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direction is the development of wireless and IoT-enabled platforms. Optical sensors equipped with
Bluetooth or 5G capabilities can facilitate continuous, remote health monitoring by seamlessly transmitting
real-time physiological data to cloud-based analytics platforms [217,235] . System-level design for such platforms
should consider tight power and thermal budgets (e.g., duty-cycling of sources and readout, adaptive
sampling), electromagnetic compatibility/shielding, time-synchronized driving and detection, and robust
demodulation to maintain performance under ambient light and motion. Data integrity, on-device
compression, secure transmission, and firmware/OTA update pathways further influence clinical readiness
and maintainability. Additionally, improving optical coupling mechanisms is essential for enhancing device
reliability and reducing signal losses. Advanced alignment techniques and micro-optical components can
significantly increase the waveguide-to-fiber and waveguide-to-detector coupling efficiencies, ensuring
seamless integration with existing optical infrastructure and optimizing the performance of flexible optical
waveguides. Finally, biocompatible encapsulation, hermetic sealing around electronic interfaces, and reliable
flexible interconnects with appropriate strain-relief are critical to preserve calibration, bandwidth, and
longevity during repeated deformation and sterilization cycles.

CONCLUSION AND OUTLOOK
We have comprehensively reviewed the design and diverse biomedical applications of flexible optical
waveguides. By exploring the unique optical and mechanical properties of advanced materials such as
hydrogels, elastomers, and biodegradable polymers, our analysis underscores how these flexible platforms
overcome the limitations of traditional rigid systems. These waveguides enable high-sensitivity sensing,
minimally invasive diagnosis, and targeted therapeutic intervention, thus laying a solid foundation for real-
time health monitoring and enhanced clinical performance.

Looking ahead, flexible optical waveguides represent a rapidly evolving technology with significant potential
not only in biomedical applications but also in neuroengineering and interactive soft robotics. However, to
achieve their full potential, key challenges in material innovation, functional enhancement, miniaturization,
and system integration must be addressed. Future research should focus on developing scalable fabrication
techniques, intelligent self-powered sensing systems, and multimodal photonic integration strategies.
Overcoming these hurdles will be pivotal in advancing next-generation healthcare technologies and
establishing flexible optical waveguides as core components in emerging medical and engineering
applications. Regulatory considerations, clinical translation barriers, and commercialization pathways are
critical factors for the widespread adoption of flexible optical waveguide-based devices. Regulatory approval
processes must be navigated, ensuring that these devices meet safety and efficacy standards. Additionally,
overcoming clinical translation challenges, such as biocompatibility and long-term stability, will be key to
successful deployment in healthcare settings. Commercialization efforts will require the development of
cost-effective manufacturing processes, along with market acceptance, to realize the full potential of these
technologies in real-world applications.

DECLARATIONS
Authors’ contributions
Writing - original draft: Yang, C.; Chen, S.; Zou, Y.; Ren, Y.
Writing - review and editing: Wang, Z.; Xiao, K.; Leal-Junior, A.; Kumar, S.; Min, R.
Funding acquisition, supervision: Min, R.

Availability of data and materials
Not applicable.