All-Fibrous Directional Moisture Wicking Electronic Skins for Biomechanical Energy Harvesting and All-Range Health Sensing

Health conditioning(调理) is defined here as an intervention by eating, exercising, alternative medicine and physical therapies, which can help body to return to a balanced or healthy or optimal or improved status from a less-healthy, sub-health or diseased condition. The Traditional Chinese Medicine (TCM) is playing a more and more important role in health conditioning and become recognized all over the world. However, TCM deals with the concepts of Yin-Yang, Qi-blood and six toxins of cold, hot, fire, wind, damp and dry, which categorically forms body constitutions for diagnosis and treatment. All of these do not have a modern scientific foundation and quantitative performance indicators, but strongly based on the experience and perception of human individuals and experts. As a whole, the TCM knowledge system is incomplete, unstructured and includes much uncertainty and imprecision while its diagnosis and treatment evolve with, person, environment and time.
On the other hand, wearable electronics has been a leading research theme in the past two decades to realise health monitoring/diagnosis all over the world, which represent coming generations of healthcare by deploying biosensors on and even within the body to collect a person’s physiological parameters in real time.[1-3] However, current wearable systems serve only as mobile physiological data loggers and transmitters, just allowing the recorded biological signals to be examined remotely by a supervising physician, but having no function of online intelligent diagnosis for treatment. Moreover, the rigid and solid materials of current wearable systems make the wearable experience bad, even unfeasible due to the fact of not breathable, not flexible enough to adapt to the human body and frequent charging. These demerits greatly restrict the further development and successful transformation of wearable electronics into clothing. Compared with modern medical treatments, TCM emphasizes more individualized cure with monitoring of body change in a long term, which can match the advantage of the wearable electronics. Those TCM concepts could be quantified and qualitied by the physiological data acquired by wearable systems.
In this regard, we designed a directional moisture-wicking electronic skin (DMWES) based on the construction of heterogeneous fibrous membranes and the conductive electrospraying layer. Unidirectional moisture transfer was successfully realized by surface energy gradient and push-pull effect via the design of distinct hydrophobic-hydrophilic difference, which can spontaneously transport sweat from the skin to the air to provide breathability which is essential for human comfort. The DMWES membrane shows excellent comprehensive epidermal pressure sensing performance, high sensitivity, wide linear range, rapid response and recovery time. In addition, the single-electrode triboelectric nanogenerator (STENG) based on the DMWES can deliver a high areal power density and good cycling stability. Moreover, the superior pressure sensing and triboelectric performance enabled the DMWES for all-range healthcare sensing, including accurate pulse monitoring, voice recognition, and gait recognition. This work will help to boost the development of the next-generation breathable electronic skins in the applications of artificial intelligence (AI) and TCM knowledge formalization.