Non-invasive glucose detection with smart textiles
The increasing prevalence of diabetes worldwide has heightened the need for innovative and patient-friendly glucose monitoring technologies. Wearable devices that integrate non-invasive glucose sensors into everyday clothing can further enhance user comfort and seamlessly fit into daily routines, making health management more intuitive and less intrusive.
Smart textiles have revolutionised the landscape of wearable technology, merging the realms of fashion and advanced electronics to create garments capable of monitoring a range of physiological parameters. These innovative fabrics incorporate sensors, actuators and other electronic components, offering a seamless integration of technology into everyday clothing. Applications of smart textiles span various fields including sports, fitness, military and healthcare, providing real-time data and enhancing user experience.
In the realm of healthcare, smart textiles hold the potential to transform patient monitoring and management. By embedding sensors directly into fabrics, these textiles can continuously track vital signs such as heart rate, respiration, body temperature and activity levels. This continuous monitoring can lead to early detection of health issues, prompt interventions and personalised treatment plans, significantly improving patient outcomes and reducing healthcare costs.
One of the critical advantages of smart textiles is their ability to provide non-invasive monitoring, which greatly enhances user comfort and compliance. Unlike traditional medical devices that often require direct skin contact or implantation, smart textiles offer a non-intrusive alternative, making them ideal for long-term wear and everyday use. The flexibility and adaptability of these textiles ensure that they can conform to the body’s movements, providing accurate and reliable data without compromising comfort.
Increasing prevalence of diabetes
The increasing prevalence of diabetes worldwide has heightened the need for innovative and patient-friendly glucose monitoring technologies. According to the International Diabetes Federation, approximately 463 million adults were living with diabetes in 2019, a number projected to rise to 700 million by 2045. Traditional glucose monitoring methods, such as finger-prick blood tests, are often painful, inconvenient and discourage regular testing, leading to poor disease management and increased risk of complications.
Non-invasive glucose sensing technologies using sweat or saliva offer a compelling alternative, enabling continuous monitoring without the discomfort and inconvenience of blood draws. This can lead to better patient compliance, more accurate and timely adjustments to treatment plans and overall improved health outcomes. Wearable devices that integrate non-invasive glucose sensors into everyday clothing can further enhance user comfort and seamlessly fit into people’s daily routines, making health management more intuitive and less intrusive.
Organic electrochemical transistors
Organic electrochemical transistors (OECTs) are an emerging technology in bioelectronics, notable for their exceptional sensitivity and compatibility with biological systems. They operate by utilising a conductive polymer channel interfaced with an electrolyte, where applying a voltage to the gate electrode causes ions from the electrolyte to penetrate the polymer channel, modulating its conductivity. This ion-to-electron transduction capability is pivotal for biosensing applications. The working principle of OECTs involves three main components: the source and drain electrodes, the conductive polymer channel, and the gate electrode immersed in an electrolyte. Applying a potential between the source and drain allows current to flow through the conductive channel, and introducing a gate voltage causes ions from the electrolyte to enter the polymer, altering its conductivity and modulating the current between the source and drain. This modulation of current in response to ionic changes enables OECTs to detect various biological and chemical signals with high sensitivity.
OECTs are particularly important for biosensing applications due to their ability to directly interface with biological fluids, detect a wide range of analytes and operate at low voltages, making them safe for use in wearable devices. Their simple design, flexibility and adaptability to different substrates, including textiles, make them ideal for integration into smart fabrics, enabling real-time health monitoring.
Glucose sensing with textile-based OECTs
A textile-based organic electrochemical transistor was developed to quantitatively detect glucose levels as found in human sweat. This transistor has a layered structure, where the gate and source-drain electrodes (conductive polymer channel) are glued together by a hardened electrolyte. In this layered structure, it is essential that the conductive polymer channel is porous, allowing substances to penetrate into the electrolyte layer. The conductive channel material is made from different porous PEDOT:PSS structures produced using scaffolding material, blowing agents, or spraying a porous base material. These structures were integrated into the OECT by laminating a conductive (silver-coated) fabric with the electrolyte and placing the porous structures into the still liquid electrolyte before hardening.
For glucose detection, the electrolyte of the transistor was modified with the enzyme glucose oxidase (GOx). GOx catalyses the oxidation of glucose to gluconic acid (D-glucono-δ-lactone) and hydrogen peroxide (H2O2) using molecular oxygen as an electron acceptor. This oxidation reaction of H2O2 is further catalysed at the gate electrode, resulting in a reduction of PEDOT:PSS in the channel and thereby a decrease in channel conductivity. In this way, glucose detection with organic electrochemical transistors becomes possible.
The developed transistors were exposed to glucose solutions with concentrations found in human sweat (10 µM, 100 µM, 1 mM). Their current output at constant gate and source-drain voltage was measured and contrasted to the transistors’ reaction towards 0.9% saline solution and distilled water. Transistors with the GOx modified electrolyte show much higher sensitivity towards glucose than towards other tested analytes. The current changes by about 10% (10 µM) to 50% (1 mM) depending on the glucose concentration. These outcomes prove that not only the qualitative detection but also the quantitative measurement of glucose levels is possible.
A glance into the future
Textile-based organic electrochemical transistors offer significant potential for continuous, non-invasive monitoring of glucose levels, crucial for managing diabetes and other health conditions. However, further research is needed to address challenges such as cross-sensitivity, long-term durability, mechanical stress resistance and optimisation of the sensing components. Future studies should focus on comprehensive testing under various physiological conditions, investigating the reaction and recovery times of these devices, exploring their reusability, and improving the robustness of the porous PEDOT:PSS structures and their integration into the OECT structure. Overcoming these challenges will be essential for the successful implementation of OECTs in real-world applications, paving the way for advancements in wearable biosensing technologies and contributing to better health outcomes and disease management.
The author
Rike Brendgen (MSc) is a research associate at the Research Institute for Textiles and Clothing (FTB) at Niederrhein University of Applied Sciences, Mönchengladbach, Germany. In her research, she focuses on smart textiles, especially organic electrochemical transistors and sensor development. Brendgen is currently involved in two research projects: Enamel (Encapsulating Materials and Processes for E-Textiles, Cornet 379EN) and Edu4SmartTex (International and Interdisciplinary Bachelor‘s Degree Program "Smart Textiles", DAAD/German academic exchange service).
Caption: Rike Brendgen, the author of this article, and one of the developed glucose measuring smart textiles.