Humidity-responsive PCL/ICs/PVA pad with directional water transport for fruit preservation

A smart humidity-responsive antimicrobial pad with directional water transport (DWT) was developed to address the rapid spoilage of fruits after harvest due to high humidity and water accumulation. This pad was fabricated from polycaprolactone/cinnamaldehyde β-cyclodextrin inclusion complexes/polyvinyl alcohol (PCL/ICs/PVA) using electrospinning and co-precipitation methods. The inclusion complexes formed by β-cyclodextrin and the guest molecule cinnamaldehyde (CIN) undergo crystalline and conformational changes upon moisture absorption, generating gaps or channels enabling humidity-responsive release of CIN. Meanwhile, capillary action, water uptake by the hydrophilic layer, and reverse water penetration resistance from the hydrophobic layer jointly promote DWT. In the PCL/ICs/PVA pad, the hydrophobic PCL coalesces free water molecules in the air to form tiny droplets to promote DWT, ICs release CIN in response to humidity, and the hydrophilic PVA absorbs droplets, together enhancing the antibacterial performance of the pad under high humidity conditions. The 14 PCL layer (electrospun from 14 wt% PCL solution) with honeycomb-like morphology was beneficial for loading ICs and humidity response. At 98 % RH, the pad with 33.3 % ICs sustained CIN release for 168 h and extended strawberry shelf life. This study holds significant implications for fruit preservation in high-humidity environments.