Pressure sensitive soft polymer optical fibers processed via microfluidic wet spinning technology

Polymer optical fibres (POFs) especially processed from soft and stretchable elastomers have recently demon-strated their potential for sensory applications. In our previous work, we have reported moulded polydimethylsilox-ane (PDMS) based POFs, which exhibited force sensitivity as low as 0.1 N and accurate pressure sensitivity within 40 kPa to 350 kPa. The classical POF processing methods such as melt spinning, thermal drawing cannot be applied to spin thermally crosslinkable PDMS based elastomers, which calls for the need of development of new processing methods. In the current work, we have presented a new methodology called microfluidic wet spinning (MWS) for the processing of soft crosslinkable POFs. A modular microfluidic chip with co-axial capillary design, consisting of core and sheath flow channels was developed for the MWS. The flow rate optimization of sheath polymer solution (sodium alginate) and core polymer (PDMS) led to the formation of PDMS fibres encapsulated in sodium alginate shell inside the wet spinning bath. The cross-linking of PDMS inside the sodium alginate shell and further removal of the shell provided PDMS POFs. The processing-property relationship of these soft POFs was established with mechanical, surface and optical characterizations data. The modulus of these soft POFs could be tuned via simple post heat treatment process, which provided the modulus dependent load and pressure sensi-tivity. Moreover, MWS based soft POFs were successfully integrated to textile patch to develop wearable pressure sensor targeted for healthcare applications. The scope of this method is not only limited to the PDMS based POFs, but can be further applied to spin