Electrochemical biosensor and method for producing the same

An electrochemical biosensor includes a substrate, a plurality of layered active metal parts, a plurality of layered electrodes, a reaction confinement layer, an electrochemical reactive layer and a cover piece. The substrate is formed with through holes each of which is defined by an interior wall surface and penetrates top and bottom surfaces. Each of the layered active metal parts is formed at least upon a respective one of the interior wall surfaces. The layered electrodes are formed on the layered active metal parts. The reaction confinement layer confines a reactor space over a region where the through holes are formed. The electrochemical reactive layer is disposed in the reactor space and is electrically coupled to the layered electrodes.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority of Taiwanese Patent Application No. 102148419, filed on Dec. 26, 2013.

FIELD

Embodiments of the invention generally relates to biosensors and methods for producing the same, and more particularly to electrochemical biosensors and methods for producing the same.

BACKGROUND

Referring toFIG. 1, an electrochemical biosensor8is adapted for measuring concentration of an analyte in a sample liquid, such as blood sugar concentration in a blood sample, or the concentration of heavy meal pollutants in a wastewater sample. As shown inFIG. 1, the electrochemical biosensor8includes an insulating substrate81, a metallic conductive layer82formed on the insulating substrate81by printing, an insulating layer83disposed to partially expose the metallic conductive layer82, a reagent-reactive layer84in electrical contact with the metallic conductive layer82, and a cover plate85. Although the electrochemical biosensor8may achieve the primary goal of measuring the analyte concentration in the sample liquid, the metallic conductive layer82, which is formed by screen printing, may exhibit relatively high electrode impedance which results in attenuation and interference of electrical output signals. In addition, the metallic conductive layer82of the electrochemical biosensor8may consume a relatively large amount of metallic raw material which increases the production cost.

Referring toFIG. 2, another electrochemical biosensor9is shown to include an insulating substrate91, a pair of electrodes92, an electrochemical reactive layer93and a cover plate94. The insulating substrate9is formed with a reaction chamber911and a pair of through holes912in spatial communication with the reaction chamber911. The electrodes92are respectively disposed in the through holes912, and the electrochemical reactive layer93is disposed in the reaction chamber911to be electrically coupled with the electrodes92. The cover plate94is disposed to cover the reaction chamber911. Although the electrochemical biosensor9may also achieve the primary function of measuring the analyte concentration in the sample liquid, the electrodes92and the substrate91are separately made, and a relatively complicated assembling procedure is therefore required. In addition, such configuration of the electrochemical biosensor9requires relatively low tolerance in making the electrodes92and the through holes911and thereby increases the production cost.

SUMMARY

Certain embodiments of the present invention provide electrochemical biosensors that may alleviate the aforementioned drawbacks, and/or methods for producing the same.

According to an aspect of the present invention, an electrochemical biosensor may include a substrate, a plurality of layered active metal parts, a plurality of layered electrodes, a reaction confinement layer, an electrochemical reactive layer and a cover piece.

The substrate is made of an electrically insulating material, has a top surface and a bottom surface opposite to the top surface, and is formed with a plurality of spaced-apart through holes. Each of the through holes is defined by an interior wall surface and penetrates the top and bottom surfaces.

Each of the layered active metal parts is formed at least upon a respective one of the interior wall surfaces.

The layered electrodes are respectively formed on the layered active metal parts.

The reaction confinement layer is disposed on the substrate and confines a reactor space over a region of the substrate where the through holes are formed.

The electrochemical reactive layer is disposed in the reactor space and is electrically coupled to the layered electrodes.

The cover piece is disposed to cover the electrochemical reactive layer.

According to another aspect of the present invention, an electrochemical biosensor may be adapted for use with a measuring device and include a substrate, an electrochemical reactive layer, a plurality of electrically-conductive vias and a cover piece.

The substrate is made of an electrically insulating material, has a top surface and a bottom surface opposite to the top surface, and is formed with a plurality of spaced-apart through holes. Each of the through holes is defined by an interior wall surface and penetrates the top and bottom surfaces.

The electrochemical reactive layer is disposed on the substrate.

Each of the electrically-conductive vias is formed at least inside a respective one of the interior wall surfaces and has a bottom part that is proximal to the bottom surface of the substrate and that is configured to have electrical contact with a corresponding portion of the measuring device, and a top part that is proximal to the top surface of the substrate and that is electrically coupled to the electrochemical reactive layer.

The cover piece is disposed to cover the electrochemical reactive layer.

According to yet another aspect of the present invention, a method for producing an electrochemical biosensor may include: forming a plurality of spaced-apart through holes in an electrically insulating substrate, the through holes penetrating top and bottom surfaces of the electrically insulating substrate; forming a plurality of layered active metal parts respectively in the through holes; forming a plurality of layered electrodes respectively on the layered active metal parts; and forming an electrochemical reactive layer on one of the top and bottom surfaces of the substrate to electrically connect the layered electrodes.

According to a further aspect of the present invention, a method for producing an electrode of an electrochemical biosensor may include steps of: forming a through hole in an electrically insulating substrate; activating at least a portion of an interior wall surface within the through hole; and forming a layer of metal-containing electrode material on the portion of the interior wall surface to produce the electrode.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Referring toFIGS. 3 to 6, a first exemplary embodiment of an electrochemical biosensor1according to the present invention is shown to include a substrate2, a plurality of layered active metal parts3, a plurality of layered electrodes4, a reaction confinement layer5, an electrochemical reactive layer6, and a cover piece7.

The substrate2, which has a top surface21and a bottom surface22opposite to the top surface21, is formed with a plurality of spaced-apart through holes231. Each of the through holes231is defined by an interior wall surface23and penetrates the top and bottom surfaces21,22. In this embodiment, the substrate2is made of an electrically insulating material and is configured in a rectangular shape. Examples of the electrically insulating material may include, but are not limited to, polyethylene (PE), polyimide (PI) and polycarbonate (PC). In this embodiment, the number of the through holes231formed in the substrate2is two, but the number of the through holes231according to the present invention is not limited to what is disclosed in this embodiment.

As shown inFIG. 5, in this embodiment, the top surface21of the substrate2has a plurality of top to-be-plated zones211that respectively extend around the through holes231, and a plurality of top separating zones212that extend respectively around the top to-be-plated zones211and that respectively isolate the top to-be-plated zones211from a top plating-free zone213of the top surface21. Similarly, the bottom surface22of the substrate2has a plurality of bottom to-be-plated zones221that respectively extend around the through holes231, and a plurality of bottom separating zones222that extend respectively around the bottom to-be-plated zones221and that respectively isolate the bottom to-be-plated zones221from a bottom plating-free zone223of the bottom surface22. In this embodiment, the top and bottom to-be-plated zones211,221, and the interior wall surfaces23are roughened, but it should be noted that, in other embodiments, the top and bottom to-be-plated zones211,221, and/or the interior wall surfaces23may be partially roughened or not roughened at all.

As shown inFIG. 6, each of the layered active metal parts3is formed at least upon a respective one of the interior wall surfaces23of the substrate2and corresponds in position to a respective one of the through holes231. In this embodiment, each of the layered active metal parts3extend outwardly from the respective one of the interior wall surfaces231to cover the top and bottom to-be-plated zones211,221which surround the respective one of the interior wall surfaces231. In some embodiments, the layered active metal parts3may be made of a material that is selected from the group consisting of palladium, rhodium, platinum, iridium, osmium, gold, nickel and combinations thereof.

Referring toFIGS. 5 and 6, the layered electrodes4are made of a metal-containing electrode material and are respectively formed on the layered active metal parts3, which correspond respectively in position to the through holes231. In this embodiment, each of the layered electrodes4includes a first layered metal part41bonded to the respective one of the layered active metal parts3, and a second layered metal part42bonded to the first layered metal part41and opposite to the respective one of the layered active metal parts3. In some embodiments, the first layered metal parts41of the layered electrodes4may be made of a material selected from the group consisting of copper, nickel, silver and combinations thereof. In some embodiments, the second layered metal parts42of the layered electrodes4may be made of a material selected from the group consisting of gold, nickel, titanium and combinations thereof. In such embodiments, gold is more preferred owing to its relatively high affinity to biological reagents. It should be noted that, in some embodiments, the layered electrodes4may be single-layered, for instance, and have only the first layered metal parts41. In some other embodiments, each of the layered electrodes4may be configured in a multilayered structure having a plurality of stacking layers made of identical material by similar processes. In this embodiment, as shown inFIG. 6, each of the layered electrodes4partially fills the respective one of the through holes231and has an annular cross-section inside the respective one of the through holes231. However, the through holes231may be completely filled up by the layered electrodes4in other embodiments in accordance with the present invention.

Referring toFIGS. 3 to 5, the reaction confinement layer5is disposed on the top surface21of the substrate2and is formed with a reactor space51over a region of the substrate2where the through holes231are formed. In this embodiment, the reaction confinement layer5is configured in a rectangular shape and has a bottom surface that is adhered to the top surface21of the substrate2. As shown inFIG. 4, a width of the reaction confinement layer5is substantially identical to that of the substrate2. It should be noted that, in some embodiments, the substrate2and the reaction confinement layer5may be integrally formed as one piece. As shown inFIG. 3, in this embodiment, the reactor space51is configured as a rectangular notch formed at a longitudinal side of the reaction confinement layer5to confine the electrochemical reactive layer6therein.

As shown inFIG. 5, the electrochemical reactive layer6is disposed in the reactor space51to cover the layered electrodes4and is electrically coupled to the layered electrodes4. The electrochemical reactive layer6may be electrochemically reactive with an analyte in a sample liquid (not shown) introduced into the reactor space51, so as to generate an output electrical signal that may be transmitted to the layered electrodes4, to which a coupling portion of an external measuring device may be coupled for reading the output electrical signal.

The cover piece7is disposed to cover the electrochemical reactive layer6. In this embodiment, a bottom surface of the cover piece7is adhered to a top surface of the reaction confinement layer5. In this embodiment, the cover piece7is configured in a rectangular shape and has a length and a width substantially identical to those of the reaction confinement layer5. The reactor space51of the reaction confinement layer5is further confined by the substrate2, the electrochemical reactive layer6and the cover piece7to forma sample-receiving space72for receiving the sample liquid. In addition, the substrate2, the reaction confinement layer5, and the cover piece7may cooperatively define a sample inlet71at the longitudinal side of the substrate2for introduction of the sample liquid into the sample-receiving space72.

By forming the layered active metal parts3on the interior wall surfaces231and on the top and bottom to-be-plated zones211,221, the layered electrodes4, which are respectively formed on the layered active metal parts3, can be tightly and firmly bonded to the substrate2via the layered active metal parts3. Moreover, the layered active metal parts3and the layered electrodes4constitute a plurality of electrically conductive vias each of which is at least formed along and inside a respective one of the through holes231. Each of the electrically conductive vias has a top part that is proximal to the top surface21and that is electrically coupled to the electrochemical reactive layer5, and a bottom part that is proximal to the bottom surface22of the substrate2and that is configured to have electrical contact with the coupling portion of the external measuring device (not shown), so that the electrical output signal resulting from the electrochemical reaction between the analyte and the electrochemical reactive layer6can be transmitted through the electrically conductive vias to the coupling portion of the external measuring device. As such, a process for assembling electrodes to the substrate can thereby be omitted, so as to simplify the manufacturing process of the electrochemical biosensor1and to enhance production efficiency thereof.

Referring toFIG. 7, a second exemplary embodiment of the electrochemical biosensor according to the present invention is shown to be similar to that of the first embodiment with the difference therebetween residing in that, in the second exemplary embodiment, the layered active metal parts3′ (only one is shown) and the layered electrodes4′ (only one is shown) are merely formed on the interior wall surfaces23′ (only one is shown), respectively, and are limited from extending therebeyond. That is to say, the electrically-conductive vias, which are composed of the layered active metal parts3′ and the layered electrodes4′, are disposed respectively inside the through holes231′ (only one is shown) and are flush with the top and bottom surfaces21′,22′ of the substrate2′. In this embodiment, the coupling portion of the external measuring device can be configured to have protrusions for enhancement of electrical contact with the electrically-conductive vias.

Referring toFIG. 8, a third exemplary embodiment of the electrochemical biosensor is shown to be similar to the second exemplary embodiment. The difference between the second and third exemplary embodiments resides in that each layered active metal parts3″ in the third exemplary embodiment is limited from extending beyond the respective one of the interior wall surfaces23″ and is not flush with the bottom surface22″ of the substrate2″. It should be noted that, in other embodiments, the layered active metal parts3″ (only one is shown) may be limited from extending beyond the interior wall surfaces23″ (only one is shown) and be not flush with the top surface21″(or be not flush with both the top and bottom surfaces21″,22″). Similar to the second exemplary embodiment, the coupling portion of the external measuring device may be configured to have protrusions for enhancement of electrical contact with the electrically-conductive vias.

Referring toFIGS. 9 and 10, a method for producing the electrochemical biosensor of the first exemplary embodiment according to the present invention includes steps as follows.

Step101: forming a plurality of the spaced-apart through holes231in the electrically insulating substrate2. Note that for the sake of simplicity, only one through hole231and components/parts associated with said one through hole231are depicted inFIG. 9. The through holes231penetrate top and bottom surfaces21,22of the substrate2. In this embodiment, the forming of the through holes231is conducted using laser. However, in other embodiments, the forming of the through holes231may be conducted using other techniques, such as mechanical punching.

Step102: forming a plurality of the layered metal parts3in the through holes231and on peripheral surface areas of the top and bottom surfaces21,22which respective extend around the through holes231. The top and bottom to-be-plated zones211,221are respectively located on the peripheral surface areas of the top and bottom surfaces21,22and have the layered active metal parts3formed thereon. In this embodiment, the forming of the layered active metal parts3includes roughening the interior wall surfaces23and the top and bottom to-be-plated zones211,221, followed by immersing the substrate2into an active metal solution. In this embodiment, the active metal solution is a Palladium-Tin colloid solution and has a palladium concentration ranging from 1 ppm to 750 ppm. Since the interior wall surfaces23and the top and bottom to-be-plated zones211,221are roughened, the layered active metal parts3formed on the top and bottom to-be-plated zones211,221may be thicker than active metal layers formed on other portions of the peripheral surface areas of the top and bottom surfaces21,22(seeFIG. 9). As mentioned hereinbefore, the interior wall surfaces23and the top and bottom to-be-plated zones211,221may be partially roughened or not roughened at all in other embodiments according to the present invention.

Step103: forming a plurality of the layered electrodes4respectively on the layered active metal parts3. In this embodiment, the forming of the layered electrodes4includes forming a plurality of the first layered metal parts41respectively on the layered active metal parts3, removing a portion of each of the layered active metal parts3and each of the first layered metal parts41from a respective one of the peripheral surface areas, and forming a plurality of second layered metal parts42respectively on the first layered metal parts41remaining on the top and bottom to-be-plated zones211,221.

The forming of the first layered metal parts41may be conducted by electroless plating. In this embodiment, the forming of the first layered metal parts41is conducted by immersing the substrate2into an electroless-plating cooper solution at a temperature ranging from 50° C. to 55° C. for 2 to 5 minutes.

The partial removal of the first layered metal parts41and the active metal parts3is conducted by laser etching, so that the top and bottom to-be-plated zones211,221are isolated respectively by the top and bottom separating zones212,222from the top and bottom plating-free zones213,223, respectively, and so that the top and bottom separating zones212,222are free of the layered active metal parts3and the first layered metal parts41. In this embodiment, the laser power ranges from 5 to 10 watts with a pulse frequency ranging from 20 to 50 kHz.

In this embodiment, the forming of the second layered metal parts42is conducted by electroplating. By virtue of the top and bottom separating zones212,222, the second layered metal parts42may be merely formed on the layered active metal parts3which are formed on the top and bottom to-be-plated zones211,221and on the interior wall surfaces23.

After the forming of the second layered metal parts42, those of the layered active metal parts3and the first layered metal parts41, which are formed on the top and bottom plating-free zones213,223are removed using, for example, chemical etching techniques.

Step104: disposing the reaction confinement layer5onto the top surface21of the substrate2to confine the reactor space51over the region of the substrate2, where the through holes231and the layered electrodes4are formed (seeFIG. 3). In this embodiment, the reactor space51has an open end that is flush with a longitudinal side of the substrate2. It should be noted that in other embodiments, the reaction confinement layer5and the substrate2may be integrally formed as one piece.

Step105: forming the electrochemical reactive layer6on the top surface21of the substrate2and in the reactor space51to electrically connect the layered electrodes4(seeFIG. 3). In this embodiment, the forming of the electrochemical reactive layer6is conducted by distributing a layer of electrochemical reagents onto the top surface21of the substrate2in the reactor space51to cover the layered electrodes4.

Step106: attaching the cover piece7onto the reaction confinement layer5to cover the electrochemical reactive layer6and the layered electrodes4(seeFIG. 3).

It is worth noting that, in some embodiments, the forming of the layered active metal parts3may be conducted by screen printing. In such embodiments, the screen printing includes applying an active metal solution onto the top and bottom to-be-plated zones211,221and allowing the active metal solution to flow into the through holes231, thereby forming the layered active metal parts3only on the top and bottom to-be-plated zones211,221and on the interior wall surfaces23. Thus, no top and bottom separating zones212,222are needed in such embodiments in accordance with the present invention.

In addition, instead of the screen printing, the layered active metal parts3may be formed using laser direct structuring techniques (developed by LPKF Laser& Electronics, AG), i.e., using laser to activate a layer of metal-ion-containing plastic material formed on the interior wall surfaces23and the top and bottom to-be-plated zones211,221.

A method for producing the layered electrode of the electrochemical biosensor of the second exemplary embodiment according to the present invention is similar to that of the first exemplary embodiment and includes the following steps of, referring toFIG. 7, forming a plurality of the spaced-apart through holes231′ on the insulating substrate2′; forming a plurality of the layered active metal parts3′ respectively on the interior wall surfaces23′ which respectively define the through holes231′; and forming a plurality of the layered electrodes4′ respectively on the layered active metal parts3′. The forming of the layered active metal parts3′ includes roughening the interior wall surfaces23′ by laser, and immersing the substrate2′ into an active metal solution to form the layered active metal parts3′. The forming of the layered electrodes4′ includes forming a plurality of the first layered metal parts41′ onto the layered active metal parts3′ by electroless plating, removing the first layered metal parts41′ and the layered active metal parts3′ on the top and bottom surfaces21′,22′, and forming a plurality of second layered metal parts42′ onto the remaining first layered metal parts41′ (i.e., those on the interior wall surfaces23′) by electroplating, so as to obtain the layered electrodes4′.

To sum up, by virtue of the electrically-conductive vias, the electrical output signal resulting from the electrochemical reaction between the analyte in the sample liquid and the electrochemical reactive layer6can be transmitted to the coupling portion of the external measuring device. As such, the production cost for the electrochemical biosensor of the present invention can be effectively lowered, and attenuation and interference of the electrical output signal can also be reduced. Moreover, the method for producing the electrochemical biosensor according to the present invention may assure relatively stable bonding between the layered electrodes4/4′/4″ and the substrate2/2′/2″, as well as to achieve a relatively simple manufacturing process.