Silk Cocoon-Inspired Thermal Management Dressing Fabricated via In Situ Electro-Blown Spinning

Abstract

The restoration of cutaneous integrity is a physiological process significantly influenced by the stability of the local microenvironment. Studies indicate that tissue repair mechanisms, such as collagen synthesis, fibroblast proliferation, and enzymatic activities, operate most efficiently within the physiological temperature range. These temperature-dependent processes are critical for maintaining cellular metabolism and the coordinated cascade of wound healing phases. Deviations from this range can severely compromise healing; low temperatures lead to vasoconstriction and reduced blood perfusion, resulting in local ischemia and decreased oxygen delivery that impairs immune cell function and slows enzymatic activity, while high temperatures can trigger oxidative stress through excessive Reactive Oxygen Species (ROS) generation and promote sustained inflammation. The challenge of maintaining optimal wound temperature is compounded by environmental extremes, where direct solar radiation can cause local hyperthermia while indoor environments may lead to excessive heat loss. However, clinical wound care faces multifaceted challenges as traditional dressings typically lack thermal regulation capabilities. Furthermore, these conventional materials, predominantly hydrophilic gauze and cotton-based products, readily absorb wound exudate and mechanically integrate with the wound bed through interlocking of fibrin networks and tissue ingrowth into the dressing matrix. This integration creates strong adhesive forces that necessitate traumatic removal, causing severe pain and secondary tissue damage that disrupts newly formed epithelium and delays healing. Additionally, advanced in-situ fabrication technologies that could potentially create customized, conformal dressings face practical limitations: portable electrospinning (ES) is hindered by charge accumulation and subsequent electrostatic repulsion on dielectric human skin, which deflects incoming fibers and reduces deposition efficiency, whereas Blow Spinning (BS) often suffers from low deposition accuracy due to airflow turbulence and aerodynamic rebound upon surface impact. To comprehensively address these issues, this thesis presents a bio-inspired W-cocoon (Wound cocoon) dressing fabricated via a High-Speed Electro-Blow Spinning (EBS) device that synergistically combines electrostatic and aerodynamic forces while incorporating personal thermal management (PTM) principles.

The EBS device addresses portable fabrication limitations by combining a 15.4 kV electrostatic field with high-velocity coaxial airflow. This hybrid mechanism utilizes high-momentum airflow to mechanically overcome electrostatic repulsion on the skin surface and guides the fiber trajectory, while the electric field anchors the deposited fibers to prevent aerodynamic rebound. The device achieves a high deposition rate of 51 ml/h, significantly outperforming conventional methods, and enables the rapid in-situ formation of a conformal dressing in under 60 seconds.

The W-cocoon composite, composed of hydrophobic Polyvinyl Butyral (PVB)/Methyl MQ Resin and 5% Stearic Acid modified Zinc Oxide (SA@ZnO), is engineered to create an optimal thermal microenvironment for healing. The material features 92.15% solar reflectivity and 90.92% Mid-Infrared (MIR) emissivity to prevent hyperthermia under sunlight, while its low thermal conductivity of 0.0368 W m^-1 K^-1 prevents hypothermia in cool settings. This dual-mode regulation maintains the wound bed within the physiological window required for healing. Additionally, the dressing supports moisture balance with a high WVTR of 5976 g m^-2 d^-1. To protect fragile new tissue, the dressing demonstrates superhydrophobicity and hemophobicity with a Water Contact Angle (WCA) of 154°. Its surface structure minimizes blood clot infiltration, reducing adhesion force to just 1.35 mN/mm compared to 54.14 mN/mm for traditional gauze. This 40-fold reduction in adhesion effectively prevents secondary trauma during dressing changes, ensuring that the newly formed epithelial layer remains intact.

In vivo evaluations using a 12-day full-thickness wound model confirm that these optimized conditions significantly accelerate the healing process. The W-cocoon maintained a therapeutic temperature of 34.3°C under solar irradiation (3.9°C cooler than gauze) and retained 1.9°C of warmth in cool environments. Histological analysis reveals that this stable thermal buffer, combined with intrinsic antibacterial properties, effectively suppresses inflammatory markers like IL-1β and promotes rapid re-epithelialization. Ultimately, the W-cocoon establishes a superior microenvironment that expedites wound closure and recovery.