Comfort for the human body needs to be comprehensive. This complicates the technologies that are available to reach the ultimate goal of providing physiological, environmental and psychological comfort. A definition of technology that matches consumer expectations of clothing is a “feeling of relief.” In light of this definition, the fiber and textile industry will need to plan carefully when developing next-generation comfort clothing structures.
Fibrous structures are necessary to provide protection from environmental conditions—natural and/or from the human footprint—while also focusing on physiological suitability, sensory perception and performance requirements. In order to achieve this, a “systems-of-systems” approach is required.
The defense concept
Among different aspects of comfort factors, thermal, sensory (feel) and bulk (weight) are closely related. These factors are mutually interconnected and need to be balanced. This approach was adopted years ago by the U.S. Department of Defense, resulting in the Integrated Protective Fabric System, with the goal of reducing the load for military personnel while providing maximum protection.
This was achieved using a “systems-of-systems” approach, treating each required protection characteristic as a separate system and treating the fabric structure as a single comprehensive system. In the case of chemical and biological protective fabric, this uses technologies that can combat chemical and biological threats individually, while the integrated suit has the capability to counter both chemical and biological threats. Such an approach is needed to develop comfort clothing. While this may sound complicated, a multidisciplinary approach can lead to developing integrated comfort systems. Fiber science, manufacturing systems engineering, electrical, and electronics engineering all have a role to play in its development.
The ingredients needed
Three main ingredients need to be considered in the development of thermal or any other comfort-providing suits: fibers, fabric structure and external gadgets. With the advent of wearable technologies, microchips and sensors can be effectively integrated to develop lightweight, active comfort clothing.
In terms of fibers for enhanced comfort, developments have been incremental. Chemistry advances have enabled phase change materials that respond and adapt to external ambience and environmental conditions to provide balanced comfort.
Major developments have occurred in finishing treatments that can alter the surface characteristics to develop improved clothing. A well-established technology is imparting variable surface properties on each side of the fabric, making one side hydrophilic and the other side hydrophobic. This approach is useful for thermal comfort suits, as the microclimate between the fabric and the skin is an important factor that alters the thermal balance, and hence the protection.
Atmospheric plasma finishing technology is commercially viable, and such burgeoning processes can be tested out in the development of sustainable manufacturing methods for next-generation comfort fibrous structures.
Apart from fibers, fabric structures play an important role. Thermal comfort depends on the transfer of moisture vapor and the trapping of air and gas molecules, which necessitates bulky but lightweight structures. Typically, nonwoven high-loft structures are used as lining materials. Improved fibers, such as hollow fibers, sheath- and core-structured fibers, can be tried in nonwoven structures, which again will be incremental in development.
Systems-of-systems approaches are being used today in the advanced textiles industry in developing next-generation suits. For example, Chantilly, Va.-based First Line Technology LLC has been developing heat stress-reducing clothing for military personnel and firefighters. Its PhaseCore technology involves a cooling vest and follow-up immerse cooling equipment to provide enhanced heat stress-reduction capability. This systems approach utilizes phase-change material in the cooling vest, which reduces the weight for the user. Unlike ice packs that may lead to vasoconstriction, the phase-change chemistry does not overcool the wearer.
“It is essential that we focus on preventing heat stress rather than treating heat stress after it occurs,” says Amit Kapoor, the company’s president and CEO. “Going into 2019, and with the heat just a couple of months away, we must revisit how we manage and prevent heat stress—from the football field to the battlefield. Cooling systems, such as the PhaseCore Cooling Vests and the Immersion Cooling Equipment, are available that allow professionals to not just put in policies and procedures to prevent heat stress, but to also equip themselves with the tools to put those policies and procedures in effect,” says Kapoor. A key point, he adds, is that the advanced textile sector is heavily dependent on investments in research and must keep on inventing to improve the product.
Wearables are slowly entering the advanced textiles sector. Electrically activated fabric structures are on the horizon that could influence comfort technologies. These advancements are occurring rapidly in the biomedical sector, such as for wound healing.
A November 2018 article published in the American Chemical Society’s ACS Nano discussed the findings of scientists from the University of Wisconsin–Madison and researchers from Chinese institutes in Chengdu and Wuhan who are developing efficient wound-healing patches.
They have harnessed an electric field created in situ, due to the mechanical motion of the patch on the skin. This has helped with rapid wound closures by creating a balanced thermal ambience between the patch and the skin. This development showcases the need for multidisciplinary approaches in developing new thermal balance systems.
Going forward, the industrial fabric sector needs to follow the systems-of-systems approach in designing next-generation comfort clothing and should embrace multiple fields, including science, technology and engineering.
Seshadri Ramkumar, Ph.D., is the director of the Nonwovens and Advanced Materials Laboratory, Texas Tech University.
Scientists from the U.S. Army Research Institute of Environmental Medicine (USARIEM) are developing the Personal Heating Dexterity Device (PhD2) for warming hands and fingers in cold weather without gloves. The problem with working in freezing temperatures is the inevitable trade-off: either warm hands or dexterous fingers. While the PhD2 is just a prototype now, the U.S. Army continues to work to advance the technology. Photo: Dr. John Castellani (USARIEM).