Flexible and Wearable Optical System Based on U‐Shaped Cascaded Microfiber Interferometer

Abstract

flexible devices for detecting small temperature variations, pressure changes, bending, and moistness fluctuations. [21,22] Besides, more recent reports on hydrogel [23,24] show good performance on the material response-based wearable devices. However, such sensing systems have parasitic repercussions, low performance, nonintrinsic electrical security, and electromagnetic interference, which hamper the working efficiency and restrict their wide applications as wearable gadgets. [25] But, optical segments incorporated on adaptable substrates were not explored more. These systems offer exceptional benefits like distant checking capacity, high affectability, nonelectromagnetic disturbances, real-time monitoring, and intrinsic electrical security apart from features like reconfigurability and scalability. One such optical segment is optical microfibers that possess strong evanescent fields [26][27][28][29] and are sensitive to microforce or relocation. [30,31] Furthermore, when light propagates through the optical microfiber, it excites the higher-order modes that interfere with the fundamental modes of single-mode fiber to form an interference pattern whose period can be tailored depending upon the requirement and the interference pattern shifts when subjected to external perturbations.On the other hand, polydimethylsiloxane (PDMS) is an excellent material to embed optical microfiber due to its biocompatibility and robust mechanical stability [32,33] apart from providing mechanical stability to the microfiber, which otherwise is fragile and difficult to use. PDMS-incorporated optical microfiber also exhibits low loss, high-temperature steadiness with high flexibility. Such an encapsulation also solves the demerits of conventional thermometers such as glass breaking, mercury poisoning, long-term affectability, and biocompatibility. These devices can also be directly affixed to the human body to detect small bending of different body joints like the neck, knee, elbow, and arms to name few where most conventional goniometers-based system cannot be utilized like the comfort and ease provided by flexible PDMS-assisted systems. Recent reports on knot resonator, [34] straight, and bend micronanofiber [35] are very delicate due to their miniature diameter, less sensitive, difficult to mount on skin as light enters from one side and comes out from other, nontailorable performance, and uses the change in incident light intensity for monitoring, which make its widely susceptible to light source fluctuations. Hence, it remains a challenge to develop a robust and stable system, which can be skin mountable, reconfigurable with

Molecular Imprinting Polymer Nanoparticles Coupled with an Optical Sensor for Sensitive and Label-Free Detection of p-Cresol

“…The optical fiber interferometry, combined with MIP as a recognizing element, has shown a promising approach for selective and highly sensitive bio-detection with remarkable detection accuracy . The usage of fiber optic sensing platforms facilitates additional advantageous factors including compact, cost-effective, label-free, high resolution, electromagnetic disturbance-less online monitoring, and remote sensing ability. − In this paper, we have proposed a highly sensitive biochemical sensor using an optical fiber-based Mach–Zehnder interferometer (MZI) as a sensing platform functionalized with MIP-NPs as a bio-recognizing element for selective detection of toxic water pollutant p -cresol. The interferometer is constructed by inline splicing of a specialty fiber called a photonic crystal fiber (PCF) in between two single-mode fibers (SMFs) using a commercial fusion splicer producing an SMF-PCF-SMF hetero fiber structure .…”

Human Pulse and Respiration Monitoring: Reconfigurable and Scalable Balloon‐Shaped Fiber Wearables

“…[7] The recent advancement of wearable sensors has enhanced the interest in photonic sensors based on optical fiber due to its advantages of electromagnetic immunity, miniature size, better sensitivity, and fast response time. [8][9][10][11][12][13][14] In addition, high signal-to-noise ratios for physiological activities can be acquired with these optical fiber based wearables. [15] Furthermore, with the help of such optical fiber based flexible systems, the networks can be easily created for distributed sensing, offering more details on the health status of the human body.…”

“…[20][21][22] For monitoring these pulse waveforms and respiration rates, fiber based wearables are mostly reported. [8,11,[23][24][25][26] The main key factors of any wearable system are its flexibility and stretchability. To realize these aspects the embedding material properties and the probe's configurations are the main two key factors.…”

“…[ 20–22 ] For monitoring these pulse waveforms and respiration rates, fiber based wearables are mostly reported. [ 8,11,23–26 ]…”

Optical Integration in Wearable, Implantable and Swallowable Healthcare Devices

“…This involves illuminating biological tissues with light, which is subsequently absorbed and scattered upon interaction with the tissues. The reflected light provides biometric information, such as molecular content and tissue structure (Figure B). − This principle has led to the development of numerous wearable optoelectronic devices that come into direct or indirect contact with the human body surface. These devices acquire and transmit real-time data on various bioindicators such as glucose, pH, pulse, and electromyograms. − With the rapid improvement of multifunctional optical materials, flexible circuits, and diverse nanofabrication capabilities, a generation of smart wearable devices with rich and flexible functions has emerged that extend beyond biomedical indicator sensing. − These devices have gained much attention in research, especially in gesture and joint tracking for human–computer interaction, which has become a hot research topic (Figure B). − …”