Fig. 1. Fabrication and characterization of MNF-embedded PDMS patches.(a) SEM image of a 900-nm-diameter glass MNF with a bending radius of 30 μm. Inset: close-up image of the MNF showing smooth surface and uniform diameter. (b) Optical microscope image of a 1-μm-diameter glass MNF spiral guiding a 633-nm optical signal on a MgF2 substrate. (c) Photograph of a bent MNF-embedded PDMS patch. (d) Photograph of a MNF-embedded PDMS patch attached on human hand. (e) Optical microscope images of three patches with straight (left), bent (middle), and wavy (right) MNFs, respectively. (f) Optical microscope images of two MNFs guiding 532-and 633-nm signals separately. The two MNFs are assembled into side-by-side (top) and perpendicular crossing structures (bottom), with no crosstalk observed.

Fig. 2. Characterization of substrate supported SLWOSs.(a) Schematic of testing a SLWOS on a glass slide. (b) Optical field intensity distributions of 900-nm-wavelength light guiding along a 1-µm-diameter glass MNF embedded in a 5°-bent SLWOS. (c) Photograph of light leaking out of a SLWOS upon a finger touch. (d) Lateral pressure response of a SLWOS with MNF diameters of 0.8, 1.5 and 2.8 µm, respectively. (e) Pressure response of a SLWOS with a wide spectral range. (f) Typical response of a SLWOS to finger movements of tapping, non-contact movement and dragging successively. (g) Long-term operational characteristics of a SLWOS measured by alternately applying/removing a 2-kPa pressure for more than 10, 000 cycles.

Fig. 3. Characterization of suspended SLWOSs.(a) Schematic of testing suspended SLWOS. (b) Response of a suspended SLWOS to water droplets with different weights. The inset shows an optical micrograph of the SLWOS with a water droplet atop. (c) Response of a suspended SLWOS to pressure of 2.1, 1.3, 0.2 and 0.1 Pa, respectively. (d) Temporary response of a suspended SLWOS to forced oscillation frequencies of 1, 4 and 20 kHz, respectively. (e) Response of a suspended SLWOS to acoustic vibrations from human voice. (f) Photograph showing a SLWOS directly above the artery of the wrist. The inset shows a schematic of the SLWOS. (g) Measurement of wrist pulse under normal-condition (66 beats per minute).

Fig. 4. Optical data gloves and SLWOS with perpendicularly intersected 2×2 MNF arrays.(a) Photograph showing a five-sensor data glove integrated with 5 SLWOSs. (b) Bending-angle-dependent output of a typical SLWOS. (c) Close-up view of the SLWOS output within bending angles of 60.0°–60.8°. (d) Photograph showing a SLWOS consisted by a perpendicularly intersected 2×2 MNF array. (e) Schematic of the sensing areas for tactile sensing. (f) Logic outputs of a 4-input/output-port SLWOS.