A team of scientists from Lawrence Livermore National Laboratory has developed a material that is highly breathable yet protective from biological agents, in an attempt to protect soldiers from biological and chemical threats.
This material is the first key component of futuristic smart uniforms that will respond to and protect from environmental chemical hazards.
When it comes to protective clothing, high breathability is a key feature in order to prevent heat-stress and exhaustion when military personnel are on missions in contaminated environments. Current protective military uniforms are based on heavyweight full-barrier protection suits that are not high in both comfort and protection. Instead they offer a passive response to environmental threats.
The LLNL researchers have no come up with flexible polymeric membrane that are aligned with carbon nanotube (CNT) channels as moisture conductive pores. The size of these pores (less than 5 nanometers) is 5,000 times smaller than the width of a human hair.
“We demonstrated that these membranes provide rates of water vapor transport that surpass those of commercial breathable fabrics like GoreTex, even though the CNT pores are only a few nanometers wide,” said Ngoc Bui, the lead author of the paper.
The new composite material takes advantage of the properties of carbon nanotube pores. By quantifying the membrane permeability to water vapor, the team found for the first time that, when a concentration gradient is used as driving force, CNT nanochannels can sustain gas-transport rates that exceed that of a well-known diffusion theory by more than one order of magnitude.
Since their pores are very small in size (less than 5-nanometers wide), the membranes also provide protection from biological agents since biological threats like bacteria or viruses are larger — typically more than 10-nm in size.
In demonstrations the CNT membranes repelled Dengue virus from aqueous solutions during filtration tests, confirming that they will provide effective protection from biological threats by size exclusion rather than by merely preventing wetting. In addition, the results show that CNT pores combine high breathability and bio-protection into a single functional material.
Chemical agents, on the other hand, are much smaller in size and require the membrane pores to be able to react to block the threat. LLNL scientists and collaborators are now surface modifying these prototype carbon nanotube membranes with chemical-threat-responsive functional groups that will sense and block the threat like gatekeepers on the pore entrance. Another response plan, also in development, will work similarly to that of living skin that peels off when challenged with dangerous external factors. The fabric will exfoliate upon reaction with the chemical agent.
“The material will be like a smart second skin that responds to the environment,” said Kuang Jen Wu, leader of the LLNL Biosecurity & Bionanosciences Group. “In this way, the fabric will be able to block chemical agents such as sulfur mustard (blister agent), GD and VX nerve agents, toxins such as staphylococcal enterotoxin and biological spores such as anthrax.”
The new uniforms that will employ this technology could hit the field in less than 10 years.
“The goal of this science and technology program is to develop a focused, innovative technological solution for future chemical biological defense protective clothing,” said Tracee Whitfield, the DTRA science and technology manager for the Dynamic Multifunctional Material for a Second Skin Program. “Swatch-level evaluations will occur in early 2018 to demonstrate the concept of ‘second skin’, a major milestone that is a key step in the maturation of this technology.”
Story via Lawrence Livermore National Laboratory.
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