Wearable and flexible health sensing devices are nowadays crucial and the development of multi-sensing wearable textiles for non-invasive motion detection and continuous long-term biophysical signal monitoring is of primary interest. As a matter of fact, the wearable technology market forecast is at more than 20% growth rate annually and it is expected to reach over 40 billion EUR per year in the next 5 years. In this context, a central role is played by composite materials and, among them, graphene based nanocomposites are promising candidates for the development of multi-sensing wearable sensing textiles through screen printing or cast deposition techniques. Recently, several wearable polymeric sensors have been proposed. Most of them mainly focus on two aspects: movement, respiration rate and temperature detection or measurement of biopotential signals. For instance, PDMS based nanocomposites have been proposed for biopotential signal monitoring, replacing conventional electrodes. However, such biopotential sensors generally are not suitable to detect also motion, temperature or other physiological parameters, i.e. to work as multi-sensing elements. The aim of the research project is to overcome this bottleneck producing graphene based coated textiles able to conjugate electrical and piezoresistive properties with the aim of producing multi-sensing wearable sensors by direct deposition on commercial textiles (like T-shirt or fitness bands), without compromising fabric flexibility and stretchability. In addition, the coated textiles will be designed in order to guarantee washability, reusability and to prevent coating detachment. With this purpose, different designs and data processing will be proposed, investigating different polymeric matrices, shapes, sizes, etc. Then, data fusion algorithm will be developed in order to extract all the desired parameters
The final goal of this project is the development of an innovative multi-sensing graphene based coatings to be cast directly onto commercial fabrics through cast deposition or screen printing techniques, in order to realize multi-sensing graphene based wearable textiles able to detect at the same time motion, temperature, respiration rate and biopotential signals.
This goal is innovative from two points of view:
- The sensing element production
- The sensing output analysis
The sensing element production is innovative since it is aimed at realizing graphene based coatings designed in order to be biocompatible and to guarantee washability, reusability, durability, to prevent coating detachment from the textile without compromising flexibility and stretchability and to conjugate sensing properties with electrical ones.
In fact, despite extensive research efforts, the production of graphene based coatings for the realization of functionalized textiles is still an open issue due to problems in coating adhesion, properties loss during washing cycles, more delicate handling needs of coated textiles with respect to uncoated ones [24]-[26]. Furthermore, the graphene coatings must be biocompatible in order to guarantee long-term wearability and to avoid skin irritations. Hence, particular emphasis is given to this aspect and a polymer mixture (PVDF/PDMS) is also considered. Then, the produced multi-sensing graphene based textiles will conjugate piezoresistive properties with the ability to work as electrodes for the detection of biopotential signals like ECG and EMG without any skin preparation or the use of any conducting gel. This represents a great advantage since nowadays ECG measurements generally employ electrodes with a conductive gel that could dry over time, giving rise to several drawbacks such as measurement errors due to increase in both skin-electrode impedance and motion artifacts [10-12]. Moreover, conventional gelled electrodes are not waterproof and they are suitable for one-time use only and, when used for more than a couple of days, many patients develop allergic reactions or other forms of skin irritation [12-13].
It should also be highlighted that the proposed multi-sensing system is metal free since it does not contain any metallic particles, nor as nanofillers nor as remaining elements of the functionalization of carbon based nanofillers. Therefore, there are no issues concerning possible allergic reactions due to contact with metals (e.g. Nickel).
The sensing output analysis is innovative since, differently from common wearable multi sensing platforms, where each sensor can measure only a single quantity, in the proposed multi-sensing system there is an abundance of data available since each sensing element can measure different quantities at the same time. Therefore, new signal processing and data fusion algorithms will be developed, in order to separate the different bio-signals and physiological parameters detected by each multi-sensing element. This feature will allow a better accuracy of the final result.