Post-gel polymerisation shrinkage profiling of polymer biomaterials using a chirped fibre Bragg grating

Abstract

A strain profile measurement technique using a chirped fibre Bragg grating (CFBG) sensor by implementing an integration of differences (IOD) method is reported in this paper. Using the IOD method the spatial distribution of strain along the length of the CFBG is extracted from its power reflectance spectra. As a proof of concept demonstration, the developed technique is applied to measure the polymerisation shrinkage strain profile of a photo-cured polymer dental composite which exhibits a non-uniform strain distribution attributed to the curing lamp characteristics. The result from the CFBG technique is compared with that of an FBG array embedded in the dental composite and is correlated with the degree of conversion of the material which also depends on the curing lamp intensity distribution. This technology will have significant impact and applications in a range of medical, materials and engineering areas where strain or temperature gradient profile measurement is required in smaller scales.

Figure 1

A flowchart of the process involved in measuring strain/temperature profile from a CFBG.

Figure 2

(a) Schematic experimental arrangement, (b) photograph of the setup.

Figure 3

(a) PS strain profile of the dental composite measured using CFBG sensor, (b) PS strain response at 5 mm location of the dental composite specimen measured by the CFBG.

Figure 4

(a) Changes in the CFBG spectra due to PS strain, (b) evolution of PS strain within the dental composite for a duration of 10 min from cure initiation measured by the CFBG sensor.

Figure 5

(a) PS strain response at three locations of the dental composite measured by the FBG array, (b) comparison of post-gel volumetric PS of the dental composite measured by CFBG sensor and FBG sensor array.