Piezoresistive materials based on natural polymers for medical device applications

In nowadays society it has been an increase of life expectancy which has been accompanied by an increase in chronic diseases and loss of autonomy which promotes a constant demand for advanced healthcare treatments and diagnostic methods to improve the quality of life of the populations. Flexible detection devices have attracted increasing attention in recent years and are expected to continue to grow over the next decade due to their advantages in terms of user compliance for long term monitoring, improved skin-device coupling and the ability to develop low-cost and recyclable devices. Several of those sensing devices are based on the piezoresistive effect which have been used to monitor heart pulse, respiratory rate, and blood pressure, among others. Typically, these sensors are based on synthetic polymer, though the related environmental concerns are promoting their replacement by natural polymers, allowing to reduce waste and electronic waste (e-waste) accumulation in landfills and oceans, as well as the presence of microplastics. Thus, the main goal is incorporating flexible natural polymers that can replicate or even improve the properties of traditional synthetic materials while offering advantages such as non-toxicity, biocompatibility, durability, and biodegradability. In this review, flexible and sustainable piezoresistive sensors based on natural polymers for biomedical applications are presented, with potential use in areas including invasive blood pressure devices measurements, multivital signal monitoring, respiration rate monitoring and in catheter medical devices. This topic is highly relevant in current society as it bridges environmental concerns such as microplastics formation, climate change and waste management, with healthcare concerns, such ageing population, through the development of advanced environmentally friendly biomedical applications.