This work demonstrates a flexible and multifunctional sensor platform based on freestanding BaTiO₃–Au vertically aligned nanocomposite (VAN) thin films. Using a water-soluble Sr₃Al₂O₆ buffer, high-quality VAN films were transferred onto PDMS substrates, overcoming the rigidity of traditional oxide devices and enabling lightweight, flexible integration.

• A water-based transfer route successfully released BaTiO₃–Au VAN thin films onto flexible substrates. Au nanopillars embedded in a BaTiO₃ matrix provide coupled piezoelectric and plasmonic functionalities.

• The freestanding films showed excellent flexibility and recoverability under bending, with stable piezoelectric outputs for pressure sensing.

• Surface-enhanced Raman spectroscopy (SERS) was demonstrated by detecting 4-mercaptobenzoic acid, confirming strong plasmonic enhancement.

• This multifunctional thin film platform integrates mechanical and chemical sensing in one material system, paving the way for miniaturized, low-power, and wearable multi-sensing devices