Flexible and high sensitivity optical nanosensor based on laser induced graphene and iron oxide nanohybrids

Abstract

The present invention discloses a flexible optical mechanical nanosensor based on a laser induced graphene and iron oxide nanohybrid structure for simultaneous optical and mechanical sensing. A porous conductive graphene network is formed on a flexible polyimide substrate through controlled carbon dioxide laser irradiation. Iron oxide nanoparticles are generated and stabilized within the graphene framework through fiber laser induced photothermal conversion forming an interconnected FeO@LIG nanohybrid structure. The structure improves optical absorption charge transport carrier separation and photoelectric response while reducing electron hole recombination. A polydimethylsiloxane encapsulation layer enhances flexibility stability and durability. The nanosensor exhibits rapid response high sensitivity and stable multimode sensing performance under ultraviolet visible and mechanical stimulation. The scalable laser based fabrication process is suitable for wearable electronics biomedical monitoring flexible optoelectronic devices and environmental sensing applications.

Description

Flexible and High Sensitivity Optical Nanosensor Based on Laser Induced Graphene and Iron Oxide Nanohybrids

[0001] The present invention generally relates to the technical fields of nanotechnology, nanomaterials engineering, optoelectronics, and advanced optical sensing systems. More particularly, the invention pertains to the development and fabrication of a flexible, stretchable, and highly sensitive optical nanosensor based on a laser induced graphene / iron oxide nanohybrid structure capable of detecting optical stimuli with rapid electrical response and enhanced signal stability.

[0002] The disclosed invention further relates to hybrid nanostructured sensing platforms in which conductive graphene architectures are combined with metal oxide nanoparticles to improve optical absorption characteristics, charge carrier transport, and photoelectric conversion efficiency. In particular, the invention utilizes laser induced graphene (LIG) technology as a rapid and scalable method for producing porous three dimensional graphene microstructures directly on flexible substrates without requiring complex lithographic or high vacuum fabrication processes.

[0003] More specifically, the invention concerns the integration of iron oxide nanoparticles within or upon laser induced graphene networks to form multifunctional nanohybrid sensing layers exhibiting enhanced surface area, improved electron mobility, and superior interaction with incident optical radiation. The synergistic interaction between the conductive graphene matrix and semiconductive iron oxide nanostructures enables improved sensitivity, shorter response and recovery times, and stable sensing performance under varying operational conditions.

[0004] The invention also relates to flexible and wearable optoelectronic devices capable of maintaining reliable electrical and optical sensing performance under mechanical deformation including bending, stretching, compression, and twisting. The disclosed nanosensor structure is therefore suitable for next generation flexible electronics and intelligent sensing systems requiring lightweight, mechanically durable, and low power sensing components.

[0005] In certain embodiments, the invention is applicable to optical detection systems used in biomedical monitoring, environmental analysis, smart healthcare technologies, industrial safety systems, optical communication interfaces, and intelligent human machine interaction platforms. The disclosed sensing device may further be incorporated into portable electronic systems, electronic skins, smart textiles, and real time monitoring devices requiring rapid and accurate optical signal detection.

[0006] The present invention additionally relates to manufacturing methods involving laser processing, nanoparticle deposition, and nanohybrid material engineering for producing high performance optical nanosensors in a cost effective and scalable manner. The disclosed fabrication approach minimizes the need for expensive semiconductor manufacturing equipment and enables direct patterning of conductive graphene structures on flexible polymeric substrates with reduced processing complexity and fabrication time.

[0007] Furthermore, the invention pertains to optical sensing technologies utilizing nanostructured carbon based materials with enhanced physicochemical properties for improved sensing accuracy and operational durability. The combination of laser induced graphene and iron oxide nanoparticles provides a functional sensing platform capable of achieving enhanced photoresponsivity, mechanical flexibility, environmental stability, and long term operational reliability compared with conventional rigid optical sensor structures.

[0008] Accordingly, the invention falls within the interdisciplinary technical domains of flexible nanosensors, nanohybrid optoelectronic devices, laser engineered graphene materials, and advanced optical detection technologies designed for high speed, sensitive, and mechanically resilient sensing applications.

[0009] In recent years the development of flexible optical nanosensors with high sensitivity rapid response and multifunctional sensing capability has attracted significant attention in the fields of nanotechnology optoelectronics wearable electronics biomedical engineering and intelligent sensing systems. The increasing demand for lightweight flexible and highly responsive sensing devices has accelerated the development of advanced nanostructures capable of simultaneously providing optical electrical and mechanical performance. In particular the integration of graphene based materials with metallic or metal oxide nanostructures has emerged as an effective strategy for improving sensor efficiency expanding spectral response and enhancing mechanical durability in next generation sensing platforms.

[0010] Among the various graphene fabrication techniques laser induced graphene has gained considerable attention because of its rapid fabrication process low production cost environmental compatibility and ability to directly generate porous conductive graphene structures on polymeric substrates. Laser induced graphene provides several advantages including high electrical conductivity large specific surface area tunable porous morphology and compatibility with flexible substrates. These characteristics make laser induced graphene highly suitable for applications involving wearable electronics photodetectors flexible sensors biomedical monitoring systems soft robotics and internet of things technologies. Nevertheless existing laser induced graphene based sensing systems still suffer from several technical limitations including insufficient optical absorption limited photoelectric conversion efficiency inadequate sensitivity slow response under weak illumination and insufficient multifunctional integration.

[0011] Various inventions and scientific developments have attempted to improve the performance of graphene based sensing systems through the incorporation of metallic and metal oxide nanoparticles into graphene structures. However most prior technologies have focused only on individual sensing mechanisms such as gas sensing mechanical strain sensing electrochemical sensing or energy storage applications and have failed to provide an integrated optical and mechanical sensing platform with rapid response high sensitivity and mechanical stretchability. Furthermore despite extensive investigations relating to graphene hybrid nanostructures no domestic patent application identical to the present invention has been identified and the following international patent documents represent the closest known developments in the related technical field.

[0012] International Patent Application No WO2020197606A2 published in 2020 and invented by James Mitchell Tour Duy X Luong Kaichun Yang Christopher John Arnusch Swatantra Pratap Singh Amit Kumar Thakur Michael G Stanford John T Li and Steven E Presutti discloses laser induced graphene nanocomposites incorporating different metallic and oxide additives for gas sensing and electronic applications. The disclosed invention mainly focuses on gas sensors and electronic structures and does not address optical sensing functionality or stretchable sensor systems. In addition the disclosed nanocomposite structure does not utilize iron oxide nanoparticles in the specific hybrid configuration described in the present invention and no multifunctional optical sensing capability is disclosed.

[0013] United States Patent No US11014816B2 published in 2021 and invented by James M Tour Duy X Luong and Ajay Subramanian relates to the development of laser induced graphene structures including scroll type graphene configurations and methods for improving conductivity through combinations with metallic and oxide materials. Although the disclosed invention provides improvements in laser induced graphene fabrication the technology remains limited to material development and conductive structures and does not disclose any optical sensing system based on iron oxide decorated graphene hybrid structures. Furthermore no stretchable or optomechanical sensing functionality is described.

[0014] Chinese Patent Application No CN112361953A published in 2021 and invented by Yang Li Chen Xue Xu Guizhi Wang Hongli Ji Huadong and Zheng Guanghao discloses a flexible laser induced graphene based sensor capable of measuring strain and temperature using polypropylene and polydimethylsiloxane substrates. The disclosed system is directed solely toward mechanical and thermal sensing applications and lacks optical sensing capability. Additionally the invention does not utilize iron oxide nanoparticles and does not disclose any hybrid structure comprising laser induced graphene and iron oxide nanoparticles capable of providing rapid optical response.

[0015] United States Patent No US11493321B2 published in 2020 and invented by Jürgen Kosel Marco Marengo and Giovanni Marinaro discloses a laser induced graphene based sensor for detecting bending and stretching deformation on polyimide substrates. The disclosed invention is focused entirely on mechanical sensing and does not incorporate metallic oxide nanostructures or optical sensing functionality. Unlike the present invention the disclosed system does not provide simultaneous optical and mechanical response capability and lacks any optoelectronic enhancement mechanism based on nanoparticle hybridization.

[0016] United States Patent Application No US20240393305A1 published in 2024 and invented by Huanyu Cheng discloses a sensor combining laser induced graphene with vanadium oxide for gas and temperature sensing applications. Although the disclosed invention utilizes oxide modified graphene structures the employed oxide material differs fundamentally from the iron oxide nanoparticles utilized in the present invention. Moreover the disclosed system is directed toward gas and temperature sensing rather than optical detection or stretchable multifunctional sensing systems and does not disclose rapid photoresponse characteristics.

[0017] United States Patent Application No US20190088420A1 published in 2019 and invented by James M Tour Lei Li Zhiwei Peng and Jibo Zhang discloses laser induced graphene nanocomposites incorporating manganese dioxide and iron oxyhydroxide materials for energy storage and electrical applications. Although iron containing compounds are mentioned the disclosed invention is directed toward supercapacitors and energy storage systems rather than optical or optomechanical sensing applications. The disclosed structures do not utilize iron oxide nanoparticles in the form employed by the present invention and do not provide stretchable optical sensing functionality.

[0018] United States Patent No US8878157B2 published in 2014 and invented by Judy Wu and Jianwei Liu discloses self assembled multilayer graphene metal oxide nanocomposites arranged in alternating layered configurations for energy storage devices including batteries and supercapacitors. In the disclosed system graphene acts as a conductive matrix while metal oxide layers provide electrochemical functionality. The disclosed invention is primarily intended for energy storage applications and does not utilize laser induced graphene fabrication methods. Furthermore the multilayer nanocomposite structures do not exhibit rapid optical response stretchability or multifunctional sensing capability as provided in the present invention.

[0019] United States Patent Application No US20110045347A1 published in 2014 and invented by Jun Liu Daiwon Choi Rong Kou Zimin Nie Donghai Wang and Zhenguo Yang represents an earlier publication corresponding to the technology disclosed in United States Patent No US8878157B2. The disclosed invention similarly focuses on graphene metal oxide nanocomposite structures for improving energy storage capacity and reducing internal resistance in electrochemical systems. The disclosed technology neither utilizes laser induced graphene fabrication nor addresses optical sensing flexible photodetection or wearable sensing applications.

[0020] United States Patent Application No US20210332489A1 published in 2021 and invented by Jonathan Claussen Carmen L Gomes Raquel Rainier Alves Soares Robert Hjort and Cicero Cardoso Pola discloses laser induced graphene electrodes for electrochemical sensing and catalytic applications. The disclosed invention provides simplified fabrication processes using polymeric precursors such as polyimide and does not require vacuum environments or high temperature processing. However the invention is directed toward electrochemical detection systems including ion sensing pesticide detection and water splitting applications rather than optical or optoelectronic sensing. Additionally no iron oxide nanoparticle decorated graphene structure or stretchable multifunctional sensing capability is disclosed.

[0021] Despite the considerable advancements achieved in graphene based sensors nanocomposite materials and laser induced graphene technologies there remains a substantial need for an integrated sensing platform capable of simultaneously providing rapid optical response high sensitivity broad spectral detection mechanical flexibility stretchability environmental compatibility scalable fabrication and stable long term operation. Existing technologies generally address only limited aspects of sensor performance and fail to provide a unified optomechanical sensing structure combining laser induced graphene with iron oxide nanoparticles for multifunctional wearable sensing applications. Accordingly there exists a continuing need for a flexible and highly sensitive optical nanosensor capable of overcoming the limitations associated with conventional photodetectors and previously developed graphene based sensing systems while providing improved photoelectric performance mechanical durability and scalable manufacturing capability suitable for next generation intelligent sensing technologies.

[0022] Chinese Patent Application No CN112864303A discloses a preparation method of a photoelectric detector based on a laser induced graphene and perovskite composite structure. The disclosed method forms patterned laser induced graphene on a substrate and then applies a perovskite layer to obtain a photoelectric detector. Although this document is related to laser induced graphene based photodetection, it relies on a perovskite active material and does not disclose iron oxide nanoparticles, a laser assisted iron oxide decoration process, or a stretchable optomechanical nanosensor structure based on a laser induced graphene iron oxide nanohybrid.

[0023] International Patent Application No WO2022121599A1 discloses a graphene based photodetector and refers to graphene sensitized with semiconducting quantum dots for broadband wavelength sensitivity and wearable sensor applications. This invention is relevant to graphene based optical detection, but its sensing mechanism is based on graphene and quantum dot sensitization rather than laser induced graphene decorated with iron oxide nanoparticles. The disclosed structure also does not provide the specific fully laser fabricated iron oxide graphene nanohybrid and simultaneous elastic optical mechanical response of the present invention.

[0024] United States Patent No US10672933B2 discloses a hybrid metal graphene terahertz optoelectronic system and graphene based terahertz photodetectors having strong absorption and fast response in the terahertz spectrum. Although this document relates to graphene based photodetection and fast optical response, it is directed to terahertz optoelectronic architectures using hybrid metal graphene structures and does not disclose laser induced graphene on a polymeric flexible substrate, iron oxide nanoparticle decoration, or a stretchable wearable optical nanosensor.

[0025] United States Patent No US8927964B2 discloses photodetection systems in which a semiconductor film, which may include graphene, cooperates with semiconductor nanostructures to assist photogenerated carrier separation and improve photodetection performance. This invention is relevant to graphene assisted photodetection, but it is based on heterojunction photodetection using semiconductor nanostructures and does not teach laser induced graphene fabrication, iron oxide nanoparticle incorporation, or an elastic optomechanical sensor platform suitable for wearable applications.

[0026] United States Patent Application No US20140056551A1 discloses a graphene based optical modulator including an optical waveguide, a nanoscale oxide spacer and one or more graphene layers for controlling optical signals. This document is related to graphene optoelectronic devices, but it concerns optical modulation rather than optical sensing or photodetection. The disclosed device does not use laser induced graphene, iron oxide nanoparticles, PDMS based stretchable encapsulation, or a multifunctional sensor capable of responding to both optical and mechanical stimuli.

[0027] This summary is intended to introduce selected concepts related to the disclosed invention in a simplified form and is not intended to identify essential features of the claimed subject matter or to limit the scope of the invention. The invention relates to a rapid and highly sensitive elastic optical nanosensor based on a laser induced graphene and iron oxide nanoparticle nanohybrid structure capable of simultaneously responding to optical and mechanical stimuli while maintaining excellent flexibility mechanical durability and stable optoelectronic performance.

[0028] The present invention provides a multifunctional optical mechanical sensing platform based on a porous laser induced graphene structure formed on a flexible polymeric substrate and decorated with iron oxide nanoparticles in order to improve optical absorption carrier transport photoelectric conversion efficiency and sensing sensitivity. The disclosed sensing system is specifically designed for advanced wearable electronics biomedical monitoring intelligent sensing systems environmental monitoring and flexible optoelectronic applications requiring rapid response high sensitivity broad spectral detection and mechanical adaptability.

[0029] In the disclosed invention a polyimide substrate is employed as a carbon precursor material for generating a conductive porous graphene structure through controlled laser irradiation. A carbon dioxide laser is directed onto the surface of the polymeric substrate to convert selected surface regions into a three dimensional porous laser induced graphene network possessing high electrical conductivity large surface area and enhanced light trapping capability. The porous morphology generated during the laser induction process significantly improves electron mobility and facilitates rapid transport of photogenerated carriers within the sensing structure.

[0030] Following the formation of the laser induced graphene structure iron oxide nanoparticles are incorporated into the porous graphene network through a laser assisted deposition and stabilization process. In this stage an iron containing precursor solution is applied onto the graphene surface and subsequently exposed to fiber laser irradiation in order to form and uniformly stabilize iron oxide nanoparticles throughout the porous graphene matrix. The resulting nanohybrid structure establishes highly efficient conductive pathways and active optical interaction sites capable of enhancing charge separation increasing carrier transport efficiency and improving overall photoresponse characteristics.

[0031] The integration of laser induced graphene with iron oxide nanoparticles provides multiple structural and functional advantages. The porous graphene network contributes high conductivity rapid signal transfer and broad optical absorption while the iron oxide nanoparticles increase the density of active sensing sites improve light matter interaction and reduce carrier recombination effects. The synergistic interaction between the graphene framework and the iron oxide nanoparticles significantly improves sensitivity response speed signal stability and photoelectric conversion performance compared with conventional graphene based optical sensing structures.

[0032] In order to enhance flexibility mechanical durability and compatibility with wearable systems the disclosed nanohybrid sensing structure is encapsulated within or coated by a flexible polydimethylsiloxane layer. The elastomeric polymeric layer protects the internal sensing architecture against mechanical deformation environmental stress and repeated operational cycles while maintaining the stretchability and conformability of the device. The resulting sensor can be bent stretched compressed or attached onto curved and moving surfaces without significant degradation in sensing performance.

[0033] The disclosed sensor is configured to provide multimode sensing capability by simultaneously detecting optical excitation and mechanical deformation. The sensing system is capable of responding to a broad range of optical wavelengths while also detecting pressure strain bending or motion induced mechanical stimuli. The combination of optical and mechanical sensing functionality within a single flexible device enables the development of intelligent sensing systems suitable for wearable healthcare devices motion monitoring systems biomedical imaging smart textiles human machine interfaces soft robotics and environmental sensing technologies.

[0034] The fabrication method disclosed in the present invention provides significant advantages over conventional photodetector manufacturing technologies. The entirely laser based fabrication process eliminates the need for vacuum chambers complex lithography hazardous chemical etching processes or high temperature deposition systems. The disclosed manufacturing approach enables rapid low cost environmentally compatible and scalable production of flexible optical nanosensors while allowing precise pattern formation and direct integration onto flexible substrates.

[0035] The disclosed sensing platform further demonstrates rapid electrical response high operational stability repeatable sensing behavior and reliable long term performance under repeated optical and mechanical cycling conditions. The nanohybrid structure maintains its sensitivity and signal consistency even after numerous deformation cycles thereby improving device lifetime and reliability for continuous monitoring applications.

[0036] The present invention therefore provides an advanced optoelectronic nanosensor platform combining laser induced graphene iron oxide nanoparticles and flexible polymeric materials within an integrated multifunctional architecture capable of overcoming the limitations associated with conventional optical sensors photodetectors and previously developed graphene based sensing systems. The disclosed invention establishes a scalable and high performance sensing technology suitable for next generation flexible electronics wearable systems intelligent monitoring devices and multifunctional photonic sensing applications.

[0037] The rapid advancement of wearable electronics intelligent sensing systems biomedical monitoring platforms soft robotics and flexible optoelectronic devices has created an increasing demand for high performance optical sensors capable of providing rapid response high sensitivity broad spectral detection mechanical flexibility and long term operational stability. Optical sensors and photodetectors are among the most important components in modern photonic and electronic systems because they are responsible for converting optical signals into measurable electrical outputs for use in communication imaging environmental monitoring medical diagnostics security systems and human machine interaction technologies. Despite substantial progress in photodetector technologies conventional optical sensing systems continue to suffer from multiple technical limitations that restrict their performance in advanced flexible and multifunctional applications.

[0038] Conventional photodetectors are generally fabricated using semiconductor materials and complex microfabrication processes requiring vacuum deposition high temperature processing sophisticated lithography and expensive manufacturing equipment. These fabrication methods significantly increase production cost reduce scalability and limit compatibility with flexible and wearable electronic platforms. Furthermore many conventional photodetectors exhibit insufficient mechanical flexibility poor resistance to repeated deformation limited operational stability under environmental stress and inadequate adaptability to curved or dynamic surfaces. As a result these systems are not suitable for next generation wearable sensing technologies requiring lightweight stretchable and mechanically durable structures.

[0039] Another major technical problem associated with existing photodetector systems is the limited optical performance achieved under practical operating conditions. Many currently available optical sensors suffer from low optical absorption insufficient photoelectric conversion efficiency slow electrical response poor signal stability and narrow spectral sensitivity. In addition conventional sensing systems often operate effectively only within a limited wavelength range and are unable to provide simultaneous response to multiple forms of external stimuli such as optical excitation and mechanical deformation. This inability to achieve multimode sensing capability significantly restricts their functionality in integrated intelligent systems and wearable sensing applications.

[0040] Graphene based materials have attracted considerable attention because of their excellent electrical conductivity optical transparency high carrier mobility thermal stability and mechanical flexibility. However traditional graphene fabrication methods including chemical vapor deposition and mechanical exfoliation involve expensive processing conditions low production efficiency difficult transfer procedures and limited suitability for industrial scale manufacturing. Although laser induced graphene technology has emerged as a promising alternative due to its low cost rapid fabrication and environmentally compatible processing laser induced graphene structures in their conventional form still exhibit several disadvantages including limited light absorption insufficient active sensing sites nonuniform electrical response and inadequate photoelectric sensitivity for advanced optical sensing applications.

[0041] Attempts have been made to improve the performance of graphene based sensors through the incorporation of metallic and metal oxide nanostructures. Nevertheless many previously developed hybrid sensing systems remain limited to a single sensing mechanism such as gas sensing strain sensing electrochemical sensing or thermal detection and do not provide a unified sensing platform capable of simultaneously responding to optical and mechanical stimuli. Moreover previously developed systems often require complicated chemical synthesis procedures hazardous materials multistage processing or expensive fabrication conditions that reduce manufacturing efficiency and limit industrial scalability.

[0042] Existing flexible sensing devices also suffer from significant challenges related to mechanical durability and long term operational reliability. Repeated bending stretching compression or environmental exposure can lead to structural degradation instability of conductive pathways reduction in sensitivity and deterioration of signal consistency over time. In wearable and biomedical applications these limitations become especially critical because sensing devices must maintain stable and repeatable operation under continuous movement dynamic deformation and long term usage conditions.

[0043] Another important technical challenge relates to the integration of optical sensing functionality with flexible and stretchable substrates suitable for wearable systems. Many previously developed photodetectors are fabricated on rigid substrates that cannot conform to curved biological surfaces or dynamic mechanical environments. Furthermore the integration of multifunctional sensing capability within a lightweight and biocompatible structure remains insufficiently addressed in existing technologies.

[0044] Therefore there exists a significant need for a new optical nanosensor system capable of overcoming the limitations associated with conventional photodetectors graphene based sensors and previously developed flexible sensing devices. Such a system should provide rapid optical response enhanced sensitivity broad spectral detection stable photoelectric conversion excellent mechanical flexibility stretchability environmental compatibility and long term operational stability while also enabling scalable low cost and environmentally friendly fabrication. In addition there remains a need for a multifunctional sensing platform capable of simultaneously detecting optical and mechanical stimuli within a single integrated structure suitable for wearable electronics biomedical monitoring intelligent sensing systems and next generation flexible optoelectronic applications.

[0045] The present invention addresses these technical problems through the development of a rapid and highly sensitive elastic optical nanosensor based on a laser induced graphene and iron oxide nanoparticle nanohybrid structure fabricated through an entirely laser assisted process and integrated with a flexible polymeric substrate to achieve improved optical sensing performance mechanical durability multifunctional sensing capability and scalable manufacturing suitability.

[0046] In order to overcome the technical limitations associated with conventional photodetectors flexible optical sensors and previously developed graphene based sensing systems the present invention provides a rapid and highly sensitive elastic optical nanosensor based on a laser induced graphene and iron oxide nanoparticle nanohybrid structure capable of simultaneously responding to optical and mechanical stimuli while maintaining excellent flexibility mechanical stability and long term operational reliability.

[0047] The disclosed invention introduces an integrated optoelectronic sensing platform fabricated through an entirely laser assisted process in which a conductive porous graphene structure is generated directly on a flexible polymeric substrate and subsequently functionalized with iron oxide nanoparticles to improve optical absorption photoelectric conversion efficiency charge carrier transport and sensing sensitivity. The resulting nanohybrid structure enables the development of a multifunctional sensing device suitable for wearable electronics biomedical monitoring systems intelligent interfaces environmental sensing and flexible photonic applications.

[0048] According to the disclosed solution a polymeric substrate composed of polyimide is employed as the carbon precursor material because of its thermal stability flexibility and compatibility with laser processing techniques. In the initial fabrication stage a carbon dioxide laser is directed onto selected regions of the polyimide substrate under controlled irradiation conditions in order to induce localized carbonization and graphitization of the polymer surface. This laser induced conversion process forms a three dimensional porous graphene network possessing high electrical conductivity large specific surface area interconnected conductive pathways and enhanced light trapping characteristics.

[0049] The porous morphology generated during the laser induction process significantly increases the active surface area available for optical interaction and electron transport. The interconnected graphene framework facilitates rapid movement of photogenerated charge carriers while simultaneously improving the uniformity of electrical response throughout the sensing structure. The laser induced graphene network also provides excellent mechanical flexibility allowing the sensing platform to withstand repeated deformation bending stretching and compression without structural failure or significant reduction in conductivity.

[0050] In order to further improve the optical and electrical performance of the sensor the porous laser induced graphene structure is decorated with iron oxide nanoparticles through a laser assisted stabilization process. In this stage an iron containing precursor solution is deposited onto the surface of the porous graphene network and exposed to controlled fiber laser irradiation near the infrared wavelength region. The applied laser energy induces the formation nucleation and stabilization of iron oxide nanoparticles throughout the porous graphene matrix while enabling highly uniform nanoparticle distribution and strong interfacial interaction between the graphene structure and the nanoparticles.

[0051] The incorporation of iron oxide nanoparticles into the graphene framework substantially improves the sensing characteristics of the disclosed device. The iron oxide nanoparticles increase the density of active optical interaction sites enhance light absorption and facilitate efficient separation and transport of photogenerated charge carriers. In addition the nanoparticles reduce carrier recombination effects and improve electron transfer pathways within the nanohybrid structure thereby increasing signal intensity response speed and photoelectric conversion efficiency. The synergistic interaction between the porous laser induced graphene structure and the iron oxide nanoparticles provides significantly enhanced sensing performance compared with conventional graphene based optical sensors.

[0052] In a further stage of the disclosed invention the nanohybrid sensing structure is integrated with a flexible elastomeric layer composed of polydimethylsiloxane in order to improve mechanical durability environmental protection and wearable compatibility. The elastomeric polymer layer encapsulates the sensing structure while maintaining its optical and electrical functionality. The resulting device exhibits excellent flexibility stretchability and conformability allowing the sensor to adapt to curved dynamic and deformable surfaces such as human skin wearable devices flexible electronics and soft robotic systems.

[0053] The disclosed sensing platform is configured to provide multimode sensing functionality by simultaneously responding to optical excitation and mechanical deformation. The sensor is capable of detecting optical signals over a broad spectral range while also responding to pressure strain bending motion and other mechanical stimuli. The integration of optical and mechanical sensing mechanisms within a single nanohybrid structure enables highly versatile sensing performance suitable for advanced intelligent monitoring systems and wearable technologies.

[0054] The fabrication method disclosed in the present invention provides substantial manufacturing and industrial advantages over conventional sensing technologies. The entirely laser based process eliminates the need for vacuum systems complex lithography multistage chemical synthesis or hazardous chemical etching procedures. As a result the disclosed method enables rapid low cost environmentally compatible and scalable fabrication of flexible nanosensors while allowing precise pattern generation and direct integration onto flexible polymeric substrates.

[0055] The disclosed sensor further demonstrates rapid electrical response high operational stability repeatable sensing behavior and reliable long term performance under repeated optical and mechanical operating cycles. The nanohybrid structure maintains stable sensitivity and signal consistency even after repeated deformation and continuous operational exposure thereby improving device reliability lifetime and practical applicability in demanding wearable and biomedical environments.

[0056] Through the combination of porous laser induced graphene iron oxide nanoparticle functionalization and flexible polymeric encapsulation the present invention effectively solves the technical problems associated with insufficient optical sensitivity limited photoelectric conversion poor mechanical flexibility slow response speed inadequate environmental stability and complicated fabrication processes existing in conventional photodetectors and previously developed flexible sensing systems. The disclosed invention therefore provides an advanced multifunctional nanosensor platform capable of supporting next generation wearable electronics intelligent sensing systems biomedical devices environmental monitoring technologies and flexible optoelectronic applications.

[0057] The present invention provides significant improvements over conventional photodetectors flexible optical sensors and previously developed graphene based sensing systems through the integration of porous laser induced graphene iron oxide nanoparticles and flexible polymeric materials within a single multifunctional sensing platform. One of the principal advantages of the disclosed invention is the substantial enhancement in optical sensitivity photoelectric conversion efficiency and response speed. The porous laser induced graphene structure formed through controlled laser irradiation provides a highly conductive three dimensional network with large specific surface area and enhanced light trapping capability. Simultaneously the incorporation of iron oxide nanoparticles increases the density of active optical interaction sites facilitates efficient separation and transport of photogenerated charge carriers and reduces carrier recombination effects. As a result the disclosed nanosensor demonstrates rapid electrical response high signal intensity stable photoresponse and significantly improved sensing performance compared with conventional graphene based optical sensing devices.

[0058] Another important advantage of the invention is the capability of simultaneous optical and mechanical sensing within a single integrated structure. Unlike conventional sensing systems that are generally limited to a single sensing mechanism the disclosed nanohybrid sensor is capable of responding both to optical excitation and to mechanical deformation including pressure strain bending and motion. This multimode sensing functionality substantially expands the applicability of the invention in wearable electronics intelligent sensing systems biomedical monitoring platforms soft robotics human machine interfaces and flexible optoelectronic technologies. In addition the integration of the sensing structure with a flexible polydimethylsiloxane layer provides excellent mechanical flexibility stretchability and durability enabling the sensor to maintain stable performance under repeated bending stretching compression and dynamic operational conditions without significant degradation in conductivity sensitivity or signal stability.

[0059] The present invention further provides considerable advantages in terms of fabrication simplicity environmental compatibility and industrial scalability. The disclosed manufacturing process is entirely based on laser assisted fabrication and therefore eliminates the need for vacuum deposition systems complex lithographic procedures hazardous chemical etching processes and expensive multistage manufacturing techniques commonly associated with conventional photodetector production. The use of direct laser processing enables rapid low cost environmentally friendly and scalable fabrication while also allowing precise pattern generation and direct integration onto flexible polymeric substrates. These characteristics significantly improve manufacturing efficiency and support large scale industrial production of flexible nanosensors suitable for commercial applications.

[0060] In addition to the enhanced sensing and fabrication characteristics the disclosed invention demonstrates excellent operational stability repeatability and long term reliability under repeated optical and mechanical cycling conditions. The nanohybrid sensing structure maintains stable sensitivity rapid response and consistent electrical performance even after prolonged operational exposure and repeated deformation cycles. Furthermore the flexible and lightweight configuration of the disclosed nanosensor enables effective integration with wearable healthcare devices biomedical systems smart textiles environmental monitoring systems and next generation intelligent electronics. Accordingly the present invention represents a substantial technological advancement in the field of flexible optoelectronic nanosensors and provides an advanced multifunctional sensing platform capable of supporting future wearable and intelligent sensing technologies.Fig.1

[0061] illustrates the complete fabrication process and operational mechanism of the flexible FeO@LIG nanohybrid optical nanosensor from substrate preparation to multimode sensing applications.Fig.2

[0062] illustrates the preparation and fabrication process of the proposed sensor.Fig.3

[0063] illustrates the Raman spectrum comparison between pure LIG and the final modified sample used for sensor fabrication.Fig.4

[0064] illustrates the XRD pattern corresponding to pure LIG.Fig.5

[0065] illustrates the XRD pattern of the modified sample indicating graphene peaks containing iron oxide nanoparticles including hematite and magnetite phases.Fig.6

[0066] illustrates the SEM image of LIG and iron oxide nanoparticles under minimum fiber laser power conditions.Fig.7

[0067] illustrates the SEM image of LIG and iron oxide nanoparticles under maximum fiber laser power conditions.Fig.8

[0068] illustrates the comparative diagram corresponding to different fiber laser power conditions.Fig.9

[0069] illustrates the comparative optical testing results of the prepared sample under blue light wavelength excitation.

[0070] The present invention discloses an elastic and highly sensitive optical nanosensor based on a laser induced graphene and iron oxide nanohybrid structure configured for simultaneous optical and mechanical sensing applications. The disclosed nanosensor is designed to provide rapid photoelectric response high optical sensitivity broad spectral detection capability mechanical flexibility and operational stability for wearable optoelectronic and biomedical sensing systems. The fabrication procedure of the disclosed nanosensor follows a sequential laser assisted process involving substrate preparation graphene induction precursor deposition nanoparticle formation nanohybrid optimization device encapsulation and multimode sensing integration.

[0071] In one embodiment of the present invention a flexible polyimide substrate is selected as the carbon precursor material for formation of the conductive sensing structure. The surface of the polyimide film is initially cleaned using deionized water ethanol and acetone under ultrasonic conditions followed by drying in order to remove surface contaminants and improve laser processing quality. The polyimide surface is subsequently conditioned to achieve suitable surface uniformity and stability prior to laser irradiation.

[0072] In another embodiment a carbon dioxide laser system is configured under controlled processing conditions including laser power scanning speed DPI and irradiation frequency. The focused carbon dioxide laser beam is directed onto the prepared polyimide substrate according to a predefined scanning pattern. Localized photothermal conversion of the polyimide material results in carbonization and graphitization of the polymer surface thereby forming a porous three dimensional laser induced graphene structure directly on the substrate surface. The resulting laser induced graphene network possesses high electrical conductivity large specific surface area porous morphology and enhanced optical absorption capability suitable for rapid charge transport and photodetection applications.

[0073] In another embodiment an iron precursor solution is prepared by dissolving iron nitrate in deionized water to obtain a homogeneous precursor mixture. Polyvinylpyrrolidone and polyethylene glycol are added as stabilizing agents in order to improve solution uniformity nanoparticle stabilization and precursor dispersion characteristics. The prepared iron precursor solution is then deposited onto the porous laser induced graphene surface through drop casting or uniform coating techniques. The precursor solution penetrates into the porous graphene network followed by controlled drying to ensure sufficient infiltration and precursor distribution throughout the conductive graphene structure.

[0074] In another embodiment the precursor coated laser induced graphene surface is exposed to a fiber laser under controlled irradiation conditions. Laser induced photothermal conversion and localized thermal decomposition of the precursor material result in the in situ formation of iron oxide nanoparticles within the porous graphene network. Simultaneously the generated nanoparticles become anchored and stabilized throughout the conductive graphene framework thereby forming an interconnected FeO@LIG nanohybrid structure. The interaction between the iron oxide nanoparticles and the porous graphene matrix improves optical absorption enhances carrier mobility and facilitates charge separation within the sensing structure.

[0075] In another embodiment the nanohybrid structure undergoes optimization and performance control processes to improve optoelectronic characteristics and sensing efficiency. The interaction between iron oxide nanoparticles and the laser induced graphene network is engineered to enhance optical and electrical properties and improve charge transport pathways throughout the structure. Interfacial coupling between FeO nanoparticles and graphene layers is optimized to reduce electron hole recombination and increase carrier transfer efficiency. The interaction between iron oxide nanoparticles and the laser induced graphene network is engineered to enhance optical and electrical properties and improve charge transport pathways throughout the structure. Interfacial coupling between FeO nanoparticles and graphene layers is optimized to reduce electron hole recombination and increase carrier transfer efficiency. Furthermore the nanohybrid architecture improves photoelectronic performance through rapid charge separation and fast electrical response under optical stimulation.

[0076] In another embodiment a flexible protective layer composed of polydimethylsiloxane is coated or laminated onto the optimized FeO@LIG nanohybrid structure. The polydimethylsiloxane layer is subsequently cured to form an elastic encapsulation layer capable of protecting the sensing structure against mechanical damage environmental degradation and repeated deformation. The final nanosensor structure therefore exhibits high flexibility mechanical robustness and compatibility with flexible and wearable electronic systems. The total thickness of the nanohybrid structure is controlled at approximately 500µm in order to achieve balanced mechanical flexibility structural stability and efficient light and charge transport performance.

[0077] During operation the disclosed nanosensor is exposed to optical stimuli within ultraviolet and visible wavelength regions. Simultaneously the device is capable of detecting mechanical deformation including pressure strain bending and motion induced displacement. Optical stimulation modulates charge generation and photoelectric response within the FeO@LIG nanohybrid structure while mechanical deformation alters conductive pathways and electrical resistance characteristics. As a result the disclosed nanosensor enables simultaneous detection of optical and mechanical signals with high sensitivity rapid response and stable operational behavior.

[0078] In another embodiment the disclosed nanosensor is integrated into wearable electronic devices biomedical monitoring systems flexible photodetectors optoelectronic platforms environmental sensing systems and multimode sensing applications. Due to the entirely laser based fabrication process simplified manufacturing procedure enhanced mechanical flexibility and improved photoelectronic characteristics the disclosed invention provides a scalable and industrially applicable platform for next generation flexible nanosensor technologies.

[0079] The present invention is applicable in the fields of wearable electronics intelligent sensing systems biomedical monitoring flexible optoelectronic devices environmental monitoring and advanced photonic technologies. The disclosed elastic optical nanosensor based on laser induced graphene and iron oxide nanoparticle nanohybrid structures can be utilized in wearable healthcare devices smart textiles flexible electronic circuits human machine interaction systems soft robotic devices portable biomedical diagnostic equipment motion detection systems intelligent safety technologies optical imaging systems and next generation flexible electronic platforms requiring simultaneous optical and mechanical sensing capability.

[0080] The fabrication method disclosed in the present invention is entirely laser based and compatible with scalable industrial manufacturing processes. The elimination of vacuum deposition systems hazardous chemical processing and expensive multistage fabrication techniques enables rapid low cost environmentally compatible and large scale production of flexible nanosensors. Due to its high sensitivity broad spectral response rapid electrical response operational stability and excellent mechanical durability the disclosed nanosensor provides substantial industrial applicability for commercial wearable technologies biomedical devices intelligent monitoring systems flexible photonic equipment and multifunctional optoelectronic applications.

[0081] Citation List follows:

[0082] Tour J. M. Luong D. X. Yang K. Arnusch C. J. Singh S. P. Thakur A. K. Stanford M. G. Li J. T. and Presutti S. E. Laser induced graphene composites and sensors and methods for producing same Patent No WO2020197606A2 World Intellectual Property Organization.

[0083] Tour J. M. Luong D. X. and Subramanian A. Laser induced graphene structures and methods of fabrication Patent No US11014816B2 United States Patent and Trademark Office.

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Claims

What is claimed is an elastic optical nanosensor based on a laser induced graphene and iron oxide nanohybrid structure comprising a flexible polyimide substrate configured as a carbon precursor material a porous conductive laser induced graphene structure formed on the surface of the polyimide substrate through controlled carbon dioxide laser irradiation iron oxide nanoparticles stabilized and distributed within the porous graphene structure through laser assisted photothermal conversion and a flexible encapsulation layer composed of polydimethylsiloxane wherein the nanosensor is configured to simultaneously detect optical and mechanical stimuli while providing high sensitivity rapid photoelectric response mechanical flexibility and stable multimode sensing performance.The elastic optical nanosensor according to Claim 1 wherein the porous laser induced graphene structure is generated through localized carbonization and graphitization of the polyimide substrate under controlled laser irradiation parameters including laser power scanning speed irradiation frequency and beam resolution thereby forming a three dimensional conductive graphene network having high surface area enhanced optical absorption and efficient electrical charge transport characteristics suitable for optical sensing applications.The elastic optical nanosensor according to Claim 1 wherein the iron oxide nanoparticles are formed through deposition of an iron precursor solution onto the porous laser induced graphene structure followed by fiber laser induced photothermal decomposition and in situ nanoparticle stabilization such that the resulting FeO@LIG nanohybrid structure enhances carrier separation electrical conductivity optical absorption and photoelectric conversion efficiency while reducing electron hole recombination within the sensing structure.The elastic optical nanosensor according to Claim 1 wherein the interaction between the iron oxide nanoparticles and the porous graphene framework is configured to optimize interfacial charge transfer pathways improve optical and electrical properties accelerate photoinduced carrier transport and increase sensing performance under optical excitation within ultraviolet and visible wavelength regions.The elastic optical nanosensor according to Claim 1 wherein the nanohybrid sensing structure possesses a controlled thickness of approximately five hundred micrometers configured to provide balanced mechanical flexibility structural stability efficient light absorption and enhanced electrical charge transport while maintaining stable sensing performance during repeated mechanical deformation including pressure strain bending and motion induced displacement.The elastic optical nanosensor according to Claim 1 wherein the polydimethylsiloxane layer functions as an elastic protective encapsulation configured to improve mechanical durability environmental stability biocompatibility and conformability of the nanosensor onto curved and dynamic surfaces in wearable and biomedical systems.The elastic optical nanosensor according to Claim 1 wherein the nanosensor possesses multimode sensing capability configured to simultaneously generate measurable electrical responses to optical stimuli within ultraviolet and visible wavelength regions and mechanical stimuli including pressure strain bending and motion.The elastic optical nanosensor according to Claim 1 wherein the nanosensor is configured for integration into wearable electronic devices biomedical monitoring systems flexible optoelectronic platforms environmental sensing systems and multimode sensing applications through a fully laser based scalable fabrication process eliminating vacuum deposition systems hazardous chemical processing and multistage lithographic manufacturing procedures.

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