PDMS packaged microfiber knot resonator used for sensing longitudinal load change

In this paper, we proposed a sensitive load sensor probe based on microfiber resonator. The microfiber was prepared from the common single mode fiber by one-step heating-stretching method and used to fabricate a microfiber knot resonator (MKR) by micromanipulation technique. This MKR was packaged later by poly-dimethylsiloxane (PDMS) film layer in two glass slides. The load sensing performance have been explored and compared for the bare MKR structure and PDMS packaged MKR probe. The longitudinal load sensing characteristics were experimentally demonstrated with a small sensitivity of 6 p.m./N, due to the large Young's modulus and low elasto-optical effect of silica materials. In order to increase the longitudinal load sensitivity and stability of bare MKR, we chose PDMS to encapsulate MKR due to its small Young's modulus and large Poisson's ratio. The strain sensing performance of both a bare and PDMS packaged silica MKR were experimentally demonstrated and compared. The experiment results revealed a sensitivity of 94.5 p.m./N. The simple structure, low loss and easily fabrication process pave its way to a miniature strain sensor chip.