A disposable, wearable, flexible, stitched textile electrochemical biosensing platform
Introduction
The field of wearable diagnostics has been growing in recent years (Bandodkar et al., 2019; Brothers et al., 2019; Chung et al., 2019; Gao et al., 2016; Lee et al., 2018; Matzeu et al., 2015). The ability to incorporate sensing technology into wearable devices to detect specific body movements, heart rate and body temperature has obvious benefits for the medical and sportswear industries; where products that fulfil this need have already been commercialized using conventional electronics (Germer et al., 2013; Xu et al., 2019). Notably, the success of the Apple watch and Fitbit® prove that there is a consumer demand for wearable sensing devices. To date however, most of these devices are rigid, brittle and expensive; so need to be incorporated into wearable watches or jewellery. Furthermore, they are unable to detect clinically relevant biomarkers. Whilst there have been some advances in the field of soft and flexible electronics for wearable sensing applications (Jeerapan and Poorahong, 2020), they still lack the breathability and ease of integration that a complete textile diagnostic sensing platform would offer (Keren et al., 2016; Munje et al., 2017). Textile based diagnostics have the advantage of not only being flexible, breathable and wearable; but can be easily incorporated into existing clothing manufacturing processes and can be produced on an industrial scale using existing technologies and infrastructure, which makes them cheap and scalable (Choudhary et al., 2015; Lund et al., 2018; Nilghaz et al., 2013; Oberg Mansson et al., 2020). As such, they can be used to realise disposable and single use wearable sensing modalities, which are prohibited by the high cost of smart watches and rings. Examples of disposable textile biosensing applications include, but are not limited to, testing for urinary tract infections in diapers (Reches et al., 2010) or infection in bandages (Derakhshandeh et al., 2018). Another useful application of textile sensors is in the field of glucose detection. Current technology requires diabetics to take regular blood samples to obtain blood glucose measurements using a glucometer. This is both invasive and gives a periodic sampling profile. It would be preferable to have a non-invasive continuous sensing platform capable of detecting glucose in the patients' sweat; since blood glucose levels and sweat glucose levels have been found to correlate (Gao et al., 2016; Lee et al., 2018; Moyer et al., 2012). Textiles offer the perfect platform for such devices as they can be integrated into clothing and mass manufacturing processes; and naturally come into good contact with the patients’ body and sweat. Such devices also have potential uses in the sportswear industry (Lee et al., 2017; Munje et al., 2017).
Much has been done on stress and movement sensors in the field of electrochemical textile sensors. However, non-invasive biomarker detection in excreted bodily fluids such as sweat (Katchman et al., 2018), urine (Liao et al., 2006), tears (Willcox, 2019), faeces (Pang et al., 2014), blood (Piper et al., 2018; Tsimikas et al., 2006) and milk (Alsaweed et al., 2015; Murphy et al., 2016) using electrochemical textile based biosensors is not widely reported. The current state of the art in flexible wearable sensors is primarily focussed on flexible polymer substrates with sensing elements integrated onto them (Jeerapan and Poorahong, 2020). These devices lack the breathability and ease of incorporation that an all textile sensor would offer, often needing adhesives to stick the patches onto the skin (Jeerapan and Poorahong, 2020). Alternatively screen printing electronics directly onto fabrics has been employed by Jeerapan et al., (2016), although this method would also reduce the breathability of the fabric at the sensor area. The current state of the art using conductive threads mostly involve the dip coating of threads with carbon pastes (Liu and Lillehoj, 2017) or elaborate methods of Au nanowire spin coating and electrodeposition of Au (Zhao et al., 2019); neither of which have been established as commercially viable. In the initial trails of this paper dip coated threads were tested but were found to crack and/or wick slowly towards the connection through the paste or inner cavities of a dip coated multifilament, leading to temporal instability of the signal and device failure over time.
Here we report for the first time the ability to stitch and functionalise a fully functioning electrochemical system into fabrics to create a cheap, disposable, stretchable and functional diagnostic platform, using commercially available Au plasma coated threads. In the devices reported here, the connection points of the threads can be quickly and easily separated from the electrode working area and any wicking to the connections is blocked. To validate the platform, it has been functionalised to make a label free continuous glucose sensor capable of detecting glucose in human sweat across a clinically relevant range. This involved functionalising the Au thread working electrodes with a thiolate self-assembled monolayer (SAM) compromising a glucose oxidase enzyme and a redox tagged thiol (6-Ferrocenylhexanethiol) which could be used to electrochemically regenerate the enzyme in situ and achieve a truly continuous glucose monitoring system by detecting the H2O2 produced by the enzymatic oxidation of glucose. Thiolate SAMs are perhaps the most widely used method of electrochemical sensor fabrication, to the best of the authors knowledge this is the first all textile device that can be functionalised with SAMs. This allows for their rapid integration with established SAM based biosensing methods to sense a broad range of biomarkers.
Section snippets
Thread measurements in solution
Au multifilament thread (Swicofil AG, Switzerland) was taken as arrived and cut into short fragments. Nail varnish (Revlon, Sweden) was painted in the middle of each fragment and then left to dry for 1h. the threads were then cut to length so that one side of the nail varnish was 3 cm long. This was dipped into a solution of 5 mM potassium ferricyanide (III) (Sigma-Aldrich, Sweden) in 1x phosphate buffered saline (PBS, made from a 1x PBS tablet and 500 mL of Merck Millipore MilliQ Ultrapure
Device design and fabrication
The devices could be lock stitched directly into the fabrics tested using a sewing machine with a nylon top thread and the Au multifilament as the bobbin thread. The Au coated multifilament threads are commercially available plasma coated PET single filaments (triangular in structure with a base width of 20 μm, see figure S1) that have been wound together to make a multifilament of 78 individual filaments. The basic electrochemistry of these threads in a wearable woven structure have been
Conclusions and future work
The efficacy and suitability of plasma coated Au conductive threads stitched into fabrics to make stitched electrochemical sensing platforms has been established. This all textile sensing platform using Au plasma coated multifilament threads stitched into Ripstop and an elastic blended knit could be stretched by 150% without impairment of the observed electrochemical response. The ability to functionalise the stitched devices and diagnostic utility of the platform have been established by
Author contributions
A.P., M.H., and I.Ö.M. conceived the original ideas. A.P. led the project, performed the experiments, and data analysis, and wrote the manuscript. I.Ö.M. helped with the device construction and the choice of materials, electrochemical characterisation and SEM measurements. R.L. helped develop the devices for portable potentiostat integration. S.K. did work on Au thread analysis and development.
CRediT authorship contribution statement
Andrew Piper: conceived the original ideas, led the project, performed the experiments, Formal analysis, and data analysis, and wrote the manuscript. Ingrid Öberg Månsson: conceived the original ideas, helped with the device construction and the choice of materials, electrochemical characterisation and SEM measurements. Shirin Khaliliazar: Formal analysis, did work on Au thread analysis and development. Roman Landin: helped develop the devices for portable potentiostat integration.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
The authors thank Contifibre for providing Coolmax yarn, and Swicofil for guidance and discussions on the metal plasma coated yarns. The authors also acknowledge the Knut and Alice Wallenberg Foundation and the European Research Council (Grant 715268) for funding.
References (41)
- et al.
Talanta
(2021) - et al.
Trends Biotechnol.
(2018) - et al.
Biosens. Bioelectron.
(2017) - et al.
Sensor. Actuator. B Chem.
(2015) - et al.
Sensor. Actuator. B Chem.
(2017) - et al.
J. Am. Coll. Cardiol.
(2006) - et al.
J. Cell. Biochem.
(2015) - et al.
J. Appl. Physiol.
(2018) - et al.
- et al.
Digit Biomark
(2019)
Accounts Chem. Res.
J. Appl. Physiol.
Biotechnol. Bioeng.
Lab Chip
J. R. Soc. Interface
Electroanalysis
Nature
J. Am. Chem. Soc.
J. Electrochem. Soc.
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