. It examines the effects of the liquid (water and LN2), geometric parameters, and their effects on the separation and on the pressure loss across the separator, and analyzes the flow dynamics of the gas removal process. Validated numerical simulations support the experimental results and help explain the effects of the design parameters on the results.

The effect of temperature difference on the acoustic performance of Helmholtz resonator

Passive control devices such as liners and Helmholtz resonators (HRs) are commonly employed in practical applications to mitigate thermoacoustic instabilities. To safeguard the HR from being corroded by the invasion of hot flow from the combustor, a cooling flow with significantly lower temperature than that in the combustor is injected from the rear of the HR cavity. However, this results in a dynamic mixing of cold bias and hot grazing flows in the combustor, which may generate an entropy wave downstream of the HR, thereby affecting its sound absorption performance. Unfortunately, these effects are often neglected when modelling such systems. In this context, an acoustic model is derived for a one-dimensional combustor duct with distinct temperature compared to that of the attached HR. The model offers physical insights into the underlying mechanisms of the impact of HR on the acoustic fields. It considers not only the mean temperature difference between the cooling bias flow and the main flow in the combustor, but also the mean temperature difference between the up- and downstream sides of the combustor across the HR. The effect of both temperature differences on the HR’s performance will be discussed.

Unveiling full-dimensional distribution of trap states toward highly efficient perovskite photovoltaics

To gain a deep understanding and address key issues in perovskite photovoltaics, such as power conversion efficiency (PCE) and long-term stability, defect passivation and analysis of the device performance are required. Here, we proposed a non-contact characterization technique named scanning photocurrent measurement system (SPMS) for device surface detection, having conducted signal analysis and method adjustments based on perovskite photovoltaic devices. This technique enables the monitoring of minority carriers in the device, allowing for the investigation of carrier behavior based on photocurrent signals. By integrating SPMS with thermal conductance spectroscopy (TAS) and drive-level capacitance profiling (DLCP), we further simulated a spatial three-dimensional (3D) distribution of trap states in the device and analyzed the distribution of trap states matched with energy space. Through extensive case studies, we have validated the universality and accuracy of this method. The integration of trap state characterization techniques provides strong support for targeted defect passivation and performance evaluation of perovskite photovoltaic devices, yielding a highly efficient perovskite solar cell with PCE as high as 25.74%.