Fig. 1. Schematic of the wearable sensing system. LED light is directed into the photoluminescence sensor within the culture chamber (CC) that is in contact with the wound site. The photoluminescence signal is directed onto a photon detector (PD) for characterization.

Fig. 2. Schematic of (a) an HOE waveguide designed to operate at 632.8 nm wavelength and (b) the model used for the determination of the recording angles in the optical setup using λ, 476.5 nm.

Fig. 3. (a) Diagram showing the relative positions of the HOE and sensor chamber; and (b) plot of the relationship of HOE in-coupler location, angles of incidence within the substrate at/or exceeding the critical angle for TIR (TIR angles), and N+1, where N is the number of TIR events within the PDMS layer.

Fig. 4. Schematic of (a) the HOE waveguide system, which provides double functionality as in- and out-coupling for the same λ632.8 and (b) an angularly multiplexed HOE, operating for the same input angle (θ1) and λ632.8.

Fig. 5. Experimental setup for holographic recording of slanted transmission gratings using a 476.5 nm wavelength laser. S, sample holder; M, mirror; BS, beam splitter; VA, variable aperture; SF, spatial filter; and SH, shutter.

Fig. 6. Average DE versus intensity for varying recording energies (50−750  mJ/cm2).

Fig. 7. (a) Optical density spectrum of the 0.013 mmol/L methylene blue solution and (b) relative fluorescence spectrum of the excited solution.

Fig. 8. Bragg selectivity curves of the 632.8 nm and 700 nm couplers obtained with a 632.8 nm and 405 nm probe.

Fig. 9. (a) PDMS microfluidic system with methylene blue dye solution attached to glass; (b) excitation of the dye chamber with a 632.8 nm in-coupler and 700 nm out-coupler; (c) spectrum of the in-coupled (excitation) signal and the out-coupled (fluorescent dye solution) signal from the system.

Fig. 10. (a) Image of the PHSG polycarbonate waveguide coupling a 632.8 nm signal while in a slightly curved configuration; (b) Bragg selectivity curve of a sample with two multiplexed 632.8 nm couplers and the multiplexed sample probed at normal incidence with (c) a 632.8 nm beam and (d) a white light source.

Fig. 11. (a)–(c) Meeting the Bragg condition for different wavelengths (1) to (3) for the same multiplexed sample and (d) verifying the output wavelengths by spectral measurements.

Fig. 12. HOE waveguide system of four waveguides is probed with a 632.8 nm beam at normal incidence and achieving θTIR in four directions for peristrophic multiplexed gratings.