Rheological properties and screen printability of UV curable conductive ink for flexible and washable E-textiles

As a critical component for the realization of flexible electronics,multifunctional electronic textiles(etextiles)still struggle to achieve controllable printing accuracy,excellent flexibility,decent washability and simple manufacturing.The printing process of conductive ink plays an important role in manufacturing e-textiles and meanwhile is also the main source of printing defects.In this work,we report the preparation of fully flexible and washable textile-based conductive circuits with screen-printing method based on novel-developed UV-curing conductive ink that contains low temperature and fast cure features.This work systematically investigated the correlation between ink formulation,rheological properties,screen printability on fabric substrates,and the electrical properties of the e-textile made thereafter.The rheological behaviors,including the thixotropic behavior and oscillatory stress sweep of the conductive inks was found depending heavily on the polymer to diluent ratio in the formulation.Subsequently,the rheological response of the inks during screen printing showed determining influence to their printability on textile,that the proper control of ink base viscosity,recovery time and storage/loss modulus is key to ensure the uniformity of printed conductive lines and therefore the electrical conductivity of fabricated e-textiles.A formulation with 24 wt%polymer and 10.8 wt%diluent meets all these stringent requirements.The conductive lines with 1.0 mm width showed exceptionally low resistivity of 2.06×10^(-5)Ωcm Moreover,the conductive lines presented excellent bending tolerance,and there was no significant change in the sample electrical resistance during 10 cycles of washing and drying processes.It is believed that these novel findings and the promising results of the prepared product will provide the basic guideline to the ink formulation design and applications for screen-printing electronics textiles.

Naturally Crosslinked Biocompatible Carbonaceous Liquid Metal Aqueous Ink Printing Wearable Electronics for Multi-Sensing and Energy Harvesting

Achieving flexible electronics with comfort and durability comparable to traditional textiles is one of the ultimate pursuits of smart wearables.Ink printing is desirable for e-textile development using a simple and inexpensive process.However,fabricating high-performance atop textiles with good dispersity,stability,biocompatibility,and wearability for high-resolution,large-scale manufacturing,and practical applications has remained challenging.Here,waterbased multi-walled carbon nanotubes(MWCNTs)-decorated liquid metal(LM)inks are proposed with carbonaceous gallium–indium micro-nanostructure.With the assistance of biopolymers,the sodium alginate-encapsulated LM droplets contain high carboxyl groups which non-covalently crosslink with silk sericin-mediated MWCNTs.E-textile can be prepared subsequently via printing technique and natural waterproof triboelectric coating,enabling good flexibility,hydrophilicity,breathability,wearability,biocompatibility,conductivity,stability,and excellent versatility,without any artificial chemicals.The obtained e-textile can be used in various applications with designable patterns and circuits.Multi-sensing applications of recognizing complex human motions,breathing,phonation,and pressure distribution are demonstrated with repeatable and reliable signals.Self-powered and energy-harvesting capabilities are also presented by driving electronic devices and lighting LEDs.As proof of concept,this work provides new opportunities in a scalable and sustainable way to develop novel wearable electronics and smart clothing for future commercial applications.

1D-2D nanohybrid-based textile strain sensor to boost multiscale deformative motion sensing performance

The development of strain sensors with both superior sensitivity(gauge factor(GF)>100)and broad strain-sensing range(>50%strain)is still a grand challenge.Materials,which demonstrate significant structural deformation under microscale motion,are required to offer high sensitivity.Structural connection of materials upon large-scale motion is demanded to widen strainsensing range.However,it is hard to achieve both features simultaneously.Herein,we design a crepe roll structure-inspired textile yarn-based strain sensor with one-dimensional(1D)-two-dimensional(2D)nanohybrid strain-sensing sheath,which possesses superior stretchability.This ultrastretchable strain sensor exhibits a wide and stable strain-sensing range from microscale to large-scale(0.01%–125%),and superior sensitivity(GF of 139.6 and 198.8 at 0.01%and 125%,respectively)simultaneously.The strain sensor is structurally constructed by a superelastic 1D-structured core elastomer polyurethane yarn(PUY),a novel high conductive crepe roll-structured(CRS)1D-2D nanohybrid multilayer sheath which assembled by 1D nanomaterials silver nanowires(AgNWs)working as bridges to connect adjacent layers and 2D nanomaterials graphene nanoplates(GNPs)offering brittle lamellar structure,and a thin polydopamine(PDA)wrapping layer providing protection in exterior environment.During the stretching/deformation process,microcracks originate and propagate in the GNPs lamellar structure enable resistance to change significantly,while AgNWs bridge adjacent GNPs to accommodate applied stress partially and boost strain.The 1D crepe roll structure-inspired strain sensor demonstrates multifunctionality in multiscale deformative motion detection,such as respiratory motions of Sprague–Dawleyw rat,flexible digital display,and proprioception of multi-joint finger bending and antagonistic flexion/extension motions of its flexible continuum body.

Highly Stretchable and Permeable Conductors Based on Shrinkable Electrospun Fiber Mats

Wearable on-skin electrodes or conductors should be vapor permeable,strain-insensitive,isotropically stretchable and stable under cyclic stretching.Various strategies have been proposed to prepare the required conductors up to now;however,it is a challenge to fabricate them with above properties in a simple manner.In this paper,a highly permeable and stretchable conductor based on electrospun fluorine rubber fiber mat is reported.The fibers are pre-stretched in electric field during electrospinning,and they shrink isotropically by~35-40%in area after being detached from the substrate.The obtained fiber mat conductor demonstrates high stretchability up to~170%,and the resistance changes only 0.8 under 60%strain,which is superior to many other strain-insensitive conductors.The conductor possesses high stability,no cracks or structure damage are observed after washing and cyclic stretching.Moreover,the conductor is vapor permeable with a water vapor transmission rate of~850 g m−2 day−1,which is comparable to the normal water evaporation in ambient conditions,indicating that it would not disturb the sweat evaporation when being used on skin.The conductor is successfully used as stretchable yarns and electromyography(EMG)electrodes,showing high reliability in E-textiles and on-skin applications.

Wearable and washable textile-based strain sensors via a single-step, environment-friendly method

Recently, soft and stretchable strain sensors that can be incorporated into textiles have attracted significantly increasing interest for use in a diverse range of applications. However, the simple fabrication of stretchable devices that exhibit excellent sensing performance, are highly durability and are a good fit to the human body remains a challenge. Herein, we describe the fabrication of a new flexible strain sensor on a traditional polyester fabric using a one-step method that involves the reduction of graphene oxide(GO) using ascorbic acid(L-AA). The resulting textile-based strain sensors could be washed, exhibited long-term stability,and had a negative linear response that gave a good sensing response when used in wearable applications. In addition to effectively detecting human motions, the textile was modified such that it could detect ultra-large deformations. The impressive mechanical performance, durability and the ability to capture and monitor a variety of human actions and motions mean that these textile-based sensors have great potential in biomonitoring, soft co-robotics, and human-machine interactions.

Recent progress of fiber-based transistors: materials, structures and applications

Wearable electronics on fibers or fabrics assembled with electronic functions provide a platform for sensors,displays,circuitry,and computation.These new conceptual devices are human-friendly and programmable,which makes them indis-pensable for modern electronics.Their unique properties such as being adaptable in daily life,as well as being lightweight and flexible,have enabled many promising applications in robotics,healthcare,and the Internet of Things(IoT).Transistors,one of the fundamental blocks in electronic systems,allow for signal processing and computing.Therefore,study leading to integration of transistors with fabrics has become intensive.Here,several aspects of fiber-based transistors are addressed,including materials,system structures,and their functional devices such as sensory,logical circuitry,memory devices as well as neuromorphic computation.Recently reported advances in development and challenges to realizing fully integrated electronic textile(e-textile)systems are also discussed.

Breathable Kirigami‑Shaped Ionotronic e‑Textile with Touch/Strain Sensing for Friendly Epidermal Electronics

Flexible ionotronic devices have great potential to revolutionize epidermal electronics.However,the lack of breathability in most ionotronic devices is a significance barrier to practical application.Herein,a breathable kirigami-shaped ionotronic e-textile with two functions of sensing(touch and strain)is designed,by integrating silk fabric and kirigami-shaped ionic hydrogel.The kirigami-shaped ionic hydrogel,combined with fluffy silk fabric,allows the ionotronic e-textile to achieve excellent breathability and comfortability.Furthermore,the fabricated ionotronic e-textile can precisely perform the function of touch sensing and strain perception.For touch-sensing,the ionotronic e-textile can detect the position of finger touching point with a fast response time(3 ms)based on the interruption of the ion field.For strain sensing,large workable strain range(>100%),inconspicuous drift(<0.78%)and long-term stability(>10,000 cycles)is demonstrated.On the proof of concept,a fabric keyboard and game controlling sleeve have been designed to display touch and strain sensing functions.The ionotronic e-textile break through the bottlenecks of traditional wearable ionotronic devices,suggesting a great promising application in future wearable epidermal electronics.

Electromagnetic properties of electro-textiles for wearable antennas applications

Wearable,textile-based antennas get more and more attention for body-centric communications because it could be easily worn on body and integrated into clothes.Electro-textiles(e-textiles)are used as antenna patch and ground plane.The electromagnetic properties of the textiles play important roles in antenna design and performance.This paper focuses on the study of the electromagnetic properties of e-textiles for wearable antennas applications and mainly discusses the electromagnetic properties of e-textile cell and the influences of different woven densities and different e-textile materials to antenna performances.Simulation and measurement results show that if the e-textiles adopt woven pattern,then when the distance between two conductive fibers is within 2 mm,the e-textiles could be regarded as metal plane to design antennas.In addition,the results show that metalplated woven fabric could be used as metal plane to design antennas,while non-woven fabric shows distinct differences.