Optical Hydrogel Detector for pH Measurements

Measuring pH has become a major key for determining health conditions, and food safety. The traditional pH assessment approaches are costly and offer low sensitivity. Here, a novel pH sensor based on a pH-responsive hydrogel has been developed. A Fresnel lens pattern was replicated on the surface of the pH-responsive hydrogel using the replica mould method. The pH sensors were tested in a pH range of 4–7. Introducing various pH solutions to the pH sensor led to volumetric shifts as the hydrogel swelled with pH. Consequently, the dimensions of the replicated Fresnel lens changed, modifying the focal length and the focus efficiency of the optical sensor. As a result, the measured optical power at a fixed distance from the sensor changed with pH. The optical sensor showed the best performance in the acidic region when pH changed from 4.5 to 5.5, in which the recorded power increased by 13%. The sensor exhibited high sensitivity to pH changes with a short respond time in a reversible manner. The developed pH optical sensor may have applications in medical point-of-care diagnostics and wearable continuous pH detection devices.

Machine Learning Techniques for Automated Tremor Detection in the Presence of External Stressors

In this study tremor data of 25 subjects (Senile tremor = 5, Alcohol induced tremor = 9, Healthy individuals = 11) were collected using a wearable device consisting of five Inertial Measuring Units (IMUs) and an embedded optical sensor. The subjects were made to draw the Archimedes spiral under the influence of external stressors. Features were extracted from measured acceleration data and also from an optical sensor. Using the selected features few supervised machined learning algorithms were explored for automatic classification of tremor. Performance matrix used to evaluate the classifier was accuracy, recall, and precision. It is observed that the algorithms are able to accurately classify healthy, senile tremor and alcohol induced tremor.

Optical Sensor Assembly On Knee Brace For Continuous Knee Monitoring Application

Knee joint is an important part of human body. People with poor knee condition generally have limited physical movement, rendering to mental stress and agony. Knee pain can be categorized into three groups, known as acute injury, chronic injury and medical condition. Current technology to support the knee diagnosis and treatment procedures are limited to the use of manual goniometer, x-ray and magnetic resonance imaging (MRI). Alternative devices with continuous measurement capability for knee monitoring are minimum at this time, mainly due to the difficulties to cover the wide angle of the knee flexion. X-ray and MRI technologies are useful to have some insight on the knee problem, but they are not applicable for continuous monitoring. Aside from being expensive for general use of MRI, x-ray on the other hand can cause short-term side effects due to radiation exposure. The aim of this paper is to demonstrate the use of optical sensor integrated with mechanical gear system as a knee monitoring device. A plastic compartment, made by using 3D printer is used to place the sensor and the gear system. The design of the overall device allows direct attachment on a knee brace for easy placement on the knee. Based on current study, the proposed sensor has a range of motion between 0 deg. to 160 deg., 0.08 deg. resolution as well as support continuous monitoring of the knee. The sensor performance has been demonstrated for gait motion, ascending and descending stairs, sit-to-stand movement and maximum knee flexion applications.