Background

In neurology and rehabilitation the primary interest for using wearables is to supplement traditional patient assessment and monitoring in hospital settings with continuous data collection at home and in community settings. The aim of this project was to develop a novel wearable garment with integrated sensors designed for continuous monitoring of physiological and movement related variables to evaluate progression, tailor treatments and improve diagnosis in epilepsy, Parkinson’s disease and stroke.

Methods

In this paper the early development and evaluation of a prototype designed to monitor movements and heart rate is described. An iterative development process and evaluation of an upper body garment with integrated sensors included: identification of user needs, specification of technical and garment requirements, garment development and production as well as evaluation of garment design, functionality and usability. The project is a multidisciplinary collaboration with experts from medical, engineering, textile, and material science within the wearITmed consortium. The work was organized in regular meetings, task groups and hands-on workshops. User needs were identified using results from a mixed-methods systematic review, a focus group study and expert groups. Usability was evaluated in 19 individuals (13 controls, 6 patients with Parkinson’s disease) using semi-structured interviews and qualitative content analysis.

Results

The garment was well accepted by the users regarding design and comfort, although the users were cautious about the technology and suggested improvements. All electronic components passed a washability test. The most robust data was obtained from accelerometer and gyroscope sensors while the electrodes for heart rate registration were sensitive to motion artefacts. The algorithm development within the wearITmed consortium has shown promising results.

Conclusions

The prototype was accepted by the users. Technical improvements are needed, but preliminary data indicate that the garment has potential to be used as a tool for diagnosis and treatment selection and could provide added value for monitoring seizures in epilepsy, fluctuations in PD and activity levels in stroke. Future work aims to improve the prototype further, develop algorithms, and evaluate the functionality and usability in targeted patient groups. The potential of incorporating blood pressure and heart-rate variability monitoring will also be explored.

Microfluidic fiber spinning is a promising technique for assembling cellulose nanomaterials into macroscopic fibers. However, its implementation requires upscalabe fabrication processes while maintaining high strength of the fibers, which could not be previously achieved. Herein, a continuous wet spinning process based on microfluidic flow focusing is developed to produce strong fibers from cellulose nanofibrils (CNFs) and nanocrystals (CNCs). Fibers with an average breaking tenacity as high as 29.5 cN tex−1 and Young's modulus of 1146 cN tex−1 are reported for the first time, produced from nonhighly purified CNF grades. Using the same developed method, wet spinning of fibers from CNCs is achieved for the first time, reaching an average Young's modulus of 1263 cN tex−1 and a breaking tenacity of 10.6 cN tex−1, thus exhibiting strength twice as high as that of common CNC films. A rather similar stiffness of CNC and CNF spun fibers may originate from similar degrees of alignment, as confirmed by wide-angle X-ray scattering (WAXS) and birefringence measurements, whereas lower strength may primarily arise from the shorter length of CNCs compared to that of CNFs. The benefit of CNCs is their higher solids content in the dopes. By combining both CNCs and CNFs, the fiber properties can be tuned.

Recent advances in ubiquitous low-power electronics call for the development of light-weight and flexible energy sources. The textile format is highly attractive for unobtrusive harvesting of energy from e.g., biomechanical movements. Here, we report the manufacture and characterisation of fully textile piezoelectric generators that can operate under wet conditions. We use a weaving loom to realise textile bands with yarns of melt-spun piezoelectric microfibres, that consist of a conducting core surrounded by β-phase poly(vinylidene fluoride) (PVDF), in the warp direction. The core-sheath constitution of the piezoelectric microfibres results in a—for electronic textiles—unique architecture. The inner electrode is fully shielded from the outer electrode (made up of conducting yarns that are integrated in the weft direction) which prevents shorting under wet conditions. As a result, and in contrast to other energy harvesting textiles, we are able to demonstrate piezoelectric fabrics that do not only continue to function when in contact with water, but show enhanced performance. The piezoelectric bands generate an output of several volts at strains below one percent. We show that integration into the shoulder strap of a laptop case permits the continuous generation of four microwatts of power during a brisk walk. This promising performance, combined with the fact that our solution uses scalable materials and well-established industrial manufacturing methods, opens up the possibility to develop wearable electronics that are powered by piezoelectric textiles.

A series of two-component precursor fibres for carbon fibre production has been produced by air-gap spinning of kraft lignin with cellulose as the fibreforming polymer, the latter from paper grade or dissolving grade pulps. The spun precursor fibres,containing 70% lignin and 30% cellulose, demonstrate mechanical properties equivalent to commercial textile fibres. Precursor fibres based on softwood kraft lignin were treated thermally in twosteps to carbon fibres, which had mechanical properties equal to or greater than those reported for neat lignin-based carbon fibres produced by melt spinning. An advantage of the wet-spun precursor fibres developed in this project is that they are more flexible and easier to handle with a decreased risk ofbrittle fracture. The potential for further improvement for the new type of carbon fibre is very high.

Melt spinning at semi-industrial conditions of carbon black (CB) containing textiles fibers with enhanced electrical conductivity suitable for heating applications is described. A conductive compound of CB and high density polyethylene (HDPE) was incorporated into the core of bi-component fibers which had a sheath of polyamide 6 (PA6). The rheological and fiber-forming properties of a low-structured and a high-structured CB/HDPE composite were compared in terms of their conductivity. The low-structured CB gave the best trade-off between processability and final conductivity. This was discussed in terms of the strength of the resulting percolated network of carbon particles and its effect on the spin line stability during melt spinning. The conductivity was found to be further enhanced with maintained mechanical properties by an in line thermal annealing of the fibers at temperatures in the vicinity of the melting point of HDPE. By an adequate choice of CB and annealing conditions a conductivity of 1.5 S/cm of the core material was obtained. The usefulness of the fibers for heating applications was demonstrated by means of a woven fabric containing the conductive fibers in the warp direction. By applying a voltage of 48 V the surface temperature of the fabric rose from 20 to 30°C.

In this study, two different carbon fillers: carbon black (CB) and graphite nanoplatelets (GNP) are studied as conductive fillers for the preparation of conductive polypropylene (PP) nanocomposites. In order to obtain a homogenous dispersion of GNP, GNP/PP composites were prepared by two different methods: solid state mixing (SSM) and traditional melt mixing (MM). The result shows that MM is more efficient in the dispersion of GNP particles compared to SSM method. PP nanocomposites containing only one conductive filler and two fillers were prepared at different filler concentrations. Based on the analysis of electrical and rheological properties of the prepared nanocomposites, it shows that a hybridized composite with equal amounts of GNP and CB has favorable processing properties. Conductive fibers with a core/sheath structure were produced on a bicomponent melt spinning line. The core materials of these fibers are the hybridized GNP/CB/PP nanocomposite and the sheath is pure polyamide. It was found that GNPs were separated during melt and cold drawing which results in the decrease of conductivity. However, the conductivity could partly be restored by the heat treatment.