Smart Textile with Stress Control Function

Research Article

Adv Res Text Eng. 2016; 1(1): 1006.

Smart Textile with Stress Control Function

Kumar B*

Institute of Textiles and Clothing, The Hong Kong Polytechnic University, Hong Kong

*Corresponding author: Bipin Kumar, Institute of Textiles and Clothing, The Hong Kong Polytechnic University, Hong Kong

Received: October 01, 2016; Accepted: November 17, 2016; Published: December 02, 2016


Since their inception, textiles have been important in human history and significantly impacted the economic development and global trade. Although they are more popular as clothing serving two main attributes - aesthetics and protection. However, with the rapidly changing needs of consumers over a few decades, smart textiles are now generating creative and novel solutions for many engineering and medical problems. With the help of new discoveries and innovative researches, they can provide many smart functions such as colour change, temperature change, shape control, super-hydrophobicity etc. In this work, a new intelligent function, i.e. stress control, in the textile will be introduced. This novel function of stress control allows programming and storing the internal stress in the structure of textile, and also enabling it to retrieve the stored stress reversibly with an external stimulus such as heat. The paper addresses the fundamentals of stress control and the related mechanism using a viscoelastic model consists of spring and dashpot elements. As an example of the potential application, the stress control in textile can be used for smart medical compression treatment to allow pressure control for an efficient treatment of compression therapy used in chronic venous disorders. It is anticipated that the research into stress control in textiles will grow in multiple dimensions as a result of their promising potential in many stress controlling applications such as pressure garments, bandages, massage devices, 3D mattress, sensors/actuators, etc.

Keywords: Smart textile; Stress control; Shape memory polymer; Pressure garments; Stimulus responsive; Compression therapy


The demand of consumer is changing rapidly in this twenty first century, and textile are now expected to serve many other functions not just only aesthetics and protection. In this regard, the use of smart textiles has received significant attention across the globe to meet up the high expectation and provide novel technological solutions to challenging real-life problems. With the help of research and development in last two decades, many smart functions such as photochromism [1], temperature control [2], shape memory [3], super-hydrophobicity [4], auxetic [5], super conductivity [6], etc., are successfully achieved using textile substrates. These smart functions enable the textile to serve the specific demand for the application of interest. No doubt, smart textiles is an emerging research platform of this century which offers new generations of advanced fiber assemblies that could have the potential to offer unique solutions to many untouched scientific and technological challenges.

This work explores the possibility of introducing a new smart function, i.e. stress control, in the textile structure [7]. Stress is the measure of internal force between the particles inside the material body. When the material is stretched or deformed by the application of external force then the internal stresses is developed in the structure as a reaction to external force. In case of elastic material, the removal of external force or constraint causes the dissipation of the internal stresses, and the body moves to the original position. Nevertheless, the dissipation of the stress in the deformed material could also be achieved by an alternative method using external stimulus to freeze the stress without the release of external constraint [8]. Such behaviour is shown in the memory polymer network which shows freezing or releasing of the stress in the structure under constraint deformation. Because of the stress freezing in the deformed state, the memory polymer network allows shape fixing to temporarily fix the deformed shape. Once this temporary fixed shape is activated using external stimulus, e.g. heat, the frozen stress in the structure is released which push the material to go back to its original state in the absence of external constraint, this is called shape recovery. This shape control ability of the memory polymer permits programming or fixing of different deformed shapes from an original (permanent) shape, and simultaneously allows the shape recovery to the original shape. This attribute is called shape memory effect [9]. Similar to this shape memory, such memory polymer networks also demonstrate stress control ability in the structure to program different stress levels by external activation.

The function of stress control in a textile fabric could be achieved if the memory polymer filament is incorporated the structure [10- 12]. Using suitable activation programming, the memory filaments could be programmed for stress modulation in the fabric. The stress control could have significant potential in many application areas such as pressure garments, bandages, stockings, massage devices, etc. As an example, the compression bandage or stocking is used to apply pressure to limb surface [13-15]. The pressure depends on the internal stress developed in the bandage fabric upon application. The conventional bandages do not allow external pressure change as the stress in the fabric is fixed after its application on the limb. If there is possibility of stress control in the fabric, then this will allow pressure control externally by using heat stimulus. No doubt, this stress control ability should be investigated further for the detailed understanding and exploiting its smart potential applications.

Materials and Methods


The demonstration of stress control was done on memory polymer network based on segmented polyurethane network. The polymer was synthesized using PCL (Polycaprolactone diols, Mn: 4000), and MDI (4,4′-diphenyl methanediisocyanate) and BDO (1,4-butanediol). Other polymer composition, i.e. polytetramethylene ether glycol (PTMEG; Mn = 650; Aldrich Chemical Company, USA) as soft segment, and 4,4’-methylene diphenyl diisocyanate (MDI; Aldrich Chemical Company, USA) and 1,4-butanediol (BDO; Acros Organics) as hard segment, was also prepared and examined. More detailed information on the polymer synthesis and characterization could be found in the earlier publication [7,12]. The glass transition was around 400C as measured from the dynamic mechanical analysis [12].

Filament synthesis

The polymer chips were prepared for filament development using melt spinning process [12]. For melt spinning, the polymer chips were dried at 1000C for 24 hr and the filament was spun through single extruder. The working temperature during spinning was set around 2000C. The extruded filaments from the spinneret holes were finally wound on a package at the winding speed of 500 m/min. The linear density of the memory filament was 18.6 tex.

Fabric sample production

The developed filament was then used for knitting fabric samples. Some tubular fabrics were prepared on weft knitting circular machine [10]. The machine gauge was 21 needles per inch. In addition to memory filament (18.6 tex), nylon (18.9 tex) was also fed simultaneously for the knitting. The thread densities of the fabric were 12 wales/cm and 27 courses/cm. The areal density of the fabric was 310 g/m2. The circumference and thickness of the fabric tube was 22.2 cm and 0.76 mm respectively.

Stress memory test of the polymer film

For the stress control test, an Instron with a controlled temperature chamber was used. The thermo-mechanical process involved the following steps (Figure 1): [1] Stretching of the specimen to a fixed strain at higher temperature (T>Ttrans: Transition temperature); [2] Relaxing the specimen under constraint at high temperature; [3] Cooling the specimen below the Ttrans. The above steps allowed freezing the stress in the polymer. For releasing the stress, the specimen is further activated under constraint to higher temperature [7]. The tensile load during the cycle was measured using the load cell attached to the Instron grip. The thickness of the different film specimens was in the range of 0.4 to 0.5 mm. The film was cut into strips of 1 cm width for performing stress memory tests. The gauge length of the specimen was 5 cm.