Volatile organic compounds (VOC) present in exhaled breath can serve as biological markers for human physiology. The change in levels of exhaled VOCs can be indicative of bodily disorders. Detection of such low levels of VOCs can allow early detection and diagnosis of diseases. A polymer- modified Quartz Tuning Fork (QTF) is a promising, cost-effective sensor that can detect a change in ppm levels of VOCs exhaled from the breath at room temperature. Acetone and acetaldehyde are biomarkers that are readily exhaled by human beings. Increased levels of these analytes can serve as indicators for toxicity or a wide array of diseases. The present work uses an array of QTFs modified separately using TiO₂ and WO₃­ nanostructures embedded in polystyrene to successfully detect low VOC concentrations present in simulated human breath. The frequency shift obtained after exposing the sensor array to breath is noted as the sensor response. The response shows a clear distinction between healthy human breath and breath spiked with varying VOC concentrations (5 – 400 ppm). The sensor response proves it can potentially serve as an economical and non-invasive tool for disease diagnostics.

Recent advances in technology have enabled the development of affordable low-cost acoustic monitoring systems, as a response of several fields of application that require a close acoustic analysis in real-time: road traffic noise in crowded cities, biodiversity conservation in natural parks, behavioural tracking in the elderly living alone and even surveillance in public places for safety reasons. This paper presents a low-cost wireless acoustic sensor network developed to gather acoustic data to build a 24/7 real-time soundmap. Each node of the network comprises an omnidirectional microphone and a computation unit, which processes acoustic information locally to obtain nonsensitive data (i.e., equivalent continuous loudness levels or acoustic event labels) that are sent to a cloud server. Moreover, it has also been studied the placement of the acoustic sensors in a real scenario, following acoustics criteria. The ultimate goal of the deployed system is to enable the following functions: (i) to measure the Leq in real-time in a predefined window, (ii) to identify changing patterns in the previous measurements so that anomalous situations can be detected and (iii) to prevent and attend potential irregular situations. The proposed network aims to encourage the use of real-time non-invasive devices to obtain behavioural and environmental information, in order to take decisions in real-time.

Nowadays, gas sensors play a vital role in a plethora of applications. However, there are still some important shortcomings, such as the scarce selectivity and sensitivity, especially at low operating temperatures. Herein, we report the successful sensing achieved by tailoring the chemoresistive materials comprised of graphene oxide (GO) sheets well-integrated in a three-dimensional network of n-type metal oxide semiconductors (MOS). Thanks to the synergistic effect between GO and MOS under UV light, we obtained a very good sensitivity (down to 100 ppb) towards different volatile organic compounds (VOCs, i.e., ethanol, acetone, ethylbenzene, toluene) even at room temperature. Moreover, the best performing sensor (SnO₂/GO 32:1) resulted highly selective towards polar compounds, such as acetone.

The trajectory planning for ground mobile robots operating in unknown environments can be a difficult task. In many cases, the sensors used for detecting obstacles only provide information about the immediate surroundings, making difficult to generate an efficient long term path. For instance, a robot can easily choose to move along a free path that eventually will have a dead end. This research is intended to develop a cooperative scheme of visual-based aerial simultaneous localization and mapping (SLAM) that will be used for generating a safe long-term trajectory for a ground mobile robot. The general idea is to take advantage of the high-altitude point of view that aerial robots can inherently have, for obtaining spatial information of a wide area of the surroundings of the robot. In this case, it could be seen as having a zenithal picture of the labyrinth for solving the robot's path. More specifically, the system will generate a wide-area spatial map of the ground robot’s obstacles from the images taken by a team of aerial robots equipped with onboard cameras, by means of a cooperative visual-based SLAM method. At the same time, the map will be used for generating a safe path for the ground mobile robot. While the ground robot moves, its onboard sensors will be used for refining the map and thus for avoiding obstacles that were not detected from the aerial images.

We developed a highly sensitive acetone bio-sniffer (gas-phase biosensor) based on an enzyme reductive reaction to monitor breath acetone concentration. The acetone bio-sniffer device was constructed by attaching a flow-cell with nicotinamide adenine dinucleotide (NADH)-dependent secondary alcohol dehydrogenase (S-ADH) immobilized membrane onto a fiber-optic NADH measurement system. This system utilizes an ultraviolet light emitting diode as an excitation light source. Acetone vapor was measured as fluorescence of NADH consumption by the enzymatic reaction of S-ADH. A phosphate buffer that contained oxidized NADH was circulated into the flow-cell to rinse the products and the excessive substrates from the optode; thus, the bio-sniffer enables real-time monitoring of acetone vapor concentration. A photomultiplier tube detects the change in the fluorescence emitted from NADH.

The relationship between fluorescence intensity and acetone concentration was identified from 20 ppb to 5300 ppb. This encompasses the range of concentration of acetone vapor found in breath of healthy people and of those suffering from disorders of carbohydrate metabolism. Then, the acetone bio-sniffer was used to monitor exhaled breath acetone concentration change before and after meal. When the sensing region was exposed to exhaled breath, fluorescence intensity decreased and reached to saturation immediately. Then it returned to the initial state upon cessation of the exhaled breath flow. We anticipate its future use as a non-invasive analytical tool for assessment of lipid metabolism in exercise, fasting and diabetes mellitus.

Morin dye is known as a cheap and readily available selective ‘off → on’ fluorescent sensitiser when immobilised in a phase transfer membrane for the detection of Al³⁺ ions. Here, a morin derivative, NaMSA, which readily dissolves in water with good long- term stability is used in conjunction with a fibre optic transducer with lock-in detection to detect Al³⁺ in drinking water below the potability limit. The combination of a water soluble dye and the fibre optic transducer require neither membrane preparation nor a fluorescence spectrometer yet still display a high figure- of- merit. The known ability to recover morin- based Al³⁺ cation sensors selectively by exposure to fluoride (F⁻) anions is further developed enabling a complementary sensing of either fluoride anions, or aluminium cations, using the same dye with a sub- micromolar limit-of-detection for both ions. The sensor performance parameters compare favourably to prior reports on both aqueous aluminium and fluoride ion sensing.

The application of biosensors for complex samples is limited by non-specific adsorption of interfering compounds. These so-called fouling agents include a broad range of biomolecules, such as proteins and nucleic acids, as well as whole cells. Their adsorption to the electrode significantly affects the analytical characteristics of the sensor including sensitivity, reproducibility, stability, and overall reliability. Biofouling therefore is a serious challenge that has to be overcome. The majority of antifouling techniques developed for this purpose are limited in their application to optical or mass sensitive sensors because they incorporate high molecular weight compounds. Since these are highly disadvantageous for electrochemical transfer reactions, further research has to be conducted for the fabrication of electrochemical sensors. The gold standard of antifouling agents is Polyethylene glycol, which, when attached to the electrodes’ surface, forms thick and compact monolayers that unfortunately inhibit electrochemical transfer reactions. In our work, we therefore aim to investigate different strategies based on PEG that combine the polymers’ excellent antifouling properties with sufficient spacing to allow electron transfer and enable their application in electrochemical sensors. We thereby focus on the development of impedimetric sensors that utilize aptamers as bioreceptors for the fast, sensitive, and reliable detection of protein biomarkers in clinical samples.

The fast and selective determination of hydrogen peroxide (H₂O₂) is of importance not only because of strong interest to this widely applied analyte but also because of the development of enzymatic biosensors for glucose or other metabolites where the sensor for H₂O₂ can be used as the transducer. We report here electrocatalytical amperometric sensor for detection of H₂O₂. The sensor consists of a gold electrode covered by self-assembled monolayer (SAM) with immobilized p-benzoquinone. To provide highly stable immobilization of p-benzoquinone at the distance of effective electron tunneling, a new anchor compound - 1,3-dimercaptopropan-2-ol – was synthesized and used for the preparation of the SAM. Due to two thiol groups binding gold surface this compound provides a high stability of the SAM. The surface concentration of p-benzoquinone obtained from cyclic voltammetry is 2.5 ± 0.2 × 10⁻¹⁰ mol·cm⁻². Cyclic voltammetry and chronoamperometry experiments proved that the immobilized benzoquinone exhibited high electrocatalytic activity towards the decomposition of H₂O₂. Depending on the used potential range, different sensing modes can be realized. For example, one can measure electrochemical response due to the oxidation of H₂O₂ at anodic potentials or due to the reduction of oxygen formed during oxidative decomposition of H₂O₂. Also amperometric response at fixed potential of +0.4 V vs. Ag/AgCl corresponding to the oxidation of benzoquinone to hydroquinone was studied. The sensor exhibited a linear response over a concentration range of 0.1–2 mM with a low detection limit of 4.24 µM. The reproducibility of three different electrodes prepared was examined at the H₂O₂ concentration range from 0.1 till 3 mM, which resulted in a relative standard deviation below 4.2%.

Biogenic amines (BAs), produced naturally due to the decomposition of amino acids, are crucial for food industry because the formation of BAs is directly related to improper storage and the presence of bacteria; high concentrations of BAs could be related easily with the quality and spoilage of the products of this sector. The necessity to quantify quickly and efficiently these targets makes mandatory the use of alternatives to conventional analytical methods used up to now. For example, sensors combined with chemometric tools are a promising alternative for quick and informative analysis in the food sector. Chemometric tools allow to develop models for the quantification of concrete compounds in complex matrix, making it a feasible tool for the development of more user-friendly methods than the traditional used since now. This work presents a model created for the detection of histamine (Hys), cadaverine (Cad) and tyramine (Tyr) using a set of 5 modified GEC (Graphite Epoxy Composite) electrodes: ZnO, CuO, SnO₂, Bi₂O₃, and Polypyrrol, used in a voltammetric multisensory array approach. In the graphics below it could be observed the results obtained with an Artificial Neural Network (ANN) with 51 input neurons, 5 neurons in the hidden layer and 3 neurons in the output layer. The functions used for the hidden and output layers were Tansig and Purelin, respectively. The results show slopes near to 1 and intercepts close to 0, indicating the feasibility of the model.

Nature inspires a large set of bio-mimetic systems ranging from soft robotic actuators to perceptive electronic skins that enhance and support our life. The growing demand on assistive, medical and bioelectronic technologies however raises concerns on the ecological footprint of these emerging platforms, as they are often designed for a defined, limited operational lifetime. Introducing a key feature essential to nature - biodegradability - will enable soft electronic and robotic devices that reduce (electronic) waste and are paramount for a sustainable future. We here introduce materials and methods such as tough yet biodegradable materials for soft systems that facilitate a broad range of applications, from transient wearable electronics to metabolizable soft robots. These embodiments are highly stretchable, are able to heal and are resistant to dehydration. Our forms of soft electronics and robots are built from resilient bio-gels with tunable, extreme mechanical properties that uniquely combine performance and durability with degradability. They are engineered for long-term operation in ambient conditions without fatigue, but fully degrade after use through biological triggers. Electronic skins that measure pressure, strain, temperature and humidity serve as human-friendly on-skin interfaces or equip robotic systems with sensory feedback. Such advances in the synthesis of biodegradable, mechanically tough and stable gels that do not compromise in performance when compared to their non-degradable counterparts may bring bionic soft systems a step closer to nature and enable human-friendly technologies with reduced ecological footprint.