Mauro Serpelloni

Sensors are an established driver of diagnostics and prevention in the medical field, including orthopaedics. Today, the subclass of ion-selective sensors (ISSs) is on the leading edge due to its advantages, enabled by technological advancements in manufacturing, such as miniaturization, precision, accuracy, specificity, a wide measuring scale, ease of use, flexible operating conditions, and measuring speed. While ISSs’ impact on environmental and health fields is already the subject of investigation, it still needs to be analysed specifically in orthopaedics, which is the aim of this Review. A PubMed and Scopus search was performed using the keywords “ion”, “sensor”, “electrodes”, “selective”, “musculoskeletal”, “implant”, “joint replacement”, and “orthopaedic”; after systematic screening, 44 studies were included in the synthesis. First, studies were classified based on the target ion. Only a few papers treated applications specifically in orthopaedics, confirming that ISSs are still largely an unexplored frontier here. However, all of the studies targeted ions with a role also in musculoskeletal pathophysiology, thus relative ISSs could have a potential impact on orthopaedic diagnosis and treatment. Then, when described by the papers, ISSs’ technological solutions were systematically evaluated. Finally, the main ISSs development targets for reaching orthopaedic clinical application were highlighted, including biocompatibility (e.g., implantability), long-term stability, calibration, and validation. Overcoming these challenges will enable ISSs to progress from laboratory prototypes to clinically viable tools, supporting the advancement of next-generation sensorised prostheses, fixation devices, and surgical instruments, and paving the way for predictive and personalised orthopaedic medicine.

The current industrial transformation is changing the way production systems are designed, manufactured, monitored, controlled, and maintained

This work evaluates a potassium ion-selective electrode (K-ISE) fabricated using Aerosol Jet Printing (AJP) and compares its performance with that of a commercial K⁺-selective electrode (KION). Both sensors exhibit near-Nernstian behavior, with average sensitivities of 57.91 ± 5.07 mV/dec for the AJP device and 57.28 ± 5.07 mV/dec for the commercial electrode, confirming a near-Nernstian K⁺ response over the tested concentration range. Single-interferent response tests demonstrate that AJP-printed electrodes provide a more stable and less sensitive response to sodium interference (24.37 ± 1.39 mV/dec) compared to KION (33.95 ± 8.95 mV/dec), while showing comparable NH₄⁺ response and a slightly higher response toward urea than KION. Morphological analysis (OM and SEM) reveals that AJP enables smoother, more homogeneous films and improved control over the transducer/membrane interface. Unlike previous studies, this work presents a direct experimental comparison between AJP-fabricated and commercial ISEs under controlled interference conditions relevant to agricultural and environmental matrices. Although the AJP sensors exhibited near-Nernstian behavior and fast response times, their reproducibility was lower than that of the commercial electrodes (RSD = 30.12% vs. 18.45%), indicating that further optimization of the printing and membrane deposition processes is required.

Ankle–foot orthoses (AFOs) are widely used in the rehabilitation of patients with neurological or musculoskeletal disorders. However, treatment outcomes may be influenced by incorrect use of the device or by inappropriate orthosis selection. Since many types of AFOs are available, differing in materials, stiffness, and geometry, an objective evaluation tool can support clinical decision-making. This work presents the design, development, and characterization of an instrumented AFO able to quantify relevant gait parameters in an objective way. The proposed device integrates three measurement modalities in a compact wearable structure. Two longitudinal strain gauges estimate ankle plantar- and dorsiflexion angles. Two force-sensitive elements detect foot–ground contact and allow identification of stance and swing phases of the gait cycle. A single inertial measurement unit (IMU) is used to measure lateral shank inclination. The strain-gauge-based angle estimation was validated against a gold-standard motion capture system, achieving a root mean square error of approximately 1.6 degrees and showing higher accuracy than the IMU for plantar/dorsiflexion measurement, while maintaining a simple electronic architecture. The force sensors were validated using a force platform and demonstrated reliable detection of loading and unloading events. Monitoring lateral inclination through the single IMU provides additional information related to balance and potential fall risk. Data are transmitted via Bluetooth Low Energy (BLE) to a custom Python-based application for real-time visualization and recording. Overall, the results validate the electronic instrumentation and demonstrate reliable system performance, indicating that the proposed instrumented AFO represents a promising platform for objective gait assessment and future clinical applications.

The endoscopic transsphenoidal approach is a surgical method used to remove pituitary adenomas—benign tumors located near the pituitary gland. The success of this procedure depends heavily on assessing the tumor’s consistency, which is currently based on the surgeon’s tactile feedback and experience. This study presents the development of a novel sensor-based probe designed to provide real-time measurements of tissue hardness, supporting more objective surgical decision-making. The probe integrates a tunneling magneto resistance (TMR) sensor with a deformable, 3D-printed tip made of thermoplastic polyurethane. The tip features micro-beams that deform upon contact with tissue; the extent of deformation, measured by the TMR sensor, correlates with tissue stiffness. The flexible structure was fabricated using fused filament fabrication, and the process was characterized to control micro-beam dimensions by adjusting print parameters such as layer height, print speed, and nominal line width. A regression model was developed to predict beam width with high accuracy and repeatability. Eighteen probe designs, combining different beam widths (0.42 mm–0.63 mm) and numbers (3–5), were tested through indentation experiments on samples with Shore 000 hardness ranging from 51 to 83 (ASTM D2240), including a cooked egg white sample as a biological tissue analogue. Results revealed that probes with 4 and 5 beams printed at lower speeds offered superior sensitivity, linearity, and uniformity. In these configurations, the probe was able to estimate the hardness of adenoma-like materials with errors below 2%. These findings validate the proposed system’s potential for clinical use in evaluating soft to moderately firm tumors during surgery.

Wheatstone bridge (WB) is widely used in precision measurements involving strain gauges and resistive sensors. However, maintaining balance in a full-bridge configuration becomes increasingly challenging in the presence of high-resistance tolerances—especially in printed electronics, where such variations are common. Traditional compensation methods often entail increased circuit complexity, added cost, and additional sources of error. This paper proposes a novel balancing technique for fully resistive Wheatstone bridges, leveraging two voltage references to cancel the output offset even in the presence of resistor tolerances exceeding 0.1%. The method demonstrates robust performance with tolerance levels up to 20%, while preserving high linearity. Simulation results confirm that the approach achieves balanced operation and accurate output even with low-tolerance resistors (1%). Relative to the ideal sensitivity of (V_CC−V_EE), the proposed technique maintains a worst-case sensitivity of 0.8 (V_CC−V_EE), with a theoretically null output offset under balanced conditions. Furthermore, linearity error remains below 0.5% of the full-scale output (FSO), matching the performance of conventional WB circuits affected by mismatch. While the resolution of the voltage references introduces a small, predictable offset—independent of power supply variations—this error is limited to the resolution of the reference itself. Experimental validation using benchtop instrumentation corroborates the simulation findings: with resistors exhibiting 10% tolerance, the maximum deviation between measured and theoretical outputs was 2.4 mV. This deviation remains negligible in terms of estimating fractional resistance changes.