Optical Fiber-Tip Sensors Based on In-Situ µ-Printed Polymer Suspended-Microbeams

Abstract

Miniature optical fiber-tip sensors based on directly µ-printed polymer suspended-microbeams are presented. With an in-house optical 3D μ-printing technology, SU-8 suspended-microbeams are fabricated in situ to form Fabry–Pérot (FP) micro-interferometers on the end face of standard single-mode optical fiber. Optical reflection spectra of the fabricated FP micro-interferometers are measured and fast Fourier transform is applied to analyze the cavity of micro-interferometers. The applications of the optical fiber-tip sensors for refractive index (RI) sensing and pressure sensing, which showed 917.3 nm/RIU to RI change and 4.29 nm/MPa to pressure change, respectively, are demonstrated in the experiments. The sensors and their optical µ-printing method unveil a new strategy to integrate complicated microcomponents on optical fibers toward ‘lab-on-fiber’ devices and applications.

Lab-On-Fiber Technology: A Roadmap toward Multifunctional Plug and Play Platforms

“…In 2018, Yao et al presented an improved version of optical µ-printing technology, which could to directly fabricate suspended microbeams on the end face of an optical fiber [ 96 ]. To improve the deposition of SU-8 on the fiber tip, they used an ultrasonic nozzle for spray coating the fiber tip.…”

Silicone Rubber Based Highly Sensitive Fiber-Optic Fabry–Perot Interferometric Gas Pressure Sensor

“…Furthermore, these types of interferometers are compact and easy to be used. Some Fabry–Perot interferometer (FPI) sensors utilize change in the cavity length while others utilize the variation in refractive index (RI) of the cavity medium to detect pressure [ 4 , 5 , 6 , 7 ]. However, the former is more convenient for practical applications.…”

“…Many FPI pressure sensors based on the detection of cavity-length change have been reported [ 1 , 4 , 8 , 9 ]. For example, W.P.…”

“…Fu et al have reported a liquid level based pressure measurement system that employed a hollow core fiber coated with NOA65 [ 9 ]. M. Yao et al have reported one of the smallest FPI sensors using µ-Printed SU-8 polymer, coated on a fiber tip which has a sensitivity of 4.29 nm/MPa [ 4 ]. Most of the aforementioned sensors show relatively low sensitivities and are unsuitable for low pressure measurements.…”

“…Although some of these sensors exhibit high sensitivities, they involve complex fabrication processes. For example, 3D micro printing on the tip of the fiber to make a FP cavity and controlling the thickness of the reflecting surface of the cavity involves complex processes [ 4 ]. Furthermore, laser micromachining requires complex optical set ups for fabrication of side opened probes [ 8 ].…”