Advanced Functional Materials for Intelligent Thermoregulation in Personal Protective Equipment

Abstract

The exposure to extreme temperatures in workplaces involves physical hazards for workers. A poorly acclimated worker may have lower performance and vigilance and therefore may be more exposed to accidents and injuries. Due to the incompatibility of the existing standards implemented in some workplaces and the lack of thermoregulation in many types of protective equipment that are commonly fabricated using various types of polymeric materials, thermal stress remains one of the most frequent physical hazards in many work sectors. However, many of these problems can be overcome with the use of smart textile technologies that enable intelligent thermoregulation in personal protective equipment. Being based on conductive and functional polymeric materials, smart textiles can detect many external stimuli and react to them. Interconnected sensors and actuators that interact and react to existing risks can provide the wearer with increased safety, protection, and comfort. Thus, the skills of smart protective equipment can contribute to the reduction of errors and the number and severity of accidents in the workplace and thus promote improved performance, efficiency, and productivity. This review provides an overview and opinions of authors on the current state of knowledge on these types of technologies by reviewing and discussing the state of the art of commercially available systems and the advances made in previous research works.

Keywords: performance; personal protective equipment; productivity; smart textiles; thermoregulation.

Figure 1

Published data for personal thermal management from 2000 to 20 June 2020. (a) Research articles published during the last two decades. (b) Review articles and book chapters published during the last two decades. Reproduced with permission [3]. Copyright 2020, Elsevier.

Figure 2

Temperature sensors: (a) Concept of the flexible temperature sensor embedded within the fibers of a textile yarn; (b) Bending of the uncovered flexible resistance temperature detectors RTD; (c) RTD Close-up sensing area. (d) Resistance temperature detectors embedded within a braided polyester yarn; (e) Cross-section of the braided temperature-sensing yarn ((a–e) [7]); (f) Lightweight and flexible conductor materials in a thermocouple array with copper-coated cellulose textiles [8]; (g) A cross-sectional schematic of encapsulation for a thermistor within a yarn. The standard encapsulation is composed of three layers: a polymer resin, packing fibers, and a knitted sheath [9].

Figure 3

Thermal detection of smart textiles. (a) Illustration of spatiotemporal sensor mapping of the body with temperature and accelerometer (heart beat and respiration); (b) Wearable textile with embedding stretchable–flexible electronic strips; (c) Exploded view of a sensor island. Reproduced with permission [98]. Copyright © 2021, Wicaksono et al. (d) Health monitoring textile with temperature-sensing yarns; (e) A schematic of the textile thermograph (d,e) [78].

Figure 4

Schematic illustration of flexible sensors materials. Clockwise from the right top: polyimide (PI) [103], polyurethane (PU) [104], pectin [105], silk [106], cellulose [107], paper [108], ecoflex [109], polydimethylsiloxane (PDMS) [110].

Figure 5

The air treatment system of the cooling garment with front view and back view. The prototype is composed of three parts: the layers forming the garment, the air treatment system, and the distribution channels. Reproduced with permission [249]. Copyright 2019, Springer Nature.

Figure 6

Small fans and openings on ventilated jacket located at different torso sites. The both fans are placed at (a) the upper back; (b) the lower back; (c) the mid back; (d) the chest (upper front); (e) the belly (lower front). Reproduced with permission [250]. copyright 2013 Elsevier.

Figure 7

Illustrations of (a) the powers harvested by the human body [261]: (b) Several applications of wearable electronics. (c) A typical flexible thermoelectric generator (F-TEG) on a sphere. (d) The unit of the fiber-based F-TEG. Reproduced with permission [262]. Copyright 2017 WILEY. (e) A wearable thermoelectric power generator with a fiber-based flexible substrate. Reproduced with permission [263]. (f) The reported maximum ZT (ZTmax) for the fiber-based thermoelectric materials in recent years [264,265,266,267,268,269,270,271,272,273,274,275,276]. Reproduced with permission [277]. Copyright 2020, Elsevier.

Figure 8

(a) Schematic of an evaporative cooling vest. (b) Corresponding cross-sectional schematic and thermal resistance network presenting different heat and mass transfer processes involved in evaporative cooling of the wearer. (c) A plot of body cooling, convective loss, and evaporative heat fluxes. (d,e) Schematic of evaporative vests with the (d) louver and (e) slitted shading structures. Reproduced with permission [282]. Copyright 2020 Elsevier.

Figure 9

Wearable thermal textile: (a) Schematic illustration of the thermal regulation textile. The thermoregulation is established by conductive composite fibers. Adapted with permission [2]. Copyright 2017, American Chemical Society. (b) Mimic of thermo-adaptive functionality of human skin on one single Nafion flap. Reproduced with permission [4]. Copyright 2017. (c) Schematic of the ZnO nanoparticle-embedded textile. The spectrum was designed to be transparent to thermal radiation and reflective for sunlight for human body. Adapted with permission [5]. Copyright 2018 WILEY-VCH. (d) Thermal radiation management illustration of smart textiles with patterned silver strips on a PET substrate and combined VO₂ nanoparticles. The thermal textile reversibly reflected heat at high temperature and was transparent to IR light at low temperature. Adapted with permission [6]. Copyright 2019 WILEY-VCH.

Figure 10

Shape memory polymers. (a) Schematic representation of sample deformation during shape memory testing cycle. Reproduced with permission [317]. Copyright 2015, Elsevier. (b) Shape memory cycle of two hot stages (red background) and two cold stages (blue background). The shape changes occur during the hot phase. Reproduced with permission [318]. Copyright 2018 Elsevier. (c) Main stages of thermally induced shape memory polymers [319]. (d) Classification of shape-changing polymers. Reproduced with permission [320]. Copyright 2015 Elsevier.