Cantilever-amplified spindle bubble microcavity for high-sensitivity and robust fiber-optic strain sensing

Jianxin Wang; Weiqiang Wang; Jingwei Lv; Famei Wang; Wei Liu; Zao Yi; Qiang Liu; Paul K. Chu; Chao Liu

doi:10.1016/j.infrared.2025.106071

Cantilever-amplified spindle bubble microcavity for high-sensitivity and robust fiber-optic strain sensing

Jianxin Wang, Weiqiang Wang, Jingwei Lv, Famei Wang, Wei Liu, Zao Yi, Qiang Liu, Paul K. Chu, Chao Liu^*

^*Corresponding author for this work

Research output: Journal Publications and Reviews › RGC 21 - Publication in refereed journal › peer-review

2 Citations (Scopus)

Abstract

Fiber-optic Fabry-Pérot interferometric (FPI) sensors based on bubble microcavities are fundamentally limited by the sensitivity-robustness trade-off. To overcome this, we propose a spindle-shaped bubble geometry with a cladding-protruding long axis, fabricated via an improved fiber micro-shaping technique using only a commercial fusion splicer. Through parametric optimization guided by experiments and finite element simulations, we demonstrate that the protruding axis acts as a cantilever amplifier, converting axial strain (short-axis direction) into amplified displacement at the long-axis free end, thereby enhancing cavity-length modulation efficiency by 86 %. The optimized structure achieves 49.65 pm/µε strain sensitivity at 1,550 nm while withstanding bending radii ≤ 2.5 cm—surpassing Fully-embedded bubble FPIs by 32.1 % in tensile resistance and 36.2 % in bending tolerance. This innovation bridges the gap between high sensitivity and mechanical robustness, making it ideal for flexible wearables or complex wiring scenarios. © 2025 Elsevier B.V.

Original language	English
Article number	106071
Number of pages	8
Journal	Infrared Physics and Technology
Volume	151
Online published	12 Aug 2025
DOIs	https://doi.org/10.1016/j.infrared.2025.106071
Publication status	Published - Dec 2025

Funding

The work was jointly supported by the Heilongjiang Provincial Natural Science Foundation of China [JQ2023F001], National Natural Science Foundation of China [12304480], Natural Science Foundation of Heilongjiang Province [LH2021F007], China Postdoctoral Science Foundation funded project [2020 M670881], as well as City University of Hong Kong Donation Research Grants [DON-RMG 9229021 and 9220061].

Research Keywords

Fabry-Pérot interferometer
Fiber micro-shaping
Flexible wearables
Spindle-shaped bubble

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@article{6d3886adbecc4602bd20db309575dd0a,

title = "Cantilever-amplified spindle bubble microcavity for high-sensitivity and robust fiber-optic strain sensing",

abstract = "Fiber-optic Fabry-P{\'e}rot interferometric (FPI) sensors based on bubble microcavities are fundamentally limited by the sensitivity-robustness trade-off. To overcome this, we propose a spindle-shaped bubble geometry with a cladding-protruding long axis, fabricated via an improved fiber micro-shaping technique using only a commercial fusion splicer. Through parametric optimization guided by experiments and finite element simulations, we demonstrate that the protruding axis acts as a cantilever amplifier, converting axial strain (short-axis direction) into amplified displacement at the long-axis free end, thereby enhancing cavity-length modulation efficiency by 86 %. The optimized structure achieves 49.65 pm/µε strain sensitivity at 1,550 nm while withstanding bending radii ≤ 2.5 cm—surpassing Fully-embedded bubble FPIs by 32.1 % in tensile resistance and 36.2 % in bending tolerance. This innovation bridges the gap between high sensitivity and mechanical robustness, making it ideal for flexible wearables or complex wiring scenarios. {\textcopyright} 2025 Elsevier B.V.",

keywords = "Fabry-P{\'e}rot interferometer, Fiber micro-shaping, Flexible wearables, Spindle-shaped bubble",

author = "Jianxin Wang and Weiqiang Wang and Jingwei Lv and Famei Wang and Wei Liu and Zao Yi and Qiang Liu and Chu, {Paul K.} and Chao Liu",

year = "2025",

month = dec,

doi = "10.1016/j.infrared.2025.106071",

language = "English",

volume = "151",

journal = "Infrared Physics and Technology",

issn = "1350-4495",

publisher = "Elsevier B.V.",

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TY - JOUR

T1 - Cantilever-amplified spindle bubble microcavity for high-sensitivity and robust fiber-optic strain sensing

AU - Wang, Jianxin

AU - Wang, Weiqiang

AU - Lv, Jingwei

AU - Wang, Famei

AU - Liu, Wei

AU - Yi, Zao

AU - Liu, Qiang

AU - Chu, Paul K.

AU - Liu, Chao

PY - 2025/12

Y1 - 2025/12

N2 - Fiber-optic Fabry-Pérot interferometric (FPI) sensors based on bubble microcavities are fundamentally limited by the sensitivity-robustness trade-off. To overcome this, we propose a spindle-shaped bubble geometry with a cladding-protruding long axis, fabricated via an improved fiber micro-shaping technique using only a commercial fusion splicer. Through parametric optimization guided by experiments and finite element simulations, we demonstrate that the protruding axis acts as a cantilever amplifier, converting axial strain (short-axis direction) into amplified displacement at the long-axis free end, thereby enhancing cavity-length modulation efficiency by 86 %. The optimized structure achieves 49.65 pm/µε strain sensitivity at 1,550 nm while withstanding bending radii ≤ 2.5 cm—surpassing Fully-embedded bubble FPIs by 32.1 % in tensile resistance and 36.2 % in bending tolerance. This innovation bridges the gap between high sensitivity and mechanical robustness, making it ideal for flexible wearables or complex wiring scenarios. © 2025 Elsevier B.V.

AB - Fiber-optic Fabry-Pérot interferometric (FPI) sensors based on bubble microcavities are fundamentally limited by the sensitivity-robustness trade-off. To overcome this, we propose a spindle-shaped bubble geometry with a cladding-protruding long axis, fabricated via an improved fiber micro-shaping technique using only a commercial fusion splicer. Through parametric optimization guided by experiments and finite element simulations, we demonstrate that the protruding axis acts as a cantilever amplifier, converting axial strain (short-axis direction) into amplified displacement at the long-axis free end, thereby enhancing cavity-length modulation efficiency by 86 %. The optimized structure achieves 49.65 pm/µε strain sensitivity at 1,550 nm while withstanding bending radii ≤ 2.5 cm—surpassing Fully-embedded bubble FPIs by 32.1 % in tensile resistance and 36.2 % in bending tolerance. This innovation bridges the gap between high sensitivity and mechanical robustness, making it ideal for flexible wearables or complex wiring scenarios. © 2025 Elsevier B.V.

KW - Fabry-Pérot interferometer

KW - Fiber micro-shaping

KW - Flexible wearables

KW - Spindle-shaped bubble

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UR - https://www.scopus.com/record/pubmetrics.uri?eid=2-s2.0-105013355133&origin=recordpage

U2 - 10.1016/j.infrared.2025.106071

DO - 10.1016/j.infrared.2025.106071

M3 - RGC 21 - Publication in refereed journal

SN - 1350-4495

VL - 151

JO - Infrared Physics and Technology

JF - Infrared Physics and Technology

M1 - 106071

ER -

Cantilever-amplified spindle bubble microcavity for high-sensitivity and robust fiber-optic strain sensing

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DON_RMG: Fabrication, Characterization, and Properties of Functional Materials - RMGS

DON: Surface Modification and Fabrication of Advanced Materials

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Cantilever-amplified spindle bubble microcavity for high-sensitivity and robust fiber-optic strain sensing

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Research Keywords

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DON_RMG: Fabrication, Characterization, and Properties of Functional Materials - RMGS

DON: Surface Modification and Fabrication of Advanced Materials

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