Non-invasive flexible sensor based on liquid metal for human physiological detection

Flexible sensors play an important role in simulation, brain-computer interaction, intelligent robots, and biological detection. Due to the progress of modern medical means, the construction of wearable flexible sensors to realize remote and continuous monitoring of human physical indicators and physiological parameters has become a hot research topic. Non-invasive sensor is a device that can detect physiological parameters without cutting the skin or puncturing the body. They have wide application prospects in the fields of medical treatment, fitness, and daily care due to the following advantages: real-time monitoring, portability, accuracy, and cost reduction. Liquid metal has become a great candidate for constructing flexible biosensors because of its high conductivity, deformability, self-healing, and bio-friendly properties, its spontaneous formation of an oxide film due to exposure to oxygen provides a convenient reaction platform for the preparation of other materials. Two-dimensional materials are inherently superior in preparing sensors due to their great advantages unique chemical and physical properties, their high surface area-to-volume ratios and ultra-high surface sensitivity to the environment also can be used to prepare flexible sensor. This study presents an overview and introduction of biosensors fabricated by liquid metal and two-dimensional materials, including how to prepare specific two-dimensional materials based on liquid metal, and the stripping method is also included. Three kinds of applications are discussed in detail, including the detection of human glucose concentration, pulse detection, and sweat analysis, whose sensing principles depend on piezoelectric, optical, and electrochemical. At the end of the article, we summarized the current challenges faced by biosensors based on liquid metal and looked forward to its future development and future directions of advances.