Bioinspired Janus Textile with Conical Micropores for Human Body Moisture and Thermal Management

Abstract

excessively cold sensations. [5] In contrast, hydrophobic textiles such as polyester can repel water on the outside, [6] but are useless against sweat on the inside. In recent years, considerable efforts have been made to improve the sweat transport through textiles, such as doublelayer hydrophobic/hydrophilic fabrics, [7] cotton fabrics printed with fluorocarbonbased hydrophobic finishes, [8] trilayered polyurethane/ (polyurethane-hydrolyzed polyacrylonitrile-SiO 2 )/ hydrolyzed polyacrylonitrile-SiO 2 fibrous membranes, [9] and biomimetic fibrous Murray membrane. [10] However, not much attention was paid to the dissipation of heat during the sweat transporting process. Since textiles thermal insulation can decrease, and the amount of reduction varies from 2 to 8% as related to water accumulation within textiles, [11] even resulting in hypothermia. Therefore, the development of a new functional textile to achieve efficient sweat transport and prevent undesired excessive cold is urgently needed.Directional water transport is a common phenomenon widely found in nature. [12] For example, spider silk with periodic conical spindle knots can drive water droplets toward spindle knots, [13] cactus spines can transport water directionally due to the curvature gradient on the surface of the spine, [14] and shorebirds can transport prey-laden water droplets toward their mouth by opening and closing their beaks. [15] These interesting phenomena of directional water transport originate from their unique asymmetric gradient structures. Therefore, construction of an asymmetric surface structure may be a method for designing functional textiles with effective sweat transport capability.Herein, we fabricated a hydrophobic/superhydrophilic Janus polyester/nitrocellulose textile with asymmetric hydrophilic conical micropores for directional liquid transport by a simple laser perforation method (Figure 1). This Janus polyester/ nitrocellulose textile can unidirectionally pump the excessive sweat from the hydrophobic layer to the superhydrophilic layer through asymmetric hydrophilic conical micropores from large to small (LTS) openings, thereby avoiding undesired sticky and excessive cold sensations from sweat. This study provides new information for the development of functional textiles that effectively manage excess sweat for comfortable skin microenvironments.A Janus polyester/nitrocellulose membrane is a kind of commercially available material that is widely used in microfluidic Excessive sweat secreted from the skin often causes undesired adhesion from wetted textiles and cold sensations. Traditional hydrophilic textiles such as cotton can absorb sweat but retain it. A hydrophobic/ superhydrophilic Janus polyester/nitrocellulose textile embedded with a conical micropore array with a hydrophilic inner surface that can achieve directional liquid transport (with an ultrahigh directional water transport capability of 1246%) and maintain human body temperature (2-3 °C higher than with cotton textiles) is demonstrated. When the hydr...

Emerging Materials and Strategies for Personal Thermal Management

“…Inspired by the directional water transport in birds' beak, Dai et al designed hydrophobic polyester (PE) and hydrophilic nitrocellulose Janus textile with asymmetric hydrophilic conical micropores for directional sweat liquid transport, as shown in Figure 10 A. [ 20 ] The excessive sweat can be efficiently pumped from the inner side to the outer side through the asymmetric micropores to make the skin dry and cool. It is noticed that the asymmetric micropores play a significant role on the directional water transport, which should be well designed and optimized.…”

Asymmetric Surface Engineering for Janus Membranes

“…As a result, the photochemical reactions [ 82–99 ] or plasma activation [ 100–102 ] can be carried out nonuniformly along the direction of membrane thickness. The Janus structure is established through photoetching, [ 82–92 ] photodegradation, [ 93–97 ] or photoinitiated grafting [ 98,99 ] under a directional irradiation of laser or ultraviolet. Likewise, a plasma of nitrogen and oxygen is able to directly activate the surface of hydrophobic membranes, in situ producing hydrophilic amino and hydroxyl groups on one side to obtain a Janus structure.…”

“…[ 36 ] Laser drilling is used to create penetrative conical pores across the whole thickness of the Janus polyester−nitrocellulose textiles, resulting in an integration of large pore sized hydrophobic layer and small pore sized hydrophilic layer (Figure 7g). [ 86 ] The excessive sweat can be unidirectionally pumped across the conical pores from the large openings to the small ones with an extremely high transport capability of 1246% (Figure 7h). [ 86 ]…”

“…[ 86 ] The excessive sweat can be unidirectionally pumped across the conical pores from the large openings to the small ones with an extremely high transport capability of 1246% (Figure 7h). [ 86 ]…”

Omniphobic ZIF‐8@Hydrogel Membrane by Microfluidic‐Emulsion‐Templating Method for Wound Healing

“…Recent developments in bioinspired surfaces with superwettability opened new opportunities for wound dressings 14–19. By articulating the reentrant architecture of the surface, hydrophobic, even omniphobic, surfaces can be achieved using hydrophilic polymers 20–23.…”