WO2008035258A2

WO2008035258A2 - Electrochemical energy source and electronic device suitable for bioimplantation

Info

Publication number: WO2008035258A2
Application number: PCT/IB2007/053710
Authority: WO
Inventors: Remco H. W. Pijnenburg; Petrus H. L. Notten; Rogier A. H. Niessen; Johannes H. G. Op Het Veld
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2006-09-20
Filing date: 2007-09-14
Publication date: 2008-03-27
Also published as: CN101517803A; RU2009114713A; WO2008035258A3; JP2010504609A; EP2067205A2

Abstract

The invention relates to an electrochemical energy source comprising a rechargeable battery and a biofuel cell, suitable for bioimplantation. The invention also relates to an electronic device suitable for bioimplantation, said device comprising at least one electrochemical energy source according to invention, and at least one electronic component electrically connected to said electrochemical energy source according to the invention.

Description

Electrochemical energy source and electronic device suitable for bioimplantation

FIELD OF THE INVENTION

The invention relates to an electrochemical energy source suitable for bioimplantation. The invention also relates to an electronic device suitable for bioimplantation, said device comprising at least one electrochemical energy source according to invention, and at least one electronic component electrically connected to said electrochemical energy source.

BACKGROUND OF THE INVENTION

During the twentieth century, energy consumption increased dramatically and an unbalanced energy management exists. While there is no sign that this growth in demand will abate (particularly amongst the developing nations), there is now an awareness of the transience of non-renewable resources and the irreversible damage caused to the environment. In addition, there is a tend towards the miniaturization and portability of computing and communications devices. These energy-demanding applications require small, light power sources that are able to sustain operation over long periods of time, particularly in remote locations such as space and exploration. Furthermore, advances in medical science are leading to an increasing number of implantable electrically-operated devices (e.g. pacemakers). These items need power supplies that will operate for extremely long durations as maintenance would necessitate surgery. Ideally, implantable devices would take advantage of the natural fuel substances found in the body, thus would continue to draw power as long as the human or animal lives. Biofuel cells potentially seems to offer a solution to overcome these problems partially. By implanting a biofuel cell into a living human or animal body, the biofuel cell will withdraw readily available bio fuels, such as e.g. glucose from the blood stream, from renewable sources and will convert them into benign by-products with the generation of electricity. Since a biofuel cell uses concentrated renewable sources of chemical energy, a biofuel cell commonly has a relatively high energy density and a relatively long lifetime, as a result of which a biofuel cell can be made relatively small and light, and are hence ideally suitable to be implanted in a living human or animal body. Although the known implantable biofuel cell has multiple substantial advantages, the application of the known biofuel cell also has several drawbacks. A major drawback of the known miniaturized biofuel cells is that it is often not able to deliver the (peak) power needed for powering an electronic device coupled to the biofuel cell. Due to the relatively small power output of the known biofuel cell, commonly in the order of magnitude of microwatt to milliwatt, the number of current applications is limited.

It is an object of the invention to provide an improved implantable electrochemical energy source with which an improved power output can be achieved.

SUMMARY OF THE INVENTION The object can be achieved by providing an electrochemical energy source according to the invention, comprising a substrate, and at least one battery stack deposited onto said substrate, the battery stack comprising: a first battery electrode, a second battery electrode, and an intermediate solid-state electrolyte separating the first battery electrode and the second battery electrode; and at least one biofuel cell deposited onto said substrate, the biofuel cell comprising: a biofuel cell anode, and a biofuel cell cathode, said biofuel cell anode and said biofuel cell cathode being separated by a bio fuel/electrolyte chamber for receiving an externally supplied bio fuel/electrolyte. The electrochemical energy source can be considered as a miniaturized bioimplantable hybrid energy source, in which chemical energy is converted into electrical energy with use of the biofuel cell, which electrical energy is subsequently stored in the rechargeable battery stack being able to deliver the needed peak power. Both the battery stack and the biofuel cell are deposited integrally onto the same supporting substrate, as a result of which design of the integral electrochemical energy source according to the invention can commonly easily be optimized. Since the power density of an all- so lid- state battery stack is relatively high, a relatively small battery stack will commonly already be suitable to fulfill the power requirements. Since the battery stack comprises a solid-state electrolyte, leaking of the electrolyte (which will often occur in case of application of a liquid- state electrolyte) can be eliminated. Furthermore, by applying a solid-state electrolyte within the battery stack degradation of the battery stack can be counteracted, since the degradation will commonly be a result of parasitic reactions between reactants and a liquid-state electrolyte. The bio fuel/electrolyte chamber of the biofuel cell is adapted for flowthrough of body fluids, as a result of which the content of the bio fuel/electrolyte will be renewed (freshened) continuously. Consequently, a substantially inexhaustible reservoir of biofuel and electrolyte will be available for the biofuel cell to allow a continuous generation of electrical energy, and hence a permanent storage of electrical energy into the battery stack. The energy for the bio fuel cell may be supplied by glucose, acting as bio fuel, and oxygen, acting as oxidant, both of these compounds are abundant in body fluids. The electrolyte will be formed by other parts of the body fluid, such as e.g. blood plasma. It is noted, however, bio fuel cells can operate on a wide variety of (other) available fuels such as ethanol, or even waste materials. Furthermore, the application of the bio fuel cell can lead to the elimination of the Proton Exchange Membrane (PEM), since due the application of specific (bio)catalysts used, the bio fuel cell anode and the bio fuel cell cathode do not require separation. Optionally, a separate solid-state electrolyte, such as e.g. a PEM, may be deposited between the fuel cell anode and the fuel cell cathode into the biofuel/electrolyte chamber. However, it is expected that the active species will be transported through the (relatively low-resistive) body fluid rather than through the (commonly relatively high-resistive) electrolyte. Therefore, it is preferred to apply a liquid-state electrolyte, and more preferably a body fluid. The electrochemical energy source according to the invention may be used e.g. for powering bioimplantable microdevices, such MicroElectroMechanical Systems (MEMS), and implantable biomedical devices such as cardiac pacemakers, sensors, defibrillators, pain relief stimulators, microscopic wireless communication equipment, et cetera.

The first battery electrode preferably comprises a battery anode, and the second battery electrode preferably comprises a battery cathode. It is common that both a battery anode and a battery cathode are deposited during depositing of the stack onto the substrate. Preferably, at least one battery electrode of the energy source according to the invention is adapted for storage of active species of at least one of following elements: hydrogen (H), lithium (Li), beryllium (Be), magnesium (Mg), aluminium (Al), copper (Cu), silver (Ag), sodium (Na) and potassium (K), or any other suitable element which is assigned to group 1 or group 2 of the periodic table. So, the electrochemical energy source of the energy system according to the invention may be based on various intercalation mechanisms and is therefore suitable to form different kinds of batteries, e.g. Li-ion batteries, NiMH batteries, et cetera. In a preferred embodiment at least one battery electrode, more preferably the battery anode, comprises at least one of the following materials: C, Sn, Ge, Pb, Zn, Bi, Sb, Li, and, preferably doped, Si. A combination of these materials may also be used to form the battery electrode(s). Preferably, n-type or p-type doped Si is used as battery electrode, or a doped Si-related compound, like SiGe or SiGeC. Also other suitable materials may be applied as battery anode, preferably any other suitable element which is assigned to one of groups 12-16 of the periodic table, provided that the material of the battery electrode is adapted for intercalation and storing of the abovementioned reactive species. The aforementioned materials are in particularly suitable to be applied in lithium ion batteries. In case a hydrogen based energy source is applied, the battery anode preferably comprises a hydride forming material, such as ABs-type materials, in particular LaNi₅, and such as magnesium-based alloys, in particular Mg_xTii__x. The battery cathode for a lithium ion based energy source preferably comprises at least one metal-oxide based material, e.g. LiCoO₂, LiNiO₂, LiMnO₂ or a combination of these such as. e.g. Li(NiCoMn)O₂. In case of a hydrogen based energy source, the battery cathode preferably comprises Ni(OH)₂ and/or NiM(OH)₂, wherein M is formed by one or more elements selected from the group of e.g. Cd, Co, or Bi. In a preferred embodiment of the electrochemical energy source according to the invention, at least one of the bio fuel cell anode and the bio fuel cell cathode comprises at least one catalyst, preferably at least one biocatalyst. A catalyst will commonly be required to allow a specific (electro)chemical reaction within or on the fuel cell to generate electrical energy. The catalyst used may be a non-biological compound, such as for example platinum, ruthenium, rhodium, or any other suitable material. However, it is also conceivable for a person skilled in the art to apply selective biocatalysts to allow a desired chemical reaction. In general bio fuel cells based on biocatalysts fall within two distinct categories; utilizing the chemical pathways of living cells (microbial fuel cells), and those employing isolated enzymes. Microbial fuel cells can achieve high efficiency in terms of conversion of chemical energy into electrical energy; however problems associated with this approach include low volumetric catalytic activity of the whole organism and low power densities due to slow mass transport of the fuel across the cell wall. Isolated enzymes are attractive catalysts for fuel cells due to their high catalytic activity and selectivity. The theoretical current able to be generated by an enzymatic catalyst with an activity of 103 U mg-1 is 1.6 amps, a catalytic rate greater than platinum. In a particular preferred embodiment, the at least one of the biofuel cell anode and the biofuel cell cathode comprises a Self- Assembled Monolayer (SAM) onto which the at least one selective (bio)catalyst is deposited. Self-assembled monolayers (SAMs) are surfaces consisting of a single layer of molecules on a substrate. Rather than having to use a technique such as chemical vapor deposition or molecular beam epitaxy to add molecules to a surface (often with poor control over the thickness of the molecular layer), SAMs can be prepared relatively simply and quickly by adding a solution of the desired molecule onto the substrate surface and washing off the excess. Besides the relatively simple and quick deposition process of a SAM, the application of a SAM leads to a minimum use of material used in the electrochemical energy source according to the invention, which will be in favor of a compact dimensioning of the energy source. Moreover, a SAM is commonly ideally suitable for adhering (anchoring) a (bio)catalyst to the substrate in a durable manner.

Preferably, the bio fuel cell anode and the bio fuel cell cathode each comprise a bio fuel cell current collector. It is also preferred that the first battery electrode and the second battery electrode each comprise a battery current collector. By means of the current collectors the bio fuel cell and the battery stack are commonly mutually connected. Commonly, the current collectors of the bio fuel cell and the battery stack respectively will be mutually connected via one or more electronic components to be able to control the transfer of electrical energy from the bio fuel cell to the battery stack. Preferably, the at least one current collector is made of at least one of the following materials: Al, Ni, Pt, Au, Ag, Cu, Ta, Ti, TaN, and TiN. Other kinds of current collectors, such as, preferably doped, semiconductor materials such as e.g. Si, GaAs, InP may also be applied to act as current collector. The electron-conductive barrier layer, being deposited between the battery anode of the battery stack and the substrate, may be used to function as a battery current collector for the battery anode.

In a preferred embodiment the battery stack and the bio fuel cell are deposited on different sides of the substrate to achieve a physical separation of the battery stack and the bio fuel cell by means of the substrate. The deposition of the battery stack and the bio fuel cell on different sides (or spaced apart on the same side) of the substrate may facilitate the deposition process of at least one of the battery stack and the bio fuel cell. In an alternative preferred embodiment, the bio fuel cell and the battery stack are mutually stacked on top of each other, wherein the bio fuel cell may be stacked on top of the battery stack or vice versa. According to this embodiment, the application of an electrically insulating separation layer deposited between the fuel cell and the battery stack will commonly be required to prevent short-circuiting of both power sources. More preferably, the separation layer is also applied to chemically separate both power sources.

As mentioned afore the battery stack is separated from the substrate by means of a diffusion barrier layer. To counteract short-circuiting of the biofuel cell, the substrate is preferably provided with at least one electrically insulating layer separating the substrate and the biofuel cell. This electrically insulating layer is preferably made of an oxide, more preferably of hafnium oxide, silicon oxide, and/or zirconium oxide.

The electrochemical energy source preferably comprises a protective packaging covering the battery stack and/or the biofuel cell at least partially. The protective packaging is primarily adapted to protect the battery stack and/or the biofuel cell. In case the battery stack is shielded by the protective packaging, said packaging will preferably further be adapted to preserve active species within the stack and/or may be adapted to prevent atmospheric compounds, such as oxygen en nitrogen, surrounding the packaging to enter the stack, in order to protect the stack to secure a long-term performance of the electrochemical energy source according to the invention. The expression atmosphere must be considered in broad sense in this context, and can be interpreted both as the earth's (gaseous) atmosphere and as the local atmosphere within a (living) body. In a particular preferred embodiment the biofuel cell is substantially covered by the protective packaging, wherein the protective packaging is provided with at least one inlet and at least one outlet for the bio fuel/electrolyte. In this manner the biofuel cell, and in particular the fuel cell anode and the fuel cell cathode, can be protected from the atmosphere surrounding the biofuel cell. Preferably, at least a part of the protective packaging is made of an electrically insulating material to counteract short- circuiting of the electrochemical energy source via the protective packaging. Preferably, the electrochemical energy source comprises at least one barrier layer being deposited between the substrate and the battery stack, which barrier layer is adapted to at least substantially preclude diffusion of active species of the battery stack into said substrate. The barrier layer is preferably made of an electron-conductive material. The barrier layer is preferably at least substantially made of at least one of the following compounds: tantalum, tantalum nitride, titanium, and titanium nitride. The material of the barrier layer is however not limited to these compounds. These compounds have as common property a relatively dense structure which is impermeable for the intercalating species, among which lithium (ions).

In a preferred embodiment the substrate(s) is/are made of at least one of the following materials: C, Si, Sn, Ti, Ge, Al, Cu, Ta, and Pb. A combination of these materials may also be used to form the substrate(s). Preferably, n-type or p-type doped Si or Ge is used as substrate, or a doped Si-related and/or Ge-related compound, like SiGe or SiGeC. A surface of the substrate onto which the stack is deposited may be either substantially flat to obtain a substantially planar stack or may be patterned (by curving the substrate and/or providing the substrate with trenches, holes and/or pillars) to obtain a threedimensional oriented battery stack and/or biofuel cell. Advantage of the application of a threedimensional oriented stack is the increase of the contact surface per volume between both battery electrodes and the solid-state electrolyte of the battery stack and/or between both fuelcell electrodes and the bio fuel/electrolyte contained by the bio fuel/electrolyte chamber of the fuel cell. Commonly, this increase of the contact surface(s) between the components of the energy source according to the invention leads to an improved rate capability of the energy source, and hence a better battery performance (due to an optimal utilization of the contact surface area of the layers of the energy source). In this way the power density and energy density (footprint/cm²) in the energy source may be maximized and thus optimized. Preferably, at least one patterned surface of the substrate is provided with multiple cavities, wherein at least a part of the battery stack and/or at least a part of the bio fuel cell is deposited into said cavities. The nature, shape, and dimensioning of the pattern may be arbitrary, though is preferably regularly, and more preferably, formed by pillars, trenches, slits, or holes, which can be applied in a relatively accurate manner. In this manner the increased performance of the electrochemical energy source can also be predetermined in a relatively accurate manner.

The invention also relates to an bioimplantable electronic device provided with at least one electrochemical energy source according to the invention, and at least one electronic component connected to said electrochemical energy source. The miniaturized electronic device may be formed e.g. by MicroElectroMechanical Systems (MEMS), cardiac pacemakers, sensors, defϊbrilators, pain relief stimulators, and microscopic communication equipment. It will be clear that this enumaration may not be considered as being limitative. The at least one electronic component is preferably at least partially embedded in the substrate of the electrochemical energy source. In this manner a System in Package (Sip) may be realized. In a SiP one or multiple electronic components and/or devices, such as integrated circuits (ICs), actuators, sensors, receivers, transmitters, et cetera, are embedded at least partially in the substrate of the electrochemical energy source according to the invention. The at least one electronic component is preferably chosen from the group consisting of: sensing means, pain relief stimulating means, (wireless) communication means, and actuating means. It is also possible to add one or more capacitors too boost power output when needed.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is illustrated by way of the following non- limitative examples, wherein: Figure 1 shows a schematic cross section of a first embodiment of an electrochemical energy source according to the invention,

Figure 2 shows a schematic cross section of a second embodiment of an electrochemical energy source according to the invention, Figure 3 shows a perspective view of a third embodiment of an electrochemical energy source according to the invention,

Figure 4 shows a perspective view of a fourth embodiment of an electrochemical energy source according to the invention, and Figure 5 shows a schematic view of a fifth embodiment of an electrochemical energy source according to the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Figure 1 shows a schematic cross section of a first embodiment of a monolithic bioimplantable electrochemical energy source 1 according to the invention. The miniaturized energy source 1 comprises a lithium ion battery stack 2 of a battery anode 3, a solid-state electrolyte 4, and a battery cathode 5, which battery stack 2 is deposited onto a conductive substrate 6 in which one or more electronic components 7 are embedded. In this example the substrate 6 is made of doped silicon, while the battery anode 3 is made of amorphous silicon (a-Si). The cathode 5 is made Of LiCoO₂, and the solid-state electrolyte is made of LiPON. Between the battery stack 2 and the substrate 6 a lithium barrier layer 8 is deposited onto the substrate 6. In this example, the lithium diffusion barrier layer 8 is made of tantalum. The conductive tantalum layer 8 acts as a chemical barrier, since this layer counteracts diffusion of lithium ions (or other active species) initially contained by the battery stack 2 into the substrate 6. In case lithium ions would leave the battery stack 2 and would enter the substrate 6 the performance of the stack 2 would be affected. Moreover, this diffusion would seriously affect the electronic component(s) 7 embedded within the substrate 6. In this example, the lithium diffusion barrier layer 8 also acts as a battery current collector for the battery anode 3 in the electrochemical energy source 1. The energy source 1 further comprises an additional battery current collector 9 made of aluminium which is deposited on top of the battery stack 2, and in particularly on top of the battery cathode 5. The implantable energy source 1 also comprises a fuel cell 10 deposited onto the substrate 6. The fuel cell 10 comprises a fuel cell anode 11 provided with a anodic catalytic layer 12, and a fuel cell cathode 13 provided with a cathodic catalytic layer 14, wherein the space between the fuel cell anode 11 and the fuel cell cathode 13 forms a fuel cell/electrolyte chamber 15. The fuel cell/electrolyte chamber 15 is adapted for receiving a body fluid 16, such as blood. The catalytic layers 12, 14 are adapted for converting specific reactants into specific reactions products, and thereby converting chemical energy into electrical energy. In this illustrative embodiment the fuel cell 10 represents an oxyglucose cell, which could rely upon an electrochemical process in which glucose is oxidized at the fuel cell anode 11 and molecular oxygen is reduced at the fuel cell cathode 13 during operation according to the following equations:

C:.,HκO.i ÷ GM::O ^■- GCO; ■ 2 UT ^■> Zh- kme^.) 6O - * V2H €i _* Ϊ4i.' -> 24OH U-.i hncM

The fuel cell 10 and the substrate 6 are separating by an electrically insulating separation layer 17, preferably made of an oxide to prevent short-circuiting of the fuel cell 10. Both the fuel cell anode 11 and the fuel cell cathode 13 act as a fuel cell current collector. All current collectors 8, 9, 11, 13 are coupled to the one or more electronic components 7 embedded in the substrate 6 (schematically shown). In figure 1 it is clearly shown that the battery stack 2 and the fuel cell 10 are deposited onto opposite, and hence thus different, sides of the substrate 6. During operation of the implantable electrochemical energy source 1 according to the invention chemical energy stored within the body fluid 16 is converted by the fuel cell 10 into electrical energy and is subsequently stored, via the electronic component(s) 7, within the battery stack 2 to able to deliver a relatively high (peak) power output. The electrochemical energy source 1 may be implanted either in human or animal bodies. Commonly, the energy source 1 is implanted in a living body to monitor or to stimulate certain biological processes. However, it may also be conceivable to implant the electrochemical energy source 1 in a deceased body. Figure 2 shows a schematic cross section of a second embodiment of an electrochemical energy source 18 according to the invention. The electrochemical energy source 18 shown in figure 2 is substantially similar to the electrochemical source 1 according to figure 1. The implantable energy source 18 comprises a thin- film battery stack 19 of a battery anode 20, a solid-state electrolyte 21, and a battery cathode 22, which battery stack 19 is deposited onto a conductive substrate 23 in which one or more electronic components 24 are embedded. Between the battery stack 19 and the substrate 23 a barrier layer 25 for active species is deposited onto the substrate 6. In this example, the diffusion barrier layer 25 also acts as a battery current collector for the battery anode 20 in the electrochemical energy source 18. An additional battery current collector 26 is deposited on top of the battery stack 19, and in particularly on top of the battery cathode 22. The implantable energy source 18 further comprises a fuel cell 27 deposited, and in fact stacked, on top of the battery stack 23. The fuel cell 27 and the battery stack 23 are mutually separated by means of a separation layer 28. The fuel cell 27 comprises a fuel cell anode 29 provided with a anodic catalytic layer 30, and a fuel cell cathode 31 provided with a cathodic catalytic layer 32, wherein the space between the fuel cell anode 29 and the fuel cell cathode 31 forms a fuel cell/electrolyte chamber 33 for receiving a body fluid 34. Figure 3 shows a perspective view of a third embodiment of an electrochemical energy source 35 according to the invention. In contrary to the electrochemical energy source 1, 18 as shown in figure 1 and figure 2 respectively, the electrochemical source 35 shown in figure 3 comprises a one-sided patterned substrate 36, wherein a battery stack 37 is deposited onto the patterned side 36a of the substrate 36, and wherein a fuel cell 38 is deposited onto a substantially planar side 36b of the substrate 36. The battery stack 37 and the substrate 36 are mutually separated by a barrier layer 39 for active species. The barrier layers 39 also serves as an anode current collector in this example. The battery stack 37 comprises an anode 40, a solid-state electrolyte 41, and a cathode 42. The cathode 42 is connected to a cathode current collector 43. The patterned side 36a of the substrate 36 comprises multiple slits 44 in which the battery stack 37 is deposited in order to increase the contact surface between (and within) said layers 40, 41, 42, and hence the performance of the battery stack 37. The fuel cell 38 comprises a catalytically active fuel cell anode 45 and a catalytically active fuel cell cathode 46 positioned at a distance from the fuel cell anode 45. The space between the fuel cell anode 45 and the fuel cell cathode 46 serves as a receiving chamber for receiving body fluid (not shown) acting both as bio fuel and as electrolyte. Advantages of the application of an implantable hybrid electrochemical energy source have already elucidated above in a comprehensive manner.

Figure 4 shows a perspective view of a fourth embodiment of a bioimplantable electrochemical energy source 47 according to the invention. The energy source 47 comprises a double-sided patterned substrate 48. A first patterned side 48a of the substrate 48 is covered by a barrier layer 49 to block active species, and a battery stack 50 (schematically shown) successively. A second patterned side 48b of the substrate 48 is covered by an electrically insulating layer 51, and a fuel cell 52 successively. The battery stack 50 and the fuel cell 52 are constructively preferably similar to the battery stack 2 respectively the fuel cell 10 as shown in figure 1. By applying both the battery stack 50 and the fuel cell 52 are deposited onto a patterned side 48a, 48b of the substrate, the performance of both the battery stack 50 and the fuel cell 52 can be improved significantly.

Figure 5 shows a schematic view of a fifth embodiment of an electrochemical energy 53 source according to the invention. The electrochemical energy source 53 is suitable for bioimplantation, and comprises a substrate 54 on top of which electronic components 55 are applied to form an electronic device. Such a construction is also referred to as a System in Package (SiP). The electronic device 55 is powered by the electrochemical energy source 53 further comprising a microbattery stack 56, and a fuel cell 57 connected indirectly to the microbattery stack 56. Both the microbattery stack 56 and the fuel cell 57 are deposited onto the substrate 54, and are shielded by a protective packaging 58. The protective packaging 58 is preferably made of at least one insulating material, and may comprise a laminate of alternating layers, each layer of said alternating layers being made of at least one material chosen from the following group of materials: metals, polymers, and siliceous compounds. An example of alternating layers which may be applied in the laminate of the protective packaging 58 is a so-called NONON-layer configuration consisting of silicon nitride (N) and of silica (O) layers deposited on top of each other in an alternating manner. The laminate will commonly further also comprise a metal layer, which is commonly substantially impermeable both for atmospheric compounds and for migrating active species contained by the microbattery stack 56. The protective packaging 58 is provided with an inlet 59 and an outlet 60 to allow a body fluid - acting both as a biofuel and as an electrolyte - to flow continuously through the fuel cell 57 for fueling said fuel cell 57.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb "comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

CLAIMS:

1. Electrochemical energy source suitable for bioimplantation, comprising: a substrate, and at least one battery stack deposited onto said substrate, the battery stack comprising: - a first battery electrode,

- a second battery electrode, and

- an intermediate solid-state electrolyte separating the first battery electrode and the second battery electrode; and at least one bio fuel cell deposited onto said substrate, the bio fuel cell comprising:

- a biofuel cell anode,

- a biofuel cell cathode, and said biofuel cell anode and said biofuel cell cathode being separated by a bio fuel/electrolyte chamber for receiving an externally supplied bio fuel/electrolyte.

2. Electrochemical energy source according to claim 1, characterized in that the first battery electrode comprises a battery anode, and/or that the second battery electrode comprises a battery cathode.

3. Electrochemical energy source according to claim 2, characterized in that both the battery anode and the battery cathode are adapted for storage of active species of at least one of following elements: H, Li, Be, Mg, Cu, Ag, Na and K.

4. Electrochemical energy source according to claim 2 or 3, characterized in that at least one of the battery anode and the battery cathode is made of at least one of the following materials: C, Sn, Ge, Pb, Zn, Bi, Li, Sb, and, preferably doped, Si.

5. Electrochemical energy source according to one of the foregoing claims, characterized in that at least one of the bio fuel cell anode and the bio fuel cell cathode comprises at least one catalyst, preferably at least one biocatalyst.

6. Electrochemical energy source according to claim 7, characterized in that the at least one of the bio fuel cell anode and the bio fuel cell cathode comprises a self-assembled monolayer (SAM) onto which the at least one catalyst is deposited.

7. Electrochemical energy source according to one of the foregoing claims, characterized in that the bio fuel cell anode and the bio fuel cell cathode each comprises a bio fuel cell current collector.

8. Electrochemical energy source according to one of the foregoing claims, characterized in that the first battery electrode and the second battery electrode each comprises a battery current collector.

9. Electrochemical energy source according to one claim 7 or 8, characterized in that the at least one current collector is made of at least one of the following materials: Al, Ni, Pt, Au, Ag, Cu, Ta, Ti, TaN, and TiN.

10. Electrochemical energy source according to one of the foregoing claims, characterized in that the battery stack and the bio fuel cell are deposited on different sides of the substrate.

11. Electrochemical energy source according to one of the foregoing claims, characterized in that the bio fuel cell and the battery stack are mutually stacked on top of each other.

12. Electrochemical energy source according to one of the foregoing claims, characterized in that the substrate is provided with at least one electrically insulating layer separating the substrate and the biofuel cell.

13. Electrochemical energy source according to one of the foregoing claims, characterized in that the electrochemical energy source comprises a protective packaging covering the battery stack and/or the bio fuel cell at least partially.

14. Electrochemical energy source according to claim 13, characterized in that the bio fuel cell is substantially covered by the protective packaging, wherein the protective packaging is provided with at least one inlet and at least one outlet for the biofuel/electrolyte.

15. Electrochemical energy source according to claim 13 or 14, characterized in that at least a part of the protective packaging is made of an electrically insulating material.

16. Electrochemical energy source according to one of the foregoing claims, characterized in that the electrochemical energy source further comprises at least one electron-conductive barrier layer being deposited between the substrate and the battery stack, which barrier layer is adapted to at least substantially preclude diffusion of active species of the battery stack into said substrate.

17. Electrochemical energy source according to one of the foregoing claims, characterized in that the at least one barrier layer is made of at least one of the following materials: Ta, TaN, Ti, and TiN.

18. Electrochemical energy source according to one of the foregoing claims, characterized in that the substrate is at least partially made of at least one material chosen from the group consisting of: C, Si, Sn, Ti, Ge, Al, Cu, Ta, and Pb.

19. Electrochemical energy source according to one of the foregoing claims, characterized in that the substrate is provided with at least one patterned surface onto which the battery stack and/or the bio fuel cell is deposited.

20. Electrochemical energy source according to claim 19, characterized in that the at least one patterned surface of the substrate is provided with multiple cavities, wherein at least a part of the battery stack and/or at least a part of the bio fuel cell is deposited into said cavities.

21. Electrochemical energy source according to claim, characterized in that at least a part of the cavities form pillars, trenches, slits, or holes.

22. Electronic device suitable for bioimplantation, comprising at least one electrochemical energy source according to one of the claims 1-21, and at least electronic component connected to said electrochemical energy source.

23. Electronic device according to claim 22, characterized in that the at least one electronic component is at least partially embedded in the substrate of the electrochemical energy source.

24. Electronic device according to claim 22 or 23, characterized in that the at least one electronic component is chosen from the group consisting of: sensing means, pain relief stimulating means, communication means, and actuating means.

25. Electronic device according to one of claims 22-24, characterized in that the electronic device and the electrochemical energy source form a System in Package (SiP).