To maintain experimental lab course work during the COVID-19 lockdowns, we chose a hybrid approach for our electronic instrumentation course and developed thereto the Advanced Learning Platform for Analog Circuits and Automation (ALPACA). To further meet our goals and standards, the ALPACA platform has been updated, using a Raspberry Pi Pico with Python instead of an Arduino. Our educational materials and approach are illustrated here through the typical example of a relaxation oscillator assignment. As student's feedback was overall positive and grades remained comparable, we continue the use of the ALPACA in the non-COVID era.

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This manuscript presents the first practical guide to build a Raspberry Pi Pico based potentiostat for electrical and electrochemical instrumentation education. The circuit enables us to perform different types of voltammetry such as cyclic and square wave voltammetry. Voltammograms of paracetamol tablets in a neutral buffer solution were successfully recorded and compared to lab equipment. Thereafter, the effect of different scan rates and different concentrations was studied as a proof of concept. Furthermore, the experiments were expanded with measurements of other pharmaceutical tablets such as vitamin C. Over 80 nanobiology bachelor students successfully built their own potentiostat in an electronic instrumentation course. They validated their systems successfully with electrochemical experiments using paracetamol as a conventional pharmaceutical that can be performed in a classroom. The students acquired a valuable understanding of the electronic building blocks and system architecture within electrochemical instrumentation, equipping them with the requisite knowledge to effectively optimize instrumentation parameters in their future research work.

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As a final project for our electronic instrumentation practical course, non-electronic major students built their own colorimeter and measured a biochemical reaction of their choice using our recently developed Advanced Learning Platform for Analog Circuits and Automation. In this paper, we elaborate on the utilization of a final interdisciplinary project involving electronics, programming and biochemistry, and present the results and feedback from the students. Given that students considered the colorimeter project not only the most enjoyable part of our course but also highly relevant, we conclude that the colorimeter is an effective final project for our course.@en

One of the major challenges associated with e-textiles is the connection between flexible fabric-integrated wires and rigid electronics. This work aims to increase the user experience and mechanical reliability of these connections by foregoing conventional galvanic connections in favor of inductively coupled coils. The new design allows for some movement between the electronics and the wires, and it relieves the mechanical strain. Two pairs of coupled coils continuously transmit power and bidirectional data across two air gaps of a few millimeters. A detailed analysis of this double inductive link and associated compensation network is presented, and the sensitivity of the network to changing conditions is explored. A proof of principle is built that demonstrates the system’s ability to self-tune based on the current–voltage phase relation. A demonstration combining 8.5 kbit/s of data transfer with a power output of 62 mW DC is presented, and the hardware is shown to support data rates of up to 240 kbit/s. This is a significant improvement of the performance of previously presented designs.

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Sweat sensors allow for new unobtrusive ways to continuously monitor an athlete's performance and health status. Significant advances have been made in the optimization of sensitivity, selectivity, and durability of electrochemical sweat sensors. However, comparing the in situ performance of these sensors in detail remains challenging because standardized sweat measurement methods to validate sweat sensors in a physiological setting do not yet exist. Current collection methods, such as the absorbent patch technique, are prone to contamination and are labor-intensive, which limits the number of samples that can be collected over time for offline reference measurements. We present an easy-to-fabricate sweat collection system that allows for continuous electrochemical monitoring, as well as chronological sampling of sweat for offline analysis. The patch consists of an analysis chamber hosting a conductivity sensor and a sequence of 5 to 10 reservoirs that contain level indicators that monitor the filling speed. After testing the performance of the patch in the laboratory, elaborate physiological validation experiments (3 patch locations, 6 participants) were executed. The continuous sweat conductivity measurements were compared with laboratory [Na+] and [Cl-] measurements of the samples, and a strong linear relationship (R2 = 0.97) was found. Furthermore, sweat rate derived from ventilated capsule measurement at the three locations was compared with patch filling speed and continuous conductivity readings. As expected from the literature, sweat conductivity was linearly related to sweat rate as well. In short, a successfully validated sweat collection patch is presented that enables sensor developers to systematically validate novel sweat sensors in a physiological setting.

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This article presents a novel smart sensor garment with integrated miniaturized inertial measurements units (IMUs) that can be used to monitor lower body kinematics during daily training activities, without the need of extensive technical assistance throughout the measurements. The smart sensor tights enclose five ultra-light sensor modules that measure linear accelerations, angular velocities, and the earth magnetic field in three directions. The modules are located at the pelvis, thighs, and shanks. The garment enables continuous measurement in the field at high sample rates (250 Hz) and the sensors have a large measurement range (32 g, 4,000°/s). They are read out by a central processing unit through an SPI bus, and connected to a centralized battery in the waistband. A fully functioning prototype was built to perform validation studies in a lab setting and in a field setting. In the lab validation study, the IMU data (converted to limb orientation data) were compared with the kinematic data of an optoelectronic measurement system and good validity (CMCs >0.8) was shown. In the field tests, participants experienced the tights as comfortable to wear and they did not feel restricted in their movements. These results show the potential of using the smart sensor tights on a regular base to derive lower limb kinematics in the field.@en

Ammonium levels in sweat can potentially be used to measure muscle fatigue and to diagnose particular metabolic myopathies. To research the potential use of ammonia in sweat as a biomarker, a new real-time monitoring system is developed. This system consists of a capsule that is placed on the skin and ventilated with dry air. A metal-oxide gas sensor in the capsule detects the ammonia that is evaporated from sweat. The sensor system was built, and calibration experiments were performed. The sensors show good sensitivity from 27 mV/ppm to 1.1 mV/ppm in the desired measurement range of 1 to 30 ppm, respectively. A temperature and humidity sensor is integrated to compensate for temperature and humidity effects on the NH ₃ sensor.

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This paper presents a method to continuously collect and reliably measure sweat analyte concentrations during exercise. The method can be used to validate newly developed sweat sensors and to obtain insight into intraindividual variations of sweat analytes in athletes. First, a novel design of a sweat collection system is created. The sweat collection patch, that is made from hydrophilized foil and a double-sided acrylate adhesive, consists of a reservoir array that collects samples consecutively in time. During a physiological experiment, sweat can be collected from the back of a participant and the filling speed of the collector is monitored by using a camera. After the experiment, Na+, Cl- and K+ levels are measured with ion chromatography. Sweat analyte variations are measured during exercise for an hour at three different locations on the back. The Na+ and Cl- variations show a similar trend and the absolute concentrations vary with the patch location. Na+ and Cl- concentrations increase and K+ concentrations seem to decrease during this exercise. With this new sweat collection system, sweat Na+, Cl- and K+ concentrations can be collected over time during exercise at medium to high intensity, to analyse the trend in electrolyte variations per individual.

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Sweat sensor patches offer new opportunities for unobtrusive monitoring of an athlete’s physical status. This paper presents a novel sweat rate and sweat conductivity patch that is easy to prototype and can be made with common low-cost production techniques: laser cutting and standard printed circuit board (PCB) manufacturing. The device consists of a patch made from hydrophilic PET foil, a double-sided adhesive and a thin PCB with gold electrodes. Two electrodes, which are continuously in contact with the inflowing fluid, measure the sweat conductivity and a separate system with interdigitated electrodes measures the filling process of the reservoirs. Impedance measurement results of both systems demonstrate the working of the concept.@en

A wide variety of electrochemical sweat sensors are recently being developed for real-time monitoring of biomarkers. However, from a physiological perspective, little is known about how sweat biomarkers change over time. This paper presents a method to collect and analyze sweat to identify inter and intraindividual variations of electrolytes during exercise. A new microfluidic sweat collection system is developed which consists of a patch covering the collection surface and a sequence of reservoirs. Na⁺, Cl^- and K⁺ are measured with ion chromatography afterwards. The measurements show that with the new collector, variations in these ion concentrations can be measured reliably over time.

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In elite European football, 6 to 7 hamstring muscle injuries occur per team per season, which results in an absence of 14 to 180 days (Ekstrand et al. 2017). These injuries occur typically in the last part of a training or match. This implies that the accumulation of demanding actions is an important factor for hamstring injury risk. In current practice, physical player load is measured at the field by deriving the global location of the player with GPS and RFID systems. However, these systems are not able to monitor leg movement and to distinguish demanding actions like kicking, cutting and jumping.In order to monitor these actions in the field, a novel design is being developed. The design consists of five sensor nodes with IMUs (Inertial measurement units), integrated in sports tights. IMUs can measure linear accelerations, angular velocities and magnetic fields in three directions. From these measurements, 3D kinematics of the lower limbs can be derived. An iterative design approach is used to develop the tights. Four prototypes will be developed. Each prototype is tested in a football specific setting, to identify areas of improvement from a technical point of view as well as from a user’s perspective. The final aim of this research is to develop sensor tights that can be worn unobtrusively by football players in the field. Real-time data are retrieved by the coach. This allows the coach to intervene when there is a high injury risk. Keywords: wearable sensors; injury prevention; smart clothing@en

Sweating is a normal reaction of the body to exercise. Although much of sweat is water, there are many other components. These components can be an indication of the condition of the athlete. Increase of elements and salts in the tissue will also work their way through to the sweat. Measurement directly in tissue can be an excellent indicator, but a non-invasive approach is simpler to use and safer. Concentrations in sweat can also be an indication that the athlete is in danger of collapse. This paper looks into the components in sweat and how this change with exercise. The aim is to develop a simple, wearable system able to warn the athlete of the impending danger and prevent a potential accident.@en

A capacitive probe is generally used in a flex-fuel engine for measuring the ethanol content in biofuel. However, the water content in biofuel of high ethanol content cannot be disregarded or considered constant and the full composition measurement of ethanol, gasoline and water in biofuel is required. Electrical impedance spectroscopy with a customized capacitive probe operating in the 10 kHz to 1 MHz frequency range is combined with optical absorption spectroscopy in the UV spectral range between 230 and 300 nm for a full composition measurement. This approach is experimentally validated using actual fuels and the results demonstrate that electrical impedance spectroscopy when supplemented with optical impedance spectroscopy can be used to fully determine the composition of the biofuel and applied for a more effective engine management. A concept for a low-cost combined measurement system in the fuel line is presented.

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Measuring the ethanol/water ratio in biofuel of high ethanol content, such as E85, is important when used in a flex-fuel engine. A capacitive probe is generally used for measuring the ethanol/gasoline ratio. However, the water content in E85 biofuel cannot be disregarded or considered constant and full composition measurement of biofuel is required. Electric impedance spectroscopy with a customized coaxial probe operating in the 10 kHz to 1 MHz frequency range was investigated. An in-depth investigation of the electrical impedance domain has led to the conclusion that additional information is required to unambiguously determine the composition of the ternary biofuel mixture. Among the different options of measurement domains and techniques, optical absorption spectroscopy in the UV spectral range between 230 and 300 nm was found to be the most appropriate. The typical absorbance in the UV range is highly dominated by gasoline, while ethanol and water are almost transparent. This approach is experimentally validated using actual fuels.@en

The optical absorption of water-containing bio-fuel is investigated as a parameter to determine the gasoline content of this fuel. Optical measurements reveal that gasoline shows an interesting and useful spectrum with typical absorption behavior in the UV range between 230 and 300 nm. This result indicates that significant information can be obtained to determine the gasoline concentration in bio-fuel by UV absorption spectroscopy. A concept for a low-cost measurement system in the fuel line is presented, by implementing a LVOF in combination with a wide-band light source and detector arrays.@en