Toward a Disruptive "Click-and-Run" 3D Printing Concept for Manufacturing Epidermal Wearable Electrochemical Sensors.

Epidermal wearable sensing is a revolutionary concept with the potential of accomplishing a genuine digital transformation in research fields, such as sports physiology, clinical diagnostics, and health monitoring. The first wearable sweat sensor was reported 15 years ago, and despite the remarkable progress along this period, substantial challenges remain open concerning the complex nature of the manufacturing process. The recent democratization and extensive application of 3D printing technologies have made the automated fabrication of electrochemical sensors feasible, including their integration into complex structures such as microfluidic devices. Nevertheless, to the best of our knowledge, there is no evidence of full 3D printing automation (i.e., all fabrication steps) of an entirely functional epidermal wearable. In this context, we aim to contribute to the community by introducing the concept of "click-and-run" 3D printing, which refers to the complete printing of an epidermal wearable sensor (but not limited to) by just a "click" followed by a "run". The run refers to the fact that after the click, you "run" away so that no other operations need to be performed, but it also indicates that you can go directly to "run" the experiments after the click. Evidently, this new concept cannot be materialized with traditional 3D printers. Therefore, we share herein how we envision a new generation of 3D printers specifically designed for overcoming the actual issues related to the manufacturing process of wearable sensors. Accordingly, this perspective article is organized as follows: (i) an overview of the advantages of ubiquitous desktop 3D printers and their potential to facilitate click-and-run printing, (ii) a tutorial revision of the main desktop 3D printing techniques and their relationship to manufacture electrochemical sensors, (iii) the rationalization of the required parts for a wearable sensor, (iv) a review of the recent advances and achievements in 3D-printed wearable sensors, and (v) our own description of the new generation of "click-and-run" 3D printers.