Stretchable Liquid Metal Patch Antennas for Directional Strain Sensing

Stretchable antennas are increasingly important for wearable electronics, soft robotics, and conformal wireless systems that require mechanically compliant radiofrequency components capable of operating under deformation. Among various approaches, liquid metal-based antennas offer a promising combination of high conductivity and mechanical compliance. However, most existing liquid metal antennas rely on embedded microfluidic channels and cleanroom-based fabrication, which limit scalability, design flexibility, and rapid prototyping. Here, we introduce a cleanroom-free, stencil-based fabrication strategy that combines 3D printing, replica molding, and templated blade coating of oxidized eutectic gallium–indium to produce stretchable patch antennas on soft silicone substrates. By integrating multilevel fractal-inspired slot geometries, the antennas achieve lower operating frequencies within the same footprint and tunable, direction-sensitive frequency shifts under uniaxial, transverse, and biaxial stretching of up to 40%. Full-wave finite-element simulations confirm the frequency-tuning behavior. When mounted on the human elbow, the antenna conforms to joint motion and enables direction-sensitive wireless strain sensing. This platform provides a scalable, miniaturized, and mechanically robust route to stretchable liquid metal patch antennas for wearable sensing applications.