CN114428066A - A terahertz biosensor based on ELC resonators and micropores - Google Patents

Abstract

The invention discloses a terahertz biosensor based on an ELC resonator and micropores, which comprises a transmission unit and a detection unit, wherein the transmission unit comprises a first transmission unit and a second transmission unit; the transmission unit comprises a dielectric substrate and a coplanar waveguide arranged on one end face of the dielectric substrate, the coplanar waveguide is composed of a middle metal transmission line and metal grounding lines which are arranged at two sides of the metal transmission line in parallel at intervals, and the dielectric substrate and the coplanar waveguide are coaxially provided with through micropores; the detection unit comprises an ELC resonator, the ELC resonator is arranged on the other end face of the dielectric substrate opposite to the coplanar waveguide, the ELC resonator is an ELC resonance ring formed by two loops with a common capacitance gap, and the common capacitance gap is superposed with the micropore. The invention realizes the low-loss transmission of the terahertz wave, the local field enhancement and the integration of the detection of the biological molecules on the coplanar waveguide.

Description

A Terahertz Biosensor Based on ELC Resonators and Micropores

technical field

The invention belongs to the technical field of terahertz biosensing, in particular to a terahertz biosensor based on an ELC resonator and a micropore.

Background technique

Terahertz waves are electromagnetic waves with a frequency of 0.1 to 10 THz and a corresponding wavelength of 30 μm to 3 mm. As a frequency range from infrared to microwave, terahertz waves have many advantages, such as low energy, good transmission, and large bandwidth. In particular, the rotation, translation and conversion frequencies of many biological macromolecules are in the terahertz frequency band, which has a characteristic "fingerprint effect", thus promoting the development of the emerging technology of terahertz sensing and detection.

At present, most terahertz material detection and analysis are realized based on terahertz time-domain spectroscopy system. The transmission or reflection of the material is obtained by Fourier transform of the terahertz pulse signal measured in the time domain and containing the information of the sample to be tested. spectrum. Since this technique is based on the absorption properties of matter, it requires a large number of samples to obtain a distinguishable signal, and at the same time, the spectral resolution and spatial resolution are low, the detection accuracy and precision are not high, and the terahertz transmission loss in space In addition, the experimental device is bulky, has poor integration and portability, and is not practical in many practical applications. How to enhance the interaction between the terahertz wave and the measured object and improve the sensing sensitivity is the key to promoting the practical application of terahertz sensors.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a terahertz biosensor based on ELC resonators and micropores, which can realize low-loss transmission of terahertz waves, local field enhancement and integration of biomolecular detection on coplanar waveguides.

In order to achieve the above object, the solution of the present invention is: a terahertz biosensor based on an ELC resonator and a micropore, comprising a transmission unit and a detection unit;

The transmission unit includes a dielectric substrate and a coplanar waveguide arranged on one end surface of the dielectric substrate. The coplanar waveguide is composed of a metal transmission line in the middle and metal grounding lines arranged in parallel and spaced on both sides of the metal transmission line. The waveguide is coaxial with a through-hole micro-hole;

The detection unit includes an ELC resonator, the ELC resonator is arranged on the other end face of the dielectric substrate opposite to the coplanar waveguide, and the ELC resonator is an ELC resonant ring composed of two loops with a common capacitance gap. The gaps coincide with the micropores.

Further, the ELC resonator is a closed annular frame strip, and the inner side of the annular frame strip is connected with two opposite metal arms, a common capacitance gap is formed between the two metal arms, and the ends of the two metal arms are in the shape of "T". type.

Further, the side length of the annular frame strip is 73um, the width of the metal arm and the annular frame strip is 8um, and the thickness is 1.5um.

Further, the length of the dielectric substrate is 600um, the width is 400um, and the thickness is 10um.

Further, the width of the common capacitance gap is 8um, and the diameter of the micro-hole is 8um.

Further, the material of the dielectric substrate is Arlon Diclad 880.

Further, both ends of the dielectric substrate are provided with input ports and output ports connected to the coplanar waveguide.

Further, the impedances of the input port and the output port are both 50 ohms.

Further, the total length of the coplanar waveguide is 600um, the thickness is 1.5um, the width of the metal transmission line is 34um, the width of the metal grounding line is 181um, and the distance between the metal transmission line and the metal grounding line is 2um.

After adopting the above scheme, the gain effect of the present invention is:

The invention combines the coplanar waveguide loaded with the ELC resonator and the micro-hole, and realizes the low loss and high efficiency transmission of the terahertz signal in the form of a plane wave on the coplanar waveguide by designing and optimizing the coplanar waveguide structure, and resonates in the ELC. The local electric field enhancement effect is generated in the common capacitance gap of the device structure and the micro-hole, and the sensitivity of the detection area is improved. The principle of the sensor is based on the frequency shift of the resonant peak in the transmission spectrum. When biomolecules with different refractive indices pass through the pores, the resonant frequency changes, which shows high sensitivity and provides a theoretical basis and transmission for the high-sensitivity detection of low-concentration biomolecules. sense means. The terahertz biosensor based on ELC resonators and micropores has the characteristics of high detection sensitivity and micro-quantification of samples, and at the same time, the sensor has the advantages of high integration and miniaturization, and has high application prospects in the field of terahertz sensing. .

Description of drawings

Fig. 1 is the three-dimensional structure schematic diagram of the present invention;

2 is a schematic structural diagram of a coplanar waveguide according to the present invention;

Fig. 3 is the ELC resonator structure diagram of the present invention;

Figure 4 is a schematic diagram of the flow of biomolecules of the present invention;

Fig. 5 is the electric field distribution diagram of the present invention;

Fig. 6 is the transmission spectrogram of the present invention;

Numeral description: 1, dielectric substrate; 11, micro hole; 2, coplanar waveguide; 21, metal transmission line; 22, metal ground wire; 3, ELC resonator; 31, ring frame strip; 32, metal arm; 33, common capacitance gap.

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

The present invention provides a terahertz biosensor based on an ELC resonator and a micropore, as shown in FIG. 1 and FIG. 2 , including a transmission unit and a detection unit;

The transmission unit includes a dielectric substrate 1 and a coplanar waveguide 2 fixed (specifically, electroplating) on the lower end surface of the dielectric substrate 1. The coplanar waveguide 2 is formed by a metal transmission line 21 in the middle and two sides of the metal transmission line 21 are parallel and spaced apart. The metal ground wire 22 is formed of the dielectric substrate 1 and the coplanar waveguide 2 coaxially with a micro-hole 11 extending therethrough;

The detection unit includes an ELC resonator 3, the dielectric substrate 1 is used as the carrier of the sensor, the ELC resonator 3 is fixed on the upper end surface of the dielectric substrate 1, and the ELC resonator 3 is two with a common capacitance gap 33. For the ELC resonant ring formed by the loop, the common capacitance gap 33 coincides with the micro-hole 11 .

As shown in FIG. 3 , the ELC resonant ring is in the form of a closed annular frame bar 31 . The inner side of the annular frame bar 31 is connected with two opposite metal arms 32 , and a common capacitance gap 33 is formed between the two metal arms 32 . The ends of 32 are all "T" shaped.

In one embodiment, the preferred following dimensional parameters of each component of the present invention are designed:

ELC resonator 3: the side length W of the annular frame bar 31 is 73um, the width d of the metal arm 32 and the annular frame bar 31 is 8um, and the thickness is 1.5um; the width g of the common capacitance gap is 8um, The distance Lg from the two sides of the metal arm 32 to the ring frame bar 31 is 16um. By adjusting and optimizing the size parameters of the ELC resonator 33, the resonance peak of the transmission parameter appears in a specific frequency band, and the local electric field is enhanced to improve the detection area. sensitivity.

Dielectric substrate 1: The material of the dielectric substrate 1 is set to Arlon Diclad 880, and its relative permittivity εr is 2.2. As shown in Figure 2, the length of the dielectric substrate 1 is 600um, the width is 400um, and the thickness is 10um.

Coplanar waveguide 2: the width of the metal transmission line 21 is 34um, the width of the metal grounding line 22 is 181um, the distance between the metal transmission line 21 and the metal grounding line 22 is 2um, the total length of the coplanar waveguide 2 is 600um, and the thickness is 1.5 um, the metal material is gold. A micro-hole 11 is coaxially drilled at the center of the dielectric substrate 1 , and the diameter of the micro-hole 11 and the width g of the common capacitance gap are both 8um. Both ends of the dielectric substrate 1 are provided with an input port and an output port connected to the coplanar waveguide 2, and the impedances of the input port and the output port are both 50 ohms.

The application of planar transmission lines to terahertz band devices can effectively reduce the size of the terahertz system and increase its portability, which has important scientific value and practical significance. Coplanar waveguide is a high-frequency transmission line. Compared with the case where the electric and magnetic fields of the microstrip line are scattered, the energy of the coplanar waveguide is mainly concentrated in the two band gaps, with low impedance and low dispersion, so its energy loss is very high. Low. Secondly, all grounding lines of the coplanar waveguide are on the surface, which is easy to manufacture, convenient to punch holes on the dielectric substrate, easy to connect with other components, and it has a smaller size and a higher degree of integration. Structurally, this ELC resonator is simple and highly symmetrical. In nature, the ELC resonator is easier to achieve miniaturization and has good resonance characteristics compared with other shaped resonators, which is beneficial to improve the performance of the sensor. The specially designed ELC resonator has a better local electric field enhancement effect, the energy concentration is balanced, and the resonance peak of the transmission parameter can appear in the required terahertz frequency band.

The electromagnetic simulation software CST MICROWAVE STUDIO 2018 was used to simulate the terahertz electric field distribution and transmission characteristics of the biosensor structure of the present invention. As shown in FIG. 5 , local electric field enhancement is generated near the common capacitance gap 33 of the ELC resonator 3 and the micro-hole 11 , so that the sensitivity of the sensing area is increased. As shown in Fig. 4, solution pools are set at the upper and lower ends of the micropore 11, and a bias voltage is applied between the two solution pools. When the voltage source is turned on, the biomolecules in the two solution pools flow in the micropore 11. The internal resistance of the micropore 11 is increased, and the instantaneous voltage change is caused to form a pulse signal, so as to realize the detection and characterization of biomolecules. The maximum achievable electric field strength is affected by the shape of the structure, especially by the size of the common capacitance gap. Figure 6 shows the effect of changes in the refractive index of the sample on the resonant characteristics of the sensor. The transmission spectrum of particles with different refractive index sizes in microhole 11 is simulated. As shown in Figure 6, when the sample particle diameter is fixed at 6um and the refractive index increases from 1 to 5 with a step size of 1, the resonance peak appears red-shifted The phenomenon is the movement to low frequencies. FIG. 5 is the electric field distribution diagram of the structure of ELC resonator 3 (after red filtering).

The working process of the present invention is as follows: first, the biosensor is placed in a sensing system based on a terahertz vector network analyzer (VNA), then, the vector network analyzer sends an electromagnetic wave signal, and the signal is increased to a corresponding terahertz signal through a frequency doubling module. Hertz band, which enables the vector network analyzer to measure over the entire frequency range of this waveguide, the terahertz wave is transmitted on the coplanar waveguide 2 with low loss, and then, after the ELC resonator 3 is excited by the terahertz wave, the common capacitance gap 33 strongly couples the electric field to drive the entire ELC resonator 3 to achieve local electric field enhancement. When the biomolecules pass through the micropore 11, relevant information of the biomolecules is obtained, and finally the terahertz wave with the information is transmitted to the vector network analyzer through the output port to obtain the transmission characteristics of the biomolecules.

The manufacturing method of the coplanar waveguide 2 of the present invention is realized according to the following steps: selecting an Arlon Diclad 880 material (polytetrafluoroethylene, a kind of microwave circuit material with good high frequency characteristics, among solid materials, its loss and dielectric constant are the best), use absolute ethanol and acetone to clean and dry the Arlon Diclad 880 material, and then place the cleaned and dried Arlon Diclad 880 material in the magnetron. In the vacuum chamber of the sputtering equipment, the sample holder is clamped with a clamp. After the vacuum chamber of the magnetron sputtering equipment starts to discharge, the Arlon Diclad 880 material is bombarded with the discharged plasma, and then the Arlon Diclad 880 material is sputtered. A 1.5um-thick gold film was shot, and after the deposition was completed, the Arlon Diclad 880 material was bombarded with plasma. Then place the Arlon Diclad 880 material with the gold film deposited on the film spinner, spin-coat 2-4um thick positive photoresist, then place it on a baking table and bake it down to room temperature, and then place it on the photolithography machine , Take out after UV exposure with coplanar waveguide 2 mask. Next, put the exposed Arlon Diclad 880 material into a positive photoresist developer solution for development, take it out from the developer solution after the graphics are displayed, rinse it with deionized water and dry it. Put the developed Arlon Diclad 880 material into the etching solution and heat it to 60-80°C for etching, take out the Arlon Diclad 880 material with the coplanar waveguide 2 pattern etched, rinse it with deionized water and dry it. Finally, the Arlon Diclad 880 material etched out of the coplanar waveguide 2 pattern was put into acetone, the positive photoresist on the surface of Arlon Diclad 880 was removed, and then rinsed with deionized water and dried to obtain the coplanar waveguide 2. Arlon Diclad 880 is a fiberglass/PTFE braided composite with low dielectric constant and high dimensional stability.

The present invention intends to use an ArF excimer laser to manufacture the microholes 11 on the dielectric substrate 1 using laser light. This method enables the drilling of tunable apertures ranging from 100 nm to several microns. For the present invention, the preferred diameter of the laser drilled holes is about 8um.

The present invention intends to use the micro-nano processing technology to realize the manufacture of the ELC resonator 3 structure on the dielectric substrate 1 . Considering the measurement errors caused by the electrical parameters of the base material, the electrical conductivity of the metal material, the machining accuracy and the accuracy of the measuring equipment, and optimizing the sensor of the present invention in combination with the test results, it is expected to further improve the performance of the sensor.

The above descriptions are only the preferred embodiments of the present invention, and are not intended to limit the design of this case. Any equivalent changes made according to the design key of this case fall into the protection scope of this case.

Claims (9)

1. a terahertz biosensor based on ELC resonator and micropore, is characterized in that, comprises transmission unit and detection unit; The transmission unit includes a dielectric substrate and a coplanar waveguide arranged on one end surface of the dielectric substrate. The coplanar waveguide is composed of a metal transmission line in the middle and metal grounding lines arranged in parallel and spaced on both sides of the metal transmission line. The waveguide is coaxial with a through-hole micro-hole; The detection unit includes an ELC resonator, the ELC resonator is arranged on the other end face of the dielectric substrate opposite to the coplanar waveguide, and the ELC resonator is an ELC resonant ring composed of two loops with a common capacitance gap. The gaps coincide with the micropores. 2. A kind of terahertz biosensor based on ELC resonator and micropore as claimed in claim 1, it is characterized in that: described ELC resonator is a closed annular frame strip, and the inner side of the annular frame strip is connected with a relative Two metal arms, a common capacitance gap is formed between the two metal arms, and the ends of the two metal arms are in a "T" shape. 3. A kind of terahertz biosensor based on ELC resonator and micropore as claimed in claim 2, it is characterized in that: the side length of described annular frame strip is 73um, and the width of described metal arm and annular frame strip is 8um, the thickness is 1.5um. 4. A terahertz biosensor based on an ELC resonator and a micropore according to claim 1, wherein the length of the dielectric substrate is 600um, the width is 400um, and the thickness is 10um. 5 . The terahertz biosensor based on an ELC resonator and a micropore according to claim 1 , wherein the width of the common capacitance gap is 8um, and the diameter of the micropore is 8um. 6 . 6 . The terahertz biosensor based on ELC resonators and micropores according to claim 1 , wherein the material of the dielectric substrate is Arlon Diclad 880. 7 . 7 . The terahertz biosensor based on ELC resonators and micropores as claimed in claim 1 , wherein an input port and an output port connected to a coplanar waveguide are provided at both ends of the dielectric substrate. 8 . 8 . The terahertz biosensor based on an ELC resonator and a micropore according to claim 7 , wherein the impedance of the input port and the output port are both 50 ohms. 9 . 9. A kind of terahertz biosensor based on ELC resonator and micropore as claimed in claim 1, it is characterized in that: the total length of described coplanar waveguide is 600um, the thickness is 1.5um, the width of metal transmission line is 34um , the width of the metal ground line is 181um, and the distance between the metal transmission line and the metal ground line is 2um.

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