Design and Fabrication of a Flexible Gravimetric Sensor Based on a Thin-Film Bulk Acoustic Wave Resonator.

Sensing systems are becoming less and less invasive. In this context, flexible materials offer new opportunities that are impossible to achieve with bulky and rigid chips. Standard silicon sensors cannot be adapted to curved shapes and are susceptible to big deformations, thus discouraging their use in wearable applications. Another step forward toward minimising the impacts of the sensors can be to avoid the use of cables and connectors by exploiting wireless transmissions at ultra-high frequencies (UHFs). Thin-film bulk acoustic wave resonators (FBARs) represent the most promising choice among all of the piezoelectric microelectromechanical system (MEMS) resonators for the climbing of radio frequencies. Accordingly, the fabrication of FBARs on flexible and wearable substrates represents a strategic step toward obtaining a new generation of highly sensitive wireless sensors. In this work, we propose the design and fabrication of a flexible gravimetric sensor based on an FBAR on a polymeric substrate. The resonator presents one of the highest electromechanical coupling factors in the category of flexible AlN-based FBARs, equal to 6%. Moreover, thanks to the polymeric support layer, the presence of membranes can be avoided, which leads to a faster and cheaper fabrication process and higher robustness of the structure. The mass sensitivity of the device was evaluated, obtaining a promising value of 23.31 ppm/pg. We strongly believe that these results can pave the way to a new class of wearable MEMS sensors that exploit ultra-high-frequency (UHF) transmissions.

Evaluation of the Impact of Cognitive Training on Quality of Life in Patients with Multiple Sclerosis.

OBJECTIVE: The aim of this study was to evaluate the effectiveness of cognitive rehabilitation in a group of multiple sclerosis (MS) patients. METHODS: Thirty-four patients were included in this study and randomly allocated either to treatment with multidisciplinary rehabilitation plus cognitive training or to treatment with multidisciplinary rehabilitation alone. RESULTS: After 3 months of cognitive treatment, the patients assigned to the rehabilitation plus cognitive training group displayed an improvement in the cognitive test of executive function and a marked improvement in quality of life (QoL). The patients treated with multidisciplinary rehabilitation without cognitive training improved in the physical composite score alone. Both groups of patients displayed an improvement in depression, though the improvement was confirmed at the 6-month follow-up examination (p = 0.036) only in patients treated with multidisciplinary rehabilitation plus cognitive training. CONCLUSIONS: Our results indicate that the multidisciplinary rehabilitation treatment is the best approach to treat MS. The specific effect of each treatment needs to be assessed to be able to determine its role within a multidisciplinary approach. Cognitive rehabilitation is an important aspect of this multidisciplinary approach insofar as it may improve the QoL of MS people.

Nitride-Based Materials for Flexible MEMS Tactile and Flow Sensors in Robotics.

The response to different force load ranges and actuation at low energies is of considerable interest for applications of compliant and flexible devices undergoing large deformations. We present a review of technological platforms based on nitride materials (aluminum nitride and silicon nitride) for the microfabrication of a class of flexible micro-electro-mechanical systems. The approach exploits the material stress differences among the constituent layers of nitride-based (AlN/Mo, Si x N y /Si and AlN/polyimide) mechanical elements in order to create microstructures, such as upwardly-bent cantilever beams and bowed circular membranes. Piezoresistive properties of nichrome strain gauges and direct piezoelectric properties of aluminum nitride can be exploited for mechanical strain/stress detection. Applications in flow and tactile sensing for robotics are described.

Enhancing cardiovascular health monitoring: Simultaneous multi-artery cardiac markers recording with flexible and bio-compatible AlN piezoelectric sensors.

Continuous monitoring of cardiovascular parameters like pulse wave velocity (PWV), blood pressure wave (BPW), stiffness index (SI), reflection index (RI), mean arterial pressure (MAP), and cardio-ankle vascular index (CAVI) has significant clinical importance for the early diagnosis of cardiovascular diseases (CVDs). Standard approaches, including echocardiography, impedance cardiography, or hemodynamic monitoring, are hindered by expensive and bulky apparatus and accessibility only in specialized facilities. Moreover, noninvasive techniques like sphygmomanometry, electrocardiography, and arterial tonometry often lack accuracy due to external electrical interferences, artifacts produced by unreliable electrode contacts, misreading from placement errors, or failure in detecting transient issues and trends. Here, we report a bio-compatible, flexible, noninvasive, low-cost piezoelectric sensor for continuous and real-time cardiovascular monitoring. The sensor, utilizing a thin aluminum nitride film on a flexible Kapton substrate, is used to extract heart rate, blood pressure waves, pulse wave velocities, and cardio-ankle vascular index from four arterial pulse sites: carotid, brachial, radial, and posterior tibial arteries. This simultaneous recording, for the first time in the same experiment, allows to provide a comprehensive cardiovascular patient's health profile. In a test with a 28-year-old male subject, the sensor yielded the SI = 7.1 ± 0.2 m/s, RI = 54.4 ± 0.5 %, MAP = 86.2 ± 1.5 mmHg, CAVI = 7.8 ± 0.2, and seven PWVs from the combination of the four different arterial positions, in good agreement with the typical values reported in the literature. These findings make the proposed technology a powerful tool to facilitate personalized medical diagnosis in preventing CVDs.

Wearable Heart Rate Monitoring Device Communicating in 5G ISM Band for IoHT.

Advances in wearable device technology pave the way for wireless health monitoring for medical and non-medical applications. In this work, we present a wearable heart rate monitoring platform communicating in the sub-6GHz 5G ISM band. The proposed device is composed of an Aluminium Nitride (AlN) piezoelectric sensor, a patch antenna, and a custom printed circuit board (PCB) for data acquisition and transmission. The experimental results show that the presented system can acquire heart rate together with diastolic and systolic duration, which are related to heart relaxation and contraction, respectively, from the posterior tibial artery. The overall system dimension is 20 mm by 40 mm, and the total weight is 20 g, making this device suitable for daily utilization. Furthermore, the system allows the simultaneous monitoring of multiple subjects, or a single patient from multiple body locations by using only one reader. The promising results demonstrate that the proposed system is applicable to the Internet of Healthcare Things (IoHT), and particularly Integrated Clinical Environment (ICE) applications.

Flexible SAW Microfluidic Devices as Wearable pH Sensors Based on ZnO Nanoparticles.

In this work, a new flexible and biocompatible microfluidic pH sensor based on surface acoustic waves (SAWs) is presented. The device consists of polyethylene naphthalate (PEN) as a flexible substrate on which aluminum nitride (AlN) has been deposited as a piezoelectric material. The fabrication of suitable interdigitated transducers (IDTs) generates Lamb waves (L-SAW) with a center frequency ≈500 MHz traveling in the active region. A SU-8 microfluidics employing ZnO nanoparticles (NPs) functionalization as a pH-sensitive layer is fabricated between the IDTs, causing a shift in the L-SAW resonance frequency as a function of the change in pH values. The obtained sensitivity of ≈30 kHz/pH from pH 7 to pH 2 demonstrates the high potential of flexible SAW devices to be used in the measurement of pH in fluids and biosensing.

Flexible Enzymatic Glucose Electrochemical Sensor Based on Polystyrene-Gold Electrodes.

Metabolic disorders such as the highly prevalent disease diabetes require constant monitoring. The health status of patients is linked to glucose levels in blood, which are typically measured invasively, but can also be correlated to other body fluids such as sweat. Aiming at a reliable glucose biosensor, an enzymatic sensing layer was fabricated on flexible polystyrene foil, for which a versatile nanoimprinting process for microfluidics was presented. For the sensing layer, a gold electrode was modified with a cysteine layer and glutaraldehyde cross-linker for enzyme conformal immobilization. Chronoamperometric measurements were conducted in PBS buffered glucose solution at two potentials (0.65 V and 0.7 V) and demonstrated a linear range between 0.025 mM to 2mM and an operational range of 0.025 mM to 25 mM. The sensitivity was calculated as 1.76µA/mM/cm2 and the limit of detection (LOD) was calculated as 0.055 mM at 0.7 V. An apparent Michaelis-Menten constant of 3.34 mM (0.7 V) and 0.445 mM (0.65 V) was computed. The wide operational range allows the application for point-of-care testing for a variety of body fluids. Yet, the linear range and low LOD make this biosensor especially suitable for non-invasive sweat sensing wearables.

Conformable AlN Piezoelectric Sensors as a Non-invasive Approach for Swallowing Disorder Assessment.

Deglutition disorders (dysphagia) are common symptoms of a large number of diseases and can lead to severe deterioration of the patient's quality of life. The clinical evaluation of this problem involves an invasive screening, whose results are subjective and do not provide a precise and quantitative assessment. To overcome these issues, alternative possibilities based on wearable technologies have been proposed. We explore the use of ultrathin, compliant, and flexible piezoelectric patches that are able to convert the laryngeal movement into a well-defined electrical signal, with extremely low anatomical obstruction and high strain resolution. The sensor is based on an aluminum nitride thin film, grown on a soft Kapton substrate, integrated with an electrical charge amplifier and low-power, wireless connection to a smartphone. An ad-hoc designed laryngeal motion simulator (LMS), which is able to mimic the motions of the laryngeal prominence, was used to evaluate its performances. The physiological deglutition waveforms were then extrapolated on a healthy volunteer and compared with the sEMG (surface electromyography) of the submental muscles. Finally, different tests were conducted to assess the ability of the sensor to provide clinically relevant information. The reliability of these features permits an unbiased evaluation of the swallowing ability, paving the way to the creation of a system that is able to provide a point-of-care automatic, unobtrusive, and real-time extrapolation of the patient's swallowing quality even during normal behavior.

How to meet reuse and preparation for reuse targets? Shape advertising strategies but be aware of "social washing".

Preparation for reuse (PfR) is a fundamental waste management practice that is second only to prevention in the waste hierarchy. The paper, building on advertising literature, investigates how to leverage the pro-social nature of this option for giving products that have become waste a second life. To examine how advertising strategies based on emotional, functional or combined stimuli can be used to increase intention to buy these items, we carried out an experiment on 507 actual visitors a PfR items shop run by a social cooperative in Northern Italy. We found that, depending on consumers' social involvement, both emotional and functional stimuli based on the social impact of preparation for reuse tend to outperform functional stimuli and have a positive impact on brand attitudes by shaping attitudes to advertisements. Purchasing behaviour has a positive impact on attitudes toward the PfR organization and moderates the effect of emotional and combines stimuli on attitudes toward the advertisement. Since emotional stimuli can be freely used by both legitimated and opportunistic companies, the former should seek to preserve their value proposition by making it easier for consumers to recognise actually trustworthy organizations. This is possible combining the use of advertisements with the development of solid customer relationships. To this end, awareness campaigns, closer relationships with stakeholders and third-party verifiable standards and certifications should be considered to reduce the risk of "social washing" in the current second-hand market context.

Conformable surface acoustic wave biosensor for E-coli fabricated on PEN plastic film.

Over the last decades, great effort has gone into developing new biosensor technologies for applications in different fields such as disease diagnosis and detection of pollutants in water and food. Global developments in robotic, IoT technologies and in healthcare sensors require new flexible sensor technologies that are low cost and built from sustainable and reusable or recyclable materials. One of the most promising technologies is based on the development of surface acoustic wave (SAW) flexible biosensors, which are highly reproducible, reliable and wirelessly controllable. This work presents for the first time a novel aluminum nitride (AlN)-based conformable SAW immunosensor fabricated on recyclable polyethylene naphthalate. We apply it to the detection of E.Coli using a faster and innovative functionalization method that exploit Protein-A/antibody affinity. A higher sensitivity (Limit of detection-LoD, 6.54*105 CFU/ml) of the Lamb wave traveling on the polymeric device has been obtained in comparison with SAWs traveling on AlN on silicon substrate (LoD, 1.04*106 CFU/ml). Implementation of a finite element method allowed for the estimation of the single E.Coli mass of approximately 9*10-13 g. This work demonstrates the high biosensing potential of flexible polymeric SAW devices for bacteria contamination control in food chain, water and smart packaging.