In the last years, increasing interest has been addressed on wearable devices for the continuous monitoring of biochemical profiles of patients and athletes. Among various markers, lactate represents one of the most interesting to deepen the knowledge on fatigue processes, in combination with traditional electromyographic features. In this work, we propose a new, low-cost, rapid and flexible electrochemical amperometric lactate carbon biosensor fabricated by the novel technique of Aerosol Jet Printing. The developed biosensors were combined with a paper-based microfluidic system and a chitosan-based stable functionalization to allow a long-term continuous monitoring of human daily activities. The sensor performances were evaluated by static and dynamic electrochemical tests in buffered media. The limit of detection is 11±2 mM for the static setup and of 15±6 mM for the dynamic setup, while sensitivity is 0.02 μA/mM and 0.04 μA/mM, respectively, with single sigma standard deviation lower than 8%. Increasing and decreasing concentration steps of lactate induces comparable response times below 30 s. These results obtained in-vitro under controlled laboratory conditions represent a promising starting point to pursue with ex-vivo and in-vivo validation for the future development of stand-alone wearable patches for non-invasive lactate measurements.

The paper proposes the development of an innovative prototype of smart orthosis with a fully integrated multi-electrodes matrix for electromyography (EMG), to improve non-invasive personalized recording during rehabilitation. Both electrodes and conductive tracks were effectively printed onto the three-dimensional (3D) surface of the orthosis through Aerosol Jet Printing. Results from morphological and electrical characterization of printed elements showed an average thickness of 22.2 μm (relative standard deviation of 11%) with average resistivity of about 51∙10-8 Ω∙m (relative standard deviation of 10%) and an electrode-to-skin impedance comparable to the one of commercial dry electrodes. Portability and comfort were enabled by customized light-weight conditioning electronics attached to the orthosis allowing wireless data transmission. Muscular activity from three subjects was then evaluated while performing the same tasks involving multiple muscles. Results confirmed the ability of the device to monitor the activity of gastrocnemius muscle during both a sit-to-stand task and isometric contractions, both for intra- and inter-subjects’ analyses. A comparison with commercial surface EMG electrodes and with literature confirmed similar features both in time and frequency. Overall, the results presented suggest the possibility to exploit the potential to print customized electrodes onto 3D surfaces to fabricate smart personalized wearable orthoses useful to capture valuable feedback to improve effectiveness, consciousness, and interactivity during daily activities and specific exercises, for both patient and medical personnel.

Electrochemical sensors are attracting great interest for their different applications. To improve their performances, basic research focuses on two main issues: improve their metrological characteristics (e.g., repeatability, reusability and sensitivity) and investigate innovative fabrication processes. In this work, we demonstrate an innovative microstructuration technique aimed at increasing electrochemical sensor sensitivity to improve electrode active area by an innovative fabrication technique. The process is empowered by aerosol jet printing (AJP), an additive-manufacturing and non-contact printing technique that allows depositing functional inks in precise patterns such as parallel lines and grids. The 3D printed microstructures increased the active surface area by up to 130% without changing the substrate occupancy. Further, electrochemical detection of ferro/ferri-cyanide was used to evaluate the sensitivity of the electrodes. This evaluation points out a sensitivity increase of 2.3-fold on average between bare and fully microstructured devices. The increase of surface area and sensitivity are well linearly correlated as expected, verifying the fitness of our production process. The proposed microstructuration is a viable solution for many applications that requires high sensitivity, and the proposed technique, since it does not require masks or complex procedures, turns out to be flexible and applicable to infinite construction geometries.

In Smart Manufacturing, the recent opportunities provided by the Information and Communication Technologies has paved the way to a seamless connection of the manufactured product throughout its entire lifecycle, leading to the diffusion of the concepts of Smart Product and Digital Thread, that leverages digital technologies to assure a continuous flow of data encompassing the design phase of a product, manufacturing, operation, maintenance and also its eventual disposal or recycling. This compelling need to obtain a unified view of information associated with Smart Products has stimulated the so-called Internet of Services (IoS) paradigm, allowing for the sharing of products data and the execution of functions among various participants in intertwined supply chains. In these contexts, service-oriented architectures are being more and more employed to meet the complex and ever-evolving data analysis requirements, particularly when implementing Digital Thread solutions for Smart Products, where several issues must be considered, ranging from the heterogeneity of (Big) data to data sovereignty and data access policies, as information may cross the borders of multiple actors participating in intertwined supply chains. This survey discusses about the technological solutions and challenges to implement Digital Threads for Smart Products in Smart Manufacturing contexts, providing insights on opportunities for future research directions. In addition, the survey proposes a comprehensive multi-tier service-oriented architectural model to jointly tackle (Big) data heterogeneity, data sovereignty and data access policies issues, as they are only partially addressed by the research efforts examined in the literature review.

In the latest years, hydrogen peroxide quantification gained a growing interest in many fields both in industry and in the clinical environment. Among the different available methods, electrochemical transducers are of particular interest thanks to their ease of fabrication, convenient integration with microfluidics and electronics and their time and cost-effectiveness. Despite these advantages, electrochemical transducers are affected by many metrological issues. In this work, the novel technique of Aerosol jet printing (AJP) is exploited to fabricate fully printed nanostructured electrochemical sensors for hydrogen peroxide detection. Two different carbon-based printable nanostructures, carbon nanotubes (CNTs) and graphene, are employed to conveniently modify with the same technique electrodes’ surfaces. The performances of the proposed design, production process and the different functionalization are explored and discussed. After a preliminary evaluation of the electrochemical characteristics of the printed devices, tests in hydrogen peroxide are carried on. Both materials present a limit of detections (LODs) and sensitivity comparable with the ones obtained in the literature, even though CNT better performs than graphene in terms of sensitivity (20 versus 2.8 $\mu \text{A}$ mM−2). The latter presents however a signal-to-noise ratio (SNR) of 51.2 dB that outperforms the one of CNT (26.5 dB) and thus it has a better resistance against noise. Overall, both the evaluated nanostructures appear suitable to improve the metrological characteristics of printed electrochemical sensors and ease their spreading as environmental control devices, and diagnostic tools and assess quality in the industrial environment.

Temperature sensors have been widely developed to control the course of diseases, improve haptic feelings, and in multi-sensing systems to compensate for the output of other temperature-sensitive sensors. The use of additive manufacturing to produce resistive temperature detectors (RTDs) with reduced dimensions and bulkiness is attracting great interest. Among the relevant process parameters and design choices, the curing process must be considered. In this work, two different commercial metallic-based materials are cured at various temperatures to evaluate the differences in their microscopic and macroscopic behavior. The sensors were designed, developed, and evaluated for their temperature coefficient of resistance (TCR) at different curing temperatures using a programmable climatic chamber. A scanning electron microscope has been used to microscopically inspect the sensing structures with respect to the different curing temperatures. The results show insightful correlations between the macroscopic and microscopic behavior of the used inks as well as the performance of the sensors. In particular, increasing the curing temperature decreased the room-temperature resistance in all the samples by up to 70% and increased the sensitivity by up to 95%. These findings will help propose better processes as well as design choices for the development of printed resistive temperature sensors.