The global medical technology market is expected to reach over $500 billion by 2020. Drivers include and a growing aging population, increase in chronic diseases and increased demand from emerging markets.
The exponential growth in wearable consumer products and medical devices that monitor biometric data has accelerated the need for a better interface between the electronics and the user. One of major overarching technical barriers in the advance of this application is the stiffness mismatch between the rigid components and soft substrate, which often results in interconnect failure.
Commercially available and near commercial wearable devices facilitate the transmission of biomedical informatics and personal health recording. Body worn sensors, which can provide real-time continuous measurement of pertinent physiological parameters noninvasively and comfortably for extended periods of time, are of crucial importance for emerging applications of mobile medicine. Wearable sensors that can wirelessly provide pertinent health information while remaining unobtrusive, comfortable, low cost, and easy to operate and interpret, play an essential role.
Nanomaterials enable new generation wireless communication, sensors and low-power electronics for connected health and are driving innovations in wearable medical devices.
Figure 1: A sensor based on silver nanowires is mounted onto a thumb joint to monitor the skin strain associated with thumb flexing. Credit: Shanshan Yao, North Carolina State University.
Wearable sensor systems based on flexible and stretchable nanomaterials have the potential to better interface to the human skin, whereas silicon-based electronics are extremely efficient in sensor data processing and transmission. Therefore, flexible and stretchable sensors combined with low-power silicon-based electronics are a viable and efficient approach for medical monitoring. However, nanomaterials allow for a combination of these qualities and are leading to the development of flexible medical devices designed for monitoring human vital signs, such as body temperature, heart rate, respiratory rate, blood pressure, pulse oxygenation, and blood glucose have applications in both fitness and sports performance monitoring and medical diagnostics (continuous diagnosis, wound care, drug delivery, and at-home diagnostics).
Nanomaterials enable improved sensor systems, sensing mechanisms, sensor fabrication, power, and data processing requirements and the construction of high performance optical and electronic systems that can flex, bend, fold and stretch, with ability to accommodate large (>>1%) strain deformation.
Patch-type skin sensors
Skin sensors containing unique structures constructed by either intrinsically soft materials or thin film materials on elastomer substrates are growing fast in the medical and healthcare sector. These devices can be simply mounted on bodies using fixtures such as bandages and body straps or use improved approaches that allow spontaneous skin attachment by van der Waals force using ultrathin and soft materials. In addition, pressure sensitive silicon adhesives can also be used to enhance the interface between the sensors and the skin, and offer reversible adhesion for long-term skin integration.
Figure 2: Graphene-based E-skin patch.
Image credit: Ulsan University.
Nanomaterials enable improved sensor systems, sensing mechanisms, sensor fabrication, power, and data processing requirements and the construction of high performance optical and electronic systems that can flex, bend, fold and stretch, with ability to accommodate large (>>1%) strain deformation. Pressure sensors are a key component in electronic skin (e-skin) sensing systems for health monitoring. Highly sensitive piezoelectric-type nanowire and graphene-based pressure sensors have been developed.
Figure 3: Gold nanomesh conductor on hand. Photo: Takao Someya Group, University of Tokyo.
Accurate measurement of skin hydration levels is important for analyzing various skin diseases and evaluating factors (e.g., environmental, age, and hormone related to abnormal skin responses. In addition, hydration can also be used for assessing effectiveness of anti-aging treatment, moisturizing treatments and other medical therapies. Researchers have developed epidermal hydration sensors based on nanowires for application in this area.
Figure 4: Nanowire skin hydration patch.
Photo credit: Shanshan Yao, North Carolina State University.
Several companies have developed wearable hydration sensors to monitor physiological signals. Kenzen has commercialized the ECHO Smart Patch for real-time sweat analysis. Other companies with near market products include NIX and LVL.
Wearable sweat sensors
Wearable biosensors enable continuous monitoring of metabolites (e.g. for diabetes monitoring) in sweat. Electrochemical analysis of sweat using soft bioelectronics on human skin provides a new route for non-invasive glucose monitoring without painful blood collection. Graphene has been widely investigated to develop wearable sweat sensors in this area. MC10 have developed a graphene-based electronic skin patch that senses excess glucose in sweat and automatically administers drugs by heating up microneedles that penetrate the skin.
Figure 5: Wearable sweat sensor.
Image credit: Northwestern University.
GraphWear Technologies has developed a wearable, real-time dehydration, glucose, and lactic acid monitor. The patch is placed on the lower back and linked to a smartphone app. The company plans to commercialize a device by 2018.
Smart footwear is also a growing area in the medical monitoring market. Spatial and temporal plantar pressure distributions are important and useful measures in footwear evaluation, athletic training, clinical gait analysis, and pathology foot diagnosis.
However, present plantar pressure measurement and analysis systems are usually uncomfortable to wear and expensive. Several companies are developing in-shoe pressure measurement and analysis systems based on a textile fabric sensor arrays, that are soft, light, and have a high-pressure sensitivity and a long service life.
Bonbouton has developed graphene-based smart insoles for preventative diabetic healthcare. The proprietary embedded graphene sensing system passively monitors the skin’s physiological signals in order to detect early signs of foot ulcers.
The company has developed a wearable patch sensor that is capable of detecting toxins (via produced, secondary metabolites) in sweat. The Sweatronics® platform offers a rapid and mobile solution for monitoring dehydration status using sweat biomarkers Readings are available in near real time on a mobile device. www.eccrinesystems.com
Graphene Healthcare Pte Ltd.
The company is developing remote healthcare monitoring devices. www.graphenesvc.com
Developing a graphene patch, SweatSmartTM which measures dehydration, glucose, and lactic acid levels, from sweat for application in wearable health monitoring. www.graphwear.co
The company develops magnetic nanosensors for medical diagnostics. www.magarray.com
The company is designing and integrating an ultra-thin, flexible electronics based, low cost, stretchable sensor system for precision measurement of levels of human hydration and motion for military and civilian needs. http://viscallc.com