Load sensing of a microfiber knot ring (MKR) encapsulated in polydimethylsiloxane (PDMS).

A polydimethylsiloxane (PDMS) packaged microfiber knot ring (MKR) resonator was used as a load-sensing probe. Based on the large Young's modulus and low elastic effect of the silica, the load-sensing characteristic of the bare MKR was experimentally verified with a sensitivity of 6 pm/N. The sensitivity and stability were improved significantly after the MKR was encapsulated in the PDMS film. When the load was applied, the PDMS deformed due to the elastic effect, which in turn changed the length of the MKR. When the microfiber and ring diameter were 7.20 μm and 4.0 mm, respectively, a load sensitivity of 90 pm/N was experimentally demonstrated in the working range from 10 to 50 N. The corresponding strain sensitivity was 0.038 pm/με. The impacts from both the microfiber diameter and ring length on the load-sensing performance were analyzed as well. The experimental results show that the higher sensitivity needs a smaller ring diameter but is independent on the microfiber diameter. This MKR load-sensing probe is promising for exploring miniature sensor chips, due to advantages of low cost, simple and rapid fabrication, and the compact structure. [ABSTRACT FROM AUTHOR]