POC device for rapid oral pH determination based on a smartphone platform.

Salivary pH serves as a valuable and useful diagnostic marker for periodontal disease, as it not only plays a critical role in disease prevention but also in its development. Typically, saliva sampling is collected by draining and spitting it into collection tubes or using swabs. In this study, we have developed a Point-of-Care (POC) device for in situ determination of oral pH without the need for complex instruments, relying solely on a smartphone as the detection device. Our system utilizes a non-toxic vegetable colourimetric indicator, immobilized on a chitosan membrane located on a disposable stick, enabling direct sampling within the buccal cavity. An ad hoc designed 3D-printed attachment is used to ensure accurate positioning and alignment of the stick, as well as isolation from external lighting conditions. A custom-developed smartphone application captures and automatically processes the image of the sensing membrane, providing the salivary pH results. After optimizing the cocktail composition, the developed sensors demonstrated the capacity to determine pH within a range of 5.4 to 8.1 with a remarkable precision of 0.6%, achieving a very short analysis time of just 1 min. A stability study conducted on the sensing membranes revealed a lifetime of 50 days. To validate the performance of our analytical device, we compared its results against those obtained from a calibrated pH-meter, using a group of individuals. The device exhibited an average error of 2.4% when compared with the pH-meter results, confirming its reliability and accuracy.

Capacitive platform for real-time wireless monitoring of liquid wicking in a paper strip.

Understanding the phenomenon of liquid wicking in porous media is crucial for various applications, including the transportation of fluids in soils, the absorption of liquids in textiles and paper, and the development of new and efficient microfluidic paper-based analytical devices (µPADs). Hence, accurate and real-time monitoring of the liquid wicking process is essential to enable precise flow transport and control in microfluidic devices, thus enhancing their performance and usefulness. However, most existing flow monitoring strategies require external instrumentation, are generally bulky and unsuitable for portable systems. In this work, we present a portable, compact, and cost-effective electronic platform for real-time and wireless flow monitoring of liquid wicking in paper strips. The developed microcontroller-based system enables flow and flow rate monitoring based on the capacitance measurement of a pair of electrodes patterned beneath the paper strip along the liquid path, with an accuracy of 4 fF and a full-scale range of 8 pF. Additionally to the wired transmission of the monitored data to a computer via USB, the liquid wicking process can be followed in real-time via Bluetooth using a custom-developed smartphone application. The performance of the capacitive monitoring platform was evaluated for different aqueous solutions (purified water and 1 M NaCl solution), various paper strip geometries, and several custom-made chemical valves for flow retention (chitosan-, wax-, and sucrose-based barriers). The experimental validation delivered a full-scale relative error of 0.25%, resulting in an absolute capacitance error of ±10 fF. In terms of reproducibility, the maximum uncertainty was below 10 nl s-1 for flow rate determination in this study. Furthermore, the experimental data was compared and validated with numerical analysis through electrical and flow dynamics simulations in porous media, providing crucial information on the wicking process, its physical parameters, and liquid flow dynamics.

System Based on an Inertial Measurement Unit for Accurate Flight Time Determination in Vertical Jumps.

The world of elite sports has always been characterized by intense competition, where victories are often determined by minimal differences. This means that every little detail in the preparation of top-level athletes is crucial to their performance at the highest level. One of the most significant aspects to monitor is the jumping capacity, as it enables the measurement of performance, progression, and helps prevent injuries. Herein, we present the development of a system capable of measuring the flight time and height reached by the user, reporting the results through a smartphone using an Android ad-hoc application, which handles all the data processing. The system consists of an affordable and portable circuit based on an accelerometer. It communicates with the smartphone via UART using a Bluetooth module, and its battery provides approximately 9 h of autonomy, making it suitable for outdoor operations. To evaluate the system's precision, we conducted performance tests (counter-movement jumps) with seven subjects. The results confirmed the system's potential for monitoring high-level sports training sessions, as the average deviation obtained was only 2.1% (~0.01 s) in the analysis of flight time and 4.6% (~0.01 m) in jump height.

SARS-CoV-2 viral RNA detection using the novel CoVradar device associated with the CoVreader smartphone app.

The COVID-19 pandemic has highlighted the need for innovative approaches to its diagnosis. Here we present CoVradar, a novel and simple colorimetric method that combines nucleic acid analysis with dynamic chemical labeling (DCL) technology and the Spin-Tube device to detect SARS-CoV-2 RNA in saliva samples. The assay includes a fragmentation step to increase the number of RNA templates for analysis, using abasic peptide nucleic acid probes (DGL probes) immobilized to nylon membranes in a specific dot pattern to capture RNA fragments. Duplexes are formed by labeling complementary RNA fragments with biotinylated SMART bases, which act as templates for DCL. Signals are generated by recognizing biotin with streptavidin alkaline phosphatase and incubating with a chromogenic substrate to produce a blue precipitate. CoVradar results are analysed by CoVreader, a smartphone-based image processing system that can display and interpret the blotch pattern. CoVradar and CoVreader provide a unique molecular assay capable of detecting SARS-CoV-2 viral RNA without the need for extraction, preamplification, or pre-labeling steps, offering advantages in terms of time (∼3 h/test), cost (∼€1/test manufacturing cost) and simplicity (does not require large equipment). This solution is also promising for developing assays for other infectious diseases.

Digital Optical Ballistocardiographic System for Activity, Heart Rate, and Breath Rate Determination during Sleep.

In this work, we present a ballistocardiographic (BCG) system for the determination of heart and breath rates and activity of a user lying in bed. Our primary goal was to simplify the analog and digital processing usually required in these kinds of systems while retaining high performance. A novel sensing approach is proposed consisting of a white LED facing a digital light detector. This detector provides precise measurements of the variations of the light intensity of the incident light due to the vibrations of the bed produced by the subject's breathing, heartbeat, or activity. Four small springs, acting as a bandpass filter, connect the boards where the LED and the detector are mounted. Owing to the mechanical bandpass filtering caused by the compressed springs, the proposed system generates a BCG signal that reflects the main frequencies of the heartbeat, breathing, and movement of the lying subject. Without requiring any analog signal processing, this device continuously transmits the measurements to a microcontroller through a two-wire communication protocol, where they are processed to provide an estimation of the parameters of interest in configurable time intervals. The final information of interest is wirelessly sent to the user's smartphone by means of a Bluetooth connection. For evaluation purposes, the proposed system has been compared with typical BCG systems showing excellent performance for different subject positions. Moreover, applied postprocessing methods have shown good behavior for information separation from a single-channel signal. Therefore, the determination of the heart rate, breathing rate, and activity of the patient is achieved through a highly simplified signal processing without any need for analog signal conditioning.

Commercial photodiodes and phototransistors as dosimeters of photon beams for radiotherapy.

PURPOSE: The response to radiation typically used in radiotherapy treatments has been experimentally evaluated for three samples of two phototransistors (BPW85B and OP505A) and two PIN photodiodes types (VTB8440BH and BPW34S). METHODS: To that end, a staggered irradiation cycle has been applied which included dose rate values from 0.81 to 4.87 cGy/s, achieving a total absorbed dose of 21.4 Gy. The samples have been irradiated with a linear accelerator and the relations between the induced photocurrent and the average and instantaneous dose rates, and between the accumulated charge and the absorbed dose, have been determined. The radiation-induced output currents were measured by means of an external interface of the devices to a previously designed readout unit. RESULTS: Experimental results of Si PIN photodiode BPW34S have shown a sensitivity of (13.9 ± 0.5) nC/cGy, slight sensitivity dependence on dose rate, and a high linearity of the current with the average and instantaneous dose rate, requiring only 10 V of reverse bias voltage. This device thermal drift has characterized and modeled for temperature effect compensation. CONCLUSIONS: Silicon PIN photodiode BPW34S, previously tested for X-rays and Co-60 gamma ray source, can also be a reliable candidate for dose rate and absorbed skin dose determination in typical radiotherapy treatments irradiations. A low sensitivity loss below 2% up to 21.4 Gy has been measured, allowing its use as an affordable reusable skin dosimeter. Moreover, no significant difference has been observed between its response to dose-per-pulse and changing pulse repetition frequency in terms of sensitivity and dependence with dose-rate value.

Development and Evaluation of a Low-Drift Inertial Sensor-Based System for Analysis of Alpine Skiing Performance.

In skiing it is important to know how the skier accelerates and inclines the skis during the turn to avoid injuries and improve technique. The purpose of this pilot study with three participants was to develop and evaluate a compact, wireless, and low-cost system for detecting the inclination and acceleration of skis in the field based on inertial measurement units (IMU). To that end, a commercial IMU board was placed on each ski behind the skier boot. With the use of an attitude and heading reference system algorithm included in the sensor board, the orientation and attitude data of the skis were obtained (roll, pitch, and yaw) by IMU sensor data fusion. Results demonstrate that the proposed IMU-based system can provide reliable low-drifted data up to 11 min of continuous usage in the worst case. Inertial angle data from the IMU-based system were compared with the data collected by a video-based 3D-kinematic reference system to evaluate its operation in terms of data correlation and system performance. Correlation coefficients between 0.889 (roll) and 0.991 (yaw) were obtained. Mean biases from -1.13° (roll) to 0.44° (yaw) and 95% limits of agreements from 2.87° (yaw) to 6.27° (roll) were calculated for the 1-min trials. Although low mean biases were achieved, some limitations arose in the system precision for pitch and roll estimations that could be due to the low sampling rate allowed by the sensor data fusion algorithm and the initial zeroing of the gyroscope.

Light-Dependent Resistors as Dosimetric Sensors in Radiotherapy.

Safe quality control of radiotherapy treatments lies in reliable dosimetric sensors. Currently, ionization chambers and solid-state diodes along with electrometers as readout systems are accomplishing this task. In this work, we present a well-known and low-cost semiconductor sensor, the light-dependent resistor (LDR), as an alternative to the existing sensing devices for dosimetry. To demonstrate this, a complete characterization of the response to radiation of commercial LDRs has been conducted in terms of sensitivity, reproducibility and thermal correction under different bias voltages. Irradiation sessions have been applied under the common conditions in radiotherapy treatments using a hospital linear accelerator. Moreover, the same electrometer used for the ionization chamber has also been successfully used for LDRs. In comparison with the sensitivity achieved for the ionization chamber (0.2 nC/cGy at 400 V bias voltage), higher sensitivities have been measured for the proposed LDRs, ranging from 0.24 to 1.04 nC/cGy at bias voltages from 30 to 150 V, with a reproducibility uncertainty among samples of around 10%. In addition, LDR temperature dependence has been properly modeled using the simple thermistor model so that an easy thermal drift correction of dose measurements can be applied. Therefore, experimental results show that LDRs can be a reliable alternative to dosimetric sensors with the advantages of low size, affordable cost and the fact that it could be adopted with minimal changes in routine dosimetry quality control since the same readout system is fully compatible.