Biosensor system and method for analyzing a test sample using the biosensor system

Abstract

The biosensor system includes a biosensor array and a plurality of electrodes located near the biosensors. The controller is configured to selectively excite the plurality of electrodes to generate a DEP force to selectively position a test sample relative to the array of biosensors. Embodiments of the present invention also relate to methods for analyzing a test sample using the biosensor system.

Description

Technical Field

[0001] Embodiments of the present invention relate to biosensor systems and methods of analyzing a test sample using the biosensor systems. Background Art

[0002] Biosensors refer to devices for sensing and detecting biomolecules, and operate based on electronic, electrochemical, optical, and mechanical detection principles. Biosensors including transistors are sensors that electrically sense the charge, photons, and mechanical properties of biological entities or biomolecules. Detection can be performed by detecting the biological entity or biomolecule itself, or by the interaction and reaction between a specific reactant and the biological entity / biomolecule. Such biosensors can be manufactured using semiconductor processes, can quickly convert electrical signals, and can be easily applied to integrated circuits (ICs) and micro-electromechanical systems (MEMS). Summary of the invention

[0003] An embodiment of the present invention provides a biosensor system comprising: an array of biosensors; a plurality of electrodes located near the array of biosensors; and a controller configured to selectively excite the plurality of electrodes to generate a dielectrophoresis (DEP) force to selectively position a test sample relative to the array of biosensors.

[0004] Another embodiment of the present invention provides a biosensor system, comprising: a processing substrate; an interconnection layer located above the processing substrate; a device substrate located above the interconnection layer, the device substrate comprising a biosensor array electrically connected to the interconnection layer; an isolation layer located above the device substrate; a plurality of electrodes formed above the isolation layer and extending through the isolation layer and the device substrate to the interconnection layer, the plurality of electrodes being configured to receive an AC signal to establish a dielectric electrophoretic force to selectively position a test sample relative to the biosensor array.

[0005] Another embodiment of the present invention provides a method for analyzing a test sample using a biosensor system, comprising: providing a biosensor array; providing a three-dimensional (3D) test sample; collecting data about a first segment of the three-dimensional test sample by the biosensor array; generating a dielectrophoretic force to reposition the three-dimensional test sample relative to the biosensor array; collecting data about a second segment of the three-dimensional test sample by the biosensor array; and combining the data about the first segment and the second segment of the three-dimensional test sample. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Aspects of the present invention are best understood from the following detailed description when read in conjunction with the accompanying drawings. It should be noted that, in accordance with standard practice in the industry, the various components are not drawn to scale. In fact, the dimensions of the various components may be arbitrarily increased or reduced for clarity of discussion. In addition, the accompanying drawings are illustrative, as examples of embodiments of the invention, and are not intended to be limiting.

[0007] Figure 1 is a block diagram illustrating aspects of an example biosensor system according to some embodiments.

[0008] Figure 2 is a block diagram schematically illustrating an example of a bioFET according to some embodiments.

[0009] Figure 3 is a cross-sectional side view illustrating aspects of a backside sensing bioFET device according to some embodiments.

[0010] Figure 4 is a flow chart illustrating a method of performing 3D analysis of a test sample using a 2D biosensor device according to some embodiments.

[0011] FIG. 5A to FIG. 5C is a diagram showing a method according to some embodiments Figure 4 A block diagram of various aspects of the method shown in .

[0012] Figure 6 is a top view illustrating aspects of an example biosensor device according to some embodiments.

[0013] Figure 7 is a diagram showing a method according to some embodiments Figure 6 A top view of other aspects of an example biosensor device is shown in FIG.

[0014] Figure 8 is a diagram showing a method according to some embodiments Figure 6 and Figure 7 A cross-sectional side view of other aspects of an example biosensor device is shown in FIG.

[0015] Fig. 9 is a block diagram conceptually illustrating positive dielectrophoretic (DEP) forces acting on a test sample according to some embodiments.

[0016] Fig.10 is a block diagram conceptually illustrating negative DEP forces acting on a test sample according to some embodiments.

[0017] Fig.11 is a block diagram illustrating an example of electrode activation to generate DEP forces according to some embodiments.

[0018] Fig.12is a block diagram illustrating another example of electrode activation to generate DEP forces according to some embodiments.

[0019] Fig.13 is a block diagram illustrating another example of electrode activation to generate DEP forces according to some embodiments.

[0020] Fig.14 is a block diagram illustrating another example of electrode activation to generate DEP forces according to some embodiments.

[0021] Fig.15 is a block diagram illustrating another example of electrode activation to generate DEP forces according to some embodiments.

[0022] Figures 16 to 20 A method for forming a Figures 6 to 8 An example of the process of electrodes of a biosensor device is shown in FIG. DETAILED DESCRIPTION

[0023] The following disclosure provides many different embodiments or examples for realizing the different features of the provided subject matter. Specific examples of components and arrangements are described below to simplify the present invention. Of course, these are only examples and are not intended to be limiting. For example, in the following description, forming a first component above or on a second component may include an embodiment in which the first component and the second component are directly contacted, and may also include an embodiment in which an additional component may be formed between the first component and the second component so that the first component and the second component may not be in direct contact. In addition, the present invention may repeat reference numbers and / or letters in various examples. This repetition is for the purpose of simplicity and clarity, and does not itself indicate the relationship between the various embodiments and / or configurations discussed.

[0024] Additionally, for ease of description, spatially relative terms such as "below," "beneath," "lower," "above," "upper," etc. may be used herein to describe the relationship of one element or component to another element or component as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or during operation in addition to the orientation depicted in the figures. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein should likewise be interpreted accordingly.

[0025] Generally, as used herein, "biosensor" refers to an analytical device for detecting chemical substances, which combines a biological component and a physicochemical detector. Such biological components can include, for example, cells, cell populations, tissues, microorganisms, organelles, cell receptors, enzymes, antibodies, nucleic acids, etc. Such biologically derived materials or biomimetic components interact with, bind to, or recognize the analyte under study.

[0026] As used herein, the term "bioFET" refers to a field effect sensor with a semiconductor transducer, and more specifically, to a biosensor based on a field effect transistor (FET). In a bioFET, the gate of a metal oxide semiconductor field effect transistor (MOSFET) is replaced by a biological or biochemically compatible layer or a biofunctionalized layer of immobilized probe molecules used as surface receptors, which controls the conduction of the semiconductor between the source contact and the drain contact of the MOSFET. In essence, a bioFET is a field effect biosensor with a semiconductor transducer. The absolute advantage of a bioFET is the prospect of label-free operation. Specifically, a bioFET can avoid expensive and time-consuming labeling operations, such as labeling analytes with fluorescent or radioactive probes.

[0027] The typical detection mechanism of a bioFET is the conductance modulation of the transducer due to the binding of the target biomolecule or bioentity to the sensing surface of the bioFET or to the receptor molecules fixed on the sensing surface of the bioFET. When the target biomolecule or bioentity is bonded to the sensing surface or the fixed receptor, the drain current of the bioFET changes due to the potential of the sensing surface. This change in drain current can be measured, and the bonding of the receptor to the target biomolecule or bioentity can be identified. A wide variety of biomolecules and bioentities can be used to functionalize the sensing surface of the bioFET, such as ions, enzymes, antibodies, ligands, receptors, peptides, oligonucleotides, organ cells, organisms, and tissue fragments. For example, in order to detect ssDNA (single-stranded deoxyribonucleic acid), the sensing surface of the bioFET can be functionalized with fixed complementary ssDNA chains. Similarly, in order to detect various proteins, such as tumor markers, the sensing surface of the bioFET can be functionalized with monoclonal antibodies.

[0028] Biosensors are commonly used for two-dimensional (2D) analysis of test samples, such as cell culture. However, three-dimensional (3D) cell analysis is desired to obtain additional information about the test sample. Compared with typical 2D cell culture, 3D cell analysis can provide more relevant information. For example, an array of 2D electrodes or image sensors can be used to monitor 3D cells. However, such an arrangement only obtains partial information from the daughter cells that actually contact the surface of the 2D biosensor. Based on this incomplete information, it may be difficult to obtain an accurate behavioral profile of the entire 3D cell.

[0029] According to aspects of the present invention, a 3D cell to be analyzed is manipulated on a semiconductor biosensor platform using a technique such as dielectrophoresis (DEP) to analyze the entire 3D cell. For example, such a DEP technique can be configured to capture, lift, and rotate 3D cells for monitoring and analysis using a semiconductor biosensor platform. In general, DEP refers to a phenomenon in which a force acts on a dielectric particle when it is subjected to an inhomogeneous electric field. The force does not require that the particle be charged. In embodiments disclosed herein, manipulation of cells using DEP provides a method for implementing 3D electrical cell detection using a 2D sensor.

[0030] Figure 1 is a block diagram of an exemplary biosensor system 100 according to the present invention. Figure 1 As shown, the example biosensor system 100 may include a sensor array 102, a fluid delivery system 104, an electrode array 106, and a controller 108, among other things. The sensor array 102 may have at least one sensing element for detecting a biological or chemical analyte.

[0031] The sensor array 102 may include an array of bioFETs 110, examples of which are shown in Figure 2 Shown in. Figure 2 The bioFETs 110 shown in can be functionalized to detect specific target analytes, and different sensors can be functionalized using different capture reagents for detecting different target analytes. The bioFETs can be arranged in multiple rows and columns to form a two-dimensional array of sensors. In some embodiments, each row of bioFETs is functionalized using a different capture reagent. In some embodiments, each column of bioFETs is functionalized using a different capture reagent.

[0032] The fluid delivery system 104 can deliver one or more fluid samples to the sensor array 102. The fluid delivery system 104 can be a microfluidic well positioned above the sensor array 102 to contain fluids above the sensor array 102. The fluid delivery system 104 can also include microfluidic channels for delivering various fluids to the sensor array 102. The fluid delivery system 104 can include any number of valves, pumps, chambers, channels designed to deliver fluids to the sensor array 102. The electrode array 106 can include a plurality of electrodes configured to manipulate a sample, such as a cell, to be analyzed by the sensor array.

[0033] The controller 108 can send and receive electrical signals to the sensor array 102 and the electrode array 106 to position the sample as needed to perform biological or chemical sensing measurements. The controller 108 can also send electrical signals to the fluid delivery system 104 to, for example, actuate one or more valves, pumps, or motors. The controller 108 may include one or more processing devices, such as a microprocessor, and may be programmable to control the operation of the electrode array 106, the sensor array 102, and / or the fluid delivery system 104. Examples of various electrical signals sent and received from the sensor array 102 will be discussed in more detail below.

[0034] The example bioFET 110 may include a vertical fluid gate (VFG) 112, a source region 114, a drain region 116, a sensing film 118, and a channel region 120. The fluid delivery system 104 applies a fluid 122 over the sensing film 118. The fluid 122 may contain an analyte. The sensing film 118 may be an electrical insulating layer and a chemical insulating layer that separates the fluid 122 from the channel region 120. The sensing film 118 may include a capture reagent layer, etc. The capture reagent is specific to the analyte and is capable of binding to a target analyte or a target reagent. When the analyte is bound, a change in electrostatic potential occurs at the surface of the sensing film 118, which in turn results in an electrostatic gating effect of the bioFET 110 and a measurable change in the current (e.g., Ids current 126) between the source electrode and the drain electrode. The voltage applied to the vertical fluid gate 112 may also change Ids126. In other words, the output signal of bioFET 110 is Ids 126, which is related to the voltage applied to vertical fluidic gate 112. In one embodiment, the bioFET may be a dual-gate backside FET sensor, but other types of bioFETs are also within the scope of the present invention.

[0035] Figure 3 A backside sensing bioFET device 130 is shown in accordance with some disclosed embodiments. A back-end-of-line (BEOL) interconnect structure 136 is disposed over a handle substrate 138, and a device substrate 134 is disposed over the BEOL interconnect structure 136. A reference electrode 132 is disposed over the device substrate 134. The handle substrate 138 may be, for example, a bulk semiconductor substrate, such as a bulk substrate of single crystal silicon.

[0036] The interconnect structure 136 may include a multi-layer interconnect (MLI) structure having conductive lines, conductive vertical interconnect pathways (vias), and / or intervening dielectric layers (e.g., interlayer dielectric (ILD) layers). The interconnect structure 136 may provide various physical and electrical connections to the bioFET 110. The conductive lines may include copper, aluminum, tungsten, tantalum, titanium, nickel, cobalt, metal silicides, metal nitrides, polysilicon, combinations thereof, and / or other materials that may include one or more layers or liners. The intervening dielectric layer (e.g., an ILD layer) may include silicon dioxide, fluorinated silicate glass (FGS), SILK (a product of The Dow Chemical Company, Michigan), BLACKDIAMOND (a product of Applied Materials, Santa Clara, California), and / or other suitable insulating materials. The MLI structure may be formed by suitable processes typical of CMOS manufacturing, such as CVD, PVD, ALD, plating, spin coating, and / or other processes.

[0037] The device substrate 134 houses the bioFET 110 and can be, for example, a semiconductor layer of a semiconductor on insulator (SOI) substrate or a bulk semiconductor substrate. The bioFET 110 includes a pair of source regions 114 / drain regions 116, and in some embodiments, includes a back gate electrode 148. The source region 114, the drain region 116 have a first doping type and are respectively arranged in the device substrate 134 on opposite sides of the channel region 120 of the bioFET 110. The channel region 120 has a second doping type opposite to the first doping type and is arranged in the device substrate 134, laterally located between the source region 114, the drain region 116. The first doping type and the second doping type can be, for example, n-type and p-type, respectively, or vice versa. In some embodiments, as shown in the figure, the bioFET 110 is arranged to pass through the device substrate 134, extending from the top surface of the device substrate 134 to the bottom surface of the device substrate 134. In some other embodiments, the source region 114, the drain region 116, and the channel region 120 are disposed at the underside of the device substrate 134 (lower portion of the device substrate 134). In some embodiments, the bioFET 110 is disposed within a well region 140 of the device substrate 134 having a second doping type and / or electrically coupled to the BEOL interconnect structure 136. A back gate electrode 148 is disposed below the device substrate 134, laterally between the source region 114, the drain region 116, and spaced apart from the device substrate 134 by a gate dielectric layer 142 of the bioFET 110. In some embodiments, the back gate electrode 148 is electrically coupled to the BEOL interconnect structure 136 and / or is metal, doped polysilicon, or a combination thereof.

[0038] The isolation layer 144 is disposed above the device substrate 134 and includes a sensing well 146. The sensing well 146 extends into the isolation layer 144 to be adjacent to the channel region 120 and is at least partially lined by the biosensing film 118. Additionally, in some embodiments, the sensing well 146 extends through the isolation layer 144 to expose the channel region 120 and / or is laterally disposed between the source region 114 and the drain region 116. In some embodiments, the sensing well 146 and the lined biosensing film 118 extend laterally to span the boundaries of the channel region 120 and the source region 114 and the drain region 116 to partially cover the source region 114 and the drain region 116. The isolation layer 144 may be, for example, silicon dioxide, a buried oxide (BOX) layer of an SOI substrate, some other dielectric, or a combination thereof. The biosensing film 118 lines the sensing well 146 and, in some embodiments, covers the isolation layer 144. Although in Figure 3 1 , but in some other embodiments, the biosensing film 118 may have an opening depending on the application (e.g., for external wiring pads). In addition, the biosensing film 118 is configured to react with or bind to a biological entity to promote a change in the conductance of the channel region 120, so that the presence of the biological entity can be detected based on the conductance of the channel region 120. The biosensing film 118 can be, for example, titanium nitride, titanium, a high-k dielectric, some other material configured to react with or bind to a biological entity, or a combination thereof. The biological entity can be, for example, DNA, ribonucleic acid (RNA), a drug molecule, an enzyme, a protein, an antibody, an antigen, or a combination thereof. The biosensing film 118 can include materials for any specific biomolecule binding. In an embodiment, the biosensing film 118 includes a high-k dielectric material, such as HfO2. In an embodiment, the biosensing film 118 includes a metal layer, such as Pt, Au, Al, W, Cu, and / or other suitable metals. Other exemplary biosensing films 118 include high-k dielectric films, metals, metal oxides, dielectrics, and / or other suitable materials. As a further example, the biosensing film 118 includes HfO2, Ta2O5, Pt, Au, W, Ti, Al, Cu, oxides of these metals, SiO2, Si3N4, Al2O3, TiO2, TiN, SnO, SnO2; and / or other suitable materials. The biosensing film 118 may include multiple material layers. The biosensing film 118 may, for example, have a thickness of less than about 100 nanometers.

[0039] In some embodiments, the reference electrode 132 is disposed above the sensing well 146. In other embodiments, the reference electrode 132 can be positioned indirectly or directly on the isolation layer 144 laterally adjacent to the sensing well 146. The reference electrode 132 can optionally be disposed indirectly or directly below the biosensing membrane 118. In some embodiments, the reference electrode 132 includes platinum (Pt), gold (Au), silver (Ag), silver chloride (AgCl), or a combination thereof. The thickness of the reference electrode 132 can be in the range of about 500 angstroms to about 1 μm. By separating the reference electrode 132 from the device substrate 134, contamination introduced by the reference electrode 132 is effectively prevented.

[0040] Although Figure 3 The embodiment includes a back gate electrode 148 and a gate dielectric layer 142, but it should be understood that the back gate electrode 148 and the gate dielectric layer 142 may be omitted in other embodiments. The sensing well 146 is exposed to the fluid 122. As the fluid 122 is applied to the bioFET device 130, a reference bias voltage is applied to the reference electrode 132.

[0041] During operation, a test sample is suspended in the fluid 122 and applied to the sensing well 146 to detect the presence of a biological entity. In addition, after the fluid 122 is applied to the sensing well 146, the fluid 122 can be biased to a reference potential to enhance the detection of the biological entity. The reference electrode 132 provides a reference potential to the fluid 122, for example, by an external power source that can be controlled by the controller 108.

[0042] Figure 4 is a flow chart illustrating a method for performing 3D analysis of a test sample (such as a cell or a cell population) using a 2D biosensor array, and FIG. 5A to FIG. 5C Conceptually shows Figure 4 Other aspects of the method. In general, the method includes repositioning a 3D test sample relative to the biosensor array so that multiple different areas of the sample are sequentially placed in contact with the sensor array for analysis. The data collected from each sample area is then combined to obtain a 3D analysis of the test sample using the 2D sensor array. More specifically, the method 200 includes loading a test sample such as a cell or a cell population into the biosensor device 130 at step 210. At step 212, the cells are "captured" or placed on the biosensor array 102. As described above, Figure 1 The biosensor system 100 shown in FIG. 1 includes an electrode array 106 configured to selectively apply various DEP forces to manipulate a test sample relative to the sensor array 102. A controller 108 may be programmed or operated to apply appropriate electrical signals to the electrode array 106 to generate the desired DEP forces.

[0043] Thus, in some examples, a positive DEP force is used to capture the sample in step 212. In other embodiments, the sample contacts the sensor array 102 via gravity. Figure 5A A 3D test sample 250 including cells or a group of cells is shown. A first region 252 of the sample or cells 250 contacts the sensor array 102. At step 214, the biosensor 102 analyzes or detects the test sample 250 to obtain test data about the first region 252 of cells at step 216.

[0044] As described above, multiple areas of the test sample are analyzed and the data is combined to generate a 3D analysis of the sample. If additional areas of the test sample 250 are determined for analysis at step 220, the method proceeds to step 230. At step 230, the test sample 250 is lifted by a DEP force (such as a negative DEP force) such that Figure 5A The first region 252 is shown lifted off the biosensor 102 . Figure 5B An arrow 256 is shown representing a negative DEP that lifts the sample 250 off the biosensor 102. In step 232, the sample 250 is rotated by applying a rotational DEP force. As will be discussed further below, the controller 108 is operable to apply various electrical signals to the electrode array 106, such as a rotational AC signal to apply a desired rotational force to the sample 250. Figure 5B , the rotational force is represented by arrow 258. Figure 5B As shown, the sample 250 is rotated until the second region 254 is positioned to be placed on the biosensor array 102. Figure 4 In step 234, if Figure 5C As shown, the sample 250 is allowed to sink from its elevated position so that the second region 254 of the sample 250 contacts the biosensor 102. The method 200 then returns to step 212 where a positive DEP is applied to capture the sample 250 on the biosensor 102. In some embodiments, gravity is sufficient to place the test sample 250 on the biosensor 102, and step 212 may be omitted.

[0045] Once all test areas of sample 250 have been analyzed as determined in step 220, the test data for each sample area is combined in step 222 to produce a 3D analysis of the cells of the 3D sample.

[0046] Figure 61 is a top view showing various aspects of the electrode array 108 and biosensor array 102 of the biosensor system 100. In the example shown, the electrode array 108 includes two electrode groups or patterns. The first electrode group 154 ​​includes electrodes E1, E2, E3 and E4 located in a common plane on the corresponding four sides of the biosensor array 102. The second electrode group 156 includes electrodes E5, E6, E7 and E8, and electrodes E5, E6, E7 and E8 are also located in a common plane on the corresponding four sides of the biosensor array 102. In the example shown, the first electrode group 154 ​​is located outside the second electrode group 156, and the electrode groups 154 and 156 are in the same plane. Other embodiments can use more or fewer electrodes in the electrode array.

[0047] Figure 7 Examples of other components of a biosensor device 150 including a biosensor array 102 and an electrode array 106 are shown. Figure 7 A reference electrode 132 of a bioFET device 130 is shown configured to be positioned above a sensor array 102, as will be discussed further below. A microfluidic cover 152 is configured to cover the reference electrode 132 and the sensor array 102. Microfluidic walls further surround the sides of the device 150 to create a microfluidic channel that contains the fluid 122 and receives a test sample positioned relative to the sensor array 102 for analysis.

[0048] Figure 8 It is along Figure 6 A side cross-sectional view of the biosensor device 150 taken along line AA of FIG. Figure 3 The sensor array 102 and electrode array 108 of the backside sensing bioFET device 130 are shown (for ease of discussion, the Figure 8 130). The biosensor device 150 includes an interconnect structure 136 disposed above a handle substrate 138. In some examples, the electrical interconnect structure disposed in the interconnect layer 136 is metal, but other conductive materials may alternatively be used as described above. The device substrate 134 is disposed above the interconnect structure 136. The handle substrate 138 may be, for example, a bulk semiconductor substrate, such as a bulk substrate of single crystal silicon, and the substrate 134 may be, for example, a semiconductor layer or a bulk semiconductor substrate of a semiconductor on insulator (SOI) substrate.

[0049] An isolation layer or BOX layer 144 is disposed over the device substrate 134 , and a reference electrode 132 is disposed over the biosensor array 102 . Figure 8A cross-sectional view of a portion of the electrode array 108 is shown, including electrodes E2 and E4 of the first electrode set 154 and electrodes E6 and E8 of the second electrode set 156. Electrodes E6, E8 may be made of any suitable conductive material, such as gold, platinum, carbon, etc. In the illustrated embodiment, the electrodes of the first electrode set 154 and the second electrode set 156 are formed above the isolation layer 144 and are coplanar with each other. The electrodes further extend through the isolation layer 144 and the device substrate 134 to the interconnect layer 136. The electrode array 106 may thus be connected to a voltage source that applies various signals to the electrodes of the electrode array under the control of the controller 108 to manipulate the test sample, such as in conjunction with Figure 4 and FIG. 5A to FIG. 5C as described.

[0050] In the example shown, the electrode array 106 is configured to selectively move the test sample 250 to capture the test sample 250 on the biosensor array 102 and to separate the test sample 250 from the biosensor array 102 by DEP forces. Fig. 9 and Fig.10 This concept is shown in Fig. 9 As shown, a positive DEP is generated to move the test sample 250 toward the biosensor array 102, while Fig.10 A negative DEP is generated in the non-uniform electric field to move the test sample 250 away from the biosensor array 102. More specifically, the test sample 250, such as a cell or a cell group, experiences a net force in the non-uniform electric field and is pushed toward Fig. 9 field maximum (positive DEP) or is pushed toward Fig.10 Field minimum in (negative DEP).

[0051] The amplitude of the positive and negative DEPs can be modified by the actuation frequency of the AC signal applied to the electrodes. Fig.11 , electrodes E5-E6 of the second or inner electrode set 156 are configured to generate a positive DEP to capture the test sample 250 on the biosensor array 102. Electrodes E1-E4 of the first electrode set 154 are floating, and each electrode E5-E8 of the second or inner electrode set 156 is grounded. An actuation signal is applied from a voltage source 160 to the reference electrode 132 to generate a positive DEP. Figure 1 The controller 108 shown can be configured to control the voltage source 160. In the example shown, the reference electrode actuation signal VRE is determined according to VRE=Vo*sin(w1t), where the AC signal frequency w1 is selected to obtain an effective positive DEP to push the test sample 250 toward the biosensor array 102 and capture the test sample 250 on the biosensor array 102.

[0052] Fig.12The application of an actuation signal to generate a negative DEP to lift the test sample 250 off the biosensor array 102 is shown. The electrodes E5-E6 of the second or inner electrode set 156 are configured to generate a negative DEP to lift the test sample 250 off the biosensor array 102 against gravity. The electrodes E1-E4 of the first electrode set 154 are again floating, and each of the electrodes E5-E8 of the second or inner electrode set 156 is grounded. An actuation signal is applied from a voltage source 160 to the reference electrode 132 to generate a negative DEP. In the example shown, the reference electrode actuation signal VRE is determined according to VRE=Vo*sin(w2t), where the AC signal frequency w2 is selected to obtain an effective negative DEP to lift the test sample 250 against gravity.

[0053] Additionally, as discussed above, the electrode array 106 (see Figure 1 ) is configured to selectively rotate a test sample to align a desired portion of the test sample with the biosensor array 102. For example, the illustrated electrode array 106 is energized by the controller 108 to rotate the test sample about at least one of a first axis, a second axis extending perpendicular to the first axis, or a third axis extending perpendicular to the first and second axes. Figures 13 to 15 An example arrangement for rotating the test sample 250 about these three axes is shown. Figures 13 to 15 X, Y, and Z axes are shown, with the X axis extending laterally in and out of the drawing, the Y axis extending perpendicularly to the X axis in a left-right direction, and the Z axis extending perpendicularly to the X and Y axes in an up-down direction.

[0054] Fig.13 An example is shown in which the electrode array 106 is configured and an actuation signal is applied to rotate the test sample 250 about the Z axis. Fig.12 As shown, after the test sample is lifted off the biosensor array 102 by the negative DEP force, the test sample is rotated about the vertical axis. Fig.13 In the example of FIG. 1 , electrodes E1, E2, E3, and E4 surround the biosensor array 102 and are thus located on each of the four sides of the biosensor array 102. Fig.13 As shown, each of the electrodes E1, E2, E3 and E4 is separated from their adjacent electrodes by 90 degrees. In other words, the E1 electrode has a phase angle of 0 degrees, the E2 electrode has a phase angle of 90 degrees, the E3 electrode has a phase angle of 180 degrees, and the E4 electrode has a phase angle of 270 degrees.

[0055] To stimulate the electrodes to move the test sample 250 about the Z axis, the inner electrode set 156 is not used, so the electrodes E5-E8 and the reference electrode 132 are all floating. The controller 108 is configured to apply voltages V1, V2, V3, and V4 to the electrodes E1, E2, E3, and E4, respectively, wherein the voltages V1-V4 are determined according to the following formula:

[0056] V1=Vo*sin(wt)

[0057] V2=Vo*sin(wt+0.5π)

[0058] V3=Vo*sin(wt+π)

[0059] V4=Vo*sin(wt+1.5π)

[0060] The AC signal frequency w is determined based on the type of test sample and the microfluidic fluid solution. In some embodiments, the AC signal frequency is, for example, 10k to 50 MHz.

[0061] Fig.14 An example is shown, where Fig.12 After the test sample 250 is lifted off the biosensor array 102 by the negative DEP force, the electrode array 106 is configured and an actuation signal is applied to rotate the test sample 250 about the X-axis. Fig.14 In the example of , electrodes E1, E3, E5 and E7 and reference electrode 132 are not used and are therefore floating. Electrodes E2 and E4 are grounded. Voltages V6 and V8 are applied to electrodes E6 and E8, respectively. Voltage signals V6 and V8 are determined according to the following formula:

[0062] V6=Vo*sin(wt)

[0063] V8=Vo*sin(wt+θ),

[0064] Wherein θ is about 40-90 degrees depending on the specific electrode shape and design.

[0065] Fig.15 An example is shown, where Fig.12 After the test sample 250 is lifted off the biosensor array 102 by the negative DEP force, the electrode array 106 is configured and an actuation signal is applied to rotate the test sample 250 about the Y axis. Fig.15 In the example of , electrodes E2, E4, E6 and E8 and reference electrode 132 are not used and are therefore floating. Electrodes E1 and E3 are grounded. Voltages V5 and V7 are applied to electrodes E5 and E7, respectively. Voltage signals V5 and V7 are determined according to the following formula:

[0066] V5=Vo*sin(wt)

[0067] V7=Vo*sin(wt+θ),

[0068] Wherein θ is about 40-90 degrees depending on the specific electrode shape and design.

[0069] Figures 16 to 201 shows steps in a process for forming an electrode array 106 of a biosensor device 150. In some examples, the electrode array 106 is formed on an isolation layer 144 to surround the biosensor array 102. As an example, Figures 16 to 20 The formation of one of the electrode arrays 106 is shown. The remaining electrodes are fabricated in a similar manner. Fig.16 In the Figure 3 The bioFET array 102 of the array of dual-gate backside bioFET devices 130 is shown. As disclosed above, the structure includes an interconnect structure 136 arranged above a processing substrate 138 and a device substrate 134 arranged above the interconnect structure 136. The processing substrate 138 can be, for example, a bulk semiconductor substrate, such as a bulk substrate of single crystal silicon. The device substrate 134 houses the biosensor array 102 and can be, for example, a semiconductor layer of a semiconductor on insulator (SOI) substrate or a bulk semiconductor substrate. An isolation layer or BOX layer 144 is arranged above the device substrate 134, wherein a sensing film 118 is disposed on the device substrate 134. In the example shown, the electrode array 106 is connected to other structures, such as a controller 108 and various voltage sources, via the interconnect layer 136. In Fig.16 In FIG. 1 , an opening 170 extends through the sensing film 118 , the isolation layer 144 , and the device substrate 134 to a conductive pad 172 in the interconnect layer 136 .

[0070] like Fig.17 As shown, a metal layer 174 is deposited over the sensing film 118, for example, by a metal sputtering process. The conductive layer lines the opening 170 and may include a metal material such as platinum (Pt), gold (Au), silver (Ag), silver chloride (AgCl), or a combination thereof. Fig.18 In the embodiment of the present invention, a photoresist (PR) mask 176 is deposited over the conductive layer 174 and patterned. The PR mask is patterned into an etching mask to etch the metal layer 170. A typical photolithography process may be used to deposit the PR mask, cure the photoresist, expose the photoresist to patterned light, and develop the photoresist to produce a desired pattern.

[0071] exist Fig.19 In the embodiment, the etching process removes portions of the metal layer 174 according to the PR mask 176. The etching process can be a dry etch. The dry etch can use a chlorine-based or fluorine-based etchant in a plasma process. In one embodiment, the etching process utilizes an endpoint system, where the etching process detects an endpoint material (e.g., an IMD material) and a signal that the etching endpoint has been reached. At the endpoint, the etching process continues for a defined duration to over-etch an additional amount of material to ensure complete removal of the conductive material of the metal layer 174. Fig. 20 In the process, the PR mask 176 is removed to expose the formed electrode pattern 106 .

[0072] Thus, the disclosed examples provide biosensor systems and methods that collect data for 3D analysis of 3D test samples (such as cell cultures). Such 3D analysis can provide additional, more relevant information about the test sample. An array of 2D biosensors can collect 3D information about a 3D test sample by repositioning the test sample relative to the biosensor to collect data on multiple segments of the test sample. These data are then combined to provide a 3D analysis.

[0073] According to some disclosed embodiments, a biosensor system includes an array of biosensors and a plurality of electrodes located proximate the biosensors. A controller is configured to selectively actuate the plurality of electrodes to generate a DEP force to selectively position a test sample relative to the array of biosensors.

[0074] In the above biosensor system, the plurality of electrodes are located on four sides of the array of the biosensor.

[0075] In the above-mentioned biosensor system, wherein the plurality of electrodes are located on four sides of the array of the biosensor, wherein the controller is configured to stimulate the plurality of electrodes to selectively generate the dielectrophoretic force to capture the test sample on the array of the biosensor.

[0076] In the above biosensor system, wherein the plurality of electrodes are located on four sides of the biosensor array, wherein the controller is configured to stimulate the plurality of electrodes to selectively generate the dielectrophoretic force to separate the test sample from the biosensor array.

[0077] In the above-mentioned biosensor system, wherein the multiple electrodes are located on four sides of the array of the biosensor, wherein the multiple electrodes include: a first electrode, a second electrode, a third electrode and a fourth electrode, which are located on a common plane and are respectively located on the first side, the second side, the third side and the fourth side of the array of the biosensor; a fifth electrode, a sixth electrode, a seventh electrode and an eighth electrode, which are located on the common plane and are respectively located on the corresponding first side, the second side, the third side and the fourth side of the array of the biosensor; and a reference electrode, which is located on the first electrode, the second electrode, the third electrode, the fourth electrode, the fifth electrode, the sixth electrode, the seventh electrode and the eighth electrode and the array of the biosensor.

[0078] In the above-mentioned biosensor system, the multiple electrodes are located on four sides of the array of the biosensor, wherein the multiple electrodes include: a first electrode, a second electrode, a third electrode and a fourth electrode, which are located on a common plane and are respectively located on the first side, the second side, the third side and the fourth side of the array of the biosensor; a fifth electrode, a sixth electrode, a seventh electrode and an eighth electrode, which are located on the common plane and are respectively located on the corresponding first side, the second side, the third side and the fourth side of the array of the biosensor; and a reference electrode, which is located on the first electrode, the second electrode, the third electrode, the fourth electrode, the fifth electrode, the sixth electrode, the seventh electrode and the eighth electrode and the array of the biosensor, wherein the controller is configured to apply a first alternating current (AC) signal having a first predetermined frequency to the reference electrode to establish positive dielectrophoresis to capture the test sample on the array of the biosensor, and to apply a second alternating current signal having a second predetermined frequency to the reference electrode to establish negative dielectrophoresis to separate the test sample from the array of the biosensor.

[0079] In the above-mentioned biosensor system, wherein the plurality of electrodes are located on four sides of the array of the biosensor, wherein the plurality of electrodes include: a first electrode, a second electrode, a third electrode and a fourth electrode, which are located on a common plane and are respectively located on the first side, the second side, the third side and the fourth side of the array of the biosensor; a fifth electrode, a sixth electrode, a seventh electrode and an eighth electrode, which are located on the common plane and are respectively located on the corresponding first side, the second side, the third side and the fourth side of the array of the biosensor; and a reference electrode, which is located on the first electrode, the second electrode, the third electrode, the fourth electrode, the fifth electrode and the eighth electrode. The controller is configured to apply an AC signal to each of the first electrode, the second electrode, the third electrode and the fourth electrode, wherein the AC signal applied to the first electrode has a phase angle of 0 degrees, the AC signal applied to the second electrode has a phase angle of 90 degrees, the AC signal applied to the third electrode has a phase angle of 180 degrees, and the AC signal applied to the fourth electrode has a phase angle of 270 degrees to establish a dielectrophoretic force to rotate the test sample around a first axis.

[0080] In the above-mentioned biosensor system, wherein the plurality of electrodes are located on four sides of the array of the biosensor, wherein the plurality of electrodes include: a first electrode, a second electrode, a third electrode and a fourth electrode, which are located on a common plane and are respectively located on the first side, the second side, the third side and the fourth side of the array of the biosensor; a fifth electrode, a sixth electrode, a seventh electrode and an eighth electrode, which are located on the common plane and are respectively located on the corresponding first side, the second side, the third side and the fourth side of the array of the biosensor; and a reference electrode, which is located on the first electrode, the second electrode, the third electrode, the fourth electrode, the fifth electrode, the sixth electrode, the seventh electrode and the eighth electrode The controller is configured to apply an AC signal to each of the first electrode, the second electrode, the third electrode and the fourth electrode, wherein the AC signal applied to the first electrode has a phase angle of 0 degrees, the AC signal applied to the second electrode has a phase angle of 90 degrees, the AC signal applied to the third electrode has a phase angle of 180 degrees, and the AC signal applied to the fourth electrode has a phase angle of 270 degrees to establish a dielectrophoretic force to rotate the test sample around a first axis, wherein the AC signal has a predetermined frequency.

[0081] In the above-mentioned biosensor system, wherein the plurality of electrodes are located on four sides of the array of the biosensor, wherein the plurality of electrodes include: a first electrode, a second electrode, a third electrode and a fourth electrode, which are located on a common plane and are respectively located on the first side, the second side, the third side and the fourth side of the array of the biosensor; a fifth electrode, a sixth electrode, a seventh electrode and an eighth electrode, which are located on the common plane and are respectively located on the corresponding first side, the second side, the third side and the fourth side of the array of the biosensor; and a reference electrode, which is located on the first electrode, the second electrode, the third electrode, the fourth electrode, the fifth electrode, the sixth electrode, the seventh electrode and the eighth electrode and the array of the biosensor, wherein the controller is configured To apply an AC signal to each of the first electrode, the second electrode, the third electrode and the fourth electrode, wherein the AC signal applied to the first electrode has a phase angle of 0 degrees, the AC signal applied to the second electrode has a phase angle of 90 degrees, the AC signal applied to the third electrode has a phase angle of 180 degrees, and the AC signal applied to the fourth electrode has a phase angle of 270 degrees to establish a dielectrophoretic force to rotate the test sample around a first axis, wherein the controller is configured to apply a first AC signal having a first phase angle to the sixth electrode, and apply a second AC signal having a second phase angle to the eighth electrode to establish a dielectrophoretic force to rotate the test sample around a second axis perpendicular to the first axis.

[0082] In the above-mentioned biosensor system, wherein the plurality of electrodes are located on four sides of the array of the biosensor, wherein the plurality of electrodes include: a first electrode, a second electrode, a third electrode and a fourth electrode, which are located on a common plane and are respectively located on the first side, the second side, the third side and the fourth side of the array of the biosensor; a fifth electrode, a sixth electrode, a seventh electrode and an eighth electrode, which are located on the common plane and are respectively located on the corresponding first side, the second side, the third side and the fourth side of the array of the biosensor; and a reference electrode, which is located on the first electrode, the second electrode, the third electrode, the fourth electrode, the fifth electrode, the sixth electrode, the seventh electrode and the eighth electrode and the array of the biosensor, wherein the controller is configured to cross A flow signal is applied to each of the first electrode, the second electrode, the third electrode and the fourth electrode, wherein the AC signal applied to the first electrode has a phase angle of 0 degrees, the AC signal applied to the second electrode has a phase angle of 90 degrees, the AC signal applied to the third electrode has a phase angle of 180 degrees, and the AC signal applied to the fourth electrode has a phase angle of 270 degrees to establish a dielectrophoretic force to rotate the test sample around a first axis, wherein the controller is configured to apply a first AC signal having a first phase angle to the fifth electrode, and apply a second AC signal having a second phase angle to the fifth electrode to establish a dielectrophoretic force to rotate the test sample around a third axis perpendicular to the first axis and the second axis.

[0083] In the above biosensor system, wherein the array of biosensors includes a plurality of backside sensing bioFETs.

[0084] According to another embodiment, a biosensor system includes a processing substrate, an interconnection layer located above the processing substrate, and a device substrate located above the interconnection layer. The device substrate has a biosensor array electrically connected to the interconnection layer. An isolation layer is located above the device substrate. A plurality of electrodes are formed above the isolation layer and extend through the isolation layer and the device substrate to the interconnection layer. The plurality of electrodes are configured to receive an AC signal to establish a DEP force to selectively position a test sample relative to the biosensor array.

[0085] In the above-mentioned biosensor system, the multiple electrodes include: a first electrode, a second electrode, a third electrode and a fourth electrode, which are located on the corresponding first side, second side, third side and fourth side of the biosensor array; a fifth electrode, a sixth electrode, a seventh electrode and an eighth electrode, which are located on the first side, second side, third side and fourth side of the biosensor array; and a reference electrode, which is located on the first electrode, the second electrode, the third electrode, the fourth electrode, the fifth electrode, the sixth electrode, the seventh electrode and the eighth electrode and the biosensor array.

[0086] According to another example, a method includes providing a biosensor array and a 3D test sample. Data about a first segment of the 3D test sample is collected by the biosensor array. A DEP force is generated to reposition the 3D test sample relative to the biosensor array, and data about a second segment of the 3D test sample is collected by the biosensor array. The data about the first segment and the second segment of the 3D test sample are then combined.

[0087] In the above method, wherein generating the dielectrophoretic force includes generating a positive dielectrophoretic force to capture the three-dimensional test sample on the biosensor array.

[0088] In the above method, wherein generating the dielectrophoretic force includes generating a negative dielectrophoretic force to lift the three-dimensional test sample away from the biosensor array.

[0089] In the above method, wherein generating the dielectrophoretic force includes generating a rotational dielectrophoretic force to rotate the three-dimensional test sample around a predetermined axis.

[0090] In the above method, generating the dielectrophoretic force includes generating a rotational dielectrophoretic force to rotate the three-dimensional test sample around a predetermined axis, wherein generating the dielectrophoretic force includes generating a rotational dielectrophoretic force to rotate the three-dimensional test sample around at least one of a first axis, a second axis extending perpendicular to the first axis, or a third axis extending perpendicular to the first axis and the second axis.

[0091] In the above method, wherein generating the dielectrophoretic force includes selectively stimulating a plurality of electrodes located near the biosensor array.

[0092] In the above method, wherein generating the dielectrophoretic force comprises selectively stimulating a plurality of electrodes located near the biosensor array, wherein selectively stimulating the plurality of electrodes comprises applying a predetermined alternating current signal to at least one of the plurality of electrodes.

[0093] The present invention summarizes the features of several embodiments so that those skilled in the art can better understand aspects of the present invention. Those skilled in the art should understand that they can easily use the present invention as a basis to design or modify other processes and structures for implementing the same purpose and / or achieving the same advantages as the embodiments introduced herein. Those skilled in the art should also appreciate that this equivalent configuration does not deviate from the spirit and scope of the present invention, and that they can make multiple changes, substitutions and changes herein without departing from the spirit and scope of the present invention.

Claims

1. A biosensor system comprising: Arrays of biosensors; A plurality of electrodes, wherein the plurality of electrodes comprises: A first set of electrodes, including a first electrode, a second electrode, a third electrode and a fourth electrode respectively located on a first side, a second side, a third side and a fourth side of the array of the biosensor and located on a common plane; a second set of electrodes, comprising a fifth electrode, a sixth electrode, a seventh electrode and an eighth electrode respectively located on the first side, the second side, the third side and the fourth side of the array of the biosensor and located on the common plane, wherein the first set of electrodes is located outside the second set of electrodes, a reference electrode, located on the first electrode, the second electrode, the third electrode, the fourth electrode, the fifth electrode, the sixth electrode, the seventh electrode, the eighth electrode and the array of the biosensor; as well as a controller electrically connected to the plurality of electrodes, wherein the controller is configured to selectively actuate the plurality of electrodes to generate a dielectrophoretic (DEP) force to selectively position a test sample relative to the array of biosensors, Wherein, selectively positioning the test sample includes rotating the test sample to a selected area for sensing.

2. The biosensor system according to claim 1, further comprising: a fluid delivery system, in communication with the controller, Wherein, the controller is further configured to enable the fluid delivery system to deliver the test sample to the array of biosensors.

3. The biosensor system according to claim 1, wherein: The controller is configured to actuate the plurality of electrodes to selectively generate the dielectrophoretic force to capture the test sample on the array of biosensors.

4. The biosensor system according to claim 1, wherein: The controller is configured to energize the plurality of electrodes to selectively generate the dielectrophoretic force to separate the test sample from the array of biosensors.

5. The biosensor system of claim 1 , further comprising: processing substrates; an interconnect layer located above the handle substrate; A device substrate is located above the interconnect layer, wherein the device substrate includes the array of biosensors, wherein the array of biosensors is electrically connected to the interconnect layer.

6. The biosensor system according to claim 1, wherein: The controller is configured to apply a first alternating current (AC) signal having a first predetermined frequency to the reference electrode to establish positive dielectrophoresis to capture the test sample on the array of the biosensor, and to apply a second AC signal having a second predetermined frequency to the reference electrode to establish negative dielectrophoresis to separate the test sample from the array of the biosensor.

7. The biosensor system according to claim 1, wherein: The controller is configured to apply an AC signal to each of the first electrode, the second electrode, the third electrode, and the fourth electrode, wherein the AC signal applied to the first electrode has a phase angle of 0 degrees, the AC signal applied to the second electrode has a phase angle of 90 degrees, the AC signal applied to the third electrode has a phase angle of 180 degrees, and the AC signal applied to the fourth electrode has a phase angle of 270 degrees to establish a dielectrophoretic force to rotate the test sample about a first axis.

8. The biosensor system according to claim 7, wherein: The AC signal has a predetermined frequency.

9. The biosensor system according to claim 7, wherein: The controller is configured to apply a first AC signal having a first phase angle to the sixth electrode and a second AC signal having a second phase angle to the eighth electrode to establish a dielectrophoretic force to rotate the test sample about a second axis perpendicular to the first axis.

10. The biosensor system according to claim 9, wherein: The controller is configured to apply a third AC signal having a third phase angle to the fifth electrode and apply a fourth AC signal having a fourth phase angle to the seventh electrode to establish a dielectrophoretic force to rotate the test sample about a third axis perpendicular to the first axis and the second axis.

11. The biosensor system according to claim 1, wherein: The array of biosensors includes a plurality of backside sensing bioFETs.

12. A biosensor system comprising: processing substrates; an interconnect layer located above the handle substrate; a device substrate disposed above the interconnect layer, the device substrate comprising a biosensor array electrically connected to the interconnect layer; An isolation layer, located above the device substrate; a plurality of electrodes formed above the isolation layer and extending through the isolation layer and the device substrate to the interconnect layer, the plurality of electrodes being configured to receive an AC signal to establish a dielectrophoretic force to selectively position a test sample relative to the biosensor array, Wherein, the plurality of electrodes include: a first set of electrodes, including a first electrode, a second electrode, a third electrode, and a fourth electrode, located on respective first, second, third, and fourth sides of the biosensor array and located on a common plane; a second set of electrodes, including a fifth electrode, a sixth electrode, a seventh electrode, and an eighth electrode, located on the first side, the second side, the third side, and the fourth side of the biosensor array and located on the common plane, wherein the first set of electrodes is located outside the second set of electrodes; and a reference electrode located on the first electrode, the second electrode, the third electrode, the fourth electrode, the fifth electrode, the sixth electrode, the seventh electrode, the eighth electrode and the biosensor array, Wherein, selectively positioning the test sample includes rotating the test sample to a selected area for sensing.

13. The biosensor system of claim 12, further comprising: A fluid delivery system is configured to deliver the test sample to the array of biosensors.

14. A method for analyzing a test sample using a biosensor system, comprising: providing a biosensor array; Provide three-dimensional (3D) test samples; collecting data about a first segment of the three-dimensional test sample by the biosensor array; Generating a dielectrophoretic force to reposition the three-dimensional test sample relative to the biosensor array, comprising applying an alternating current signal to a first set of electrodes, a second set of electrodes, and a reference electrode, the first set of electrodes comprising a first electrode, a second electrode, a third electrode, and a fourth electrode located on respective first, second, third, and fourth sides of the biosensor array and located on a common plane, the second set of electrodes comprising a fifth electrode, a sixth electrode, a seventh electrode, and an eighth electrode located on respective first, second, third, and fourth sides of the biosensor array and located on the common plane; collecting data about a second segment of the three-dimensional test sample by the biosensor array; combining the data regarding the first segment and the second segment of the three-dimensional test sample, wherein the first group of electrodes is located outside the second group of electrodes, and the reference electrode is located on the first electrode, the second electrode, the third electrode, the fourth electrode, the fifth electrode, the sixth electrode, the seventh electrode, the eighth electrode and the biosensor array, Wherein, repositioning the three-dimensional test sample includes rotating the three-dimensional test sample to a selected area for sensing.

15. The method according to claim 14, wherein: Generating the dielectrophoretic force includes generating a positive dielectrophoretic force to capture the three-dimensional test sample on the biosensor array.

16. The method according to claim 14, wherein: Generating the dielectrophoretic force includes generating a negative dielectrophoretic force to lift the three-dimensional test sample off the biosensor array.

17. The method according to claim 14, wherein: Generating the dielectrophoretic force includes generating a rotational dielectrophoretic force to rotate the three-dimensional test sample about a predetermined axis.

18. The method according to claim 17, wherein: Generating the dielectrophoretic force includes generating a rotational dielectrophoretic force to rotate the three-dimensional test sample about at least one of a first axis, a second axis extending perpendicular to the first axis, or a third axis extending perpendicular to the first axis and the second axis.

19. The method according to claim 14, wherein: Generating the dielectrophoretic force includes selectively energizing the first electrode, the second electrode, the third electrode, the fourth electrode, the fifth electrode, the sixth electrode, the seventh electrode, and the eighth electrode located proximate to the biosensor array.

20. The method according to claim 19, wherein: Selectively energizing the plurality of electrodes includes applying a predetermined alternating current signal to at least one of the first electrode, the second electrode, the third electrode, the fourth electrode, the fifth electrode, the sixth electrode, the seventh electrode, and the eighth electrode.

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