This multidisciplinary project will exploit an established UK based team's track record comprising RF & bio-sensing engineers, battery & materials scientists, and CPI, the UK National Catapult for Printed Electronics. Centred around Additive Manufacture and aimed towards scale-up, we will transform nascent wireless skin-based sensing to the high data rate capacity offered by upcoming communications systems using license-free 24 GHz channels. This will enable new streaming of biodata for remote diagnostics, monitoring and care, as well as ultra-low impact wireless EEG for forehead/ear/hair free regions. It will make possible the use of multiple sensing tags on multiple people simultaneously monitoring physiological parameters such as accelerometery (for activity tracking), photoplesmography (for heart rate monitoring), and sweat (for metabolite monitoring). At high data rate, this represents a step change over available technologies.
Manufactured on highly flexible, potentially stretchable, substrates the skin tags take the form factor of temporary tattoos and are highly long lasting, discrete for social acceptability, and can follow the micro-contours of the skin to give a large contact surface area and consequently sensing signal-to-noise ratio. To achieve our aims, we will advance wireless mmWave devices, on-skin electronics, low-power bio-sensing, and additive manufacture. Additionally, through CPI, we will develop scale-up processes for these mmWave devices.
Through existing investments the applicant team is positioning the UK for the large scale manufacture of on-skin sensor tags. EP/P027075/1 is creating an inkjet printing based manufacturing process for sensors on flexible substrates which avoids cleanrooms, uses graphene based ink formulations for biodegradability, and can be scaled up large run roll-to-roll screen printing. EP/R02331X/1 added the capability to print TiO2/LiFePO4 batteries integrated into the platform, removing a key integration bottleneck. This new proposal 'MultiSense' seeks to build upon the manufacturing base created by these two projects, extending it to overcome the key sensing limitation of current on skin tags: that they can only monitor one parameter from one person at a time, and at a comparatively low data rate. These projects are further limited to producing first principle non-elastic, low capacity integrated batteries and UHF frequency (868 MHz) RF devices which require print resolutions similar to conventional masks for wet etching (typically 200 um). Further, our experience of UHF RFID reveals transmission delays of 6 ms, and a reliable data rate upper limit of only 400 bps (corresponding to a sample rate of just 30 Hz for a modality such as accelerometry).
In MultiSense, we propose to overcome these limitations by moving from RFID to 24 GHz ISM (Industrial, Scientific Medical) band transmission, where very substantial uncongested bandwidth is available, offering orders of magnitude higher bit rates than UHF. In addition, the smaller wavelengths will increase antenna miniaturisation on integrated elastic substrate batteries, requiring print resolutions of 50 um. The new batteries will be solid state and polymer based with elastic current collectors. We will also investigate the mmWave signal surface guiding over the skin as a mechanism to allow for inter-patch communications. Sensing robustness will be improved as minor variations/misplacements in the sensor positions could be captured, and potentially corrected for in software. This will impact on diagnostic EEG measurements where currently entire datasets (from cabled electrodes) might be abandoned when individual electrodes disconnect. To enable the measurement of skin-based transmission between patches with new dry electrode designs, we will work with International Research Visitor Professor Koichi Ito of Chiba university, an expert in human phantom design.
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