Nanomaterials are enabling flexible, wearable “E-skin” sensor devices for in vitro diagnostics and therapeutics.
Nanotechnology is a key component in diagnosing the state of diseases and offer patients with target-specific medications at the required dosage and is allowing for new advances in wearable theranostics approaches.
There is an ongoing market transition from universal medicine to individualized medicine that involves new approaches for customized theranostics based on interpersonal variation to drug response. 1
Currently utilized wearable devices for health monitoring have limited capabilities whereas nano-enabled Implantable and wearable healthcare devices will allow for devices such as pacemakers, heart rate and blood pressure monitors with increased speed and reliability.
Wearable health monitoring
In healthcare, there is a growing need to support independent living in a globally aging population and support active and healthy living. The medical industry is transforming itself through the use of digital technologies. The “Internet of Things” will impact the healthcare industry through monitoring, personalized medicine and medical diagnosis.
Remote monitoring is desirable for enabling palliative care in the home and tracking treatment programmes for persons with intellectual or cognitive disabilities in the home. The remote monitoring of biomarkers is also useful for monitoring conditions such as diabetes and perinatal monitoring and diagnosis.
Recently, human-machine interfaces as well as the healthcare system have experienced great advancement through the introduction of implanted and skin-mounted electronics (‘e-skins’). 2 3
However, the power supplying system has not kept pace with technological advances of such electronics. There is therefore need to develop new materials for power sources to meet these needs.
Nanotechnology solutions
Demand for electronics on flexible and transparent substrates has increased greatly over the past few years. The unsuitability of indium tin oxide (ITO) for flexible and stretchable electronics applications has opened up opportunities for nanomaterials.
The properties of substrates are crucial, including flexibility, surface roughness, optical transmittance, mechanical strength, maximum processing temperature, etc. Flexible integrated circuits (ICs) with complex functionalities are crucial for the development of wearable electronic devices. The development of future flexible electronics relies on novel materials that are:
• Mechanically flexible.
• Lightweight.
• Low-cost.
• Electrically conductive.
• Optically transparent.
Nanomaterials enable new generation wireless communication, sensors and low-power electronics for connected health and are driving innovations in wearable medical devices.
Graphene, other 2D materials, silver nanowires and carbon nanotubes as well as organic and polymer-based active materials are viewed as important materials for the development of wearable electronics for implementation in healthcare and fitness monitoring, electronic devices incorporated into clothing and ‘smart skin’ applications (such as printed graphene-based sensors integrated with other 2D materials for physiological monitoring). 4 5
Figure 1: Wearable health monitor incorporating graphene photodetectors.
Image credit: ICFO.
Flexibility
Nanomaterials are enabling development 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 such as graphene are naturally suitable for integration with flexible, soft or glass substrates owing to their two dimensional nature and can potentially offer the electronic performance needed for low-power GHz systems.
Figure 2: Graphene-based E-skin patch.
Image credit: Ulsan University.
Sensors
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. 6 7 In April 2016, researchers from the University of Tokyo developed a flexible OLED display capable of being placed on a person’s skin. 8
Figure 3: Smart e-skin system comprising health-monitoring sensors, displays, and ultraflexible PLEDs.
(A) Schematic illustration of the optoelectronic skins (oe-skins) system. (B) Photograph of a finger with the ultraflexible organic optical sensor attached. (C) Photographs of a human face with a blue logo of the University of Tokyo and a two-color logo. The brightness can be changed by the operation voltage. (D) Photograph of a red seven-segment PLEDs displayed on a hand.
Image credit: Someya Laboratory.
Energy storage
A crucial challenge is developing fully integrated, lightweight, wearable and high-performance energy-storage devices to power the functioning devices in a wearable system. Flexible graphene supercapacitors have been fabricated to meet this challenge. 9 10
Commercial activities
Graphwear Technologies (www.graphwear.co) are developing a graphene patch which measures dehydration, glucose, and lactic acid levels, from sweat for application in wearable health monitoring.
Swiss Federal Institute of Technology (EPFL) spin-off Xsensio (www.xsensio.com), created in 2014 is developing “Lab-on-SkinTM” wearable devices. The devices are wearable intelligent stamps that analyze biomarkers (e.g. electrolytes, proteins, molecules, bacteria) at the surface of the skin to provide real-time health monitoring. The company’s product comprises a zero‐power, capillary nanofluidic channels interface for on‐body, sweat surface‐collection and delivery for for analyte detection in biofluids
REFERENCES
1. Blanchet KD. Redefining personalized medicine in the postgenomic era: developing bladder cancer therapeutics with proteomics. BJU Int. 2010; 105: i-iii.
2. D. –H. Kim, J. Viventi, et al., Nat. Mater. 9 (2010) 511.
3. X. Pu, L. Li, H. Song, C. Du, Z. Zhao, C. Jiang, G. Cao, W. Hu, Z. L. Wang, Adv. Mater., 27 (2015) 2472.
4. Stretchable, Porous, and Conductive Energy Textiles, http://pubs.acs.org/doi/abs/10.1021/nl903949m
5. Solution-Processed Graphene/MnO2 Nanostructured Textiles for High-Performance Electrochemical Capacitors, http://pubs.acs.org/doi/abs/10.1021/nl2013828
6. Taxel-addressable matrix of vertical-nanowire piezotronic transistors for active and adaptive tactile imaging, https://www.ncbi.nlm.nih.gov/pubmed/23618761
7. Stretchable and Multimodal All Graphene Electronic Skin, http://onlinelibrary.wiley.com/doi/10.1002/adma.201505739/full
8. Ultraflexible organic photonic skin, http://advances.sciencemag.org/content/2/4/e1501856
9. Wearable energy-dense and power-dense supercapacitor yarns enabled by scalable graphene–metallic textile composite electrodes, http://www.nature.com/ncomms/2015/150611/ncomms8260/full/ncomms8260.html
10. High-Performance Multifunctional Graphene Yarns: Toward Wearable All-Carbon Energy Storage Textiles, http://pubs.acs.org/doi/abs/10.1021/nn406026z
