CN111112035A - Transmit-receive integrated all-optical ultrasonic transducer device and preparation method thereof - Google Patents
Transmit-receive integrated all-optical ultrasonic transducer device and preparation method thereof Download PDFInfo
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- CN111112035A CN111112035A CN201911359474.4A CN201911359474A CN111112035A CN 111112035 A CN111112035 A CN 111112035A CN 201911359474 A CN201911359474 A CN 201911359474A CN 111112035 A CN111112035 A CN 111112035A
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Abstract
The invention belongs to the technical field of photoacoustic detection, and discloses a transmitting-receiving integrated all-optical ultrasonic transducer device and a preparation method thereof, wherein the device comprises a structured base (2), a suspension membrane (3), a double-clad optical fiber (1) and an F-P cavity (4) which are constructed by matching the structural base with the suspension membrane; the suspension film is a composite photoacoustic conversion film, can absorb the energy of laser beams of the exciting light, convert the laser beams into ultrasonic waves and emit the ultrasonic waves outwards, and realizes the emission of sound waves; meanwhile, ultrasonic wave echo can be received, a returned signal of the sound wave is induced through deformation, the cavity length of the F-P cavity and the returned detection light signal are influenced, and the returned detection light signal is detected, so that the sound wave can be received. The invention improves the structure of each component and the matching working mode thereof, and the like, and can complete the whole process of ultrasonic wave transmitting and receiving on one suspension film by utilizing the suspension film and the further constructed F-P cavity, so that the device structure is more compact, the photoacoustic imaging operation is simpler and more accurate, and the result is more accurate.
Description
Technical Field
The invention belongs to the technical field of photoacoustic detection, and particularly relates to a transmitting-receiving integrated all-optical ultrasonic transducer device and a preparation method thereof.
Background
An ultrasonic transducer is an energy conversion device that operates in an ultrasonic frequency range and can transmit ultrasonic signals and convert acoustic signals in an external sound field into other signal (e.g., electrical signals). The ultrasonic wave has strong penetrating power, good clustering performance and large information carrying capacity, and is easy to realize rapid and accurate online nondestructive detection and nondestructive diagnosis, so the ultrasonic wave is widely applied to the aspects of industry, agriculture, national defense, biomedicine, scientific research and the like. The new ultrasonic transducer based on the photoacoustic effect is gradually a hot point of research due to its advantages of wide frequency band, high frequency, etc. Meanwhile, by means of an advanced micro-nano processing technology, the size of the transducer is expected to be further reduced, the imaging spatial resolution is further increased, and the problems of low sensitivity, poor anti-interference performance and the like of the traditional ultrasonic transducer can be improved to a greater extent.
The current ultrasonic transducer structure based on the photoacoustic effect mainly adopts a design of separating acoustic emission and acoustic reception functions, such as a scanner-free wide-field photoacoustic endoscope and imaging system (patent publication No. CN108852262A), which increases the complexity of photoacoustic signal processing in the imaging process, and requires higher device packaging accuracy and larger packaging size to be unfavorable for device miniaturization.
In the photoacoustic technology, a composite material composed of various carbon-based micro-nano structures (carbon nanotubes, carbon black, carbon fibers, etc.) and Polydimethylsiloxane (PDMS) is often used as a photoacoustic conversion layer due to its high laser absorption rate and high thermal expansion coefficient.
Disclosure of Invention
In view of the above defects or improvement needs of the prior art, an object of the present invention is to provide a transceiver-integrated all-optical ultrasonic transducer device and a manufacturing method thereof, wherein structures of components and their cooperating working modes are improved, a suspended film and a further configured F-P cavity are utilized, so that the suspended film can absorb laser beam energy to convert into ultrasonic waves and transmit the ultrasonic waves in a sound wave transmitting stage, and the intensity of the sound waves can be sensed and transmitted back to a signal in a sound wave receiving stage, thereby completing the whole process of transmitting and receiving the ultrasonic waves on one suspended film; the receiving and transmitting integrated device has the advantages of more compact structure, simpler photoacoustic imaging operation and more accurate result.
To achieve the above object, according to one aspect of the present invention, there is provided a transceiver-integrated all-optical ultrasonic transducer device, characterized by comprising a structured base having a cavity structure, a suspension film at one end of the structured base, and a double-clad optical fiber inserted into the cavity structure of the structured base; the suspension film is directly and tightly connected with one end of the structural base or tightly connected with the end of the structural base through a hard transparent material, so that the port of the end of the structural base is sealed, and meanwhile, the cavity structure of the structural base is kept in a closed state at the same time; the double-clad optical fiber is used for simultaneously transmitting two lasers of excitation light and detection light, wherein the cladding of the double-clad optical fiber is used for transmitting the excitation light, and the fiber core of the double-clad optical fiber is used for transmitting the detection light and simultaneously reversely transmitting a returned detection light signal; the laser emergent end face of the double-clad optical fiber is positioned in the structured base, a space is formed between the laser emergent end face and the sealing surface of the sealing port of the structured base, and the sealing port of the structured base is also used for being mainly matched with the laser emergent end face of the double-clad optical fiber to further form a sealing space so that the sealing space is correspondingly formed into an F-P cavity;
the suspension film is a composite photoacoustic conversion film, can absorb the energy of the laser beam of the exciting light, convert the laser beam into ultrasonic waves and emit the ultrasonic waves outwards, and the function of transmitting and receiving the sound waves of the integrated all-optical ultrasonic transducer device is realized; meanwhile, ultrasonic wave echoes can be received, the strength of the returned signal is sensed through different mechanical deformation degrees of the ultrasonic wave echoes, the cavity length of the F-P cavity can be influenced through different deformation degrees, the returned detection light signal is further influenced, and the function of receiving the sound wave by the transmitting-receiving integrated all-optical ultrasonic transducer device can be realized through detecting the returned detection light signal.
As a further preferred aspect of the present invention, the double-clad optical fiber has an outer diameter satisfying:
i. the outer diameter of the double-clad optical fiber is matched with the inner diameter of the cavity structure of the structured base, and the sealing port of the structured base can be directly matched with the laser emergent end face of the double-clad optical fiber to further form a sealing space;
or: the laser emitting end face of the double-clad fiber is positioned in a fiber sleeve, the outer diameter of the fiber sleeve is matched with the inner diameter of the cavity structure of the structured base, and the sealing port of the structured base is matched with the laser emitting end face of the double-clad fiber through the fiber sleeve to further form a sealing space.
As a further preferred of the present invention, the structured base is at least one of metal, plastic, plexiglass, and polymer;
preferably, the structured base is Polydimethylsiloxane (PDMS); the hard transparent material is quartz glass.
As a further preferable mode of the present invention, the suspension film is a composite material film composed of a carbon-based micro-nano structure and Polydimethylsiloxane (PDMS), or a composite material film composed of black ink and Polydimethylsiloxane (PDMS), or a composite material film composed of a metal material and Polydimethylsiloxane (PDMS), wherein the metal material is a metal film, a metal array, a metal micro-nano structure, or a metal nanoparticle; preferably, the carbon-based micro-nano structure is a carbon nano tube, carbon black particles, carbon fibers, graphene or football alkene;
more preferably, the suspension membrane is a PDMS-candle carbon black particle-PDMS sandwich type composite material film formed by sequentially arranging a first polydimethylsiloxane layer, a candle carbon black particle layer and a second polydimethylsiloxane layer.
As a further preferable aspect of the present invention, for the F-P cavity, a metal film is further plated on an inner wall of the F-P cavity opposite to the laser emission end face, so as to increase a contrast of the F-P cavity.
As a further preferred aspect of the present invention, a circulator and a coupler are further provided at the tip of the double-clad optical fiber.
According to another aspect of the present invention, the present invention provides a method for manufacturing the above-mentioned transceiver-integrated all-optical ultrasonic transducer device, which is characterized by comprising the following steps:
(1) mixing a PDMS front matrix and a curing agent, standing to remove bubbles, pouring the liquid PDMS prepolymer after standing into a mold with a preset shape, and demolding after curing to obtain the structured base;
(2) spin-coating a first layer of PDMS prepolymer on a substrate, then inverting the spin-coated substrate above candle flame, and carrying out evaporation coating on candle carbon black particles to form a candle carbon black particle layer; then, continuously spin-coating a second layer of PDMS prepolymer on the candle carbon black particle layer, and integrally curing to obtain a flexible PDMS-candle carbon black particle-PDMS sandwich type composite material film deposited on the substrate; then peeling the PDMS-candle carbon black particle-PDMS sandwich type composite material film from the substrate to obtain an independent flexible PDMS-candle carbon black particle-PDMS sandwich type composite material film;
(3) for the structured base obtained in the step (1), treating the target bonding end face of the structured base by using an oxygen plasma machine, treating the surface of a quartz glass sheet to be bonded by using the oxygen plasma machine, aligning the structured base with the quartz glass sheet, attaching the target bonding end face of the structured base and the surface of the quartz glass sheet to be bonded to realize bonding, and sealing one end of the structured base; and (3) then, attaching the independent flexible PDMS-candle carbon black particle-PDMS sandwich type composite material film obtained in the step (2) to the quartz glass sheet from the outside to enable a first PDMS layer obtained by solidifying the first PDMS prepolymer to be in direct contact with the quartz glass sheet, and simultaneously inserting a double-clad optical fiber from the open end of the structured base to enable the sealed port of the structured base to be mainly matched with the laser emergent end face of the double-clad optical fiber to further form a sealed space, wherein the sealed space is an F-P cavity, and the transceiving integrated all-optical ultrasonic transducer device can be obtained.
As a further preferred aspect of the present invention, in the step (3), the independent flexible PDMS-candle carbon black particle-PDMS sandwich-type composite material film is attached to the quartz glass sheet from the outside, specifically: and placing the independent flexible PDMS-candle carbon black particle-PDMS sandwich type composite material film on the water surface of pure water, fully unfolding the sandwich type composite material film by using the surface tension of water, then lifting the sandwich type composite material film from the water by using a bonded quartz glass-structured base, and finally drying.
According to another aspect of the present invention, there is provided a method for manufacturing the above-described transceiver-integrated all-optical ultrasonic transducer device, including the steps of:
(1) mixing a PDMS front matrix and a curing agent, standing to remove bubbles, pouring the liquid PDMS prepolymer after standing into a mold with a preset shape, and demolding after curing to obtain the structured base;
(2) spin-coating a first layer of PDMS prepolymer on a substrate, then inverting the spin-coated substrate above candle flame, and carrying out evaporation coating on candle carbon black particles to form a candle carbon black particle layer; then, continuously spin-coating a second layer of PDMS prepolymer on the candle carbon black particle layer, and integrally curing to obtain a flexible PDMS-candle carbon black particle-PDMS sandwich type composite material film deposited on the substrate; then peeling the PDMS-candle carbon black particle-PDMS sandwich type composite material film from the substrate to obtain an independent flexible PDMS-candle carbon black particle-PDMS sandwich type composite material film;
(3) performing surface treatment on the target bonding end face of the structured base obtained in the step (1) by using an oxygen plasma machine; meanwhile, aiming at the independent flexible PDMS-candle carbon black particle-PDMS sandwich type composite material film obtained in the step (2), taking the surface of a first layer of PDMS layer obtained correspondingly after the first layer of PDMS prepolymer is cured as the target bonding surface of the sandwich type composite material film, and treating the target bonding surface of the sandwich type composite material film by utilizing the surface of an oxygen plasma machine; then, aligning the structured base with the sandwich type composite material film, and attaching the target bonding end face of the structured base with the target bonding surface of the sandwich type composite material film to realize bonding, so that one end of the structured base is sealed; and then, inserting a double-clad optical fiber from the open end of the structured base, so that the sealed port of the structured base is mainly matched with the laser emergent end surface of the double-clad optical fiber to further form a sealed space, and the sealed space is an F-P cavity, so that the receiving and transmitting integrated all-optical ultrasonic transducer device can be obtained.
In a further preferred embodiment of the present invention, in the step (2), the cured thickness of the first layer of PDMS prepolymer is 10 to 30 μm, and the cured thickness of the second layer of PDMS prepolymer is 20 to 50 μm;
preferably, before the first layer of PDMS prepolymer is coated on the substrate in a spin coating manner, the substrate is subjected to surface silanization treatment in advance; more preferably, the surface silanization treatment is performed in a vacuum environment.
Generally, by the above technical solution conceived by the present invention, the following beneficial effects can be obtained:
(1) the transmitting-receiving integrated all-optical ultrasonic transducer device provided by the invention utilizes the photoacoustic effect and the F-P cavity principle to realize the function integration of ultrasonic signal transmitting and receiving, and on one hand, the photoacoustic conversion layer in the suspension membrane absorbs exciting light to radiate ultrasonic waves outwards to show ultrasonic wave transmitting; on the other hand, the reflected ultrasonic waves enable the suspension film to generate mechanical vibration, so that the cavity length of the F-P cavity is changed, the change of the detection optical signals is caused, and the ultrasonic wave receiving is realized; compared with a non-transmitting and receiving integrated photoacoustic detector, the device has the advantages of more compact packaging structure, simpler signal processing and more benefit to acoustic wave imaging. The suspension film is used for absorbing energy of the excitation laser beam and finally converting the energy into ultrasonic waves to be emitted outwards in the sound wave emission stage, and the suspension film serves as a sensitive structure responding to sound echo in the sound wave receiving stage; the cladding of the double-clad optical fiber is used for transmitting the excitation light, and the fiber core is used for bidirectional transmission of the detection optical signal.
(2) The preparation method provided by the invention has the advantages of mature basic process, simple process, process feasibility, compact structure and easiness in packaging.
(3) The preparation method provided by the invention can be used for preparing various laser ultrasonic transducers with different sizes and even micro laser ultrasonic transducers. The structured base is used for determining the size of the receiving and transmitting integrated all-optical ultrasonic transducer, taking the hollow cylindrical structured base as an example, the outer diameter of the hollow cylinder corresponds to the size of the whole outer diameter of the device, and the size can be flexibly adjusted. In the transmitting-receiving integrated all-optical ultrasonic transducer device, the suspension film is taken as a composite material film consisting of a carbon-based micro-nano structure and Polydimethylsiloxane (PDMS), the thickness of each PDMS layer in the suspension film determines the waveform of ultrasonic waves, and the evaporation time greatly influences the frequency and the intensity of photoacoustic signals by taking CSPs evaporation by candle flame as an example, so that the frequency and the intensity of the photoacoustic signals can be flexibly adjusted according to actual requirements.
The transmitting-receiving integrated photoacoustic ultrasonic transducer device realizes the transmitting and receiving of ultrasonic signals by using an all-optical method, has a compact structure, is easy to package, has strong anti-electromagnetic interference capability, is simpler in signal processing, is more beneficial to ultrasonic imaging, and has extremely high operability in the manufacturing process.
Drawings
Fig. 1 is a schematic view of a transceiver-integrated all-optical ultrasonic transducer device according to the present invention.
Fig. 2 is a schematic view of the working principle of the transceiver-integrated all-optical ultrasonic transducer in the present invention.
FIG. 3 is a schematic view of a device manufacturing process provided in example 1 of the present invention.
The meanings of the reference symbols in the figures are as follows: 1 is double-clad fiber, 2 is structured base, 3 is suspended film, and 4 is F-P cavity.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
In general, the transceiver-integrated all-optical ultrasound transducer apparatus of the present invention includes: structured base, suspended film, double-clad optical fiber, wherein: one end of the structured base is used for inserting a double-clad optical fiber (the cladding region of the double-clad optical fiber is used for transmitting excitation light with large energy density, and the single-mode characteristic of a fiber core is used for transmitting detection light.) and the other end of the structured base is used for fixing a suspension film and constructing a Fabry-Perot cavity (F-P cavity) interference structure between the end face of the optical fiber and the suspension film.
The end of the structured base fixed with the suspended membrane is well sealed, and the cavity structure of the structured base is matched with the double-clad optical fiber or the corresponding ceramic ferrule. The structural cavity of the structural base can be designed in advance, wherein the size of the cross section is determined by the size of the double-clad optical fiber and the size of a corresponding fixing device (such as a ceramic ferrule); a depth dimension that depends on the fiber insertion depth and the cavity length of the F-P cavity; the stiffness, young's modulus, poisson's ratio, etc. of the suspended membrane will affect the properties of the transducer. The suspension membrane is used for absorbing energy of an excitation laser beam in an acoustic wave transmitting stage and converting the energy into ultrasonic waves through a photoacoustic effect to be transmitted outwards, and in an acoustic wave receiving stage, an acoustic echo signal is applied to the suspension membrane to cause the suspension membrane to generate mechanical deformation, so that the measurement is carried out through an interference structure.
Example 1
Fig. 1 shows a schematic diagram of a transceiver-integrated all-optical transducer device according to embodiment 1.
As shown in fig. 1, the transceiver-integrated all-optical ultrasonic transducer device includes: the double-clad optical fiber comprises a double-clad optical fiber 1, a structured base 2 and a suspension film 3; the inner wall of the structured base 2 has the same shape as the side of the cylinder and can be fitted with the outer wall of a fiber ferrule (not shown in fig. 1), such as a ceramic ferrule or a metal ferrule, that holds the double-clad fiber 1. Wherein, the cladding of the double-clad optical fiber 1 is used for transmitting the excitation light, and the fiber core is used for transmitting the detection light; the structural base 2 is used for fixing the double-clad optical fiber and the suspension film, and defines the cavity length of the F-P cavity together with the exit end face of the double-clad optical fiber (the exit end face of the double-clad optical fiber is vertical to the optical axis, and the distance between the plane of the exit end face of the double-clad optical fiber and the end face of the structural base 2 is the cavity length of the F-P cavity); the suspension film 3 is matched with the double-clad optical fiber 1 to form an F-P cavity 4 (a pore space between the exit end face of the double-clad optical fiber and the suspension film 3 at the tail end of the structured base 2 corresponds to the F-P cavity, and a transmission medium of the F-P cavity is air); the suspension membrane 3 is used for absorbing excitation light energy and converting the excitation light energy into sound energy; the suspended membrane 3 is used for receiving ultrasonic waves and returning a detection signal through the action of an F-P cavity.
Specifically, in combination with the schematic diagram of the working principle shown in fig. 2, the transceiver-integrated all-optical ultrasonic transducer is an ultrasonic transducer device based on the transceiver-integration of a suspended membrane and a double-clad optical fiber. Different from the situation that the ultrasonic transmitting and receiving functions are divided in the traditional design, the ultrasonic transducer is integrated with the transmitting and receiving functions: on one hand, the photoacoustic conversion layer in the suspended membrane absorbs the excitation light to radiate ultrasonic waves outwards, and the ultrasonic waves are emitted; on the other hand, the reflected ultrasonic waves cause the suspension film to generate mechanical vibration, so that the cavity length of the F-P cavity is changed, the change of the detection optical signal is caused, and the ultrasonic wave reception is shown.
In this embodiment, the structured base 2 is obtained by curing a Polydimethylsiloxane (PDMS) prepolymer; the suspension film 3 is a sandwich structure of PDMS-candle carbon black particles (CSPs) -PDMS, the sandwich structure can also be compounded with a quartz glass sheet, at the moment, the CSPs are completely wrapped in PDMS colloid, and compared with the carbon nano tube, the adoption of the CSPs can obviously reduce the process complexity and the cost. Of course, if the cost and the complexity of the preparation process are not considered, the mixture of the carbon nanotubes and the PDMS colloid can be used as the suspension film 3, and at this time, the carbon nanotubes and the PDMS in the obtained suspension film 3 tend to be uniformly mixed without any obvious sandwich structure due to the limitation of the process.
It should be noted that one end of the structural cavity is well sealed (i.e. the semi-open inner cavity consisting of only the structured base 2 and the suspension film 3 without the double-clad fiber 1 inserted), which is achieved by the irreversible bonding process between the PDMS colloid (corresponding to the structured base 2) and the quartz glass.
Taking the structured base 2 as a hollow cylinder as an example (the end surfaces of the cylinder are both circular rings), fig. 3 shows a schematic flow chart of a manufacturing process of the transceiver-integrated all-optical ultrasonic transducer, and as shown in fig. 3, the manufacturing method includes the following steps:
s10, preparing a structured base:
and S101, designing and preparing a mould with the required structural cavity size.
Specifically, the acoustic emission and acoustic reception effects required to be achieved by the transceiver-integrated ultrasonic transducer can be initially obtained through simulation or experimental measurement, the size of the structural cavity can be designed in advance on the premise of considering the overall size of the device, and then the mold is processed according to the required size of the structural cavity. The smoother the surface of the mold used to contact the annular end face of the structured base 2 to be bonded is, the better, so that the open cavity surface of the structured base 2 (i.e., the annular end face of the structured base 2 to be bonded) can meet the bonding requirements of PDMS after demolding.
S102, mixing the PDMS precursor and the curing agent, and standing to remove bubbles.
Specifically, the PDMS precursor and the curing agent are uniformly mixed according to a certain proportion to obtain a liquid PDMS prepolymer, and then the liquid PDMS prepolymer is kept stand to remove bubbles. Preferably, the pre-matrix and the curing agent are fully mixed according to the volume ratio of 10:1, and then the mixture is placed into a vacuum air extractor to be kept still for removing bubbles. It is to be noted that the young's modulus of the prepared suspension layer 3 is influenced by the ratio of the pre-matrix to the curing agent, and the larger the ratio, the smaller the young's modulus, and at this time, the softer the composite photoacoustic conversion layer.
S103, pouring the liquid PDMS prepolymer after standing into the mould for curing.
Specifically, the liquid PDMS prepolymer after standing is poured into the mold for curing treatment. Preferably, the curing process temperature is 65-85 ℃ and the curing time is 2 hours.
And S104, demolding to obtain the structured base.
Specifically, the fully cured structured base is removed from the mold. In the demolding process, the cleanliness of the cavity surface of the structured base 2 needs to be maintained so that the subsequent bonding process can be performed in sequence; after demolding, the base 2 can be inverted in a closed device box and kept clean.
S20, preparing a flexible film (PDMS-CSPs-PDMS film):
s201, spin coating a first layer of PDMS prepolymer on a substrate.
Specifically, the substrate needs to be placed in a vacuum environment for surface silanization treatment before the first layer of PDMS is coated in a spinning mode, so that the subsequent stripping process becomes easy; the thickness of the first layer of PDMS is 10-30 μm in this embodiment (of course, the thickness can be flexibly adjusted according to actual requirements, for example, it can be considered comprehensively to avoid that the thermal energy generated by laser is diffused into the surrounding medium due to too thin layer, or that the absorption and attenuation of the ultrasonic energy is negatively affected due to too thick layer).
S202, inverting the spin-coated substrate above the candle flame, and performing CSPs evaporation.
Specifically, the substrate coated with the first layer of PDMS is directly inverted above candle flame without curing treatment, and CSPs evaporation is carried out; preferably, the evaporation process needs to control the substrate to be kept horizontal, and the evaporation time of each evaporation area of the substrate is uniformly controlled, so that the CSPs layer is uniformly distributed. The thickness of the CSPs layer can be controlled by the total evaporation time, different laser absorption intensities are determined by the thicknesses of the different CSPs layers, and meanwhile, the thicker CSPs layer can ensure that the flexible composite photoacoustic conversion layer has small fluctuation on the laser absorption intensity when deforming, so that the thickness of the CSPs layer can be flexibly adjusted according to actual needs.
S203, spin coating a second layer of PDMS prepolymer on the CSPs layer.
Specifically, after the CSPs evaporation coating is completed and the substrate is cooled, a second layer of PDMS prepolymer is directly spin-coated on the CSPs layer. Preferably, the flatness and cleanliness of the bonding region need to be guaranteed by the second layer of PDMS, and the flatter and cleaner the better, the implementation of the bonding process is guaranteed, and the reliability of the device is improved.
S204, curing to obtain a flexible film, and stripping the substrate and the flexible film.
Specifically, the substrate on which the step S203 is completed is subjected to a curing process. Preferably, the curing process parameters are consistent with those in step S103; after curing, the flexible film is peeled from the substrate and the flexible film is placed in the sealed device case.
Generally, the thickness of the cured first layer of PDMS may be 10-30 μm, the thickness of the cured second layer of PDMS may be 20-50 μm, and the thickness of each layer of PDMS will determine the waveform of the ultrasonic wave; the thickness of the quartz glass layer may be 50-200 μm.
S30, bonding the structured base and the quartz glass sheet:
specifically, the PDMS surface (i.e. the open cavity surface) of the structured base and the surface of the thin quartz plate are subjected to oxygen plasma surface treatment to form irreversible tight bonding; the PDMS surface of the structured base to be bonded and the surface of the thin quartz plate can be naturally aligned and attached after being processed for 1min in an oxygen plasma machine. Preferably, the PDMS surface to be bonded can be cleaned with ethanol, dried with nitrogen and then treated in an oxygen plasma machine.
The surface of the oxygen plasma machine is used for treating the open cavity surface of the structured base and the surface of the quartz glass sheet; naturally aligning the two surfaces subjected to the attaching treatment to obtain a first united body;
of course, the thickness of the thin quartz glass plate needs to be chosen flexibly according to the requirements in consideration of the influence of the thin quartz glass plate on the ultrasonic transmitting and receiving performance, and the thickness of the quartz glass plate in the embodiment is 180 μm (of course, other thickness values in 50-200 μm can be used).
S40, attaching the flexible film to enable the incident laser to pass through the first layer of PDMS in the flexible film and then be absorbed by the CSPs therein:
spreading the flexible film by using the surface tension of water, and supporting the flexible film by using the first combination obtained in the above S30 to make the flexible film spread on the quartz glass sheet; drying to obtain the second combined body.
S50, inserting a double-clad optical fiber, and assembling to obtain the receiving and transmitting integrated all-optical ultrasonic transducer device:
the protective sleeve layer of the double-clad optical fiber is stripped (the original double-clad optical fiber sequentially comprises the protective sleeve layer, the inner cladding layer and the fiber core from outside to inside), the processed end face is inserted into the optical fiber sleeve, then the optical fiber sleeve is inserted into the cavity of the second coupling body, the end face of the optical fiber keeps a certain distance with the quartz slice, and the distance is the cavity length of the F-P cavity and can be flexibly adjusted according to actual requirements; and finally, connecting the circulator and the coupler to assemble to obtain the transmitting-receiving integrated all-optical ultrasonic transducer device.
Of course, if the outer diameter of the double-clad optical fiber after the protective jacket layer is removed is matched with the inner diameter of the structured base, the jacket layer of the double-clad optical fiber can be stripped, the processed end face is inserted into the cavity of the second coupling body, and the end face of the optical fiber keeps a certain distance from the quartz slice. And finally, similarly, connecting the circulator and the coupler to assemble to obtain the transceiving integrated all-optical ultrasonic transducer device.
Example 2
This example is substantially the same as example 1 except that the sandwich-type structure of PDMS-candle carbon black particles (CSPs) -PDMS has no additional composite glass.
At this time, steps S30, S40 of the preparation method of example 1 need to be adjusted as a whole as follows, and the other steps S10, S201, S202, S203, S50 remain unchanged while step S204 does not need to be performed:
s30, bonding the structured base and the flexible film:
specifically, the second PDMS layer of the substrate in S203 is bonded to the open cavity surface of the base, so as to obtain the united body 1.
At this time, the sealing of the structural cavity is realized by an irreversible bonding process between the PDMS colloid (corresponding to the structured base 2) and the PDMS colloid (corresponding to the suspended film 3). The bonding procedure was the same as in example 1.
And S40, separating the first PDMS layer which is suspended and cured in the step S201 from the substrate to obtain a combination of the base and the flexible membrane. The combination 1 with the substrate removed is called combination 2. In order to ensure the flatness of the flexible membrane, a stress may be applied to the membrane to make it convex or concave. The substrate may be a glass plate.
Example 3
In this embodiment, substantially the same as embodiment 2, the sandwich structure of PDMS-candle carbon black particles (CSPs) -PDMS is directly bonded to the PDMS surface (i.e., the open cavity surface) of the structured base, and only the quartz glass is additionally disposed outside the sandwich structure, so that the structural cavity of the device can obtain higher rigidity to meet the application occasions requiring other requirements for mechanical strength.
At this time, the preparation method is compared with example 2, steps S10, S20, S30, S50 all remain unchanged:
the substrate mentioned in S20 needs to be preferably a thin quartz glass sheet, such as a quartz glass layer with a thickness of 50-200um (the specific material, thickness, characteristics can be changed according to the application).
S40 need not be performed, and complex 1 obtained in S30 is equivalent to complex 2 in S50.
In addition to the above embodiments, the specific material used for forming the carbon-based micro-nano structure of the suspended membrane may be selected by referring to related prior art, such as carbon nanotube, carbon black particles, carbon fiber, graphene, football alkene, and the like, and in addition, the carbon-based micro-nano structure may be replaced by black ink (for example, black nail polish), and in a specific application, the carbon-based micro-nano structure may also be replaced by a metal film, a metal array, a metal micro-nano structure, or metal nanoparticles. The above embodiment only takes quartz glass as an example, and of course, other hard materials (i.e., other hard transparent materials) with good light permeability may be used instead of quartz glass to participate in the construction of the transceiver-integrated all-optical ultrasonic transducer device.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (10)
1. A transmit-receive integrated all-optical ultrasonic transducer device is characterized by comprising a structured base (2) with a cavity structure, a suspension film (3) positioned at one end of the structured base (2), and a double-clad optical fiber (1) inserted into the cavity structure of the structured base (2); the suspension film (3) is directly and tightly connected with one end of the structural base (2) or tightly connected with one end of the structural base through a hard transparent material, so that the end port of the structural base (2) is sealed, and meanwhile, the cavity structure of the structural base (2) is kept in a closed state at the same time; the double-clad optical fiber (1) is used for simultaneously transmitting two lasers of excitation light and detection light, wherein the cladding of the double-clad optical fiber (1) is used for transmitting the excitation light, and the fiber core of the double-clad optical fiber (1) is used for transmitting the detection light and simultaneously reversely transmitting a returned detection light signal; the laser emitting end face of the double-clad fiber (1) is positioned in the structured base (2), a gap is formed between the laser emitting end face and the sealing surface of the sealing port of the structured base (2), and the sealing port of the structured base (2) is also used for being mainly matched with the laser emitting end face of the double-clad fiber (1) to further form a sealing space, so that the sealing space is correspondingly formed into an F-P cavity (4);
the suspension film (3) is a composite photoacoustic conversion film, can absorb the energy of the laser beam of the excitation light, convert the laser beam into ultrasonic waves and emit the ultrasonic waves outwards, and achieves the function of transmitting sound waves of the receiving and transmitting integrated all-optical ultrasonic transducer device; meanwhile, ultrasonic echoes can be received, the strength of the returned signal can be sensed through different mechanical deformation degrees of the ultrasonic echoes, the cavity length of the F-P cavity (4) can be influenced through different deformation degrees, the returned detection light signal is further influenced, and the function of receiving the sound waves by the transmitting-receiving integrated all-optical ultrasonic transducer device can be realized through detecting the returned detection light signal.
2. The transceiver-integrated all-optical ultrasonic transducer device according to claim 1, wherein the double-clad optical fiber (1) has an outer diameter satisfying:
i. the outer diameter of the double-clad optical fiber (1) is matched with the inner diameter of the cavity structure of the structured base (2), and a sealing port of the structured base (2) can be directly matched with the laser emergent end face of the double-clad optical fiber (1) to further form a sealing space;
or: the laser emitting end face of the double-clad optical fiber (1) is positioned in a fiber sleeve, the outer diameter of the fiber sleeve is matched with the inner diameter of the cavity structure of the structural base (2), and the sealing port of the structural base (2) is matched with the laser emitting end face of the double-clad optical fiber (1) through the fiber sleeve to further form a sealing space.
3. The transceiver-integrated all-optical ultrasound transducer device according to claim 1, wherein the structured base (2) is at least one of metal, plastic, plexiglass, and polymer;
preferably, the structured base (2) is Polydimethylsiloxane (PDMS); the hard transparent material is quartz glass.
4. The transmit-receive integrated all-optical ultrasonic transducer device according to claim 1, wherein the suspension film (3) is a composite material film composed of a carbon-based micro-nano structure and Polydimethylsiloxane (PDMS), or a composite material film composed of black ink and Polydimethylsiloxane (PDMS), or a composite material film composed of a metal material and Polydimethylsiloxane (PDMS), wherein the metal material is a metal film, a metal array, a metal micro-nano structure or metal nanoparticles; preferably, the carbon-based micro-nano structure is a carbon nano tube, carbon black particles, carbon fibers, graphene or football alkene;
more preferably, the suspension membrane (3) is a PDMS-candle carbon black particle-PDMS sandwich type composite film formed by sequentially arranging a first polydimethylsiloxane layer, a candle carbon black particle layer and a second polydimethylsiloxane layer.
5. The transmit-receive integrated all-optical ultrasonic transducer device according to claim 1, wherein a metal film is further plated on an inner wall of the F-P cavity (4) opposite to the laser exit end face for the F-P cavity (4) to increase the contrast of the F-P cavity.
6. The transceiver-integrated all-optical ultrasonic transducer device according to claim 1, wherein a circulator and a coupler are further provided at the front end of the double-clad optical fiber (1).
7. The preparation method for preparing the transceiver-integrated all-optical ultrasonic transducer device according to any one of claims 1 to 6, comprising the steps of:
(1) mixing a PDMS front matrix and a curing agent, standing to remove bubbles, pouring the liquid PDMS prepolymer after standing into a mold with a preset shape, and demolding after curing to obtain the structured base;
(2) spin-coating a first layer of PDMS prepolymer on a substrate, then inverting the spin-coated substrate above candle flame, and carrying out evaporation coating on candle carbon black particles to form a candle carbon black particle layer; then, continuously spin-coating a second layer of PDMS prepolymer on the candle carbon black particle layer, and integrally curing to obtain a flexible PDMS-candle carbon black particle-PDMS sandwich type composite material film deposited on the substrate; then peeling the PDMS-candle carbon black particle-PDMS sandwich type composite material film from the substrate to obtain an independent flexible PDMS-candle carbon black particle-PDMS sandwich type composite material film;
(3) for the structured base obtained in the step (1), treating the target bonding end face of the structured base by using an oxygen plasma machine, treating the surface of a quartz glass sheet to be bonded by using the oxygen plasma machine, aligning the structured base with the quartz glass sheet, attaching the target bonding end face of the structured base and the surface of the quartz glass sheet to be bonded to realize bonding, and sealing one end of the structured base; and (3) then, attaching the independent flexible PDMS-candle carbon black particle-PDMS sandwich type composite material film obtained in the step (2) to the quartz glass sheet from the outside to enable a first PDMS layer obtained by solidifying the first PDMS prepolymer to be in direct contact with the quartz glass sheet, and simultaneously inserting a double-clad optical fiber from the open end of the structured base to enable the sealed port of the structured base to be mainly matched with the laser emergent end face of the double-clad optical fiber to further form a sealed space, wherein the sealed space is an F-P cavity, and the transceiving integrated all-optical ultrasonic transducer device can be obtained.
8. The method according to claim 7, wherein in the step (3), the separate flexible PDMS-candle carbon black particle-PDMS sandwich type composite film is externally attached to the quartz glass plate by: and placing the independent flexible PDMS-candle carbon black particle-PDMS sandwich type composite material film on the water surface of pure water, fully unfolding the sandwich type composite material film by using the surface tension of water, then lifting the sandwich type composite material film from the water by using a bonded quartz glass-structured base, and finally drying.
9. The preparation method for preparing the transceiver-integrated all-optical ultrasonic transducer device according to any one of claims 1 to 6, comprising the steps of:
(1) mixing a PDMS front matrix and a curing agent, standing to remove bubbles, pouring the liquid PDMS prepolymer after standing into a mold with a preset shape, and demolding after curing to obtain the structured base;
(2) spin-coating a first layer of PDMS prepolymer on a substrate, then inverting the spin-coated substrate above candle flame, and carrying out evaporation coating on candle carbon black particles to form a candle carbon black particle layer; then, continuously spin-coating a second layer of PDMS prepolymer on the candle carbon black particle layer, and integrally curing to obtain a flexible PDMS-candle carbon black particle-PDMS sandwich type composite material film deposited on the substrate; then peeling the PDMS-candle carbon black particle-PDMS sandwich type composite material film from the substrate to obtain an independent flexible PDMS-candle carbon black particle-PDMS sandwich type composite material film;
(3) performing surface treatment on the target bonding end face of the structured base obtained in the step (1) by using an oxygen plasma machine; meanwhile, aiming at the independent flexible PDMS-candle carbon black particle-PDMS sandwich type composite material film obtained in the step (2), taking the surface of a first layer of PDMS layer obtained correspondingly after the first layer of PDMS prepolymer is cured as the target bonding surface of the sandwich type composite material film, and treating the target bonding surface of the sandwich type composite material film by utilizing the surface of an oxygen plasma machine; then, aligning the structured base with the sandwich type composite material film, and attaching the target bonding end face of the structured base with the target bonding surface of the sandwich type composite material film to realize bonding, so that one end of the structured base is sealed; and then, inserting a double-clad optical fiber from the open end of the structured base, so that the sealed port of the structured base is mainly matched with the laser emergent end surface of the double-clad optical fiber to further form a sealed space, and the sealed space is an F-P cavity, so that the receiving and transmitting integrated all-optical ultrasonic transducer device can be obtained.
10. The method according to any one of claims 7 to 9, wherein in the step (2), the cured thickness of the first layer of PDMS prepolymer is 10 to 30 μm, and the cured thickness of the second layer of PDMS prepolymer is 20 to 50 μm;
preferably, before the first layer of PDMS prepolymer is coated on the substrate in a spin coating manner, the substrate is subjected to surface silanization treatment in advance; more preferably, the surface silanization treatment is performed in a vacuum environment.
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