Passively Powered Non-invasive Human Body Sensing on Bio-Degradable Conformal Substrates

Over the last decade excellent non-invasive sensing platforms have become available for capturing real-time health and lifestyle data, with the fitbit and Apple Watch being well known examples. However, current 'wearable' sensors all have major limitations: they connect to the body using straps and similar which do not maintain a good connection over long time periods; they have high power consumptions meaning the device must be taken off and recharged, at best, every couple of days; they contribute a significant amount to electronic waste. They are thus far from realising their true potential. This challenge is recognised by the EPSRC, with 'Disruptive technologies for sensing & analysis' being a core part of the 2015 Healthcare Technologies strategy. We propose to tackle this challenge by advancing novel material manufacturing approaches to realise next generation 'conformal' sensor nodes. This will make a disruptive next generation sensor platform for the very long term monitoring of a number of body parameters (motion, electrophysiological and temperature data) which is very different to current bio-sensing approaches.

Our novel manufacturing will enable sensors which are:
- Mounted on a conformal substrate, attaching directly to the skin without a strap, and maintaining contact for several days at a time.
- Manufactured using inkjet printing to allow minimal waste and responsive manufacturing, potentially tailoring each sensor to each person. Graphene nanoparticle based inks will replace current silver nanoparticle inks which, due to the inert nature of graphene, avoids the electronic waste issues associated with silver inks.
- Tailored with new ink and substrate formulations so that both the graphene ink and conformal substrate are 'transient'. That is, they work for a period of time and then naturally decompose into safe, inert and easily removed components, enabling easy use and disposal.
- 3D in nature by using 'popup' structures manufactured on pre-stressed substrates. This will allow 'actuated antennas', coupling the mechanical and electromagnetic properties of a 3D antenna in order to allow simultaneous sensing and transmission using the antenna component, significantly reducing the device size as conventional instrumentation can be removed.
- Ultra low power using a novel switching strategy to allow secure digital transmission over an RFID wireless link without the need for a dedicated, high power, analogue-to-digital converter microchip.
- Increased in wireless powering range, by devising reduced size epidermal antennas that exploit magnetically coupled loops in tattoo antennas with under 3 times the surface area of current approaches, reducing ink use for digital fabrication.
- Optimized for robustness to motion interference, allowing the collection of high quality signals in real-world, out-of-the-lab situations.
- Suitable for scale-up manufacturing with roll-to-roll and/or sheet fed printing of key elements, integrating with pick and place capabilities.
- Integrated into initial complete system demonstrators which will be showcased to our partners, covering the use of long term sensor nodes with people who are elderly and with children.

Collectively these represent a step change beyond 'wearable' devices available today. Our new sensors will be customisable battery-less RFID tags that can operate more than a metre from a powered reader, stay attached for many days at a time, and with a controlled lifetime set by the transient nature of the manufacturing. At this early stage we do not propose to target any one clinical application area, but rather to make the next generation of technologies for conformal on-body sensor nodes that collect longitudinal information relevant to a number of disease areas. We will work with our partners through pathways to impact activities to maximise the possibility of exposure to relevant end users in healthcare scenarios.

Health and society
The increasing costs of healthcare and the ageing population are two of the major challenges facing the UK. The proposed research will directly tackle these through the creation of new non-invasive sensors for long term sensing without requiring an explicit battery. These will have the potential to bring forward treatment to make it timelier and more effective, delay treatment to minimise interventions, and to shorten the time required to assess dosage. Thus the successful outcomes will have far-reaching impact on quality of life for users, and potentially carers who could be freed from performing tasks on behalf of the people they care for. The outcomes, particularly if they allow treatments to be delayed, could also allow many people to remain living at home rather than in care facilities, saving NHS and social care resources. A number of project partners are present to help ensure that this latent impact is exploited for potentially vulnerable users, particularly children and the elderly.

Economy
To reach the wider population through translation and commercialisation it is highly likely that patentable IP will be produced. (In the areas of 3D antennas, printable graphene ink formulations, and wireless power autonomy, amongst others.) This IP will be exploited in collaboration with University Intellectual Property offices and the project's industrial partners for the creation of small businesses, licenses to larger businesses, and hence economic growth. The investigators have a strong track record in doing this. Our current sensor tag technologies are being developed by Evidentia under the name 'Onables' developing new on-skin payment systems with interest from VISA ltd, and this effort has led to 2 new jobs at Evidentia. The current project will generate new impact by on-shoring advanced manufacturing of high-tech devices and the associated supply chains. The 2014 BIS 'Future of Manufacturing' report identifies key benefits to the UK economy in terms of trade surplus and robustness against recession as a consequence of 'on-shoring of manufacturing' and we will ensure that the equipment and skills present to do this are in the UK and will directly contribute to this BIS objective.

Knowledge and people
The research programme will make a step change in the critical mass of engineering and physical sciences skills in the UK to tackle emerging challenges in manufacturing and in healthcare. It will do this by making cross cutting advances that impact many technical areas, building knowledge in printed sensor node manufacture, materials for transient electronics, long term vital sign monitoring, and others. In addition, while the specific research carried out will be very focused on skin mounted transient conformal sensors, sensor driven interventions are emerging in a number of areas, from structural monitoring to energy management. It is thus highly likely that the technical advances arising from this research will impact these areas too, facilitating printed sensor based monitoring and feedback in several modalities and situations that are not currently possible. This will lead to wide ranging impact on scientific knowledge. A number of public engagement events based on the research are also built into the programme. These will ensure the manufacturing skills pathway is complete: giving skill and knowledge dissemination beyond the immediate research team; inspiring future engineers and scientists; and allowing the general public to connect with research leaders. Whenever possible the physiological data collected during the work will be made publicly available, providing a rich new data source for researchers worldwide in data mining experiments. Similarly, elements of hardware and software which do not fall within the commercialisation strategy will be made publically available under an appropriate open source license.