TWI432728B - A radio frequency (rf) biosensor - Google Patents

Description

RF biomedical sensor

The present invention relates to a biomedical sensor, and more particularly to a radio frequency biomedical sensor based on a microwave filter.

With the current research and development, biomedical test wafers can be roughly divided into capillary electrophoresis wafers and affinity-bonded wafers. Both wafers provide fast and accurate sequencing of deoxyribonucleic acid (DNA), testing of various human diseases, screening and development of new drugs, quantitative release control of drugs, and food and environmental testing. , a large and automated operating platform. For example, DNA detection wafers have been widely used in genetic testing. Therefore, the biomedical test wafer can accomplish the goal that cannot be achieved by traditional biomedical testing. For example, current cancer detection methods often need to wait until the patient has a considerable degree of symptoms, even when the disease is ill, can be detected; however, the technology of using biomedical wafers can help doctors detect early cancers in just a few minutes. The patient's cancer genetic factors can be further understood for early prevention. Technically, wafers produced by Bio-micro electro mechanical systems (BioMEMS) process technology have been well developed. However, BioMEMS has the disadvantages of high process difficulty, high cost and short life span.

Take cancer cells as an example. When cancer cells in the body develop to 107 cells (about 0.2cm) Tumors of large and small size, cancer cells can be metastasized by inducing angiogenesis. When the cancer cells develop to a tumor size of about 1 cm, they can be observed by the instrument (general health check), but at this time, the development of cancer cells cannot be completely controlled. At present, it is possible to discover the development of cancer cells at an early stage through imaging medical and biochemical tests.

In image detection, general medical examination items include X-ray photography, ultrasound or computerized tomography, and it is difficult to find tumors below 0.8 cm. Although tumors can be found by these images, the tumors found at this time are greater than 0.9- At 1.0 cm, it is possible that metastasis has begun to occur and therefore cannot be effectively controlled or treated. In biochemical tests, the use of specific binding between molecules is often used. For example, patients with AIDS (Acquired immune deficiency syndrome) often detect the number of "helper T cells (TH)" and "toxic T cells (Tc)" in the body. The cells specifically express CD4 and CD8 protein molecules, so they can accurately capture these cells by using a monoclonal antibody with high affinity to CD4 or CD8. The fluorescent molecules are labeled, and after being measured, the number of helper T cells or poisonous T cells can be determined according to the intensity of the fluorescent signal. Some cancers must be developed to a certain size, and their tumor marker substances can be detected. Even some cancers do not secrete tumor marker substances. Therefore, tumor markers may not be able to sensitively screen out the presence of cancer cells, and it is impossible to confirm which kind of cancer occurs. Therefore, the sensitivity and specificity of this method need to be strengthened.

Another biochemical test method, "DR-70", is different from general tumor markers. The principle is to detect the substances produced by human cells in response to the presence of cancer cells. When cancer cells start to enter the interstitial cells by carcinoma in situ, connective tissues of the human body. Fibrinogen Degradation Product (FDP, fibrinogen cleavage product) will be produced. If the cleavage product exceeds the normal value, it indicates that the body has progressed from the carcinoma in situ to the stage of invasive cancer. DR-70 can detect less than 106 cells in cancer cells, which is the current sensitive biochemical test, but this analysis will be affected by capsular plasmin infection, pneumonia, general acute infection, autoimmune disease, external trauma (truma< 30days), hemolysis during blood draw, pregnancy and other physiological conditions interfere. Therefore, it is important to develop non-invasive, high sensitivity, high specialty, real-time and inexpensive inspection tools.

In addition, after studying the doctoral thesis and patents of universities in China, the research on the biomedical sensing chips of universities such as National Taiwan University, Chengdu University, Qingda University, Jiaotong University, Yangming and Central University has achieved good results. Whether it is in microfluidic biomedical wafers, electrophoresis wafers with a small sample separation function, micro-electrospray nozzle wafers for protein sample detection, cell counting wafers and DNA replication wafers, there are quite a lot of research results. However, the biomedical sensing wafers developed by domestic academic institutions have not used microwave filters as the basic structure, and the biological characteristics of cancer cells are detected by high-frequency electromagnetic waves (>10 GHz). Therefore, the research of RF biosensing chips based on new microwave filters is quite innovative and forward-looking.

In order to solve the above problems, it is desirable to provide a biomedical sensor that provides non-invasive, high sensitivity, high specificity and instantness to overcome the disadvantages of the prior art.

The main object of the present invention is to provide a radio frequency biomedical sensor that non-invasively detects the presence of cancer cells in an animal, the correlation between high frequency biological reactions and cancer cell metastasis.

To achieve the above primary object, the present invention provides an RF biomedical sensor comprising an insulating substrate, a ground plane, a filter circuit, at least one cell detecting region, and a protective layer. The ground plane is deposited on the back side of the insulating substrate in a semiconductor process. The filter circuit is deposited on the insulating substrate in a semiconductor process and has first and second signal input and output ports. The cell detection region is disposed in the filter circuit and has an equivalent capacitance effect. The protective layer is overlaid on the filter circuit and defines an opening in the cell detection region, the first signal input port and the second signal output port.

A radio frequency biomedical sensor according to the present invention, wherein the filter circuit is a Conductor-backed Coplanar Waveguide (CBCPW) line structure.

An RF biomedical sensor according to the present invention, wherein the filter circuit operates at a frequency of 10 GHz.

According to the radio frequency biomedical sensor of the present invention, the cell detection area is one of a finger insertion electrode, a low characteristic impedance transmission line, and a ring resonator.

A radio frequency biomedical sensor according to the present invention, wherein the material of the filter circuit is one of gold (Au) and silver (Ag).

The above and other objects, features, and advantages of the present invention will become more apparent and understood.

100‧‧‧RF biomedical sensor

110‧‧‧Filter circuit

111‧‧‧First signal input and output埠

112‧‧‧Second signal output

120‧‧‧ ground plane

130‧‧‧cell detection area

140‧‧‧Protective layer

150‧‧‧Insert substrate

200‧‧‧Band-pass filter lumped element equivalent circuit

300‧‧‧Equivalent circuit of lumped element with rejection filter

Figure 1a shows the structure of the RF biomedical sensor.

Figure 1b shows a side view of the RF biomedical sensor.

Figure 2a shows the lumped element equivalent circuit of the bandpass filter.

Figure 2b shows the lumped element equivalent circuit with a rejection filter.

Figure 3a shows a preferred embodiment of the RF biomedical sensor.

Figure 3b shows the equivalent circuit of the RF biomedical sensor.

Figure 4 shows the frequency response of the RF biomedical sensor.

While the invention may be embodied in various forms, the embodiments illustrated in the drawings It is not intended to limit the invention to the particular embodiments illustrated and/or described.

The invention discloses a new type of radio frequency biomedical sensor 100 based on a dual-mode bandpass filter, and cooperates with a semiconductor process to realize a circuit for detecting liver cancer cells (Human hepatoma cells, HepG2). The number, size and high frequency bioreactivity analysis, including equivalent RLGC value, Permittivity, loss tangent (tan δ ), quality factor (Q) and characteristic impedance of liver cancer cells (Characteristic impedance) and so on as the basis for preliminary research and development. The cell detection area 130 of the RF biosensor 100 has an equivalent capacitance effect, and the design method is simple, which can effectively reduce the process cost and improve the accuracy and sensitivity during measurement.

Please refer to FIG. 1a and FIG. 1b, which shows the structure and side view of the RF biosensor 100. The RF biomedical sensor 100 includes an insulating substrate 150, a ground plane 120, a filter circuit 110, at least one cell detecting region 130, and a protective layer 140. The ground plane 120 is deposited on the back surface of the insulating substrate 150 in a semiconductor process. The filter circuit 110 is deposited on the insulating substrate 150 in a semiconductor process and has first and second signal output ports 112. The cell detection region 130 is disposed in the filter circuit 110 and has an equivalent capacitance effect. The protective layer 140 is coated on the filter circuit 110 and defines an opening above the cell detection region 130, the first signal input port 111 and the second signal input port 112. The filter circuit 110 is a back conductor coplanar waveguide line structure. The insulating substrate 150 is a glass substrate. The material of the ground plane 120 is one of gold (Au) and silver (Ag). The material of the filter circuit 110 is one of gold (Au) and silver (Ag). The cell detection region 130 is one of a finger insertion electrode, a low characteristic impedance transmission line, and a ring resonator. According to a preferred embodiment of the present invention, the filter circuit 110 and the ground plane 120 are both composed of Au (2 μ m) and Ni (20 nm), the operating frequency of the filter circuit 110 is at 10 GHz, and the protective layer 140 The material is SU8 photoresist.

Please refer to FIGS. 2a and 2b, which show the lumped element equivalent circuits 200, 300 of the band pass filter and the band reject filter. Wherein, L ₁ , L ₂ and L ₃ are inductances; C ₁ , C ₂ and C ₃ are capacitances and the input/output terminals are represented by 50 Ω impedance. In the first-order and complex-order filter circuits 110, the circuits formed by the finger-insertion electrodes, the low-inductance impedance transmission lines, and the ring resonators all have equivalent capacitances (i.e., C ₁ , C _{2 ,} and C ₃ ). Cells can be placed at their equivalent capacitance and serve as cell detection zone 130. Please refer to Fig. 3a, which shows a preferred embodiment of the RF biosensor 100. The RF biomedical sensor 100 is based on a bimodal filter. The length of the bimodal resonator is a Guided wavelength ( λ g). From the input to the output, the 90° electron length (ie, the distance of ab) has a perturbative structure (ie, cell detection region 130 with equivalent capacitance). The input/output to the perturbation point is an electron length of 135° (ie the distance between ac and bc). In the absence of a perturbation structure, when the input resonant frequency is excited, its output will not resonate. However, by adding a perturbation structure to the ring resonator, the two orthogonal modes produced will reach the coupling. The RF biomedical sensor 100 is based on a back conductor coplanar waveguide line, and is convenient for designing a resonator and a semiconductor high frequency probe for measurement, Ground-Signal-Ground (GSG) 111, 112. The advantages. The general dual mode loop filter needs to have the following conditions:

1. The input must be separated from the output by an electronic length of 90°.

2. There is a perturbation structure (as the cell detection region 130 having an equivalent capacitance) in the ring resonator, causing a discontinuity phenomenon in the traveling of the electromagnetic wave, exciting the resonance frequency and generating a pass band.

3. The overall circuit structure must be symmetric (Symmetrical) (c-d is the plane of symmetry).

Please refer to FIG. 3b, which shows the equivalent circuit of the RF biosensor 100. The Even mode and Odd mode equivalent circuits of the dual mode filter. Let Zr be the characteristic impedance of the toroidal transmission line and Zp be the characteristic impedance of the perturbation structure (lower characteristic impedance, equivalent to capacitance), and define Kz (Kz=Zp/Zr) as the ratio of the two impedances. When the ring resonator is not attached with the perturbation structure Zp, its total electron length corresponds to a half wavelength (resonance frequency fr). Let the electron length of the perturbation structure Zp be 2 θ p, from the point d to the point c (the perturbation structure Zp) is θ ₁ , from the point a (or point b) to the point c (the perturbation structure Zp) θ ₂ ( θ ₂ = θ ₁ -45°). The even mode resonant frequency f _Oe and the odd mode resonant frequency f _Od will satisfy: the even mode resonant frequency f _Oe :

Where f' _Oe = f _Oe /fr, f' _Oe is the normalized mode resonant frequency. Odd mode resonance frequency f _Od :

Where f' _Od = f _Od /fr, f' _Od is the odd-mode resonant frequency after normalization. Adjusting the electron length of the perturbation structure 2 θ p determines the formation of the pass band. The frequency response of a typical bimodal filter. The dual-mode filter has the advantages of simple design, small size, and high passband attenuation rate, and is quite suitable as an infrastructure for RF biomedical sensing wafers.

In the measurement, the instrument needs to use the G-S-G high-frequency probe station (Probe station) 111, 112 Vector network analyzer (VNA) HP 8510C, the measurement range is between 0.045 ~ 50GHz. Please refer to FIG. 4, which shows the frequency response of the RF biosensor 100. For example, the number of cells during the incubation process can be known via conventional cell counting methods. The cells are then placed in the detection area of the RF biosensing chip to observe the frequency response under high frequency measurement (including the center frequency, bandwidth, and implant loss of the passband). Loss) and return loss in the presence of loaded (unloaded) and unloaded cells (Unloaded), and then analysis of cell size, quantity and high frequency dielectric properties (eg: equivalent of liver cancer cells) Resistance (R), inductance (L), conductance (G) and capacitance (C) values, dielectric constant and loss tangent). When using a network analyzer, you need to implement error correction first, where Including Random errors, Systematic errors, and Drift errors. The random number error mainly comes from the noise of the system itself and the reliability of the components in the instrument. This part cannot be removed by correction. The systematic error mainly comes from the circuit design of the measuring instrument itself, and the error can be removed by correction. The drift error is mainly due to the different performance of the system under different conditions at different times. The main reason is the change of the ambient temperature. Such errors can be removed by repeated correction. Generally, the system error should be reduced to below -50dB after correction to reduce errors in measurement. After the wafer is detected, the wafer is immersed in a PBS (phosphate buffer saline) buffer, and shaken by an ultrasonic oscillator for 30 minutes to remove the cells remaining on the wafer. After the shock is completed, the RF biosensor 100 Can be reused.

Taking liver cancer cells as an example, when there are no cells and cells in the detection area, the frequency response of the filter passband is shifted. Depending on the amount of offset, the equivalent RLGC value, dielectric constant and loss tangent of the cells can be further calculated. From the offset, four sets of scattering parameters (S-parameters) are obtained, which are S ₁₁ , S ₁₂ , S ₂₁ and S _{22 respectively} , and substituted into equation (3), and the propagation constant γ (f) can be obtained:

among them

The complex propagation constant can be rewritten as: γ ( f ) = α _t ( f ) + jβ ( f ) (4)

Where α _t (f) is the decay constant and β (f) is the phase constant, respectively

The effective dielectric constant ε _eff (f) can be obtained by the formula (6). Characteristic impedance (Z ₀ ) is

According to the following formula, the equivalent resistance (R), inductance (L), conductance (G) and capacitance value of the cell (C) γ ( f ) × Z ₀ ( f ) = R + jωL (8)

γ ( f ) / Z ₀ ( f )= G + jωC (9)

By the following formula, the dielectric constant of the cell ε _eff = (1- q ) + qε _r (10)

Where q is the structural factor of the microstrip line. The loss tangent can be expressed as follows:

While the present invention has been described in its preferred embodiments, it is not intended to limit the scope of the invention, and various modifications and changes can be made without departing from the spirit and scope of the invention. As explained above, various modifications and variations can be made without departing from the spirit of the invention. Therefore, the scope of the invention is defined by the scope of the appended claims.

100‧‧‧RF biomedical sensor

110‧‧‧Filter circuit

111‧‧‧First signal input and output埠

112‧‧‧Second signal output

120‧‧‧ ground plane

130‧‧‧cell detection area

140‧‧‧Protective layer

150‧‧‧Insert substrate

Claims (8)

An RF biomedical sensor comprising: an insulating substrate; a ground plane deposited on a back surface of the insulating substrate by a semiconductor process, wherein the ground plane is composed of Au (2 μ m) and Ni (20 nm); a filter circuit is deposited on the insulating substrate by a semiconductor process, and has a first signal input port and a second signal input port, wherein the filter circuit is Au (2 μ m) and Ni (20 nm) Constructed; at least one cell detection region disposed in the filter circuit, the cell detection region having an equivalent capacitance effect; and a protective layer overlying the filter circuit and in the cell detection region, The first signal input port and the second signal output port define an opening. The radio frequency biomedical sensor of claim 1, wherein the filter circuit is a back conductor coplanar waveguide line structure. An RF biomedical sensor according to claim 1, wherein the filter circuit operates at a frequency of 10 GHz. An RF biomedical sensor according to claim 1, wherein the insulating substrate is a glass substrate. The radio frequency biomedical sensor of claim 1, wherein the material of the ground plane is one of gold (Au) and silver (Ag). An RF biomedical sensor according to claim 1, wherein the material of the filter circuit is one of gold (Au) and silver (Ag). An RF biomedical sensor according to claim 1, wherein the cell detection region is one of a plug-in electrode, a low-inductance impedance transmission line, and a ring resonator. The radio frequency biomedical sensor of claim 1, wherein the material of the protective layer is SU8 photoresist.