Smart fibers for medical devices

Abstract

Disclosed are antenna fiber sensors and systems incorporating the sensors, methods of making the sensors, and methods of using the sensors. The sensor is a thermoplastic elastomeric polymer cladding enclosing metal wires thermally co-drawn into an antenna fiber. Further, the sensors are used with an RF generator to monitor electromagnetic pulse along the transmission line and measure location along the fiber. The antenna fiber sensor provides sensitive distributed pressure, temperature, and proximity measurements for various procedures and interfaces, particularly medical procedures such as vascular operations.

Description

Docket No. 144578.00411  SMART^FIBERS^FOR^MEDICAL^DEVICES^ ^ Cross^Reference^to^Related^Application^

[0001] The present application claims priority to U.S. Provisional Patent ApplicationNo. 63 / 510,493 that was filed June 27, 2023, the entire contents of which are herebyincorporated by reference in its entirety.^^^ Technical^Field^

[0002] The disclosure relates to smart fiber antenna sensors, for sensing parameterssuch as pressure, proximity, and temperature at locations along their length.Background

[0003] Imbuing sensing and processing capabilities to the material objects enablestheir integration as active nodes into the Internet of Things (IoT) and recreating their digitaltwins in a metaverse. Specifically, fibers and textiles with data sensing and processingcapabilities have conformal properties that allow imbuing them as part of a thin coating oras an upholstery to the surface of any existing object with an arbitrary 3D surface shape. Dueto its thin, flexible, and elastic form-factor, incorporation of the sensory fiber, or the sensorytextile comprised of multiple interweaved fibers, onto the surface of a functional object canbe done seamlessly, without modifying or hindering preexisting functionality of the object,while turning the entire surface of the object into a distributed sensory matrix, tactile andreactive to its environment, like the skin of living organisms.

[0004] Medical devices are one area in which advanced sensor technology may beapplied. Medical treatments and surgical operations have a variety of challenges even withadvancements over conventional sensing technology, such as complex integration intodevices during the manufacturing process, challenges with visualizing the position of a singlesensor leading to extended procedure times and over-exposure to radiation, accurate real-time data collection, and not having quantifiable verification of intraprocedural treatmentsuccess. Additionally, most of the sensing devices are stand alone, well delineatedmacroscopic or mesoscopic objects at least partly made of hard materials, such as plastics,metals, and semiconductors. As such, when integrated into a medical device, they mightDocket No. 144578.00411 significantly modify its geometry, formfactor, and biomechanical compatibility with theenvironment (living tissue) into which they are implanted or introduced, resulting indiminished overall short-term device performance, or increasing the risk of inflammation,scarring, or rejection of the device, thus hindering its long-term use. Thin, flexible, elastic,and biocompatible sensing fibers that can provide distributed monitoring of parameterssuch as pressure, spatial proximity, and temperature, particularly while moving in a bloodvessel or other body cavity during medical procedures, are needed to overcome some of thecurrent challenges.

[0005] A novel development in soft electronics pioneered flexible sensors, replacingconventional sensors in several applications, including health care. Their unique propertiesin sensing, monitoring, and human-machine interfacing make them an ideal replacement forconventional sensors. Wearable sensors, electronic skins, flexible textiles, and soft fibersensors are substantial improvements in soft electronics, where physiologic monitoring isfacilitated by high sensitivity, resolution, accuracy, and comfort. Specifically, smart fibers areexcellent candidates for novel sensors which provide enhanced functionalities in complex,miniaturized structures such as distributed measurements.

[0006] The human vascular system is a complex, branched network consisting ofvarious diameter vessels. Blood pressure is one of the fundamental parameters inphysiologic monitoring. Measurement accuracy is vital for many diagnoses and treatments,such as minimally invasive operations that use guidewires and catheters to access thevascular system in order to treat cardiac conditions, such as angioplasty and cardiac ablation.Existing solutions commonly used in these operations provide single-point pressuremeasurements with embedded pressure sensor(s) along the tip of the device, which arechallenging to manufacture and limited in the data that can be provided. Distributedpressure sensor fibers bring an innovative approach to multipoint measurements wherefibers are capable of measuring pressure in multiple locations with high sensitivity andresolution.Summary^

[0007] The present disclosure addresses the above drawbacks by providing fibers,systems, and method for distributed sensing of parameters such as pressure, proximity, andDocket No. 144578.00411 temperature at any point along the length of the fibers, in order to provide real-timefeedback to a user.

[0008] According to an aspect of the present disclosure, an antenna fiber sensor isdescribed comprising a polymer cladding with an outer surface, a length extending betweena proximal end and a distal end along a first axis, a width, and a thickness; one or more poressurrounded by the polymer cladding and distributed between the proximal end and thedistal end of the cladding, and one or more wires extending within the polymer cladding andbetween the proximal end and distal end of the cladding. The polymer is a composite ofthermoplastic elastomer and a dielectric-constant modifying filler. The one or more poreshas a diameter less than the width and thickness of the polymer cladding.

[0009] According to another aspect of the present disclosure, an antenna fiber sensorsystem is described, comprising: i) the antenna fiber sensor; ii) a radio frequency (RF)generator and receiver; and iii) passive or active electronics coupling the RFgenerator / receiver to the antenna fiber sensor for the choice of the electromagnetic (EM)mode combination. The passive or active electronics coupling allows choosing or invokingthe respective sensing modalities.

[0010] A further aspect of the present disclosure are methods of sensing using thedisclosed antenna fiber. An aspect is a method for sensing within a vessel using the antennafiber system that includes inserting the antenna fiber sensor into a vessel; transmitting anelectromagnetic signal from an RF generator; receiving a reflected electromagnetic signal atthe RF receiver; detecting impedance changes in the reflected electromagnetic signal;converting the detected impedance changes in the reflected electromagnetic signal into achange in characteristic of the antenna fiber sensor; and detecting the location of the changein characteristic along the antenna fiber sensor.

[0011] According to another aspect of the present disclosure, a method of making anantenna fiber sensor is described. The method includes the steps of: producing a polymercladding preform including one or more channels and one or more passages, and thermallydrawing the polymer cladding preform with one or more wires feeding into the one or morepassages. In the methods, the polymer cladding is a composite of a thermoplastic elastomerand a dielectric-constant modifying filler.Docket No. 144578.00411  Brief^Description^of^the^Drawings^

[0012] FIGS 1A-1C are schematics of the antenna fiber sensor. FIG.1A is a schematicof an example antenna fiber sensor, according to aspects of the present disclosure. FIG.1B isa schematic of the example antenna fiber sensor of FIG. 1A acted on by stresses P1 and P2along the length of the sensor, illustrating a stress-sensing mode of operation based in thelocal distortion to the propagating mode refractive index involving fiber deformation. FIG.1C is a schematic of the antenna fiber sensor of FIG. 1A experiencing a local distortion to thepropagating mode refractive index by an insertion of a foreign object into the mode’s electricfield.

[0013] FIGS. 2A-2H illustrate an antenna fiber sensor system. FIG. 2A is an exampleantenna fiber sensor system according to aspects of the present disclosure. FIG. 2B is aschematic of the components of an example antenna fiber sensor system according toaspects of the present disclosure. FIG. 2C is an electromagnetic pulse waveform that is sentby an RF generator and the received waveform that indicates voltage changes based ondeformation points along an example antenna fiber sensor system, according to aspects ofthe current disclosure. FIG.2D is a schematic of an example antenna fiber system and appliedpressure at multiple points of the fiber by a finger corresponding to the waveforms of FIG.2C. FIG. 2E is an exemplary cross-section of the antenna fiber sensor including the shapes(Sh(x,y)) and refractive indices (n) of the cladding, core, and electrodes, according to aspectsof the current disclosure. FIG. 2F is a schematic of an example embodiment of a multi-material fiber antenna with 1 mm diameter, doped glycerol liquid core, and copper wires,according to aspects of the present disclosure. FIG. 2G is a schematic of an exampleembodiment of a multi-material fiber antenna with 1 mm diameter, air-filled core, andcopper wires. FIG. 2H is a schematic of an example embodiment of a multi-material fiberantenna with 0.4 mm diameter, air-filled core, and tungsten wires.

[0014] FIGS. 3A-3C illustrate modes of an antenna fiber sensor. FIG. 3A is a schematicof an example asymmetric mode in a two-wire antenna fiber sensor for pressure sensing,according to aspects of the present disclosure. FIG. 3B is a schematic of an examplesymmetric mode in a two-wire antenna fiber sensor for proximity sensing, according toaspects of the present disclosure. The red and blue arrows in FIG. 3A and 3B showschematically the direction and magnitude of the electric field at the electrode-claddingDocket No. 144578.00411 interfaces, the green arrows are the direction and magnitude of the electric field created bythe mode in the fiber and its surrounding. FIG. 3C shows plots of the superposition resultsof symmetric and asymmetric modes for simultaneous pressure and proximity sensing.

[0015] FIG. 4 is a schematic illustrating the processing by the returned signal to atime-domain reflectometer (TDR) for analyzing the location and sensed measurement on theantenna fiber sensor, according to aspects of the current disclosure.

[0016] FIGS. 5A-5C illustrate sensing methods with the antenna fiber sensor. FIG. 5Ais a schematic of two sensing methods either by (i) changes in capacitance by fiberdeformation or by (ii) changes in the fiber’s refractive index by changing dielectric constantas a result of a foreign object penetrating the fiber’s evanescence field, according to aspectsof the current disclosure. FIG. 5B is a schematic of electronic testing methods for (i) fiberdeformation, (ii) proximity measurements, and (iii) distributed measurement setup withmultiple weights at multiple points along the length of a fiber, according to aspects of thecurrent disclosure. FIG.5C illustrates electromagnetic simulation of an air-filled core copperwire antenna fiber sensor using COMSOL Multiphysics software where (i) shows theelectrical field norm of the fiber on the vertical axis, (ii) shows the COMSOL simulation ofelectrical field of a 1 mm fiber, and (iii) shows the electrical field norm of the fiber on thehorizontal axis, according to aspects of the current disclosure.

[0017] FIGS. 6A-6B illustrate connection of an antenna fiber sensor to a radiofrequency (RF) system. FIG. 6A is schematic of a socket for connecting the wires to the RF-generator and receiver of an example antenna fiber sensor system. FIG. 6B shows images ofthe steps of inserting the wires in the socket for connecting to an RF-generator and receiver,according to aspects of the present disclosure.

[0018] FIG.7 shows images of a measurement setup for the capacitance measurementof glycerol and BaTiO3 nano-powder doped glycerol at different distances between theparallel plates of a Hippotronics OC-TC Oil Tester for the measurement cell using an LCRMeter (Hioki 3536 LCR Meter), according to aspects of the present disclosure.

[0019] FIGS. 8A-8C illustrate capacitance measurement for doped and undopedglycerol. FIG. 8A illustrates the capacitance of undoped and BaTiO3 nano-powder dopedglycerol as measured by the setup in FIG. 7. FIG. 8B is a plot illustrating the compleximpedance amplitude measurements of undoped glycerol and BaTiO3 nano-powder dopedDocket No. 144578.00411 glycerol at different distances between the parallel plates in the measurement cell of FIG. 7using an LCR Meter (Hioki 3536 LCR Meter). FIG. 8C is a plot illustrating the compleximpedance phase angle measurements of undoped glycerol and doped glycerol at differentdistances between the parallel plates in the measurement cell of FIG. 7 using an LCR Meter(Hioki 3536 LCR Meter).

[0020] FIGS. 9A-9C illustrate an antenna fiber sensor wire and core elements. FIG. 9Ais a schematic of an antenna fiber sensor with copper wires and a glycerol-filled core (Cu-Gly) (i) and its associated sensitivity curve (ii) and distributed pressure measurement (iii),according to aspects of the present disclosure. FIG. 9B is a schematic of an antenna fibersensor with copper wires and an air-filled core (Cu-Air) (i) and its associated sensitivitycurve (ii) and distributed pressure measurement (iii), according to aspects of the presentdisclosure. FIG. 9C is a schematic of an antenna fiber sensor with tungsten wires and an air-filled core (W-Air) (i) and its associated sensitivity curve (ii) and distributed pressuremeasurement (iii), according to aspects of the present disclosure.

[0021] FIGS. 10A-10B illustrate associated measurement with an antenna fibersensor. FIG. 10A is a schematic of a 1 mm Cu-Air antenna fiber sensor and its associatedpressure sensitivity limit measurements with sub-gram weights. Load of 0.1 g translates intopressure of 0.1 kPa, 0.2 g into 0.2 kPa, etc.. FIG. 10B is a schematic of a 0.4 mm miniaturizedW-Air antenna fiber sensor and its associated proximity measurements, using metallicobjects of increasing diameter (color coded in graphs) brought to 4 mm from the fiber.

[0022] FIGS. 11A-11C illustrate signal measurement with the antenna fiber sensor.FIG.11A is a schematic of a Cu-Gly antenna fiber sensor (panel a) and a plot of its associatedfull-width at half-maximum (FWHM) and amplitude of the signal at 6, 16, 26, and 36 cm usinga 20 g weight (FWHM of 4-6.5 cm) (panel b). FIG.11B is a schematic of a Cu-Air antenna fibersensor (panel a) and a plot of its associated FWHM and amplitude of the signal at 6, 16, 26,36, and 46 cm using a 20 g weight (FWHM of 1.15-1.4 cm) (panel b). FIG. 11C is a schematicof a W-Air antenna fiber sensor (panel a) and a plot of its associated FWHM and amplitudeof the signal at 6, 16, 26, 36, and 46 cmusing a 10 g weight (FWHM of 1.2-2.7 cm) (panel b).

[0023] FIGS 12A-12D illustrate pressure measurement with an antenna fiber sensor.FIG. 12A is a schematic of a measurement setup for hydrostatic pressure measurements, inDocket No. 144578.00411 which the fiber vertically oriented is partly immersed in the liquid, and the liquid is graduallyadded to cover a longer section of a fiber.

[0024] FIG. 12B is a plot of hydrostatic measurement results of Cu-Air antenna fibersensor within a fluid column of deionized water at different levels, covering an increasingfiber height. The RF electronics is coupled to the antenna fiber sensor invoking all the sensingmodalities simultaneously. The pronounced step in the signal at the water-air interface isdue to the symmetric mode sensing the jump in the dielectric constant at the water-airinterface, i.e., substance identification. Additionally, the signal baseline of the sectionimmersed in water decreases as the longer section of the fiber is immersed, indicating anincrease in average hydrostatic pressure in the immersed section, sensed by antisymmetricmode. FIG.12C is a plot of linear approximation of the hydrostatic pressure measurementsfrom the measurement setup and results of FIGS. 12A-12B.

[0025] FIG. 12D is a schematic of the measurement setup for hydrostatic andhydrodynamic pressure measurement. The entire fiber is immersed in water, and increasingthe reservoir height can change the column pressure. The fiber is inserted into the 3D-printed tube with periodically changing diameters, simulating vasculature with cloth-inlaidsections.

[0026] FIG. 12E is set of plots illustrating the change in column pressure. When thetubing in FIG. 12D is sealed, the change in column pressure results in a uniform change inthe hydrostatic pressure signal.

[0027] FIG. 12F is set of plots illustrating the change in column pressure. When thetubing in FIG. 12D is open, the change in the column pressure results in increasingdifferential pressure change, overlayed on the jumps in pressure at the locations of changingthe inner diameter of the vasculature model, as is indicated in FIG. 12F (left). Aftersubtracting the average pressure drop between the water column and air, its apparent that,according to Bernoulli’s principle, the pressure in hydrodynamic conditions is lower in thesection of the vasculature model that has a smaller inner diameter (FIG 12 F (right)), i.e. inhydrodynamic conditions the fiber is capable of locating cloth-inlaid pre-ischemic bloodvessel sections with high specificity.

[0028] FIGS. 13A-13C illustrate temperature measurement with an antenna fibersensor. FIG. 13A shows a temperature measurement setup with antenna fiber sensors,Docket No. 144578.00411 according to aspects of the present disclosure. FIG. 13B is a plot and thermal image of anantenna fiber sensor with a glycerol core doped with BaTiO3. FIG. 13C is a plot and thermalimage of styrene-ethylene-butylene-styrene (SEBS) cladding.

[0029] FIG.14 is a flowchart of the steps for using an antenna fiber sensor for sensingpressure, according to aspects of the current disclosure.

[0030] FIGS. 15A-15C illustrate thermal drawn antenna fiber sensor. FIG. 15A is aschematic of the thermal drawing process of the antenna fiber sensor preform with the infillof doped glycerol by a syringe. FIG. 15B shows microscopy images of cross-sections of a Cu-Gly antenna fiber sensor (i), Cu-Air antenna fiber sensor (ii), and a miniaturized W-Airantenna fiber sensor (iii), according to aspects of the current disclosure. FIG. 15C showsspooled fiber of the Cu-Gly antenna fiber sensor (i), the Cu-Air antenna fiber sensor (ii) , andthe W-Air antenna fiber sensor (iii).

[0031] FIG. 16 illustrates an example method of forming elastomer cladding dopedwith nanofiller, in which BaTiO3 nanoparticles are premixed with SEBS to form a compositesheet for the cladding elastomer.

[0032] FIG. 17 illustrates an example method of forming glycerol doped with BaTiO3nano-powder by manual and magnetic stirring.

[0033] FIG. 18 depicts a transparent SEBS polymer sheet prepared by meltingpolymer pellets (left) into sheets (right).

[0034] FIG. 19 illustrates a preform in a vacuum oven arranged for consolidation ofSEBS polymer sheets. The white rods and blocks are to confine the preform structure fromsagging or collapsing and apply a light pressure in order to assist the consolidation.

[0035] FIGS. 20A-20B illustrate a SEBS polymer preform. FIG. 20A illustrates a topview of a SEBS polymer preform after consolidation. FIG.20B illustrates a side view of a SEBSpolymer preform after consolidation.

[0036] FIGS. 21A-21B illustrate SEBS polymer preform printing. FIG. 21A shows athree-dimensional (3D) printing process of SEBS polymer preform, according to aspects ofthe present disclosure. FIG. 21B illustrates 2 cm wide square preform with hollow channeland two holes for the wires, side (left) and top (right) view.

[0037] FIGS. 22A-22D illustrate a fiber draw process. FIG.22A is a typical preform fordraw arrangement with two spools of 75 µm copper wires. FIG. 22B is a side view of theDocket No. 144578.00411 preform (~2 cm wide) and copper wires on the preform holder of FIG. 22A. FIG. 22C is Apreform after the draw is finished. FIG.22D is a spool of typical fiber (~0.5 mm thick)resulting from the draw process.

[0038] FIGS. 23A-23D illustrate a fiber drawing system. FIG. 23A is a cross-sectionalview of a preform being inserted into a fiber drawing system. FIG. 23B is a cross-sectionalview of a preform being heated in a fiber drawing system. FIG. 23C is a cross-sectional viewof a beginning of a fiber draw in a fiber drawing system. FIG. 23D is a cross-section view of afiber draw in a fiber drawing system.

[0039] FIGS. 24A-24B illustrate methods for creating the liquid-filled core of anantenna fiber sensor. FIG. 24A shows incorporation of liquid into a hollow core via manualinjection. FIG. 24B shows the incorporation of liquid into a hollow core via suction of theliquid from an open syringe during drawing.

[0040] FIGS. 25A-25B illustrate corresponding parameters for fiber drawing withliquid-filled core. FIG. 25A is a plot of drawing parameters (diameter, speed) of liquidglycerol in SEBS. FIG. 25B is a plot of drawing parameters (tension, temperature) of liquidglycerol in SEBS.

[0041] FIGS. 26A-26B illustrate variation for antenna fiber sensor fabrication. FIG.26A shows a setup for fabrication of an antenna fiber sensor in which the hollow core isperiodically collapsed or broken up using 2 cm magnets. FIG. 26B shows a collapsed area ofthe antenna fiber sensor using the setup of FIG. 26A.

[0042] FIG. 27 is a schematic of the optimization for reducing the interfacial tensionbetween a viscous liquid core preserved in another viscous liquid, from the core’s cylindricalvolume and its breakup into periodic spheres during the breakup process.

[0043] FIG. 28 illustrates the evolution of a breakup of the core between twopolymers, according to aspects of the present disclosure.

[0044] FIGS. 29A-29C illustrate the breakup of doped glycerol corecontinuously fedthrough a hot furnace of a tapering setup vs. heated on the hot plate. FIG. 29A shows the as-drawn fiber. FIG 29B illustrates the wavy pattern showing the beginning but incompleteprocess of breakup of the fiber fed through a furnace), and FIG. 29C illustrates the breakupof doped glycerol core using a hot plate.^Docket No. 144578.00411  Detailed^Description^

[0045] Described are antenna fiber sensors and antenna fiber sensor systems forsensing pressure from forces on the fiber and objects near the fiber at positions along thefiber length, methods of making the antenna fiber sensors, including fabricating the fibers bythermal drawing technique, and methods for sensing using the antenna fiber sensors, forexample, pressure, temperature, proximity of an object, and location in the surroundingenvironment. Methods of sensing may include using TDR analysis, for example, to collecthigh-resolution distributed pressure measurements. For instance, a possible clinical use ofthe antenna fiber sensor includes locating with high specificity the cloth-inlaid reduced innerdiameter pre-ischemic sections of blood vessels in 3D printed models, while used in stress-sensing antisymmetric-mode coupled configuration. Further, the antenna fiber sensor maybe used for material identification.

[0046] Sensor

[0047] Referring to FIG. 1A, a non-limiting example, the antenna fiber sensor 100 is afiber with a polymer cladding 102 extending between a proximal end and a distal end. Thepolymer cladding 102 of the antenna fiber sensor may be made of polymer with high level ofelasticity which provides maximum deformation by compression of the sensor. In a non-limiting example, the polymer is a thermoplastic elastomer. For example, the thermoelasticpolymer may be one of, but is not limited to, styrene-ethylene-butylene-styrene (SEBS),cyclic olefin copolymer (COC), elastomeric cyclic olefin copolymer (ECOC), polysulfone(PSU), poly(methyl methacrylate) (PMMA), polycarbonate (PC), polyvinylidene fluoride(PVDF), polyetherimide (PEI), or polydimethylsiloxane (PDMS).

[0048] The polymer cladding 102 of the antenna fiber sensor 100 may further be acomposite of a polymer, such as the thermoplastic elastomers described previously, and adielectric-constant modifying filler. In a non-limiting example, the composite may include0% to 50% of the dielectric-constant modifying filler by volume. The amount of filler may betuned to achieve a desired mean field dielectric constant εf. In a non-limiting example thedielectric-constant modifying filler may be one of, but not limited to, ferroelectric oxidesincluding barium titanate (BaTiO3) and strontium titanate (SrTiO3), metal and transitionmetal oxides including Calcium copper titanate (CaCu3Ti4O12), La2−xSrxNiO4, andderivates thereof, intrinsic or doped semiconductors including silicon (Si), germanium (Ge),Docket No. 144578.00411 and gallium antimonide (GaSb), or conductors including silver (Ag) and carbon (C). In a non-limiting example, the dielectric-constant modifying filler has a particle size range of 10 nm –500 nm. In a preferred embodiment, the particle size of the dielectric-constant modifyingfiller is 50 nm – 200 nm.

[0049] In a non-limiting example, the polymer cladding 102 houses one or more wires104. The wires may extend the length of the sensor. In a non-limiting example, the wires maybe metal or conductive polymer composite. In a non-limiting example, the metal wires mayinclude a metal with a melting point greater than 400 °C. In another non-limiting example,the melting point of the wires is higher than the softening point of the cladding. The metalmay include, but is not limited to, copper (Cu), zinc (Zn), silver (Ag), or tungsten (W). In anon-limiting example, the conductive polymer wires may be, but are not limited to, carbonblack-doped polycarbonate (CPC), carbon black-doped polyvinylidene fluoride (PVDF),carbon black-doped polyetherimide (PEI), carbon nanotube-doped CPC, carbon nanotube-doped PVDF, carbon nanotube-doped PEI, or combinations thereof.

[0050] In a non-limiting example, the antenna fiber sensor 100 further includes oneor more pores 106 surrounded by the polymer cladding 102. The one or more pores 106may be hollow, filled, partially filled, or any combination thereof based on achieving adesired field dielectric constant ε2. As will be described in further detail, the one or morepores or channels are added, introduced, or formed within the polymer cladding, such asduring the formation of the antenna fiber sensor 100. The one or more pores 106 may beenclosed within the cladding and do not extend to the outer surface of the polymer cladding.Further, the one or more pores 106 may be distributed throughout the cladding. The poresmay be distributed throughout the length of the sensor cladding 102. Alternatively, the pores106 may be one or more channels extending the length of the polymer cladding 102.Alternatively, the pores 106 may be channels that extend at least a partial length of thepolymer cladding 102. For example, the channels may extend the full length between theproximal and distal end of the cladding. In the embodiments, the one or more channels donot extend to the outer surface of the polymer cladding. The one or more channels mayalternatively be referred to as cores herein.

[0051] The introduction of pores or channels into the cladding makes it deformableunder hydrostatic and hydrodynamic conditions, which is critical for the successfulDocket No. 144578.00411 applications in the medical realm, such as for local sensing of changes in vascular bloodpressure in pre-ischemic blood vessels or in bodily liquids in locally partly obstructedurinary tract, as is described herein.

[0052] In a non-limiting example, the one or more pores 106 may be filled or partiallyfilled with one of a gas or a liquid. For example, the gas may include nitrogen, oxygen, or inertgases such as helium or argon. Alternatively, the one or more pores 106 may be filled with acolloidal liquid. For example, the colloidal liquid may include, but is not limited to, glycerolor polyethylene glycol doped with a high dielectric constant filler. In a non-limiting example,the high dielectric constant filler is BaTiO3 or SrTiO3.

[0053] In a non-limiting example, one or more pores 106 are distributed along thelength of the antenna fiber sensor 100 and one or more wires 104 extend along the length ofthe sensor. The one or more pores 106 may be parallel to the one or more wires 104. Forexample, where the one or more pores are one or more channels, the one or more channelsand the one or more pores extend the length of the sensor in parallel to each other.

[0054] In a non-limiting example one pore or one channel may be transverselyarranged in the center of the polymer cladding. Further, one or more wires may be arrangedin parallel to the central pore or channel.

[0055] Alternatively, a wire 104 may be transversely centered in the polymercladding 102. Further one or more pores or channels 106 may be arranged in parallel to thecentral wire 104.

[0056] In a non-limiting example, the antenna fiber sensor ranges from 0.2 to 2 mmin diameter.

[0057] FIGS. 1A-1C further depicts a polymer cladding 102 with multiple pores 106and one central core M1 of metal or conductive polymer microwire(s) 104; M2-optionalconductive layer Faraday cage 108; ε1-elastic cladding polymer 102 with dielectric constantε1 ;ε2-pore 106 filled with gas or liquid with dielectric constant ε2. D-is the fiber thickness.

[0058] Referring now to FIG. 1B, the principle of operation for spatial resolution isshown. An RF signal 110 with vacuum wavelength λv is coupled to the fiber-guided modeusing TDR transmitter. The RF signal 110 has a step function envelope 112. In a non-limitingexample, the fiber mode for a single wire fiber would be a Sommerfeld-Zenneck mode.Alternatively, for a pair of parallel wires in the fiber, it will be a parallel wire transmissionDocket No. 144578.00411 line mode, and so forth. The wavelength of the mode in the fiber is λf ≈ λv / √(εf), where εf isthe mean-field approximation dielectric constant of the fiber, defined by ε1, ε2, and M1.Objects are applied to the fiber along its axis at points P1 and P2, creating local distortionsto the εf, i.e., scattering centers. Scattering results in reflections from P1114 and P2116. Ina non-limiting example, if the distance between P1 and P2 is larger than λf, two distinctsignals delayed by the λf / c from each other will be recorded at the RF-coupled end using TDRreceiver. Alternatively, if the distance between P1 and P2 is smaller than λf, there will be nosuch distinction, and the reflected signals will combine into a single one. In other words, λf / cdefines the longitudinal resolution for sensing the externally imposed distortions to the fibermode.

[0059] Referring to FIG.1C, the principle of operation for a proximity sensing mode isshown. In this configuration, M2 is absent, and the mode diffraction limit λf / 2 is larger thanthe fiber thickness D. In that case the evanescent field 118 of the fiber mode will have asignificant component penetrating outside the fiber. An object placed within the distanceλf / 2 from the fiber and not touching the fiber will still create a distortion to the fiber mode,producing reflection depicted in FIG.1B. Alternatively, if λf / 2 is smaller than D, then the fibercladding has to deform by applying a stress in order to distort the fiber mode locally andcreate the reflection signal depicted in FIG. 1B. M2 can be added to make sure that proximitysignal doesn’t create any artefacts, and the measurement is purely a stress measurement, asis desired for some of the physiological monitoring applications. It should be noted that if M2is added to the fiber while the diffraction limit is larger than the fiber thickness, nopropagating mode will exist in the fiber, and fiber cannot be used as a distributed sensoreither for stress or proximity.

[0060] Sensor system

[0061] As illustrated in FIGS. 2A-2H, an antenna fiber sensor system is disclosed thatmay be used to sense at least one of a pressure, temperature, proximity of an object, andlocation in surrounding environment at one or more points along its length. The systemincludes at least one antenna fiber sensor, such as any of the previously described sensorconfigurations, and an RF generator. In a non-limiting example, the RF generator may be aTDR or a VNA.Docket No. 144578.00411

[0062] Referring to FIGS. 2A-2B, an antenna fiber sensor 200 is connected to a TDRhead 204 of an oscilloscope 206 using a custom-designed 3D printed socket 202 and 50-ohmconnection wires to receive and transfer electromagnetic pulse, in a non-limiting example.

[0063] In a non-limiting example, the socket 202 is positioned at the proximal end ofthe antenna fiber sensor 200 and coupled to the one or more wires within the sensor (seeFIGS. 6A-B). The socket 202 contacts each of the metallic wires in the fiber to coaxial cores(the coax cables’ “signals”) for transmitting a radio frequency (RF) signal to and from thewires, while the braided jackets (the coax cables’ “grounds”) are shortened, forming acommon ground. The socket 202 is further coupled to a RF generator, such as the TDR 204or alternatively a vector network analyzer (VNA). Thus, the socket 202 provides an electricalconnection between the RF generator 204 and the one or more wires of the antenna fibersensor 200. The socket 202 may immobilize the coax-fiber interface region, throughequipping each separate compartment housing the fiber and each of the coaxes with grippingfins, intended to maximize mechanical stability and minimize the electrical transmissionnoise. In a non-limiting example, the socket may be 3D printed in biocompatible plastic, suchas an autoclavable dental resin (Dental SG, Formlabs Inc.), using a stereolithography printer(Form 3B, Formlabs Inc.). Alternatively, the 3D printed socket is designed and manufacturedusing a CAD-CAM prototyping approach, such as 1) 3D printing and assembly of the 3Ddesign of the socket components, or 2) injection molding of the 3D design of the socketcomponents into 3D printed or CNC machined molds that are the negative of the socketcomponents followed by component assembly.

[0064] In one aspect, time domain reflectometry is traditionally used in the qualityassessment of transmission lines over long distances. A pulse is sent along a cable and anydiscontinuities along the path where the submitted signal propagates is reflected to theoscilloscope. Any change in impedance along the cable induces a reflection, such as thesocket connecting the TDR to the fiber, changes in the dimensions of the fiber's cross-sectional geometry, reaching the end of the fiber segment, and any damage or partial ruptureof the wires.

[0065] In a non-limiting example the location of a deformation on the fiber isconsidered an RC shunt, where the time delay between the incoming pulse feed and the back-Docket No. 144578.00411 reflected signal from the RC shunt resolves the location of the deformation. Voltage changeon the location of deformation may be measured by reflectometry as shown in FIGS. 2C-2D.

[0066] TDR measurements are done by applying a sharp step voltage, for example arise time < 7 picoseconds, through a lumped port onto a transmittance line (the fiber) andmeasuring the reflectance (and transmittance) as function of time. The sharp step functionpropagates as a RF signal through the fiber, reflecting from local changes in the impedance( ^^).^^^ ൌ ^^ ^ ^^ି ^బ ൗ ^బ ି ^ ∆^ ∆^ା ^^ା ^బ ൌ ^^ା ^^ൗ ൌ ^^ା ^ ^^ା (1)^ ା ^ ଶ^బା ∆^ ଶ^బand the changed impedance. The approximation is valid for small changes.

[0067] A two-wires transmittance line is characterized by the fiber’s impedance ^^:^^ ൌ ^ோା^ఠ^ ^ ^ ^^ൗ ^^ (2)conductance, inductance, and capacitance between the wires, and ^^ is the angular frequency.The approximation is correct for a lossless transmittance line with highly conductive wires.For all standard line geometries (coaxial, 2-wires, and 2-plates), equation 3 is useful:^^ ൌ ^ ^^ൗ ఌ ^^^ ൌ ^^ ∙ ∙ ^ (3)isa geometrical factor (1 / √2 ^^ for coaxial, 1 / √ ^^ for 2-wires, and 1 for 2-plates transmittanceline).

[0068] When an RF signal propagates through a conductor, a change in the impedancecause a part of the signal to reflect relative to ΔZ / Z. The phase of the reflectance is similarlyaffected by the direction of ΔZ. From∆^ ^ ൌ െ∆^^ (4)

[0069] The formula of the capacitance of 2-plates wire is given in eq. 5.1, and thecapacitance for 2- wire transmittance line (such as the one used in this work) is given in eq.5.2:Docket No. 144578.00411  ^^^^^௧^^ൌఌ^ௗ (5.1) గఌ^^

[0070] Applied pressures on the elastic cladding, such as by a finger or a metal weight,compresses the fiber. This compression changes the central core shape as the metal wiresapproach each other, as illustrated in FIG. 2E. The change in the distance between the wires∆ ^^ changes the impedance of the fiber: ∆^∆^^^^௧^^ൌௗௗ (6.1)inthe distance between the wires. As discussed later, the electric field of the RF signal expandsfar outside the waveguide. Therefore, a local change in the environment of the fiber changesthe effective dielectric constant of the fiber. The change can be added to equation 6:∆^ ^^௧^^ൌ∆ௗെ∆ఌ^^ ௗ ଶ∙ఌ(7.1)

[0072] According to aspects of the current disclosure, the antenna fiber sensor is amulti-material fiber where the cladding, a core central channel, and the metal wires havedifferent shapes and refractive indexes. In FIGS. 2F-2H different antenna fiber sensorembodiments are shown. FIG. 2F is a non-limiting example of an antenna fiber sensorincludes 75 μm copper wires aligned horizontally and embedded in SEBS cladding and aglycerol core (Cu-Gly antenna fiber sensor) doped with barium titanate (BaTiO3) to increasethe dielectric coefficient by multiple orders of magnitude, since barium titanate is a commondielectric reinforcement material with a relative permittivity of 2000.

[0073] FIG. 2G is a non-limiting example of an antenna fiber sensor with an air-filledcore and 75 μm copper wires aligned vertically and confined in SEBS cladding (Cu-Air fiber).Docket No. 144578.00411

[0074] FIG. 2H is a non-limiting example of a miniaturized fiber antenna with an air-filled core and 25 μm tungsten wires aligned vertically and confined in SEBS cladding (W-Airfiber). Integration of the fiber antenna on biomedical devices such as guidewires andcatheters require microscale fiber diameter, and tungsten shows higher durability in lowermicron dimension. This miniaturization by the use of thinner W wires provides a theoreticaldownsizing towards ~100 μm cross section, significantly smaller than the ~1mm Cu-Airfiber of FIG. 2G. The fiber is drawn at a higher speed to experimentally achieve a diameter ofabout 400 μm.

[0075] FIG. 3A (top) shows the antisymmetric mode electric field schematics in thetypical fiber antenna cross section and the corresponding wiring to the RF generator througha transformer balun (bottom) allowing to invoke this mode in an exclusive manner. FIG. 3B(top) shows the symmetric mode electric field schematics in the typical fiber antenna crosssection and the corresponding wiring to the RF generator while the fiber wires shortened toeach other (bottom) allowing to invoke this mode in an exclusive manner. FIG. 3C shows acomparative stress sensitivity (left) and proximity sensitivity (right) of the fiber antennaoperated in different modes – symmetric (referred to as “common”) antisymmetric (referredto as “transformer”), and the superposition of the two (referred to as “standard”).In the embodiments, an antenna fiber sensor system comprises an antenna fiber sensor asdisclosed; a radio frequency (RF) generator and receiver; and a passive or active electroniccoupling the RF generator / receiver to the antenna fiber sensor. The passive or activeelectronic coupling the RF generator / receiver to the antenna fiber sensor provide the choiceof the electromagnetic (EM) mode combination, which allows invoking the respectivesensing modalities. The sensing modalities for a fiber with two wires are: a passive or activebalun transformer for invoking the antisymmetric mode is connected, as in FIG. 3A, whichenables exclusive sensing of stress / temperature; an impedance-matching resistorconnected in series to shortened wires of the fiber, as in FIG. 3B, enabling exclusive sensingfor proximity / substance identification; and an impedance-matching resistor connected inseries to one of the antenna fiber wires while the other wire is grounded, making the fibersensitive to all sensing modalities as described herein.

[0076] Referring to FIG.4, an example system 400 for processing the sensed signal byan antenna fiber sensor system is shown. In a non-limiting example, the system 400 may beDocket No. 144578.00411 an RF-generator, specifically a TDR or VNA. The system 400 includes an input 402, such asthe reflected electromagnetic signal affected by a change in the antenna fiber sensorcharacteristic as a result of, but not limited to, a pressure, proximity, or temperaturemeasurement. The system 400 further includes a processor 404. In some embodiments, theprocessor 404 can be any suitable hardware processor or combination of processors, suchas a central processing unit (“CPU”), a graphics processing unit (“GPU”), and so on. Theprocessor 404 may communicate with a data analyzer 406 including software 408 and data410. In a non-limiting example, the software 408 analyzes the input signal to detect changesin the originally transmitted electromagnetic signal and reflected electromagnetic signal.This detected change in the electromagnetic signal form the data 410 output from thesoftware 408. In a non-limiting example, the processor 404 receives the data 410 andproduces an output 412. The output 412 may inform about the degree, type, and location ofthe signal change from the input 402.

[0077] As shown in the non-limiting example of FIG. 5A, antenna fiber sensors maysense a signal in two different ways: 1) through local impedance change and resulting backreflection due to pressure-induced deformation of the fiber when stress is applied (i), and 2)as a result of foreign object entering the fiber’s proximity which changes the local refractiveindex of the fiber mode by interfering with its evanescent field penetrating outside the fibercladding (ii), thus creating a local impedance change resulting in back reflection of a portionof the propagating RF signal.

[0078] In a non-limiting example, the antenna fiber sensors may be tested in anexample set-up shown in FIG.5B. In panel (i) antenna fiber sensors are stabilized using a 3D-printed fiber holder. A 3D-printed plastic pedestal is used between metal weights to analyzeonly the capacitance change by the deformation of the fiber by eliminating proximity. In analternative setup, the plastic pedestal is removed for proximity measurements in panel (ii).Single-point measurements are done using one metal weight on a specified location on thefiber. Additionally, multipoint measurements may also be performed by locating metalweights in multiple locations simultaneously as shown in panel (iii).

[0079] In a non-limiting, demonstrated example, a Keysight DCA-X N1000Aoscilloscope and N1055A, 35GHz TDR Module (Keysight, US) were used to characterize allantenna fiber sensor designs. Metal wires at the beginning of 40 cm long fibers were exposedDocket No. 144578.00411 by melting and cleaving the cladding. The proximal end of the fibers connecting to thesockets were sealed by heating and pressing on them with a glass. One of the metal wireswas connected to the middle of the 50-ohm connection cable, and the other was grounded.A fiber holder and weight pedestal were 3D printed from polycarbonate (PC) using Fortus450mc FDM printer (Stratasys, USA). Fibers were straightly stabilized inside a groovedchannel on the PC fiber holder. PC pedestals were used between fiber and metal weights toeliminate the proximity effect. Various metal weights were located on the fibers to measurethe pressure applied. The base line of the measurement is the pedestal only, and for eachweight the measurement was taken as the change from the base line, divided by theamplitude of the voltage step. The measurements were smoothed using a frequencydropping of wavelength smaller than 1 cm in the signal, and a moving average with diameterof 0.5 cm. This combination does not affect the FWHM of the measurements on the pedestal,has small effect on the amplitude of the signal, and dramatically improves the SNR. Eachmeasurement is averaged over 128 samples, taking 1-2 seconds, depending on the time scaleof the measurement. Voltage resolution is <10μV.

[0080] In a non-limiting example, when an electromagnetic signal propagatesthrough the antenna fiber sensor at high frequencies, the fiber works as a waveguide.Electromagnetic simulation of the antenna fiber sensor may be performed using COMSOLMultiphysics® software to investigate its waveguide properties, for example, as illustratedin FIG. 5C. Relative permittivity and permeability of all materials, the geometry of the fiber,and the frequency of the TDR signal are defined in the simulation module. FIG. 5C shows asimulation of a 1mm antenna fiber sensor with copper wires and air-core (Cu-Air fiber) with35 GHz signal by the reflectometer. Three guided fiber modes with different fiber refractiveindexes are obtained by the given parameters. As a result, an evanescence field on the basicmode of fiber, the lowest mode with the highest refractive index, is observed outside theantenna fiber sensor since the refractive index of the fiber core is lower than the refractiveindex of the fiber cladding as illustrated in FIG. 5C. The waveform of the propagatedelectromagnetic signal in the antenna fiber sensor is observed to be similar to the transverseelectric wave (TE) since the electrical field was perpendicular to the waveguide. Thiswaveguide mode provides the capability of proximity measurement to the antenna fibersensor in addition to deformation measurement for pressure-sensing. The diffraction limitDocket No. 144578.00411 of the fiber that serves as a waveguide may be calculated to determine the minimum fiberdiameter, which can confine the electrical field inside using equation 8:^^ ൌ ఒଶ^ (8) 35thefiber is calculated at around 1.3. The diffraction limit of the antenna fiber sensor is calculatedas 3.5 mm with these parameters. As a result of the diffraction limit calculation, the fiberdiameter should be at least 3.5 mm to confine the electrical field inside. Fiber with a 1 mmdiameter, with the refractive indexes of selected core and cladding materials, is smaller thanthe calculated diffraction limit of 3.5 mm. Since a 3.5 mm fiber diameter is not suitable forintegrating the fiber in microscale devices, core and cladding refractive indexes may beincreased to confine the electrical field in the fiber to minimize the diffraction limit.

[0081] FIGS. 6A-6B shows an example of the 3D printed socket and its assembly aspreviously described.

[0082] In a non-limiting example, FIGS. 7 and 8A-8C describe the modification andcharacterization of dielectric constant of the pores using doped glycerol with BaTiO3nanoparticles in embodiments of the antenna fiber sensors. In an example experimentalsetup, the capacitance and impedance spectroscopy of 100% glycerol and a 3:1 glycerol–BaTiO3 mixture was performed. 350mL volumes of each viscous liquid were measuredbetween two immersed 25.44mm copper plates 230μm and 960μm apart in a mechanicalsetup designed for that purpose (Hippotronics OC-TC Oil Tester) (FIG. 7). The result of themeasurements is shown in FIG, 8A-C.

[0083] Referring now to FIGS. 9A-9C, results of pressure sensing by the antenna fibersensors in terms of their sensitivity, spatial resolution, and distribution are shown, accordingto non-limiting aspects of the present disclosure. Electrical reflectometry analysis ofpressure-sensing fibers may be performed using a 35 GHz TDR module connected to amainframe oscilloscope. In a non-limiting experimental example, a step function with 7picoseconds rise time and 0.2V amplitude propagates through the parallel wire transmissionlines of the fiber antennas while the oscilloscope monitors the voltage on the port as afunction of time. The electronic setup and connection diagram schemas may be those of FIGS.Docket No. 144578.00411 2B-2C. Three fiber configurations' sensitivity and dynamic pressure range (FIGS. 9A panel(i), 9B panel (i), and 9C panel (i)) were analyzed using metal weights with different massfrom 0.1 g to 100 g. A 3D-printed plastic pedestal was placed between fiber and metal weightto distinguish deformation from proximity effects that affect the effective dielectriccoefficient and to allow uniform perpendicular pressure application (as shown in FIG. 5Bpanel (i)). Measurements without the pedestal, where the weight sits or leans on top of theholder, 4 mm above the fiber, were also performed to quantify the fiber’s sensitivity toproximity effect. The pedestals used were 1 cm long and weight 0.3 g. With the pedestals, themetal weights were 5 mm above the fibers. The applied pressure of the weights on the fiberalong the 1 cm of the pedestal is:^^^^^ ൌ ^^^^^ (9)base line of the measurement is the pedestal only, and for each weight the measurement istaken as the change from the base line, divided by the amplitude of the voltage step.

[0084] In the TDR, reflection of the step function from a deformation in the fiber wasmeasured after a time equivalent to twice the transit time of the signal to the deformation,therefore the conversion between the time of the measurement and the location is given by:^^ ൌ ^௧ଶ^^^^ (10)and ^^^^^ is the effective refractive index. Equation 10 allows for extrapolation of ^^^^^ of thedifferent fibers, using the known locations of the applied pressure and the correspondingmeasurements in time. Equation 10 is then used to convert the measurements from time todistance.

[0085] In a non-limiting experimental example as show in FIG. 9A panel (ii), thesensitivity curve of fiber with liquid core (Cu-Gly fiber) showed a single positive slope until40 KPa and an additional, gradually overtaking negative slope when higher pressure wasapplied, until becomes purely negative past 80 kPa. The pressure applied by 100 gr weightnegatively changes the sensitivity curve. This behavior indicates proximity affected themeasurements significantly until the higher pressures. Measurements are affectedsignificantly by deformation rather than proximity at high pressures since the sensitivityDocket No. 144578.00411 curve behaves negatively due to the horizontal metal wires in the fiber diverging bycompression.

[0086] In the example above, both fiber designs with air-core (FIGS. 9B-9C) resultedin higher sensitivity since the liquid core is replaced with a more compressible air corebetween the metal wires located horizontally instead of vertically. The Cu-Air fiber design,showed the highest sensitivity (FIG. 9B panel (ii)). The dynamic pressure range of theminiaturized fiber (W-Air fiber) is observed to be higher than the other two designs, up to300 kPa, as shown in FIG. 9C panel (ii). The antenna fiber sensor works as a distributedpressure sensor where localized deformations by applied stress and proximity are detectedwith high sensitivity.

[0087] Further, multipoint pressure-sensing was also performed by applying stresson multiple locations on the fiber simultaneously using metal weights with differentheaviness, as illustrated by FIG. 5B panel (iii). The signal peak of the voltage change in theCu-Gly fiber design is significantly wider than the air-filled fiber designs due to the liquidcore. Each measurement point on the air-filled fiber designs indicates the same ability ofpressure-sensing with high sensitivity as a result of distributed sensing (FIGS. 9B panel (iii)and 9C panel (iii)).

[0088] In another measurement example according to FIG.9C panel (iii), stress by thesame weights on the same locations simultaneously and separately may be applied on theW-Air fiber design to investigate the durability and repeatability of the fiber performance.The W-Air fiber is durable with the same sensing accuracy for repeated measurements.

[0089] All three fibers showed sensitivity to unidirectional pressure 1-2 orders ofmagnitude higher than previously reported result13 for distributed sensing. The Cu-Gly fibershowed an initial signal in the same direction as the other two, even though the differentorientation of the wires is predicted to generate a signal of opposite direction. However, thesensitivity shows transition between two clear regions, indicated in FIG. 9A panel (ii)^by thedotted lines. The first region, a rapid increase in the signal with small weights, is believed toindicate a small in the effective dielectric constant of the fiber due to realignment andmovement of the fiber relative to the holder and the pedestal, eliminating or reducing airpockets around the fiber. This effect is amplified by the coarse surfaces of the 3D printedelements. The second region, a slower change in the signal at higher pressures, is believed toDocket No. 144578.00411 be the actual deformation of the air gap. This is corroborated by the linear increase in thesignal at high pressures for the air-gapped fibers (Cu-Air and W-Air), indicating an increasein capacitance, while the signal decreases in high pressures for the Cu-Gly fibers,corresponding to decrease in capacitance. This behavior is expected for the Δd, generated bythe applied pressure. When high pressure was applied (by finger, above 1 Kg, not shownhere), the signal for Cu-Gly changed direction, while the signal for the air gaped fiberincreased without changing direction, further supporting the assumption that the high-pressure slope is due to deformation. The slopes, maximum sensitivity and impedance of thevarious fiber are summarized in Table 1.TABLE 1: Sensitivity and Impedance of the fibersinimpedance within the measured range for all three fibers.

[0091] In FIG. 10A, the fibers according to aspects of the current disclosure showhigher sensitivity than the pressure sensors on the market by a significant voltage differenceobtained with lower applied stress. The fibers according to aspects of the current disclosureare characterized by below 0.1Kpa sensitivity since 0.1 g weight with 1 mm width located on1 mm fiber diameter corresponds to 0.1 kPa. Since the signal-to-noise ratio of the signalobtained by 0.1 g applied stress is low, the example antenna fiber sensors presented in thecurrent disclosure are highly capable of measuring pressure lower than 0.1 KPa (FIG. 10A).

[0092] The accuracy of measuring impedance by signal reflectance drops with theimpedance squared. Assuming a small change in the impedance in the measurements, thesensitivity of the voltage measurement by the oscilloscope is limited by (from equation 1):Docket No. 144578.00411  Cu-we can, 11,expect Cu-Air to be 6 times more sensitive than W-Air due to lower impedance. As shown, itis about 7 times more sensitive. There may be signal loss due to the high mismatch in thefiber coupling.

[0094] As conveyed above, deformation measurements are isolated from proximityto distinguish the effect of applied stress as the pressure-sensing mechanism. Since the fibersensors according to aspects of the current disclosure are capable of both deformation andproximity measurements, proximity and deformation are isolated by using metal weights 4mm away on the fiber sensor without using the plastic pedestal in between in the followinganalysis, as shown in FIG.10B. In an example measurement, 2 g, 20 g, and 200 g weights(6.98mm, 14.93 mm, and 24.93 mm width) are located 4 mm away from the miniaturized W-Air fiber. Since the weights' width increases proportionally with their heaviness, the highestvoltage change occurs by applying 200 g with 24.93mm width (Figure 10B). This proximitysensing by the fiber sensors described herein may be useful in many application fields, suchas touch board screens and cyber-physical interfaces.

[0095] Strong dispersion limits the overall fiber length, which is functional forpressure-sensing applications. In a non-limiting example, the FWHM of the signals from the1 cm pedestal was measured for the fibers at different locations for a constant weight (FIGS.11A-11C). To overcome the broadening of the signal width due to dispersion when anelectromagnetic signal propagates through the fiber, the TDR according to aspects of thecurrent disclosure resolves space to the frequency and analyzes the fiber's spatial resolution,indicating the closest possible distance between two measurement locations and overallfunctional fiber length. In a non-limiting example, a 50 cm fiber length is durable forpressure-sensing since the measurements at the end location of the fiber are still in a sensiblespatial resolution range. The spatial resolution for the Cu-Gly fiber, Cu-Air fiber, and W-Airfiber are illustrated in FIGS. 11A-11C. Cu-Air antenna fiber sensors display a high spatialresolution and low dispersion with a FWHM of 1.15 cm at 6 cm and 1.4 cm at 46 cm. W-AirDocket No. 144578.00411 antenna fiber sensors displayed a higher dispersion with FWHM of 1.2 cm at 6 cm and 2.7cm at 46 cm, indicating dependence of the dispersion on the geometry of the fiber. Cu-Glyantenna fiber sensors displayed a high FWHM or 4-6.5 cm, possibly due to high dispersionfor dispersion of high frequency signal in the glycerol-BaTiO3 solution. Fiber designs with aircores result in a high spatial resolution of 1 cm, which is ideal for a distributed sensor (FIGS.11B-11C).

[0096] Multimaterial, functional fiber pressure sensors are ideal alternatives formicrosystems to commercial pressure sensors due to their minimized dimensions,preserved functionality, and easy integration with any device. As such, functionality in afluidic environment is crucial for measurements such as blood pressure in the vascularsystem.

[0097] In a non-limiting example, the functionality of the fibers according to aspectsof the present disclosure are characterized in a fluidic environment to measure thehydrostatic pressure by levels of a fluid column. Referring to a measurement setup in FIG.12A, water is filled in a closed graduate cylinder system where the pressure-sensing fiber(Cu-Air) is stabilized to measure hydrostatic pressure with respect to heights (FIG. 12B).Output voltage drastically decreases on the water-air interface at all heights. Measurementsat 40cm, 50cm, and 55cm on fiber were linearly analyzed with sensitivity of 0.4 mV / kPa.(FIG. 12C).

[0098] In a demonstrated example, long fibers were sealed on the bottom, and bothmetal wires were exposed on top to connect with the TDR module. The hydrostatic pressureof the water was measured with a setup that includes a 50 cm-long sealed and leakproofglass cylinder. A glass rod was located in the middle of the cylinder to immobilize the fiberduring measurements. The fiber was glued on the center of the glass rod fixed on the topcover of the glass graduated cylinder. The top cover has an embedded SMA connector toenable fiber and TDR module connection. This connection was designed specially to protectthe connection from the liquids. The glass graduate cylinder has five outlets on the front sidefor insertion of a pressure transducer to compare TDR results with transducer values. Dueto the known hydrostatic pressure data from the literature, deionized water was chosen assample liquids. The graduated cylinder was filled with liquid until each of the fiveDocket No. 144578.00411 measurement points was submerged, and measurements were taken at each location withboth TDR and the pressure transducer.

[0099] The antenna fiber sensors disclosed herein display two orders of magnitudehigher pressure sensitivity than previously reported for distributed sensing. The high resultsare likely due to change of the dielectric coefficient of the environment of the fiber. Evenconsidering only the pressure sensitivity of the fibers, Cu-Air displays sensitivity an order ofmagnitude higher than any previously reported, with high spatial resolution and lowdispersion. This is the first reported distributed system with the potential to measurehydrostatic pressure.

[0100] In a non-limiting example, the antenna fiber sensor may also sensetemperature differences along the length of the sensor. The thermal differential expansionof the cladding affects the wire separation, in turn affecting the field distribution of theantisymmetric mode. The local sensing of the temperature, similar to stress sensing, resultsfrom the RF reflection from the temperature-deformed location of the antenna fiber due tothe mode mismatch at this location when compared to the rest of the fiber. The dielectriccoefficient of the material of the fiber can also change as function of temperature. Theaforementioned changes in separation and dielectric properties will change the impedanceof the fiber and can be measured using the previously mentioned procedures. The fiber canbe doped with nano or microparticle with high temperature dependent dielectric properties,,such as SrTiO3 or BaTiO3, in order to increase the thermal sensitivity . As shown in FIGS.13A-13C fiber antenna can serve as a multipoint temperature sensor with ~1cm resolutionand sub-1 deg. sensitivity. In FIG.13A two fibers, hollow core and Cu-Gly core are shown sideby side with heating elements 1 cm wide arranged at two locations below the fibers,contacting them thermally, in a group of three at 11-14 cm from the fiber sockets, and a singleelement at 22-23 cm from the fiber sockets. FIG.13B and 13C (top) demonstrate Cu-Gly corefiber and hollow core fiber response V / V0 [a.u.], respectively, to the heat resulting from thevoltage of 2v (blue line), 4v (orange line), 6v (yellow line), 8v (purple line), and 10v (greenline) applied to the resistive heating elements, as function of location along the fibersmeasured in centimeters, overlayed against the heat map collected by the thermal camera.The fibers are painted black to prevent the thermal emissivity noise in the thermal camerareadings. The table provides the calibration of the peak V / V0 values in FIG.13B and 13C (top)Docket No. 144578.00411 to the respective peak temperatures collected by the thermal camera in FIG. 13B and 13C(bottom).

[0101] In a non-limiting example, the effects of temperature may be detected in aregion of inflammation in a tissue or organ.

[0102] In a non-limiting example, the RF generator generates an electromagneticsignal which is transmitted to the one or more wires of the antenna fiber sensor. Theelectromagnetic signal is reflected back to the RF generator upon reaching the distal end ofthe sensor or due to some change in the characteristic of the fiber sensor. For example, thechange in characteristic includes, but is not limited to, a change in the impedance of theelectromagnetic signal due to a change in the dielectric constant of the antenna fiber sensor.In a non-limiting example, the dielectric constant may be affected by, but not limited to, apressure, temperature, proximity of an object, or dielectric constant of the surroundingenvironment.

[0103] In a non-limiting example, pressure may include hydrostatic pressure ordynamic pressure. Alternatively, the pressure may include a stress causing a deformation atone or more locations along the length of polymer cladding. For example, a deformation inthe antenna fiber sensor inserted into a vessel of a subject may be caused by, but not limitedto, a blood pressure, a change in blood pressure, a curvature of a vessel, and an obstructionof a vessel. In another example, deformation in the antenna fiber sensor inserted into aurinary tract of a subject may be caused by, but not limited to a pressure in the urinary tract,a change of pressure in the urinary tract, a stricture of the urinary tract, and obstruction ofthe urinary tract. In another example, the deformation is caused by at least one of a pressureor change in pressure in a pleural cavity, abdominal cavity, or digestive tract.

[0104] In a non-limiting example, the parameter of the surrounding environment mayinclude pH. pH sensing occurs when the antenna wires are exposed to the environmentthrough the cladding pores, and a reference material, standard to the pH sensors, is presentas an additional core spanning the fiber length. Local changes in pH will be expressed as alocal change in the wire's affinity to the electric potential, directly expressed in the localchange in response to RF signal propagation. ^

[0105] According to the present disclosure, a method for sensing, for example withina vessel or body lumen, using an antenna fiber system is described. As shown in FIG. 14, theDocket No. 144578.00411 antenna fiber system may include the system and sensors described above. The method1400 includes inserting the antenna fiber sensor into a vessel at step 1402. Thereafter, anelectromagnetic signal is transmitted from the RF generator at step 1404. At step 1406, thereflected electromagnetic signal is received. The reflected signal is analyzed to detectimpedance changesat step 1408. The change in impedance may occur as a result of, but notlimited to, a stress applied to the antenna fiber sensor, an object in proximity to the antennafiber sensor, or a temperature difference. At step 1410, impedance changes are convertedinto a change in the characteristic of the sensor. At step 1412, the location of the change incharacteristic along the antenna fiber sensor is detected.

[0106] According to the present disclosure, a method of making an antenna fibersensor is described. The antenna fiber may include the sensors described above. The methodincludes the steps of: producing a polymer cladding preform including one or more channelsand one or more passages, and thermally drawing the polymer cladding preform with oneor more wires feeding into the one or more passages. In embodiments, the polymer claddingis a composite of a thermoplastic elastomer and a dielectric-constant modifying filler.

[0107] Referring to FIG. 15, the antenna fiber sensors may be fabricated using VLSI-Fi (Very large-scale integration on fibers), a technique that combines VLSI phenomena withthe thermal drawing technique for fiber devices. The VLSI-Fi involves the thermal drawingof macroscale 3D printed preforms into microscale fiber devices. VLSI-Fi is a three-stepprocess where a rod, typically a cylinder or parallelogram, called a preform, is 3D printed.The preform consists of a cladding made of a material chosen for its structural propertiesthat house a core structure composed of dissimilar materials typically chosen to provide afunction to the fiber device. The assembled preform, often going through additionalconsolidation to confine all material tightly together, is then placed in an upright format tosoften and pull down like taffy into a fiber. During this second step, the cross-section ispreserved and scaled-down orders of magnitude smaller.

[0108] As will be described in further detail below, the drawn fiber can go throughthermal treatments to change the material properties and break up the gas or liquid-filledhollow core into periodic spheres by enhancing interfacial stress between core materials.For example, the central core channel has periodic breakups of doped glycerol with BaTiO3.Docket No. 144578.00411

[0109] In a non-limiting example, preforms are shaped by consolidatingsuperimposed, transparent SEBS sheets. A convergence method is used to introduce metalwires to the preform by a custom design 3D printed head where two metal wires on spoolsare stabilized in parallel and freely unspooled by fiber pulling. The preform is heated abovethe glass transition temperature of polymer cladding inside a furnace and pulled with aparticular draw speed and tension by a capstan while its cross-section is preserved (FIG15A). For the Cu-Gly fiber, a syringe injects preheated glycerol doped with BaTiO3. into thecore channel without applying pressure, since a pressurized injection may result in arounded core shape (FIG. 15B panel (i)). The doped glycerol is removed to draw a hollowcore in the Cu-Air fiber and W-Air fiber designs. The hollow cores are elongated for easierdeformation under perpendicular pressure (FIG. 15B panel (ii) and 15B panel (iii)) whileminimizing the distance between the wires.

[0110] In one non-limiting example, 14cm long preforms are drawn into over 100mof fibers and spooled (FIG. 15C panels (i)-(iii)). The sensing properties of the fibers are thentested using time-domain reflectometry analysis. According to this example, the segments ofthe Cu-Gly fiber used for measurements have a width of 670±40μm, a height of 320±20 μm,a distance between the center of wires of 350±30 μm, and a diameter of glycerol gap of170±20 μm. Air pockets are visible around the wires. The segments of the Cu-Air fiber usedfor measurements have a width of 950±20 μm, a height of 440±20 μm at the side, and acurving height of 540±20 μm at the center. The copper wires are 290±10 μm from each otherwith a 125±20 μm air gap. The segments of the W-Air fiber used for measurements have awidth of 430±20 μm, a height of 205±10 μm at the side, a curving height of 270±10 μm at thecenter. The copper wires are 200±20 μm from each other with a 100±10 μm air gap. Thedimensions of W-Air and Cu-Air were chosen to have similar sensitivity according toequation 6.2.

[0111] In a non-limiting example, a procedure for modifying the dielectric constant ofthe cladding is shown in FIG. 16, wherein nanofillers are premixed into the claddingelastomer. The pellets of SEBS are dissolved in toluene, and a 1:2 of BaTiO3 nanoparticles toSEBS by weight is mixed into the resulting liquid, while stirring. Then the mixture is pouredinto a flat tray, and the toluene is evaporated, leaving a composite SEBS:BaTiO3 sheet, that isthen used for preform fabrication as above.Docket No. 144578.00411

[0112] Referring now to FIG.17, a non-limiting example of the preparation of BaTiO3-doped glycerol for filling the core(s) or pore(s) is shown. In this experimental example,biocompatible glycerol mineral oil (Sigma Aldrich, G5516) is mixed at a 1:3 and 1:9 w / wratio with barium titanate 100nm-sized nanopowder (SSNano, 1401GC) at roomtemperature while stirred magnetically at 400 rpm. In a non-limiting example, this dielectricliquid may be heated and stirred during a drawing process to fill a core or preform core asdescribed in further detail below.

[0113] In a non-liming example of forming the antenna fiber sensor, SEBS was usedfor a cladding preform. SEBS pellets (Kraton, US G1657, elastic properties as 23 MPa tensilestrength, and %750 elongation break) as shown in FIG. 18 (left) were evenly spread on ametal sheet and surrounded by PTFE bars (McMaster-Carr, U.S.) on all edges to create 1-2mm thick transparent SEBS sheets. SEBS pellets on the metal sheet were first melted in avacuum oven at 180-200°C, preferably 175oC for 2-4 hours to merge the pellets. Polymerpellets were dispersed in between two steel plates uniformly and Teflon sheets and barswere used to set the thickness of the sheets and to prevent the pellets from sticking to thesteel plates sticking on them, as shown in FIG. 18. After the PTFE bars are removed, metalweights are put on top of the pellets covered with PTFE film (McMaster-Carr, US) to create athin SEBS sheet. The sheet was relocated into the vacuum furnace for 4-6 more hours. PTFEfilms were needed on both top and bottom of the pellet sheet to prevent sticking on thesurface and for easy removal afterward. A transparent SEBS sheet was obtained 4 hourslater. The thickness of the sheets is typically 2-3mm (FIG. 18, right).

[0114] In a non-limiting example of the method for forming antenna fiber sensors,prepared SEBS sheets were cut into rectangular layers to create the preform geometry. Thesheet was cut in multiple slabs to assemble the multilayer preform construct as shown inFIG.19. Steel plates were aligned with Teflon spacers along the preform to provide pressureon the multilayer preform to push layer-by-layer merging while the polymer is softenedunder heat. For internal channels in the preform, Teflon slabs are used to preserve theirgeometry during the consolidation process. The TPE sheets are cut and stacked to form astructure that has hollow cores for the incorporation of wires and to form pores, hollow orfilled with liquid later in the drawing process. The outer dimensions of the preform for fiberswith air gap are 15 mm to 30 mm, 14cm long. The dimensions of the inner channels were 1-Docket No. 144578.00411 2mm for wire channels and 2mm to 10mm for the central air gap channel. The outerdimensions of the preform for the fiber with liquid core are 25mm to 33mm, 14cm long. Thedimensions of the inner channels are 3-4mm for wire channels and 2mm for the centralliquid channel. The multilayer structure is vertically oriented, similar to a sandwich, andconsolidated in a vacuum oven at 1750C to 180°C for 2 hours using a lightweight on top tomerge all layers. FIGS. 19 and 20A-10B show preforms before and after the consolidation.

[0115] In a non-limiting example as shown in FIG. 21A, a 3D printing setup is shownfor forming the antenna fiber sensor preform as an alternative or in addition to methoddescribed immediately above. For example, Fused Deposition Modeling (FDM) method of 3Dprinting was used to create dimensionally accurate and consistent preforms for the sensingfiber. The 3D printer body is a LulzBot Taz with a SKR pro v1.2 mainboard and runs withcustom Marlin firmware. A Mahor XYZ v4 Pellet Extruder with a 0.8mm nozzle was used toreplace the standard filament extruder in order to print SEBS. A textured Overture BuildSurface was placed on the print bed to increase adhesion. Preform 3D files were sliced andconverted to G-code using Ultimaker Cura. The print settings were adjusted as needed usingPronterface. Models were sliced in Cura with the following key settings: Nozzle temperature235°C, build plate temperature 50°C, layer height 0.32 mm, wall line count 1, top / bottomlayers 0, infill density 100%, infill pattern lines, print speed 25 mm / s, first layer speed 10mm / s, retraction off, print cooling off, print flow 150%. The G-code was then run on theprinter through Pronterface, where the flow was further increased by 175%. SEBS pelletswere loaded into the extruder in small portions to prevent overheating within the extruder.The models were then printed, resulting in the infill being free of voids. FIG. 21B shows thesamples of 3D printed preform structures.

[0116] In a non-limiting example, the thermal draw is performed by a proceduresimilar to the fabrication of an optical fiber. A preform is dropped slowly into the tubefurnace at an elevated temperature until it becomes a viscous liquid and drips down, carryinga thin thread. That thread is grabbed onto at the bottom of the furnace by a tractor andspooled. Driven by volume conservation, the scale down in fiber cross-section compared tothat of the preform is defined by the ratio between the fiber draw speed by the spooler(typically meters or tens of meters per minute) and the preform feed speed into the furnace(typically millimeters per minute). FIGS. 22A-22D and FIGS. 23A-23D show the typicalDocket No. 144578.00411 preform arrangement before and after the draw and the different stages of the draw itself,specifically for the case of fiber antenna device, where the wires are incorporated byconfinement of the preform cladding around the wire, attached to the bait off, and thusspooled down into the fiber at the draw speed rate. The hole in the preform accommodatingthe wire is initially wider than the wire, and reduces in size to confine tight around it in thedraw cone, as the cladding cross-section is scaled down.

[0117] In a non-limiting example of making an antenna fiber sensor with a liquid core(Cu-Gly antenna fiber sensors), the prepared SEBS preform is fixed to a hollow handlethrough which two 75μm copper wires (Goodfellow, US, CU00-WR-000120) sitting on near-frictionless spools are fed through the hollow side core channels of the preform. The setupis introduced into the vertical furnace with three zones of heat of a drawing tower (Optogear,Finland). A wire at the bottom end of the preform is fixed with a weight of 5g to initiatetension in the draw as the drawing cone forms as the preform begins to soften in the furnace.The preform with liquid core and copper wires is thermally drawn at the set temperaturesof zone 1 (top), 2 (middle), and 3 (bottom) were 120°C, 250°C, and 135°C at heating, 180°C,270°C, and 195°C at startup, and 180°C, 270°C, and 195°C at the draw settings. The fiber isdrawn with 0.40mm / min feed speed and 4m / min draw speed. The target fiber diameter isset up to 250 microns.

[0118] In a non-limiting example of making an antenna fiber sensor with an air core(Cu-Air and W-Air antenna fiber sensors), the preform is vertically fixated to the preformholder PTFE rod, where two 75-micron copper wires (GoodFellow, US, CU00-WR-000120)or two 25-micron tungsten wires (GoodFellow, US, W-00-WR-000130) are aligned on topusing a custom-design wire feeding mechanism (suture fiber ref.). Metal wires are carefullyfed inside the side channels and loosely fixated on the metal wire on the bottom, which holdsa 5g weight to pull the bait off. The preform with air gap and tungsten wires are thermallydrawn at the set temperatures of zones 1, 2, and 3 were 120°C, 250°C, and 135°C at heating,180°C, 270°C, and 195°C at startup, and 180°C, 270°C, and 195°C at the draw settings. Thefiber is drawn with 0.40 mm / min feed speed and 4m / min draw speed. The target fiberdiameter is set up to 180 microns.

[0119] In a non-limiting example, a liquid, such as undoped glycerol or BaTiO3-dopedglycerol as previously described may be incorporated into the hollow core of preform duringDocket No. 144578.00411 thermal drawing. In FIG. 24A, the liquid may be manually injected using a syringe.Alternatively, in FIG. 24B, the liquid may be incorporated via suction during drawing froman open syringe. The setup of FIG.24B, wherein the open syringe hanging about the preform,in which we fill its content with new doped glycerol mixed and heated at 200°C, is effectivefor flowing the liquid into the hollow core during the draw. The fiber draw creates negativepressure in the hollow core, resulting in a natural suction from the syringe, which output ishermetically sealed to the hollow channel on the top of the preform. This approach addressesthe potential challenge of controlling pressurization during the draw relative to the manualinjection approach.

[0120] In a non-limiting example, an automated syringe injector may be used to fillliquid into the core if the flow rate is controllable to set a continuous flow, and suitable withmetal syringe usage in order to maintain the liquid temperature high enough which isneeded to stabilize the viscosity of the liquid for easy flow and preform temperature forcontinuous drawing.

[0121] In a non-limiting example, FIGS. 25A-25B show typical data of the drawingparameters of liquid glycerol in SEBS.

[0122] In a non-limiting example, the antenna fiber sensor may undergo post-processing, such as to form discrete liquid or gas-filled pores as is described with referenceto FIGS. 26A-26B. For example, a fiber with a repeating 2 cm collapsed section and 2 cm un-collapsed section was created. This was done by heating the fiber and applying periodicpressure for several minutes on the hot plate (FIGS. 26A-26B). Collapsing or reheating thefiber to initiate a capillary breakup of the hollow or liquid filled core can be used to creatediscontinuity in the hollow cores, forming closed pores.

[0123] In a non-limiting example, the core may be broken up into an array of spheresalong its axis as a result of the tension between two viscous liquids facing each other. In orderto reduce the interfacial tension between the two materials, they naturally adopt theconfiguration that decreases their interacting surface area, as illustrated in FIG. 27.Experimentally, FIG. 28 shows the evolution of a core breaking up.

[0124] A more optimized breakup was conducted using an automated taperingsetup20 and multiple runs were done to achieve the desired breakup. FIG.29A illustrates thissetup. This stage of the fabrication process is still being optimized. FIG. 29B show the levelDocket No. 144578.00411 of progress, where a wavy pattern is observable but not yet a full breakup in the time rangeexpected. In an example procedure, preliminary results using uniform heating on a hot platewere achieved for glycerol-doped SEBS core as shown in FIG. 29C. The breakup takes placearound 205°C-215°C.

[0125] Breaking up a continuous core into isolated gas or liquid-filled sectionsprovides regions along the antenna fiber sensors’ length that are more sensitive to astimulus. This embodiment results in improved signal to noise ration without affecting thespatial resolution, assuming the distance between discrete gas or liquid-filled sections issmaller than the spatial resolution defined by the TDR bandwidth.

[0126] In a non-limiting example, the method further includes forming a preform witha plurality of planar sheets of the thermoplastic elastomer polymer or the composite of athermoplastic elastomer and a dielectric-constant modifying filler, the planar sheets beingequal dimensions; stacking the plurality of planar sheets by their largest surface area suchthat each outer edge of each planar sheet of the plurality of planar sheets align; and heatingthe plurality of stacked planar sheets to consolidate the perform. In embodiments, in formingthe plurality of planar sheets, a length of each planar sheet in is larger than its width. (see,FIGS. 19 to 24).

[0127] In a non-limiting example, a large planar sheet of the polymer or composite iscut to form the plurality of planar sheets of polymer or composite of equal dimensions.Further, one or more channels and one or more passages are cut along the of the stack of theplurality of planar sheets using molds configured for forming one or more pores andenclosing one or more wires, respectively. (see, FIG. 18)

[0128] Alternatively, each planar sheet is three-dimensionally (3D) printed. Forexample, each planar sheet may be 3D printed and then stacked as previously described, oreach 3D printed planar sheet is 3D printed on top of another 3D printed planar sheet. In anon-limiting example, the one or more channels and one or more passages may be cut alongthe length of the stack of the plurality of planar sheets using molds as described above.Alternatively, openings for each of the one or more channels and one or more passages areprinted in each of the planar sheets to form the one or more channels and one or morepassages when the plurality of planar sheets are stacked. (see, FIGs. 21A-21B).Docket No. 144578.00411

[0129] In a non-limiting example, the polymer and dielectric-constant modifying fillerare mixed in solution before forming each of the plurality of planar sheets.

[0130] In a non-limiting example, thermally drawing the polymer cladding preformincludes: inserting the polymer cladding preform in a preform holder; inserting the one ormore wires into the one or more passages; feeding the polymer cladding preform and one ormore wires into a heater until a bait-off drops off the polymer cladding preform forming atapering region and a starting end of the antenna fiber sensor; and grabbing the starting endof the antenna fiber sensor and wrapping it around a capstan and spooling it onto a spool.(see, FIG. 22 and 23).

[0131] In a non-limiting example, the liquid is heated and injected into the one ormore channels during the thermal drawing of the polymer cladding preform. The liquid maybe manually injected during the thermal drawing. Alternatively, the liquid may be injectedby suction force during the thermal drawing of the polymer cladding preform. (FIG. 24)

[0132] In a non-limiting example, the thermal drawing is performed by first heatingthe polymer cladding preform and wires and optional filling. A thermal drawing furnace mayhave distinct temperature zones (e.g., top, middle, bottom). In a non-limiting example, thetop, middle, and bottom temperatures may be 120°C, 250°C, and 135°C, respectively. At thestart-up of the thermal drawing, the top, middle, and bottom zones of the furnace may beincreased to 180°C, 270°C, and 195°C, respectively. In a non-limiting example, the draw mayproceed at the start-up temperature. In a non-limiting example, the fiber is drawn with a 0.40mm / min feed speed and a 4 m / min draw speed. Alternatively, the temperatures and feedand draw speeds may be adjusted based on the polymer cladding preform compositematerials and desired fiber diameter.

[0133] In this description, it will be readily apparent to one skilled in the art thatvarying substitutions and modifications may be made to the invention disclosed hereinwithout departing from the scope and spirit of the invention. The invention illustrativelydescribed suitably may be practiced in the absence of any element or elements, limitation orlimitations which is not specifically disclosed herein. The terms and expressions which havebeen employed are used as terms of description and not of limitation, and there is nointention that in the use of such terms and expressions of excluding any equivalents of thefeatures shown and described or portions thereof, but it is recognized that variousDocket No. 144578.00411 modifications are possible within the scope of the invention. Thus, it should be understoodthat although the present invention has been illustrated by specific embodiments andoptional features, modification and / or variation of the concepts herein disclosed may beresorted to by those skilled in the art, and that such modifications and variations areconsidered to be within the scope of this invention.

[0134] Citations to a number of non-patent references are made throughout thisdisclosure. The cited references are incorporated by reference in their entireties. In the eventthat there is an inconsistency between a definition of a term in this specification as comparedto a definition of the term in a cited reference, the term should be interpreted based on thedefinition in the specification.

[0135] References1. Wang, C., Wang, C., Huang, Z. & Xu, S. Materials and Structures toward Soft Electronics.Adv.^Mater.^30, 1801368 (2018).2. Yin, L. et^al.^A stretchable epidermal sweat sensing platform with an integrated printedbattery and electrochromic display. Nat.^Electron.^5, 694–705 (2022).3. Wang, X., Gu, Y., Xiong, Z., Cui, Z. & Zhang, T. Silk-molded flexible, ultrasensitive, andhighly stable electronic skin for monitoring human physiological signals. Adv.^Mater.^26,1336–1342 (2014).4. Leber, A. et^al.^Soft and stretchable liquid metal transmission lines as distributed probesof multimodal deformations. Nat.^Electron.^3, 316–326 (2020).5. Yu, L. et^al.^Flexible Multi-Material Fibers for Distributed Pressure and TemperatureSensing. Adv.^Funct.^Mater.^30, 1908915 (2020).6. Pozar, D. M. Microwave^Engineering,^4th^Edition. (Wiley, 2011).7. Liu, Z., Wu, H., Ren, W. & Ye Molecular Sciences and Chemical Engineering, Z.-G. B. T.-R.M. in C. Piezoelectric and ferroelectric materials: Fundamentals, recent progress, andapplications. in (Elsevier, 2022). doi:https: / / doi.org / 10.1016 / B978-0-12-823144-9.00069-8.8. Anderson, G. P. & Taitt, C. R. Chapter 2 - EVANESCENT WAVE FIBER OPTIC BIOSENSORS.in (eds. Ligler, F. S. & Taitt, C. R. B. T.-O. B. (Second E.) 83–138 (Elsevier, 2008).doi:https: / / doi.org / 10.1016 / B978-044453125-4.50004-8.Docket No. 144578.00411  9. Faccini de Lima, C. et^al.^Towards Digital Manufacturing of Smart Multimaterial Fibers.Nanoscale^Res.^Lett.^14, 1–16 (2019).10. US20210333131A1 Gumennik et al.  11. van der Elst, L. et^al.^3D Printing in Fiber-Device Technology. Adv.^Fiber^Mater.^2021^32^3, 59–75 (2021).12. van der Elst, L. A. et al. Microstructured Electroceutical Fiber-Device for Inhibition ofBacterial Proliferation in Wounds. Adv Mater Interfaces 2201854 (2022)doi:10.1002 / ADMI.202201854.13. US20220401616A1 Sen et al.14. Nakata, S., Shiomi, M., Fujita, Y., Arie, T., Akita, S., & Takei, K. (2018). A wearable pHsensor with high sensitivity based on a flexible charge-coupled device. *NatureElectronics*, 1, 596-603. https: / / doi.org / 10.1038 / s41928-018-0152-615. Wencel, D., Abel, T., & McDonagh, C. (2014). Optical Chemical pH Sensors. Anal. Chem.,86(1), 15-29. https: / / doi.org / 10.1021 / ac403516816. Paschew, G., Klatt, S., Lienig, J., Arndt, K.-F., & Adler, H.-J. P. (2008). Sensors 2008, 8(1),561-581. https: / / doi.org / 10.3390 / s8010561

Claims

Docket No. 144578.00411  CLAIMS^We claim:

1. An antenna fiber sensor comprising:a polymer cladding with an outer surface, a length extending between a proximalend and a distal end along a first axis, a width, and a thickness, wherein the polymercladding is a composite of a thermoplastic elastomer and a dielectric-constant modifyingfiller;one or more pores surrounded by the polymer cladding and distributed between theproximal end and the distal end of the cladding, wherein the one or more pores has adiameter less than the width and thickness of the polymer cladding; andone or more wires extending within the polymer cladding and between the proximalend and distal end of the cladding.

2. The antenna fiber sensor of claim 1, wherein the polymer cladding has a width in arange of about 200 µm to 2 mm.

3. The antenna fiber sensor of claim 1, wherein the polymer cladding has a thickness,and the one or more pores and one or more wires are contained within the claddingthickness.

4. The antenna fiber sensor of claim 1, wherein the one or more pores are locatedparallel to the one or more wires.

5. The antenna fiber sensor of claim 1, wherein the one or more pores are channelsextending through the polymer cladding from the proximal end to the distal end ofthe polymer cladding.

6. The antenna fiber sensor of claim 1, wherein the polymer cladding has one pore andthe one pore is located about a center of the polymer cladding.Docket No. 144578.00411 7. The antenna fiber sensor of claim 6, wherein the one or more wires is locatedparallel to the pore in the center of the polymer cladding.

8. The antenna fiber sensor of claim 1, wherein the one or more wires is located aboutthe center of the polymer cladding.

9. The antenna fiber sensor of claim 1, wherein the thermoplastic elastomer is selectedfrom the group consisting of styrene-ethylene-butylene-styrene (SEBS), cyclic olefincopolymer (COC), elastomeric cyclic olefin copolymer (ECOC), polysulfone (PSU),poly(methyl methacrylate) (PMMA), polycarbonate (PC), polyvinylidene fluoride(PVDF), polyetherimide (PEI), and polydimethylsiloxane (PDMS).

10. The antenna fiber sensor of claim 1, wherein the dielectric-constant modifying filleris selected from ferroelectric oxides including barium titanate (BaTiO3) andstrontium titanate (SrTiO3), metal and transition metal oxides including Calciumcopper titanate (CaCu3Ti4O12), La2−xSrxNiO4, and derivates thereof, intrinsic ordoped semicondutors including silicon (Si), germanium (Ge), and galliumantimonide (GaSb), and conductors including silver (Ag) and carbon (C).

11. The antenna fiber sensor of claim 10, wherein the amount of dielectric-constantmodifying filler in the polymer cladding ranges from more than 0% to about 50% byvolume that allows tuning a mean field dielectric constant εf.

12. The antenna fiber sensor of claim 11, wherein the dielectric-constant modifyingfiller has particles in a size range of 10 nm – 500 nm.

13. The antenna fiber sensor of any one of claims 1-12, wherein the sensor is flexible,compressible, or both.

14. The antenna fiber sensor of claim 1, wherein the one or more pores are filled orhollow.Docket No. 144578.00411 15. The antenna fiber sensor of claim 14, wherein the one or more pores are completelyfilled or partially filled.

16. The antenna fiber sensor of claims 14 or 15, wherein the one or more pores arefilled with a gas or a liquid.

17. The antenna fiber sensor of any one of claims 14 to 16, wherein the one or morepores are filled with air, glycerol, or a colloidal liquid.

18. The antenna fiber sensor of any one of claims 14 to 17, wherein the one or morepores are filled with a colloidal liquid including glycerol or polyethylene glycoldoped with a high dielectric constant filler.

19. The antenna fiber sensor of claim 18, wherein the high dielectric constant filler isBaTiO3 or SrTiO3.

20. The antenna fiber sensor of claim 1, wherein the one or more pores has a dielectricconstant ε2.

21. The antenna fiber sensor of claim 1, wherein the one or more wires are a metal orconductive polymer composite.

22. The antenna fiber sensor of claim 21, wherein the metal is copper (Cu), zinc (Zn),silver (Ag), or tungsten (W).

23. The antenna fiber sensor of claim 21, wherein the conductive polymer composite iscarbon black-doped polycarbonate (CPC), carbon black-doped polyvinylidenefluoride (PVDF), carbon black-doped polyetherimide (PEI), carbon nanotube-dopedCPC, carbon nanotube-doped PVDF, carbon nanotube-doped PEI, or combinationsthereof.Docket No. 144578.00411  24. The antenna fiber sensor of any one of claims 1-23, further comprising a socketpositioned at the proximal end of the polymer cladding and coupled to one or morewires.

25. The antenna fiber sensor of claim 24, wherein the socket is electrically coupled to aradio frequency (RF) generator.

26. The antenna fiber sensor of claim 25, wherein the RF generator is a time-domainreflectometer (TDR) or a vector network analyzer (VNA).

27. The antenna fiber sensor of claim 1, wherein the antenna fiber sensor can sense atleast one of a pressure, temperature, proximity of an object, and location insurrounding environment along the length of the antenna fiber sensor.

28. The antenna fiber sensor of claim 27, wherein the antenna fiber sensor can sensechanges in hydrostatic pressure.

29. The antenna fiber sensor of claim 27, wherein the antenna fiber can sense changesin physiological pressure.

30. The antenna fiber sensor of claim 27, wherein the antenna fiber sensor can sensechanges in temperature.

31. An antenna fiber sensor system, comprising:i) the antenna fiber sensor of any of claims 1 to 30;ii) radio frequency (RF) generator and receiver andiii) passive or active electronics coupling the RF generator / receiver to the antennafiber sensor for the choice of the electromagnetic (EM) mode combination.Docket No. 144578.00411  32. The antenna fiber sensor system of claim 31, wherein the RF generator is a time-domain reflectometer (TDR) or a vector network analyzer (VNA).

33. The system of claim 31 or 32, further comprising a socket positioned at the proximalend of the polymer cladding and coupled to the one or more wires, wherein antennafiber sensor is electrically coupled to the RF generator through the socket.

34. The system of any one of claims 31 to 33, wherein an electromagnetic signal istransmitted from the RF generator to the one or more wires and reflected back tothe RF generator from the one or more wires.

35. The system of claim 34, wherein the RF generator receives the reflectedelectromagnetic signal from the one or more wires in the antenna fiber sensor todetermine a change in characteristic of the antenna fiber sensor.

36. The system of claim 35, wherein the change in characteristic of the fiber sensor is atleast one of a deformation and a location in a surrounding environment.

37. A method for sensing within a vessel using the antenna fiber sensor system of claim31, the method comprising:inserting the antenna fiber sensor into a vessel;transmitting an electromagnetic signal from the RF generator;receiving a reflected electromagnetic signal at the RF receiver;detecting impedance changes in the reflected electromagnetic signal;converting the detected impedance changes in the reflected electromagnetic signalinto a change in characteristic of the antenna fiber sensor; anddetecting a location of the change in characteristic along the antenna fiber sensor.

38. The method of claim 37, wherein the electromagnetic signal from the RF generatoris a step function.Docket No. 144578.00411 39. The method of claim 37, wherein the impedance changes are a result of changes in arefractive index of the antenna fiber sensor.

40. The method of claim 39, wherein the refractive index changes as a result of a changein a dielectric constant of the antenna fiber sensor.

41. The method of any one of claims 37-40, wherein the change in characteristic of theantenna fiber sensor is at least one of: a stress causing a deformation at one or morelocations along the length of the polymer cladding; a proximity of an object to one ormore locations of the antenna fiber sensor; a type of one or more objects causing adeformation at one more locations along the length of the polymer cladding; and atype of one or more objects in proximity to one or more locations of the antennafiber sensor.

42. The method of claim 41, wherein the type of the object is organic or inorganic.

43. The method of claim 41 or claim 42, wherein the deformation is caused by at leastone of a blood pressure, a change in blood pressure, a curvature of a vessel, andobstruction of a vessel.

44. The method of claim 43, wherein the deformation is caused by at least one of apressure in a urinary tract, a change of pressure in a urinary tract, a stricture of aurinary tract, and obstruction of a urinary tract.

45. The method of claim 43, wherein the deformation is caused by at least one of apressure in a pleural cavity, abdominal cavity, or digestive tract.

46. The method of claim 40, wherein the change in dielectric constant is caused by achange in an environment surrounding the antenna fiber sensor.

47. A method of making an antenna fiber sensor, the method including the steps of:Docket No. 144578.00411  producing a polymer cladding preform including one or more channels andone or more passages, wherein the polymer cladding is a composite of athermoplastic elastomer and a dielectric-constant modifying filler; andthermally drawing the polymer cladding preform with one or more wiresfeeding into the one or more passages.

48. The method of claim 47, wherein producing the polymer cladding preform furtherincludes the steps of:forming a plurality of planar sheets of the polymer cladding of equaldimensions, wherein a length of each planar sheet is larger than its width;stacking the plurality of planar sheets by their largest surface area such thateach outer edge of each planar sheet of the plurality of planar sheets align; andheating the plurality of stacked planar sheets to consolidate the preform.

49. The method of claim 48, wherein each planar sheet of the plurality of planar sheetsis cut from a larger planer sheet of the polymer cladding.

50. The method of claim 48, wherein the one or more channels and one or morepassages are cut along a length of the stack of the plurality of planar sheets usingmolds.

51. The method of any one of claims 48-50, wherein the plurality of planar sheets isformed and stacked by 3D printing of the polymer cladding.

52. The method of claim 51, wherein the one or more channels and one or morepassages are printed in each of the plurality of planar sheets.

53. The method of claim 48, wherein the thermoplastic elastomer and the dielectric-constant modifying filler are mixed in solution before forming the plurality of planarsheets.Docket No. 144578.00411 54. The method of any one of claims 47-53, wherein the thermoplastic elastomer isselected from the group consisting of styrene-ethylene-butylene-styrene (SEBS),cyclic olefin copolymer (COC), elastomeric cyclic olefin copolymer (ECOC),polysulfone (PSU), poly(methyl methacrylate) (PMMA), polycarbonate (PC),polyvinylidene fluoride (PVDF), polyetherimide (PEI), and polydimethylsiloxane(PDMS).

55. The method of any one of claims 47-54, wherein the dielectric-constant modifyingfiller is selected from ferroelectric oxides including barium titanate (BaTiO3) andstrontium titanate (SrTiO3), metal and transition metal oxides including Calciumcopper titanate (CaCu3Ti4O12), La2−xSrxNiO4, and derivates thereof, intrinsic ordoped semiconductors including silicon (Si), germanium (Ge), and galliumantimonide (GaSb), and conductors including silver (Ag) and carbon (C).

56. The method of any one of claims 47-55, wherein the amount of dielectric-constantmodifying filler in the polymer cladding ranges from more than 0% to about 50% byvolume.

57. The method any one of claims 47-56, wherein thermally drawing the polymercladding preform includes:inserting the polymer cladding preform in a preform holder;inserting the one or more wires into the one or more passages;feeding the polymer cladding preform and one or more wires into a heateruntil a bait-off drops off the polymer cladding preform forming a tapering regionand a starting end of the antenna fiber sensor; andgrabbing the starting end of the antenna fiber sensor and wrapping it arounda capstan and spooling it onto a spool.

58. The method of any one of claims 47-57, wherein the one or more channels extend alength of the polymer cladding preform.Docket No. 144578.00411 59. The method of any one of claims 47-58, wherein the one or more channels are filledwith a dielectric constant-modified liquid.

60. The method of claim 59, wherein the dielectric constant-modified liquid is heatedand injected into the one or more channels during the thermal drawing the polymercladding preform.

61. The method of claim 60, wherein the dielectric constant-modified liquid is manuallyinjected or injected by suction force during the thermal drawing of the polymercladding preform.

62. The method of any one of claims 59-61, wherein the dielectric constant-modifiedliquid includes one of a colloidal liquid including glycerol or polyethylene glycoldoped with barium titanate (BaTiO3) or strontium titanate (SrTiO3).

63. The method of any one of claims 47-62, further including post-processing of theantenna fiber sensor.

64. The method of claim 63, wherein post-processing includes applying pressure at oneor more locations along the length of the antenna fiber sensor after heating,providing one or more discrete break-ups in the one or more channels to form oneor more pores.

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