3D printing of fiber-integrated plasmonic micro-grating tip enabling high-resolution real-time and in-site refractive index sensing

•Fabricating a micro-size gold tip sensor via a 3D printing technology.•This sensor has high spatial resolution, high sensitivity and fast response speed.•Measuring the refractive index change at a point in the liquid in real time.•Measuring the refractive index distribution of liquid boundary layer in site.