Sensors for respiratory monitoring can be classified into wearable and non-wearable systems. Wearable sensors can be worn in several positions, the chest being one of the most effective. In this paper, we have studied the performance of a new piezoresistive breathing sensing system to be worn on the chest with a belt. One of the main problems of belt-attached sensing systems is that they present trends in measurements due to subject movements or differences in subject constitution. These trends affect sensor performance. To mitigate them, it is possible to post-process the data to remove trends in measurements, but relevant data from the respiration signal may be lost. In this study, two different detrending methods are applied to respiration signals. After conducting an ex-perimental study with 21 subjects who breathed in different positions with a chest piezoresistive sensor attached to a belt, detrending method 2 proved to be better at improving quality of respiration signals.

The need to monitor electrocardiogram (ECG) in continuous yet comfortable manners has propelled the development of many wearable ECG devices that could replace the roles of traditional systems, such as the Holter monitor. However, despite the reduced form factor and weight, commercially available devices rely on the use of aggressive adhesives for attachment to the skin due to the bulky and rigid electronic module as well as conductive hydrogels to acquire the biopotential. Since the adhesives and gels are known to cause skin irritation and injuries, there has been a critical need to develop a wearable system, which is both compact and safe for the user. Recently, a stretchable and dry-contact ECG device has been reported and the feasibility to continuously transmit ECG safely and reliably has been demonstrated. In this study, we report a further improvement in device weight and size of the device by implementing a two-electrode design as well as optimized power management strategies allowing for robust transmission of continuous ECG on a reduced power budget. With the device weighing just 5.2 g, ECG with a higher signal-to-noise ratio (22 dB) than the previous value (17 dB) could be obtained during excessive user movement, such as running and exercising. Along with the combination of data compression, buffered Bluetooth transmission of 1 min, and a low-power ECG front-end, continuous assessment of ECG could be achieved over 24 h, a milestone for continuous transmission of ECG, the proposed system will bring a paradigm shift in continuous cardiac monitoring.

This study presents the spatio-temporal assessment of the Pugllohuma peatland’s surface variability, a highland wetland (over 4100 m.a.s.l.) in the Sustainable water conservation area Antisana, Ecuador. This assessment provided information of the surface variability during dry and wet season. The temporal variability was investigated through the pressure, rain, relative humidity, temperature, and wind, records of two near meteorological stations, while the spatial variability was investigated through images of the Sentinel-1 mission from 2017 to 2019, as well as, elevation and slope data. Their classifications were carried out by using R programming language and Google Earth Engine, and the results were published in the UI service in Google Apps Script.

Transferring laser-based sensors into industrial applications, for instance for the contact-& destruction-free inline quality control of alumina alloys, is very challenging due to laser-safety requirements and the complex implementation in individual technological infrastructures. In order to open laser-based sensor technology even for small to medium size enterprises, we introduce a prototyping platform for laser-based sensor technologies that enables the fast, error-free, flexible and low cost transformation into industry. As an example, the transformation of the laser-based sensor concept using coherent light scattering at technical insulating films is shown. The transformation of this type of sensor for inline quality control is particularly demanding due to the requirement of probing transparent conversion coatings, with a thickness of less than 70 nm so that commonly applied electronic techniques fail. The conversion films are produced on the top of cold-rolled, unpolished alumina so that coherently scattered laser light is regarded as superposition from diffuse scattering processes at the surfaces/interfaces, inclusions and/or layer imperfections. Analysis is realized by extending the principle approach of reflectometry by considering the role of diffuse and specular scattering together with the concepts of light interferometry. The functionality of the transformed sensor is successfully validated using five different conversion coating thicknesses on AA3003 alumina substrates.

In this study, a lettuce leaf was monitored using a bioimpedance spectroscopy technique for 19 hours (6 am to midnight). Water was supplied just after 6 am, and the leaves were irradiated with growing LEDs from 8 am to 8 pm. During 19 hours, at every hour, the impedance (resistance and capacitance) of the lettuce was obtained at various frequencies from 1 to 100 kHz. A significant change of impedance after events (watering and LED on) was observed. It implies BIS impedance monitoring can be used for near-realtime monitoring of plant growth. The experimental analysis shows that the bioimpedance system can be used to quantitatively measure the growth and health status of the lettuce leaf. Moreover, the authors propose to use four parameters, the characteristic frequency and the phase of Cole-Cole graph, and the resistance ratios R_100kHz/R_1kHz, and R_100kHz/R_50kHz for plant leaf monitoring. When the leaf enters healthier conditions, the characteristic frequency of Cole-Cole graph is getting smaller and the phase is getting bigger. These facts were predicted by referring to the previous articles. However, the authors found the characteristic frequency and the phase angle are not enough to explain the healthiness of lettuce leaf. The proposed two resistance ratio shows different aspects of the healthiness of lettuce leaf during 19 hours more clearly.

Innovative biocompatible organic materials with piezoelectric properties have a great potential for the development of wearable sensors for monitoring physiological parameters. Among them, Chitosan (CS) is a natural, biodegradable, antibacterial and low cost biopolymer that shows an interesting piezoelectric behaviour. In this context, this work reports on a protocol where plain chitosan films (CS-F) are exploited to easily create a piezoelectric flexible wearable patch. By adapting a simple drop casting method reported in, we here demonstrate that a 70 μm thick CS-F can exhibit good piezoelectric properties. The structure of CS-F was analysed thanks to XRD technique: the spectrum reveals peaks of partially crystalline chitosan film, indicating presence of organized polymeric chains. Piezoresponse Force Microscopy scans confirmed the presence of domains with opposite polarization directions with an extrapolated value of piezoelectric coefficient d₃₃ of 2.54 pC/N. A microfabrication process for patch realization has been set up. The top electrode was created by simple thermal evaporation of gold directly onto the free-standing CS-F. This bilayer was then precisely cutted using a cutting plotter and assembled on the copper bottom electrode. The complete patch can be conformally applied on the skin. The ability of the device to sense physiological movements was validated by an ad hoc measurement set up generating strain pulses; open circuit voltage peaks up to 20 mV were detected. This sensor represents an important step towards totally biocompatible and biodegradable wearable devices.

Microneedle arrays for minimally invasive continuous sensing in the dermal interstitial fluid (ISF) have been demonstrated in both amperometric and potentiometric modes, however there are no publication where microneedle arrays have been modified with lignin nanoparticles. Lignin, the most abundant polyphenol in nature, is the main byproduct in the pulp and paper manufacturing industry and biorefinery. Lignin nanoparticles (LNPs), easily produced by green methods, offer unique properties and have therefore gained interest for electrode modification. In this work, we have developed a novel green LNPs modified microneedles electrode platform for pain free continuous monitoring of glucose in artificial interstitial fluid (ISF). The gold surface of the microneedles has been modified with LNPs and electrochemically characterized. Functionalization with glucose oxidase enzyme and with an Osmium polymer as redox mediator allowed the continuous monitoring of glucose. The performance of the LNPs/microneedle biosensor for glucose detection was assessed in artificial interstitial fluid and in human serum, both spiked with glucose. The results reveal that the new LNPs microneedles biosensor holds interesting promise for the development of biocompatible, wearable, real-time monitoring devices to be used in clinical care and sport medicine. The proposed LNPs microneedles platform can be applied also for the detection of other important bioanalytes (such as lactate, hormones, etc).

Implantable pressure sensors represent an important part of research activity in laboratories. Unfortunately, their use is limited by cost, autonomy and temperature-related drifts. The cost of use depends on several parameters, in particular the low battery life and the need for miniaturization to be able to implant the animals and monitor them over time that is long enough to be physiologically relevant. This paper study the possibility to reduce the thermal drift of implantable sensors. To quantify and compensate for thermal drift, we have developed the equivalent model of the piezoresistive probe by using the cadence software. Our model takes into account the temperature [34°C – 39°C] and also the pressure [0 - 300 mmHg]. We were thus able to identify the source of the drift and thanks to our model we were able to compensate for it thanks to compensation circuits added to the conditioning circuits of the sensor. The maximum relative drift of the sensor is (0.1 mV/°C)/3.6mV (2.7%), a drift of the conditioning circuit is (0.98 mV/°C)/916mV (0.1%) and the whole is (13.4 mV/°C)/420mV (32 %). The compensated sensor show a relative maximum drift of (0.371 mV/°C)/405 mV (0.09%). The output voltage remains stable over the measurement temperature range.

For reasons of availability and cost, patients are sent home earlier and earlier, with limited follow-up due to the complexity and size of medical devices. In this context, researchers from IETR and MIPS laboratories are working on a device which should monitor the progress of a patient, in order to detect early the aggravation of a disease such as Chronic Obstructive Pulmonary Disease (COPD) or diabetes with walking disorders. The device is based on flexible piezoelectric thin films (3 µm thick) that can be used as podiatric sensors and have been developed by the IETR laboratory. The originality of this work resides both in the approach to the design of the gait monitoring device, because carried out directly in consultation with a doctor from the University Hospital of Nantes and a podiatrist, and in the portability of the device that should eventually allow the follow-up of a patient at home. For this study, the flexible piezoelectric sensors have been elaborated using a Chemical Solution Deposition (CSD) process and a commercial aluminum (Al) foil as substrate. In order to increase the flexibility of sensors and to aid its insertion in a shoe, piezoelectric films have been encapsulated by lamination into polyethylene terephthalate (PET, 150 μm). In this paper, elaboration and characterizations of flexible piezoelectric sensors, analog to digital converter and wireless communication protocol used for data transmission, are presented.

The indium tin oxide (ITO) coated glass was used as a working electrode for electrochemical deposition of conducting polymer polypyrrole (Ppy). Before polymerization, the electrode surface was additionally modified with triethoxymethylsilane (TEMS) to provide better adhesion of polypyrrole to the surface of ITO. Polymerization of Ppy was performed electrochemically as it was described in a previous study. The ionic strength of the solution was supported by LiClO₄. Since the dissolved CO₂ in the solution forms the weak acid and thus the pH of a solution can be slightly changed the electrochromic response to the pH changes was evaluated. Britton – Robinson buffer (BRB) was used as the model system for evaluation of the electrochromic response of polypyrrole at different pH values and concentrations of NaHCO₃, which was a source of CO₂ in the solution. For the evaluation of electrochromic response in the presence of CO₂ the double potential step chronoamperometry method was applied and UV-Vis absorption spectra were registered. To gain insight into the charge transfer phenomenon in more detail, the cyclic voltammetry experiments at different glass/ITO_(TEMS)/Ppy electrode potential sweep rates were performed.