Photonic skin for pressure and strain sensing

Abstract

In this paper, we report on the strain and pressure testing of highly flexible skins embedded with Bragg grating sensors recorded in either silica or polymer optical fibre. The photonic skins, with a size of 10cm x 10cm and thickness of 1mm, were fabricated by embedding the polymer fibre or silica fibre containing Bragg gratings in Sylgard 184 from Dow Corning. Pressure sensing was studied using a cylindrical metal post placed on an array of points across the skin. The polymer fibre grating exhibits approximately 10 times the pressure sensitivity of the silica fibre and responds to the post even when it is placed a few centimetres away from the sensing fibre. Although the intrinsic strain sensitivities of gratings in the two fibre types are very similar, when embedded in the skin the polymer grating displayed a strain sensitivity approximately 45 times greater than the silica device, which also suffered from considerable hysteresis. The polymer grating displayed a near linear response over wavelength shifts of 9nm for 1% strain. The difference in behaviour we attribute to the much greater Young’s modulus of the silica fibre (70 GPa) compared to the polymer fibre (3 GPa)

Ultra Small Integrated Optical Fiber Sensing System

“…Data acquisition rates are varying between 100 kHz and 10 MHz, depending on the required measurement detail and associated resolution. The fiber sensor is embedded in an artificial sensing skin as discussed in [ 20 , 21 ]. Firstly and by means of demonstration, the operation of the sensing system was qualitatively proven by manually touching and releasing the fiber sensing skin and dynamically monitoring the system ( modulation mode as schematically shown in Figure 3 ) resulting in accurate tactile sensing measurements ( Figure 15 ).…”

“…Fiber embedding techniques are discussed in more detail in [20,21]. The final result is then a polymer foil with both integrated driving optoelectronics and optical sensor elements.…”

“…As already mentioned in Section 3.3, not only the optoelectronic driving units but also the fiber sensors themselves can be embedded in polymer sheets with a typical thickness of 1 mm. Fiber embedding techniques are discussed in more detail in [ 20 , 21 ]. The final result is then a polymer foil with both integrated driving optoelectronics and optical sensor elements.…”

An optomechatronic curvature measurement array based on fiber Bragg gratings

“…Curvature sensors have been developed using hybrid long-period fiber grating and tilted FBG for improving sensitivity [4][5][6], the thin-film bridge-type optical fiber sensor array for monitoring the bending direction and curvature [7,8], superstructure FBG [9], and FBG combined with longperiod optical fiber grating with temperature compensation [10][11][12][13][14][15]. Moreover, some complex optical sensing structures and multifunctional sensing devices have been developed, and these have double-clad fiber with a depressed inner cladding for sensing the bend, refractive index, and temperature [16], a multiple-mode fiber optic structure for sensing the temperature and strain-independent curvature [17], and an FBG eccentric-cored optical fiber for measuring the strain, bend, and temperature [18]. The optomechatronic system provides solutions to complex problems by integrating optical and mechatronic technologies [19].…”

Photonic crystal fiber Bragg grating based sensors – opportunities for applications in healthcare

“…Second, the use of polymer optical fibers which can withstand much larger mechanical deformations before breaking than their silica counterparts and which are inherently more bio-compatible 5,6 . Third, the embedding of OFS in flexible and stretchable polymer materials that provides solutions for wearable biomedical sensor devices [7][8][9] .…”