3D-Printed Liquid Cell Resonator with Piezoelectric Actuation for In-Line Density-Viscosity Measurements.

The in-line monitoring of liquid properties, such as density and viscosity, is a key process in many industrial areas such as agro-food, automotive or biotechnology, requiring real-time automation, low-cost and miniaturization, while maintaining a level of accuracy and resolution comparable to benchtop instruments. In this paper, 3D-printed cuboid-shaped liquid cells featuring a rectangular vibrating plate in one of the sides, actuated by PZT piezoelectric layers, were designed, fabricated and tested. The device was resonantly excited in the 3rd-order roof tile-shaped vibration mode of the plate and validated as a density-viscosity sensor. Furthermore, conditioning circuits were designed to adapt the impedance of the resonator and to cancel parasitic effects. This allowed us to implement a phase-locked loop-based oscillator circuit whose oscillation frequency and voltage amplitude could be calibrated against density and viscosity of the liquid flowing through the cell. To demonstrate the performance, the sensor was calibrated with a set of artificial model solutions of grape must, representing stages of a wine fermentation process. Our results demonstrate the high potential of the low-cost sensor to detect the decrease in sugar and the increase in ethanol concentrations during a grape must fermentation, with a resolution of 10 µg/mL and 3 µPa·s as upper limits for the density and viscosity, respectively.

Troubleshooting Complex Vascular Cases in the Kidney Transplant Recipient: Vascular Anomalies, Challenging Vessel Diseases, and Procedural Disasters.

PURPOSE OF REVIEW: To update the most relevant literature regarding complex cases during kidney transplant setting that recipient presents by himself, especially during implantation surgery due to vascular diseases and/or urinary tract anomalies. RECENT FINDINGS: Increasing age of donors and recipients is leading to an increased complexity of kidney transplant implantation surgery. In addition, the high peripheral vascular disease prevalence worldwide increases difficulty of surgery and decreases long-term outcomes as well. Moreover, it also increases transplant morbidity and mortality, both overall and cardiovascular, and finally clearly decreases graft survival. However, dialysis alternative has even worse outcomes in terms of mortality, with a proportional risk of death 2.66 higher compared with transplanted patients. Aorto-iliac prosthesis and 3rd and 4th transplants in occupied iliac fossae do also represent a challenging situation with a clearly increased morbidity and mortality. In some of those particular conditions, orthotopic kidney transplant technique is an alternative with good functional and survival outcomes, but not exempt of complications. Kidney transplant in vascular complex recipients has worse outcomes compared with conventional non-risky population. It remains a challenging surgical and medical procedure with higher morbidity and mortality, and decreased graft survival. However, dialysis mortality is still even greater and a transplant attempt might be justified. Orthotopic kidney transplant technique might play a role in selected patients with aorto-iliac unworkable segments or even in patients with special urinary tract conditions.

Troubleshooting Complex Vascular Cases in the Kidney Graft: Multiple Vessels, Aneurysms, and Injuries During Harvesting Procedures.

PURPOSE OF THE REVIEW: To update the most relevant literature regarding complex vascular cases in kidney transplant setting involving the graft, especially during the harvesting procedure and back-table preparation from the subsequent implant. RECENT FINDINGS: Challenging situations affecting the kidney graft such as multiple vessels, renal artery aneurysms, kidney anatomical anomalies, or major injuries do not contraindicate the transplant, but require an exhaustive graft viability assessment and several bench surgery techniques. Graft vessel conditioning in the back-table might include simple anastomosis between them, enlarging with venous patch or reconstruction with donor or synthetic grafts. Compared with conventional transplant, literature reports longer warm ischemia time (40 vs 32 min) and slightly increased rates of delayed graft function (10.3% vs 8.2%) and vascular complications (10.8% vs 8.1%), but similar graft and patient survival. Kidney graft vascular complex cases require exhaustive assessment, meticulous harvesting, good surgical technique in the bench table, and proper surgery in the recipient. Despite its complexity, vascular complex kidney transplant offers comparable outcomes in the long term to conventional population when technically well performed, with slightly increased rates of vascular complications and delayed graft function.

A Geometrical Study on the Roof Tile-Shaped Modes in AlN-Based Piezoelectric Microcantilevers as Viscosity⁻Density Sensors.

Cantilever resonators based on the roof tile-shaped modes have recently demonstrated their suitability for liquid media monitoring applications. The early studies have shown that certain combinations of dimensions and order of the mode can maximize the Q-factor, what might suggest a competition between two mechanisms of losses with different geometrical dependence. To provide more insight, a comprehensive study of the Q-factor and the resonant frequency of these modes in microcantilever resonators with lengths and widths between 250 and 3000 µm and thicknesses between 10 and 60 µm is presented. These modes can be efficiently excited by a thin piezoelectric AlN film and a properly designed top electrode layout. The electrical and optical characterization of the resonators are performed in liquid media and then their performance is evaluated in terms of quality factor and resonant frequency. A quality factor as high as 140 was measured in isopropanol for a 1000 × 900 × 10 µm³ cantilever oscillating in the 11th order roof tile-shaped mode at 4 MHz; density and viscosity resolutions of 10-6 g/mL and 10-4 mPa·s, respectively are estimated for a geometrically optimized cantilever resonating below 1 MHz.

Morbidity and mortality of emergency surgery in octogenarian patient.

OBJECTIVE: To evaluate the health outcomes (postoperative morbidity and mortality) and the functional status at discharge of elderly patients older than 80 years who underwent emergency surgery. METHOD: Patients > 80 years of age who underwent emergency surgery during one year at the Marqués de Valdecilla University Hospital, Santander, Spain. Preoperative data (age, sex, type of surgery, comorbidity) and postoperative data (complications) were evaluated, as well as in-hospital mortality, at 30 days and 6 months after surgery. RESULTS: Five-hundred-sixty-eight patients underwent emergency surgery between 2018 and 2019. After the review, 407 patients were included in the study. Average age: 86.9 years. Women 61.7%. Mean hospital stay: 10.4 days. Traumatic interventions 41.3%, vascular surgery 19.7%, general-digestive surgery 25.3%. Medium ASA risk: 2.88. Functional status at discharge: 3.15. Postoperative complications: Clavien-Dindo I 40.8%, II 40.3%, IIIA 3.4%, IIIB 2.5%, IVA 3.9%, IVB 2.0% and V 7.1%. Hospital mortality 7.1%, 30-day mortality 10.3%, mortality at 6 months 24.6%. CONCLUSIONS: Patients > 80 years of age undergoing urgent surgery have high preoperative comorbidity, postoperative complications, and high mortality at 30 days and 6 months after surgery. This mortality is more significant in those ASA IV, nonagenarians and those undergoing high-risk surgery.

OBJETIVO: Evaluar los resultados en salud (morbilidad y mortalidad posoperatorias) y el estado funcional al alta de los pacientes mayores de 80 años sometidos a cirugía de urgencia. MÉTODO: Pacientes de edad > 80 años sometidos a cirugía de urgencia durante 1 año en el Hospital Universitario Marqués de Valdecilla, Santander, España. Se evaluaron datos preoperatorios (edad, sexo, tipo de cirugía, comorbilidad) y posoperatorios (complicaciones), así como mortalidad hospitalaria, a los 30 días y a los 6 meses de la cirugía. RESULTADOS: En 2018-2019 fueron operados de urgencia 568 pacientes, de los cuales 407 fueron incluidos en el estudio. Edad media: 86.9 años. El 61.7% fueron mujeres. Estancia media hospitalaria: 10.4 días. El 41.3% fueron intervenciones traumatológicas, el 19.7% cirugía vascular, el 25.3% cirugía general-digestiva. Riesgo ASA medio: 2.88. Estado funcional al alta: 3.15. Complicaciones posoperatorias: Clavien-Dindo I 40.8%, II 40.3%, IIIA 3.4%, IIIB 2.5%, IVA 3.9%, IVB 2.0% y V 7.1%. Mortalidad: hospitalaria 7.1%, a los 30 días 10.3% y a los 6 meses 24.6%. CONCLUSIONES: Los pacientes > 80 años sometidos a cirugía urgente presentan elevada comorbilidad preoperatoria, complicaciones posoperatorias y elevada mortalidad a 30 días y 6 meses de la cirugía. Esta mortalidad es más significativa en los ASA IV, nonagenarios y sometidos a cirugía de alto riesgo.

Design and Characterization of a Planar Micro-Conveyor Device Based on Cooperative Legged Piezoelectric MEMS Resonators.

This paper reports the design, fabrication, and performance of a hybrid piezoelectric planar micro-conveyor based on Micro-Electromechanical Systems (MEMS) bridge resonators and featuring 3D-printed vertical legs. The device includes two cooperating silicon plate resonators with an area of 5 × 1 mm2, actuated by an integrated aluminum-nitride (AlN) piezoelectric thin film. An optimally designed array of 3D-printed projection legs was attached to the plates, to convert the standing-wave (SW) vertical vibrations into horizontal rotations or translations of the supported slider. An open-loop control strategy based on burst-type driving signals, with different numbers of sinusoidal cycles applied on each of the resonators, allowed the cooperation of the two bridges to set up prescribed trajectories of small flat objects, up to 100 mg, with positional accuracy below 100 nm and speeds up to 20 mm/s, by differential drive actuation. The effect of the leg tip and sliders' surface finish on the conveyor performance was investigated, suggesting that further optimizations may be possible by modifying the tribological properties. Finally, the application of the micro-conveyor as a reconfigurable electronic system, driven by a preprogrammed sequence of signals, was demonstrated by delivering some surface-mount technology (SMD) parts lying on a 65 mg glass slider.

Biodiversity and ecosystem services mapping: Can it reconcile urban and protected area planning?

Land-use changes, especially urbanization, have largely impacted the capacity of ecosystems to deliver ecosystem services (ES) on which human wellbeing depends. The current sectorial landscape and territorial planning approaches that separately address protected areas and urban areas have proven ineffective in conserving biodiversity. To address this important challenge, integrated territorial planning has been claimed to be able to better reconcile interests between nature conservation and urban planning, and ES supply and demand mapping may be a useful tool for such purposes. In this study, we quantitatively mapped biodiversity and the supply and demand of eight ES along an urban-rural gradient in the region of Madrid (Spain). Then, we clustered the municipalities in this gradient into four groups based on their common biodiversity and ES supply and demand characteristics. Additionally, we reviewed the urban plans from these municipalities and the management plans of three protected areas, analysed the references to ES in the plans, and searched for potential conflicts between urban and protected area planning aims. We found that municipalities with highly coupled ES supply and demand are in high altitude areas, coinciding with protected areas, while in urban areas, the ES demand exceeds the supply. Municipalities exhibiting a high demand for regulating ES usually include them in their plans, while municipalities with a high supply of regulating ES do not. Given the several conflicts between protected areas and urban planning that we detected, we discuss the utility of mapping biodiversity and ES supply and demand beyond administrative boundaries to overcome the challenge of integrating spatial planning approaches, especially in the context of urban-rural gradients and megacities. We also explore the utility of these methods for coordinating urban planning tools to achieve integrated territorial planning.

Miniature Autonomous Robot Based on Legged In-Plane Piezoelectric Resonators with Onboard Power and Control.

This work reports the design, fabrication, and characterization of a centimetre-scale autonomous robot with locomotion based on in-plane piezoelectric resonators and 3D-printed inclined legs. The robot consists of a pair of cooperative piezoelectric motors, an electronic power circuit and a battery-powered microcontroller. The piezoelectric motors feature a lead zirconate titanate (PZT) plate of dimensions 20 mm × 3 mm × 0.2 mm vibrating on its first extensional resonant mode at around 70 kHz. A particular position of 3D-printed inclined legs allowed the conversion of the in-plane movement into an effective forward thrust. To enable arbitrary trajectories of the robot on a surface, two parallel piezoelectric plate motors were arranged in a differential drive scheme. The signals to excite these plates were generated by the microcontroller and adapted by a supplementary electronic circuit to increase the effective voltage supplied by the onboard battery. The fully assembled robot had a size of 27 mm × 15 mm and a weight of 7 g and reached a linear speed of approximately 15 mm/s and a rotational speed of up to 50 deg./s. Finally, the autonomous robot demonstrated the ability to follow pre-programmed paths.

Comparative Study of Traveling and Standing Wave-Based Locomotion of Legged Bidirectional Miniature Piezoelectric Robots.

The use of wave-based locomotion mechanisms is already well established in the field of robotics, using either standing waves (SW) or traveling waves (TW). The motivation of this work was to compare both the SW- and the TW-based motion of a 20-mm long sub-gram glass plate, with attached 3D printed legs, and piezoelectric patches for the actuation. The fabrication of the robot did not require sophisticated techniques and the speed of motion was measured under different loading conditions. In the case of the TW mechanism, the influence of using different pairs of modes to generate the TW on the locomotion speed has been studied, as well as the effect of the coupling of the TW motion and the first flexural vibration mode of the legs. This analysis resulted in a maximum unloaded speed of 6 bodylengths/s (BL/s) at 65 V peak-to-peak (Vpp). The SW approach also examined different modes of vibration and a speed of locomotion as high as 14 BL/s was achieved, requiring, unlike the TW case, a highly precise location of the legs on the glass supporting platform and a precise tuning of the excitation frequency.

Motion of a Legged Bidirectional Miniature Piezoelectric Robot Based on Traveling Wave Generation.

This article reports on the locomotion performance of a miniature robot that features 3D-printed rigid legs driven by linear traveling waves (TWs). The robot structure was a millimeter-sized rectangular glass plate with two piezoelectric patches attached, which allowed for traveling wave generation at a frequency between the resonant frequencies of two contiguous flexural modes. As a first goal, the location and size of the piezoelectric patches were calculated to maximize the structural displacement while preserving a standing wave ratio close to 1 (cancellation of wave reflections from the boundaries). The design guidelines were supported by an analytical 1D model of the structure and could be related to the second derivative of the modal shapes without the need to rely on more complex numerical simulations. Additionally, legs were bonded to the glass plate to facilitate the locomotion of the structure; these were fabricated using 3D stereolithography printing, with a range of lengths from 0.5 mm to 1.5 mm. The optimal location of the legs was deduced from the profile of the traveling wave envelope. As a result of integrating both the optimal patch length and the legs, the speed of the robot reached as high as 100 mm/s, equivalent to 5 body lengths per second (BL/s), at a voltage of 65 Vpp and a frequency of 168 kHz. The blocking force was also measured and results showed the expected increase with the mass loading. Furthermore, the robot could carry a load that was 40 times its weight, opening the potential for an autonomous version with power and circuits on board for communication, control, sensing, or other applications.

Bidirectional Linear Motion by Travelling Waves on Legged Piezoelectric Microfabricated Plates.

This paper reports the design, fabrication and performance of MEMS-based piezoelectric bidirectional conveyors featuring 3D printed legs, driven by linear travelling waves (TW). The structures consisted of an aluminium-nitride (AlN) piezoelectric film on top of millimetre-sized rectangular thin silicon bridges and two electrode patches. The position and size of the patches were analytically optimised for TW generation in three frequency ranges: 19, 112 and 420 kHz, by the proper combination of two contiguous flexural modes. After fabrication, the generated TW were characterized by means of Laser-Doppler vibrometry to obtain the relevant tables of merit, such as the standing wave ratio and the average amplitude. The experimental results agreed with the simulation, showing the generation of a TW with an amplitude as high as 6 nm/V and a standing wave ratio as low as 1.46 for a device working at 19.3 kHz. The applicability of the fabricated linear actuator device as a conveyor was investigated. Its kinetic performance was studied with sliders of different mass, being able to carry a 35 mg silicon slider, 18 times its weight, with 6 V of continuous sinusoidal excitation and a speed of 0.65 mm/s. A lighter slider, weighting only 3 mg, reached a mean speed of 1.7 mm/s at 6 V. In addition, by applying a burst sinusoidal excitation comprising 10 cycles, the TW generated in the bridge surface was able to move a 23 mg slider in discrete steps of 70 nm, in both directions, which is a promising result for a TW piezoelectric actuator of this size.

Piezoelectric MEMS Resonators for Cigarette Particle Detection.

In this work, we demonstrate the potential of a piezoelectric resonator for developing a low-cost sensor system to detect microscopic particles in real-time, which can be present in a wide variety of environments and workplaces. The sensor working principle is based on the resonance frequency shift caused by particles collected on the resonator surface. To test the sensor sensitivity obtained from mass-loading effects, an Aluminum Nitride-based piezoelectric resonator was exposed to cigarette particles in a sealed chamber. In order to determine the resonance parameters of interest, an interface circuit was implemented and included within both open-loop and closed-loop schemes for comparison. The system was capable of tracking the resonance frequency with a mass sensitivity of 8.8 Hz/ng. Although the tests shown here were proven by collecting particles from a cigarette, the results obtained in this application may have interest and can be extended towards other applications, such as monitoring of nanoparticles in a workplace environment.

Generation of Linear Traveling Waves in Piezoelectric Plates in Air and Liquid.

A micro- to milli-sized linear traveling wave (TW) actuator fabricated with microelectromechanical systems (MEMS) technology is demonstrated. The device is a silicon cantilever actuated by piezoelectric aluminum nitride. Specifically designed top electrodes allow the generation of TWs at different frequencies, in air and liquid, by combining two neighboring resonant modes. This approach was supported by analytical calculations, and different TWs were measured on the same plate by laser Doppler vibrometry. Numerical simulations were also carried out and compared with the measurements in air, validating the wave features. A standing wave ratio as low as 1.45 was achieved in air, with a phase velocity of 652 m/s and a peak horizontal velocity on the device surface of 124 µm/s for a driving signal of 1 V at 921.9 kHz. The results show the potential of this kind of actuator for locomotion applications in contact with surfaces or under immersion in liquid.

Potential of Piezoelectric MEMS Resonators for Grape Must Fermentation Monitoring.

In this study grape must fermentation is monitored using a self-actuating/self-sensing piezoelectric micro-electromechanical system (MEMS) resonator. The sensor element is excited in an advanced roof tile-shaped vibration mode, which ensures high Q-factors in liquids (i.e., Q ~100 in isopropanol), precise resonance frequency analysis, and a fast measurement procedure. Two sets of artificial model solutions are prepared, representing an ordinary and a stuck/sluggish wine fermentation process. The precision and reusability of the sensor are shown using repetitive measurements (10 times), resulting in standard deviations of the measured resonance frequencies of ~0.1%, Q-factor of ~11%, and an electrical conductance peak height of ~12%, respectively. With the applied evaluation procedure, moderate standard deviations of ~1.1% with respect to density values are achieved. Based on these results, the presented sensor concept is capable to distinguish between ordinary and stuck wine fermentation, where the evolution of the wine density associated with the decrease in sugar and the increase in ethanol concentrations during fermentation processes causes a steady increase in the resonance frequency for an ordinary fermentation. Finally, the first test measurements in real grape must are presented, showing a similar trend in the resonance frequency compared to the results of an artificial solutions, thus proving that the presented sensor concept is a reliable and reusable platform for grape must fermentation monitoring.