About the Project
Currently devices for wearable electronics are emerging1, but the energy harvesting and storage devices available nowadays are inadequate to be integrated into the textile and fibres for wearable electronics. Most of the portable electronic devices are driven by Li-ion batteries which are hard and stiff, and therefore cannot withstand bending or stretching without breaking. In addition, Li-ion batteries require daily charging from a power source, a technology that is incompatible with wearables. For advancing wearable electronics it is crucial to develop self-charging devices on textiles that are integrated with a wide range of wearable devices.
Human-generated mechanical energy is a ubiquitous energy source, but is generally wasted. Emerging technologies for harvesting human energy convert mechanical energy into electricity using piezoelectric, pyroelectric, and triboelectric2 effects. Among them, the triboelectric nanogenerator (TENG), having a laminated structure of several materials, converts mechanical energy into electricity using the coupling effects between triboelectrification and electrostatic induction. The working principle requires two dissimilar surfaces to be oppositely charged upon contact. Compared to other technologies, TENGs have advantages of low cost, high efficiency, high power density, light weight, and great manufacturability3. However, this field is still in its infancy and more research is needed to develop and implement TENGs as self-charging devices on textiles.
This project aims to develop TENG devices for wearable electronics. Graphene and nanocellulose, materials that combine outstanding mechanical, electrical, and triboelectric properties with bio- and textile compatibility will be investigated. Graphene has excellent mechanical4, electrical5, optical6, thermal7 conductivity, chemical resistance8, coating compatibility with textiles9, and its properties can be enhanced to unprecedented levels through chemical and physical bonding of different elements to its surface10 (i.e. graphene functionalisation). Although the first steps have been recently achieved towards the use of graphene in TENG11,12, i.e. as an electrode, as a triboelectric material, the technology is still far away from becoming smart clothing.
The functionalization of graphene which will be investigated in this project will open the way to tailor desired triboelectric properties and surface morphologies. Cellulose, the most abundant natural polymer on Earth, is another excellent candidate as triboelectric material, bringing unprecedented natural degradability, recyclability and biocompatibility to TENG systems. Nanocellulose-based mesoporous structures will be of particular interest for mechanical energy harvesters13. Taking advantage of the abundant hydroxyl groups on cellulose molecules, nanocellulose structures will be functionalized via simple wet-chemistry reactions and their electrical properties will be drastically tuned. This will allow to rationally tune the triboelectric polarity for TENG applications13. Finally, nanostructuring the materials to produce a metasurface in a TENG device will be used to amplify the produced energy by increasing the contact area of the surfaces and thus to enhance the power output.
The student will benefit from the CDT cohort by having access to outstanding experimental characterisation facilities and to the stimulating intellectual environment being able to connect to related research projects in the metamaterials themes.
1 Trung et al. Adv. Mater. (2016) 28, 4338;
2 Zi et al. Adv. Mater. (2015) 27, 2340;
3 Wang et al. ACS nano (2013) 7, 9533;
4 Lee et al. Science (2008) 321, 385;
5 Murali et al. Appl. Phys. Letters (2009) 94, 243114;
6 Nair et al. Science (2008) 320, 1208;
7 Balandin et al. Nano Letters (2008) 8, 902;
8 Kahng et al. Nanotechnology (2012) 23, 075702;
9 Neves et al. Sci. Rep. (2015) 7, 09866;
10 Khrapach et al. Adv. Mater. (2012) 24, 2844;
11 Huang et al Sci. Rep. (2015) 5, 13942;
12 Chu et al. Nano Energy (2016);
13 Small 2017, 1702240.
Funding Notes
The studentship is part of the UK’s Centre of Doctoral Training in Metamaterials (XM2) based in the Departments of Physics and Engineering on the Streatham Campus in Exeter.
XM2 studentships are of value around £90,000, which includes £11,000 towards the research project (travel, consumables, equipment etc.), tuition fees, and an annual, tax-free stipend of approximately £14,500 per year for UK/EU students.
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