Despite tremendous recent efforts, noninvasive sweat monitoring is still far from delivering its early analytical promise. Here, we describe a flexible epidermal microfluidic detection platform fabricated through hybridization of lithographic and screen-printed technologies, for efficient and fast sweat sampling and continuous, real-time electrochemical monitoring of glucose and lactate levels. This soft, skin-mounted device judiciously merges lab-on-a-chip and electrochemical detection technologies, integrated with a miniaturized flexible electronic board for real-time wireless data transmission to a mobile device. Modeling of the device design and sweat flow conditions allowed optimization of the sampling process and the microchannel layout for achieving attractive fluid dynamics and rapid filling of the detection reservoir (within 8 min from starting exercise). The wearable microdevice thus enabled efficient natural sweat pumping to the electrochemical detection chamber containing the enzyme-modified electrode transducers. The fabricated device can be easily mounted on the epidermis without hindrance to the wearer and displays resiliency against continuous mechanical deformation expected from such epidermal wear. Amperometric biosensing of lactate and glucose from the rapidly generated sweat, using the corresponding immobilized oxidase enzymes, was wirelessly monitored during cycling activity of different healthy subjects. This ability to monitor sweat glucose levels introduces new possibilities for effective diabetes management, while similar lactate monitoring paves the way for new wearable fitness applications. The new epidermal microfluidic electrochemical detection strategy represents an attractive alternative to recently reported colorimetric sweat-monitoring methods, and hence holds considerable promise for practical fitness or health monitoring applications.

Wearable sensors for noninvasive monitoring of physiological parameters is a growing technology in the clinical field. Especially in neonates, the development of portable and nonharmful monitoring devices is urgently needed because they cannot provide any feedback about discomfort or health complaints. However, in infant monitoring, only wearable sensors measuring physical parameters for vital signs have been developed. Here, we describe the first chemical wearable sensor for newborn monitoring. This fully integrated pacifier operates as a portable wireless device toward noninvasive chemical monitoring in the infant’s saliva. The infant’s mouth movements on the pacifier result in efficient saliva pumping and promote unidirectional flow from the mouth to the electrochemical chamber. The integrated electrochemical detection chamber, containing the enzymatic biosensor, is located outside of the oral cavity. The capabilities of the platform were studied for glucose detection in diabetic adults and compared to their blood levels with good correlation, demonstrating the sensor’s good performance. This baby-friendly device integrates saliva sampling with electrochemical sensing, along with miniaturized wireless electronics on a single pacifier platform. Such integration simplifies the infant′s health monitoring in a real-time and selective fashion, representing the first wearable sensor focusing on chemical saliva sensing in newborns. This initial demonstration of glucose monitoring introduces new possibilities for metabolites monitoring in infants and neonates using saliva as a noninvasive sample.

The lack of compact integration, including fusing of skin-interfaced direct, rapid independent data visualization along with light, safe stretchable batteries, hinders progress towards the creation of fully autonomous comprehensive wearable monitoring platforms. Here we present a highly integrated epidermal sensing platform combining electrochemical sensors with stretchable battery and ultra-low power digital display that instantaneously visualizes the results via 10 individually addressable electrochromic pixels. The all-around stretchable patch can operate independently as a standalone device to directly display the concentration of various electrolytes or metabolites, freeing it from any wired or wireless connection to other equipment. Fabricated via high-throughput printing of customized elastomeric inks, the integrated system presents robust mechanical performance, enduring over 1500 stretching cycles without affecting its sensing and display capabilities. The fast-responding display exhibits stability over 10,000 ON/OFF cycles, and upon coupling with the high-performance stretchable battery, can serve 14,000 sensing sessions in a week-long usage. Merging ultra-low power consumption, independent operation, rapid data display and superior mechanical performance, this fully autonomous multifunctional self-sustainable wearable sensing platform is of high practicality and convenience for diverse practical applications in professional sports, personalized wellness management, and beyond. MainSoft electronics have gathered considerable attention over the past decade as attractive alternatives to their rigid bulky counterparts, for applications in on-body sensing and human-machine interfacing. [1][2][3][4] In particular, many integrated epidermal sensing systems have been developed as "labs-on-the-skin", capable of recording a myriad of mechanical, electrical, physiological, and electrochemical signals, towards applications in healthcare, wellness and tness. [5][6][7][8] The current development of wearable sensors has evolved from the study of physical and chemical sensors alone towards the integration of sensors with energy management, signal acquisition, and data interfacing electronics. 9-14 Due to the lack of high-performance wearable batteries, most wearable electronics currently operate with commercial lithium polymer pouches or coin cells, which are rigid, unsafe, and bottlenecks the product design.Avoiding such battery-related design limitations, conformal epidermal sensors were often designed with wired connections or short-range power delivery schemes, which in turn compromise the system autonomy and limit the user's mobility. 9,11,15−18 Furthermore, such integrated sensors rely on wireless data transmissions, which calls for the need for external devices (e.g., computers, mobile smartphones, customized receivers) for users to obtain the sensing results. 9,11,19−21 Such lack of direct access to sensing results has led to the inconvenience and impracticality of many existing wearable sensors in their rea...

A flexible skin‐mounted microfluidic potentiometric device for simultaneous electrochemical monitoring of sodium and potassium in sweat is presented. The wearable device allows efficient natural sweat pumping to the potentiometric detection chamber, containing solid‐contact ion‐selective Na+ and K+ electrodes, during exercise activity. The fabricated microchip electrolyte‐sensing device displays good analytical performance and addresses sweat mixing and carry‐over issues of early epidermal potentiometric sensors. Such soft skin‐worn microchip platform integrates potentiometric measurement, microfluidic technologies with flexible electronics for real‐time wireless data transmission to mobile devices. The new fully integrated microfluidic electrolyte‐detection device paves the way for practical fitness and health monitoring applications.