Energy generation module comprising pressure or temperature transducer, set of modules connected in series or in parallel, and use thereof

Abstract

The object of the invention is an energy generation module comprising a pressure or temperature transducer, characterized in that it comprises a hermetic chamber (5) with a bottom and walls, wherein the walls of the chamber (5) are constituted by a substrate silicon layer (3) on which a buried oxide layer (2) is disposed, and the bottom constitutes a hermetic sealing lid (4) on which a fluid layer of a substance that undergo a phase transition during operation of the module (12) is present, furthermore the cavity is closed from above by a bistable membrane (1) that is susceptible to deformation due to the pressure difference between the inside and the outside of the chamber (5), on the membrane a piezoelectric layer (7) is disposed, on which a metal electrode (6) is disposed, simultaneously, a first electrical contact (9) is disposed on the metal electrode (6), while a second electrical contact (10) is disposed on the silicon membrane (1), simultaneously, inside the chamber (5), the fluid substance is present, part of which undergoes the liquid-gas phase transition during operation of the module (11). The object of the invention is also a set of modules according to claims 1 and 2, connected in parallel or in series in a modules matrix. The object of the invention is also the use of the set of modules according to the invention for powering loT network nodes.

Description

[0001] Energy generation module comprising pressure or temperature transducer, set of modules connected in series or in parallel, and use thereof

[0002] The invention relates to an energy generation module comprising a transducer susceptible to pressure or temperature fluctuations, as well as a set of modules connected in series or in parallel and the use thereof for powering loT network nodes.

[0003] Various microtransducers comprising piezoelectric materials for converting energy in one form into useful energy in another form are disclosed in W02002084754. In one embodiment, a piezoelectric microtransducer can function either as a thermal microengine, converting thermal energy into electrical energy, or as a thermal micropump, consuming electrical energy to transfer thermal energy from a low-temperature heat source to a high- temperature radiator. In another embodiment, the piezoelectric microtransducer is used to convert the kinetic energy of an oscillating or vibrating body, on which the microtransducer is disposed, into useful electrical energy. The piezoelectric microtransducer is also used to extract work from a pressurized fluid stream. A combustion microengine and a Rankine- cycle thermal microengine have also been disclosed, wherein a single fluid acts as the working fluid and the fuel.

[0004] JP2009165931 discloses a method for manufacturing a capacitive ultrasonic transducer, which improves mechanical properties of the membrane and the performance while suppressing the increase in parasitic capacitance. The manufacturing method for the capacitive ultrasonic transducer includes the following processes: preparing a Silicon On Insulator (SOI) substrate having an active layer on a carrier substrate separated by an insulating layer; forming a through-hole in the active layer or the carrier substrate; forming a cavity by introducing a fluid for etching an insulating layer from the through-hole formed in the active layer or the carrier substrate and etching the insulating layer; forming an insulating film inside the cavity created by etching the insulating layer; and sealing the through-hole after forming the insulating film inside the cavity.

[0005] The solution described in application EP22461520 presents an energy generation module that can covert pressure changes into electrical energy. It comprises a pressure transducer with a cavity and a membrane that can deform due to the pressure difference between the fluid inside and outside the cavity. A piezoelectric element that can convert the membrane's motion energy into electrical energy is also connected to the pressure transducer. The cavity is sealed, and the membrane is selected so as to respond to daily changes in atmospheric pressure. The piezoelectric element consists of multiple elongated elements arranged in space, capable of engaging with the pressure transducer. When the pressure change exceeds a predetermined value, the release of the energy occurs.

[0006] Numerous piezoelectric materials and structures, as well as appropriate energy harvesting methods, have been disclosed in Safaei, M. et al., "A review of energy harvesting using piezoelectric materials: state-of-the-art a decade later (2008-2018)." Smart Materials and Structures 28 (2019): 113001. It is emphasized that environmental energy is generally available in the form of solar energy, thermal energy, electromagnetic waves, and vibrational energy. Among these energy sources, vibrational energy is consistently present in nature and human-made structures. Various materials and transduction mechanisms are capable of converting vibrational energy into useful electrical energy, such as piezoelectric, electromagnetic, and electrostatic generators. Energy harvesting from vibrations using piezoelectric transducers has been extensively studied due to their inherent simplicity, considerable power density, and simple design as compared to electrostatic or electromagnetic transducers.

[0007] The possibility of harvesting energy from atmospheric fluctuations was discussed in Gibran Ali, John Wagner, David Moline, Todd Schweisinger, Energy harvesting from atmospheric variations - Theory and test, Renewable Energy, Volume 74, 2015, Pages 528- 535, ISSN0960-1481, h ttp s 7 / doi . org / 10. 1016 / i .ren en e .2014.08.033. The approach is based on daily temperature fluctuations, with an assumed change of 23 °C. Such high fluctuations are not always available. Atmospheric pressure also exhibits certain daily fluctuations, which depend on the geographical region - Blancq, Frank. (2011). Daily variability of pressure: The atmospheric tide, Weather, Volume 66, Pages 306-307, 2011, ISSN1477-8696,

[0008] Commonly recognized and utilized types of environmental energy, such as vibrational, solar, or wind energy, are not always available in all locations and at all times. Consequently, the potential of energy derived from daily atmospheric pressure changes has been noted. Unfortunately, while this type of energy is commonly available, its quantity is relatively low, and the harvesting and effective utilization of this energy source is a challenge. To design an energy-generating module based on this source, it is essential to adapt it for large-scale component manufacturing and to address difficulties associated with the low levels of this type of energy.

[0009] The potential of energy resulting from daily atmospheric pressure changes is highly interesting. Unfortunately, although this form of energy is widely available, its quantity is relatively low. Therefore, harvesting and effective use of this energy source represents a great challenge. An equally important technical problem is the construction of a module capable of connecting with each other, thereby enabling efficient transformation of energy arising from atmospheric pressure or temperature changes.

[0010] Although the energy supplied by the module according to the invention is not sufficient for many traditional applications, it has been found to be adequate for numerous Internet of Things (loT) applications, which require small doses of energy delivered in peaks concentrated within narrow time intervals, as observed in: Maciej Haras, Thomas Skotnicki, "Thermoelectricity for loT - A review," Nano Energy, Volume 54, Pages 461-476, 2018, ISSN 2211-2855, https: / / doi.org / IO. 1016 / j .nanoen.2018. 10.013.

[0011] The aim of the invention was to develop a module for energy generation as a result of pressure or temperature changes, which could find application for many uses of the Internet of Things (loT) applications requiring small doses of energy delivered in peaks concentrated within narrow time intervals.

[0012] An object of the invention is an energy generation module comprising a pressure or temperature transducer, characterised in that it comprises a hermetic chamber comprising a bottom and walls, wherein the walls of the chamber are constituted by a substrate silicon layer on which a buried oxide layer is disposed, and the bottom constitutes a hermetic sealing lid on which a fluid substance is present, part of which undergoes liquid-gas phase transition during operation of the module, furthermore, the cavity is closed from above by a bistable membrane that is susceptible to deformation due to the pressure difference between the inside and the outside of the chamber, on the membrane a piezoelectric layer is disposed, on which a metal electrode is disposed, simultaneously a first electrical contact is disposed on the metal electrode, while a second electrical contact is disposed on the silicon membrane, simultaneously, inside the chamber the fluid substance is present as well as saturated vapour of said substance which underwent phase transition during operation of the module.

[0013] Preferably, the substance which undergoes phase transition during operation of the module is a compound selected from the group including chloroethane, isopropanol, ethanol, acetone, methanol, diethyl ether, chloroform, isopropanol, ethylene, gasoline, freons, liquid nitrogen.

[0014] Preferably, the membrane (1) is a silica layer of an n-type or a p-type, strongly doped at a level of at least 1019atoms per cm3.

[0015] Preferably, the silicon membrane is made in the SOI technology.

[0016] Preferably, the SOI layer is coated with a thin metal layer before application of the piezoelectric layer thereon. Preferably, the membrane is made of a metal selected from the group including aluminium, titanium, tungsten, copper, or another highly conductive material selected from the group including TiN (titanium nitride), TaN (tantalum nitride).

[0017] Preferably, the piezoelectric layer is made of a ZnO, PZT (lead zirconate titanate), PVDF (polyvinylidene fluoride) and its copolymers, barium titanate (BaTiOs), lithium niobate (LiNbCh), quartz silicate, and aluminium oxide.

[0018] Alternatively, the membrane (1) is made of metal.

[0019] Preferably, the metal membrane is made in the process of metal sputtering (sputtering) or the ALD process (atomic layer deposition) on a convex dome obtained in the resist flossing process (resist flossing) that is known and used during manufacturing of lenses used in integrated photo cameras for smartphones.

[0020] An object of the invention is also a set of modules connected in parallel or in series in a modules matrix.

[0021] The object of the invention in an example embodiment is shown in the drawing, where: Fig. 1 shows schematically the module in the variant with increased pressure inside the chamber;

[0022] Fig. 2 shows schematically the module in the variant with decreased pressure inside the chamber;

[0023] Figs. 3-5 show results of COMSOL simulations, which is a specialized software used for simulating physical phenomena and widely applied in various fields, including mechanical, electrical, biomedical, power engineering, and materials science, because it allows modelling complex engineering and scientific systems, enabling a better understanding of their operation and design optimization;

[0024] Fig. 6 shows a device - a cell according to the invention in cross-sectional view;

[0025] Fig. 7 shows a device - a cell according to the invention in top view;

[0026] Figs. 8 and 9 show embodiments, in top view, of matrixes of units connected in parallel (Fig.

[0027] 8), and unconnected, i.e., each cell isolated from the others (Fig. 9);

[0028] Fig. 10 shows the SOI membrane bulged upwards, which is under tensile strain;

[0029] Fig. 11 shows an embodiment of the metal membrane made using a technique called “resist flossing” at a scale of 100 pm;

[0030] Fig. 12 shows a possible method for making of a bistable membrane using the LOCOS (Local Oxidation of Silicon) technology, which is used before applying the STI (Shallow Trench Isolation) technology for lateral isolation in the production process of VLSI components. Demonstrator Module

[0031] During the work on solving the technical problem, a demonstrator module was made, i.e., a tool to showcase technical or conceptual capabilities without the full functionality of the final product and implemented using discrete components on the macro scale. In this macro-demonstrator of the invention, a metal box of approximately 4 cm in diameter with a concave lid was used as the chamber. A small amount of water was poured into the box, and the lid was hermetically sealed. On the lid, a piezoelectric strip with two electrodes was glued on, and the electrodes were connected to an oscilloscope. The box was heated on a hot plate until the lid abruptly switched from the concave to the convex state, which generated a distinct voltage signal recorded by the oscilloscope. This experiment demonstrated the feasibility and usefulness of the technical solution.

[0032] The Module realisation

[0033] The process of production of the energy generation module using the SOI (Silicon on Insulator) technology includes the use of advanced LSI (Large Scale of Integration) microelectronic engineering techniques. The process begins with preparation of a monocrystalline silicon (Si) substrate of proper orientation.

[0034] An insulating layer (e.g., silicon dioxide, SiO?) is deposited on the substrate, typically through a thermal oxidation process. Subsequent layers are formed using known techniques “wafer-bonding” and “smart-cut” developed, e.g., by Soitec. The membrane that reacts to the pressure changes is carefully designed and isolated from the active layer. Using successive photolithography and etching steps, the membrane-bounded cavity is formed. The shape of the cavity is tailored to the required geometry and volume. In the next step, a piezoelectric layer, such as a layer of ZnO, is deposited in regions subject to deformation due to the pressure changes, thereafter the cavity is filled with a fluid under suitable pressure, typically derived from a substance (e.g., chloroethane) which is susceptible to phase changes around temperatures and pressures corresponding to room conditions, under the influence of changes in pressure and / or temperature. . Then, the cavity is sealed with the lid, maintaining the fluid under controlled conditions.

[0035] The module undergoes multi-stage testing, including, but not limited to, measurements of membrane deformations in response to pressure changes. The piezoelectric elements and electronic components are disposed in adequate areas of the module. Upon completing all production steps, the module undergoes final testing to confirm compliance with expectations. In the case of positive results, the process moves on to mass production. In the discussed process, the use of the SOI technology allows for precise isolation of layered structures, which is critical for complex microelectronic systems such as the described energy generation module.

[0036] Membrane

[0037] The term "bistable membrane" refers to a membrane structure that has two stable deformation states, which is known as bistability. The bistable membrane has two equivalent and stable deformation states. This means that it can remain in two different states depending on environmental conditions or external stimuli. The bistable membrane can be made in two variants.

[0038] The first variant is a membrane made as a silicon layer using the SOI technology, and as a layer heavily doped to a level of at least 1019atoms / cm3and of n-type or p-type conductivity. The high doping level significantly increases the number of charge carriers (electrons in n-type silicon and holes in p-type silicon), leading to a substantial increase in electrical conductivity, and such silicon membrane can effectively conduct electric current, which is the fundamental function of an electrode.

[0039] The second variant is a membrane made of a metal selected from the group including aluminium, titanium, tungsten, copper, or other well -conducting materials, selected from the group including TiN (titanium nitride) or TaN (tantalum nitride).

[0040] The bistable membrane (1) is made of the resist flossing process (resist flossing), known and employed in the production of lenses for integrated camera modules in smartphones.

[0041] The bistable shape of the membrane (1) is obtained by subjecting the SOI silicon membrane to tensile stress through application thereon of an SiN layer in the form of a cylinder with a diameter smaller than the diameter of the chamber (5), which SiN layer has internal tensile stress resulting from a specific thermal deposition process, which is known in the art.

[0042] Alternatively, the bistable shape of the membrane (1) is obtained via two LOCOS oxidation processes of the SOI silicon membrane, known in the art, one being performed around an edge of the chamber (5) from above, while the other across the entire surface of the membrane from below through the cavity of the chamber (5).

[0043] Membrane Deformation

[0044] Membrane deformation in the context of energy generation can take either the convex or the concave form, depending on the pressure conditions. In the case of convex deformation, the membrane bulges outward from the cavity due to increased internal pressure. This means that the internal pressure is greater than the external pressure, causing the membrane to bulge upward. This process is characteristic of situations where pressure changes lead to increased force exerted by vapour / gas on the internal side of the membrane as compared to the external side of the membrane, as a result of increased internal pressure or decreased external pressure. In the case of concave deformation, the membrane bulges inward into the cavity due to reduced internal pressure. This means that the internal pressure is lower than the external pressure, resulting in the membrane arching inward. This type of deformation occurs when the membrane is subjected to less force excreted by vapour / gas on the internal side of the membrane as compared to the external side, as a result of a decrease in internal pressure or an increase in external pressure. An increase or decrease in external pressure may result from changes in atmospheric pressure, while an increase or decrease in internal pressure may arise from temperature changes that cause significant variations in the saturated vapour pressure of the substance trapped inside the chamber.

[0045] Use of the Substance Undergoing Phase Transition During Module Operation

[0046] In the first embodiment, chloroethane was used for the realisation of the system. The use of chloroethane (C2H5CI) can be associated with several disadvantages from the health, the environmental as well as the technological perspectives. In high concentrations, chloroethane is considered a toxic substance, although it is harmless in small concentrations. Despite chloroethane having some drawbacks, several potential advantages of using chloroethane can also be identified in this context. Chloroethane is a substance, which upon pressure or temperature changes can undergo phase transitions (from liquid to gaseous state and vice versa) at temperatures near room temperature. Its saturated vapour pressure responds to temperature changes approximately ten times stronger than it is the case for gas / air. This property can be exploited to generate movement of the membrane within the module, translating to energy generation. Chloroethane is relatively easy to procure on the market and can be relatively cost-effective compared to some other chemical substances. This may influence the availability and production costs of the module. Chloroethane is a substance that is generally chemically stable, meaning it retains its properties over extended periods of time. The chemical stability is crucial in terms of durability and reliability of the module. Additionally, chloroethane as a fluid can exhibit good fluidity and flow properties, which is important in the context of evenly filling the cavity and responding to changes in pressure. The pressure within the cavity can be regulated by adjusting the parameters related to the quantity and the properties of chloroethane. This may be important for optimizing the performance of the module. When using chloroethane, there is the necessity for hermetic sealing, that is tight securing against any leakage of the substance to the exterior, which is crucial for this technical solution. Any leaks could result in pressure loss, adversely affecting energy generation efficiency. Moreover, since the module includes electronic components, hermetic sealing is also required to protect them from exposure to it.

[0047] Basic parameters that may be considered in such a module include:

[0048] - pressure changes range - the internal pressure of the module cavity can vary from a few hPa to several hundred hPa in response to changing environmental conditions;

[0049] - temperature changes range - the temperature range in which the phase change of chloroethane occurs depends on its molecular structure (e.g., tri chloroethane, di chloroethane, etc.) and can be from -24°C (chloroethane boiling point) to ambient temperatures at which the module operates;

[0050] - module efficiency depends on several factors, such as the design of the membrane, the type of the piezoelectric element, the control of pressure and temperature, and the coupling with the electrical circuit. It can be expressed as a percentage and depends on how much mechanical energy can be converted into electrical energy.

[0051] Alternatively, instead of chloroethane the following are used:

[0052] - acetone, methanol, diethyl ether, chloroform, isopropanol - their rapid evaporation at low temperatures allows them to be used for detecting pressure changes,

[0053] - ethylene, gasoline, freons - these gases or low boiling point liquids are applicable in pressure transducers,

[0054] - liquid nitrogen, whose extremely low boiling point limits its use in standard pressure transducers, is however highly effective at very low temperatures.

[0055] Description of Construction of the System

[0056] The object of the invention is an energy generation module comprising a pressure transducer, which comprises a hermetic chamber (5) comprising a bottom and walls, wherein the walls of the chamber (5) are made of a substrate silicon layer (3) on which a buried oxide layer (2) (so-called BOX) is disposed, and the bottom constitutes a hermetic sealing lid (4) on which a layer of fluid chloroethane (12) is present. The hermetic sealing lid (4) is a type of seal that is made of polycarbonate or polyurethane film. A silicon lid can also be made via the wafer-bonding technology (molecular bonding). Alternatively the lid may be a glued glass plate. The thickness of the lid must ensure both sealing and rigidity of the module. Rigidity is important for protecting the device from mechanical damage and maintaining the structural stability of the entire device.

[0057] The hermetic chamber (5) ensures isolation of the internal environment from external factors. This is essential for maintaining control over the internal environment (e.g., cleanliness, moisture-free, stable pressure). The substrate silicon layer (3) serves as the mechanical and electrical base for other components. Silicon is widely used in microelectronics due to its semiconductor properties, making it ideal for integrated circuits and MEMS structures. The buried oxide layer (2) provides electrical and mechanical insulation, which is crucial for protecting the system from external influence and preserving the structural integrity of sensitive electronic components. The lid (4) seals the chamber (5), protecting its contents. It can also serve a structural role by supporting other components of the system.

[0058] The chamber (5) is closed from above by the bistable silicon membrane (1) which is susceptible to deformation due to changes of pressure between the inside and the outside of the chamber (5), on the membrane, the piezoelectric layer (7) is disposed, on which the metal electrode (6) is disposed, simultaneously, the first electrical contact (9) is disposed on the metal electrode (6), and the second electrical contact (10) is disposed on the silicon membrane (1). The metal electrode (6) and the heavily doped SOI layer (1), which serves as the second electrode, enable the conduction of electrical current and are key in the process of generating electrical signals from the piezoelectric layer (7). Optionally, the SOI layer (1) may be coated with a thin metal layer before the piezoelectric layer (7) is applied thereon. This leads to a slight complication of the design but may have a positive effect on the conductivity of the lower electrode beneath the piezoelectric layer, especially if the doping of the SOI layer is insufficient. Note - this option is not illustrated in the figures. The first and the second electrical contacts (9) and (10) allow electrical connection of the system components with external circuits, which is necessary for transferring the generated electrical energy. In this embodiment, the piezoelectric layer (7) is made of ZnO, which exhibits distinct piezoelectric properties, is chemically and thermally stable, which is important for maintaining piezoelectric properties in various environmental and temperature conditions, can be easily integrated with existing microfabrication technologies, which is crucial in the production of miniature piezoelectric devices. Furthermore, it is relatively easy to obtain and inexpensive, making it an attractive choice from a production cost perspective. Apart from ZnO, it is possible to alternatively use

[0059] - PZT (lead zirconate titanate), which has exceptionally strong piezoelectric properties, - PVDF (polyvinylidene fluoride) and its copolymers, which also exhibit piezoelectric properties, as well as flexibility, lightness, and good processing characteristics, particularly in flexible and bendable piezoelectric devices,

[0060] - Barium titanate (BaTiCh), a ceramic material with good piezoelectric properties,

[0061] - Lithium niobate (LiNbCh, quartz silicate, and aluminium oxide, which are characterized by high strength and thermal stability,

[0062] - or other materials known to a person skilled in the art, ensuring an analogous effect in the operation of the module according to the invention.

[0063] Inside the chamber (5), just above the layer of fluid chloroethane (12), there is saturated chloroethane vapour (11). The silicon membrane is designed to be sensitive to pressure and / or temperature changes. When the pressure or temperature inside the chamber (5) or outside of it increases or decreases, the membrane first accumulates elastic energy in the form of internal stress until it finally undergoes a rapid deformation - it deforms inward or outward. This rapid switch of the shape of the membrane is key to the functioning of the entire device. The piezoelectric layer disposed on the silicon membrane reacts to the deformation of the membrane. Piezoelectric materials generate an internal electric field under mechanical deformation, which attracts electrons through the external circuit, thus restoring the electroneutrality of the sample. Therefore, when the membrane (1) deforms due to pressure changes within the chamber (5), the piezoelectric layer (7) converts this deformation into electrical energy. The saturated vapour responds to temperature changes by changing pressure. In a closed system, such as in the described module, an increase in temperature causes a significant increase in vapour pressure (stronger than in the case of a gas or air), while a decrease in temperature leads to its decrease. This property of chloroethane vapour is key for the operation of the technical solution according to the invention.

[0064] The process is cyclical - changes in pressure / temperature in the environment of the module or inside the chamber (5) may be repeated, causing regular deformation and return of the membrane (1) to its original shape, which leads to cyclic generation of electrical energy.

[0065] The silicon membrane (1) is made using the SOI technology, which offers a range of technological benefits, particularly in processes such as bottom-up etching. The SOI technology ensures high precision and control over production processes. By using the insulating layer (oxide) between the silicon layers, it is possible to precisely define the thickness and properties of the silicon membrane (precise shaping of elements). Thanks to the SOI technology, the etching process of the chamber in the substrate silicon can be accurately controlled and stopped at the buried oxide layer (BOX). The buried oxide, being part of the SOI structure, serves as a natural barrier stopping the etching process. This allows achieving precise dimensions and shapes of the silicon structure without the risk of damaging it. The SOI technology enables high precision and reproducibility in the production of components, which is critical in precise applications in advanced microelectronics. Furthermore, the electrical properties of the silicon membrane can be modified by doping. The heavily doped silicon membrane (1) has modified electrical properties, allowing for precise control of electrical conductivity, where the membrane is used to generate electrical signals and functions as the conducting electrode. If the pressure / temperature inside the chamber (5) exceeds the ambient pressure, the membrane (1) deforms into a convex arch, creating a convex dome. If the internal pressure of the chamber (5) is lower than the ambient pressure, the membrane (1) deforms into a concave arch, forming a concave bowl-like shape. As a result, continuous pressure and / or temperature changes translate to movement of the membrane (1). For effective energy harvesting from the piezoelectric signal, a fundamental feature of the membrane is its bistability i.e. the build-up of internal stress within the membrane followed by a sudden switch from the concave to the convex state, or vice versa.

[0066] In an alternative embodiment, the membrane may be made of metal, such as aluminium, titanium, tungsten, copper, or other good conductors, e.g., TiN (titanium nitride), TaN (tantalum nitride), or other materials known to a person skilled in the art, which would ensure an analogous effect in the operation of the module according to the invention.

[0067] The module according to the invention was optimized using COMSOL simulations for three variants of disk size: diameters of 10 cm, 1 cm, and 1 mm. The following description pertains to experiments optimized for different pressure ranges that can occur in various applications.

[0068] Below in the tables the voltage values during the bistable switch for different disk sizes are described.

[0069] The magnitude of arching refers to the shape that arches outward or inward. It is the difference in height between the edge and the central point of the membrane.

[0070] The thickness refers to the sum of thicknesses of all layers constituting the membrane, i.e., the SOI layer (1), the piezoelectric layer (7), and the electrode layer (6).

[0071] Pressure refers to the value of pressure at which the membrane rapidly switches from the concave to the convex state or vice versa. Example 1 - Diameter 10 cm

[0072] Example 2 - Diameter 1 cm

[0073] Example 3 - Diameter 1 mm

[0074] The most interesting results relate to the membrane with a diameter of 1 mm, and are illustrated in the attached graphs. Each data point corresponds to a specific thickness of the membrane made from the solid SOI (Silicon-on-Insulator) material, the piezoelectric layer, and the metallic electrode. All simulations assume an initial membrane bulging of 20 micrometers and a disk diameter of 1 mm.

[0075] The key feature of the solution according to the invention is the bistable switch phenomenon that occurs under specific pressure. The solution was tested with three different membrane thicknesses and the respective pressures which induce the bistable switch. For example, the membrane (1) with a thickness of 5 pm requires the pressure of 16.5 kPa for the bistable switch, the membrane (1) with a thickness of 6 pm requires the pressure of 27.2 kPa, and the membrane (1) with a thickness of 13.25 pm requires the pressure of 138 kPa.

[0076] The module under investigation was subjected to tests in which the pressure applied on its surface was varied in the range from 12 kPa to 20 kPa. The diameter of the disk was 1 mm, its thickness was 5 pm, and the magnitude of arching (initial inward bulging of the membrane into the chamber) was 20 pm. Fig. 3a shows a graph depicting two relations: displacement (in micrometers) and terminal voltage (in volts) as a function of pressure (in kilopascals). The pressure range on the graph is from 12 kPa to 20 kPa. The blue line (labelled "Displacement") represents the displacement, i.e., deviation of the central point of the membrane from its initial state. Said displacement exhibits a typical bistable behaviour, being almost constant and then rapidly increasing in the pressure range from approximately 15 kPa to slightly above 16 kPa, reaching a value of approximately 34 pm, and remaining stable up to 20 kPa. The green line (labelled "Terminal voltage") represents the terminal voltage, which remains close to 0 V up to the pressure of approximately 16 kPa, then rapidly increases to approximately 1.8 V and stabilizes at this level up to 20 kPa.

[0077] Fig. 3b shows a graph depicting two different variables as a function of pressure: displacement in micrometers (pm) and total electric energy in microjoules (pJ) over a pressure range from 12 kPa to 20 kPa. The blue line (labelled "Displacement") reveals that the displacement starts to increase rapidly at the pressure of approximately 15 kPa, reaching a constant value of approximately 34 pm slightly above 16 kPa and maintaining this level up to 20 kPa. The green line (labelled "Total electric energy") represents total electric energy, which remains low until the pressure of approximately 16 kPa, then increases rapidly until it reaches a value of approximately 28 pJ at 16 kPa and remains at this level up to 20 kPa.

[0078] Fig. 4a shows a graph depicting two relations: displacement (in micrometers) and terminal voltage (in volts) as a function of pressure (in kilopascals). The pressure range on the graph is from 22 kPa to 32 kPa. The blue line (labelled "Displacement") shows the displacement, i.e., the deviation of the central point of the membrane from its initial state. Said displacement exhibits the typical bistable behaviour, being almost constant, then rapidly increasing in the pressure range of approximately 27 kPa, reaching a value of approximately 35 pm, and remaining stable up to 32 kPa. The green line (labelled as "Terminal voltage") represents the terminal voltage, which decreases mildly to a level close to 0 V up to the pressure of approximately 27 kPa, then rapidly increases to approximately 2.8 V and stabilizes at this level up to 32 kPa.

[0079] Fig. 4b shows a graph depicting two different variables as a function of pressure: displacement in micrometers (pm) and total electric energy in microjoules (pJ) over a pressure range from 12 kPa to 20 kPa. The blue line (labelled "Displacement") shows that the displacement starts to increase rapidly at the pressure of approximately 27 kPa, reaching a constant value of approximately 36 pm and maintaining this level up to 32 kPa. The green line (labelled "Total electric energy") represents the total electric energy, which remains low until the pressure of approximately 27 kPa, then increases rapidly reaching a value of approximately 45 pJ at 27 kPa and remains constant up to 32 kPa.

[0080] Fig. 5a shows a graph depicting two relations: displacement (in micrometers) and terminal voltage (in volts) as a function of pressure (in kilopascals). The pressure range on the graph is from 130 kPa to 150 kPa. The blue line (labelled "Displacement") shows the displacement i.e., the deviation of the central point of the membrane from its initial state. Said displacement exhibits the typical bistable behaviour, being almost constant, then rapidly increasing at the pressure of approximately 138 kPa, reaching a value of approximately 28 pm, and remaining stable up to 150 kPa. The green line (labelled "Terminal voltage") represents the terminal voltage, which remains negative or close to 0 V up to the pressure of approximately 138 kPa, then rapidly increases to approximately 4 V and stabilizes at this level up to 150 kPa.

[0081] Fig. 5b shows a graph depicting two different variables as a function of pressure: displacement in micrometers (pm) and total electric energy in microjoules (pJ) over a pressure range from 130 kPa to 150 kPa. The blue line (labelled "Displacement") shows that the displacement starts to increase rapidly at the pressure of approximately 138 kPa, reaching a constant value of approximately 28 pm slightly above 137 kPa and maintaining this level up to 150 kPa. The green line (labelled "Total electric energy") represents the total electric energy, which remains low until the pressure of approximately 138 kPa, then increases rapidly until it reaches the value of approximately 320 pJ at 138 kPa and remains constant up to 150 kPa.

[0082] These graphs confirm the presence of a bistable element which is activated at a predetermined pressure, causing a simultaneous increase in displacement and generation of a higher terminal voltage.

[0083] In Fig. 6, the device a cell according to the invention in a cross-sectional view is shown, and in Fig. 7, the device - a cell in a top view of the system according to the invention is presented. On the surface of the metal electrode (6), the outline of a disk-shaped cell is visible. This cell is covered by a metal electrode layer (6), a piezoelectric layer (7), and a membrane (1). On the left side, a first electrical contact (9) is disposed on the metal electrode layer (6), while on the right side, an etching is visible penetrating down the structure through the metal electrode layer (6) and the piezoelectric layer (7). This etching stops at the surface of the membrane (1), on which the second electrical contact (10) is visible in the centre of the etching. Figs. 8 and 9 show embodiments, in top view, of matrixes of units connected in parallel arrangement (Fig. 8) and unconnected, i.e., each cell isolated from the others (Fig. 9) which allows their later connection at a higher level in series, parallel, or mixed configurations.

[0084] In Fig. 8, on the surface of the metal electrode (6) schematic outlines of six disk-shaped cells are visible. These cells are covered by the metal electrode layer (6), the piezoelectric layer (7), and the membrane (1). On the left side, a first electrical contact (9) is disposed on the metal electrode layer (6), and on the right side, an etching is visible penetrating down the structure through the metal electrode layer (6) and the piezoelectric layer (7) that stops at the surface of the membrane (1). In the centre of the etching, on the surface of the membrane (1), the second electrical contact (10) is visible.

[0085] In Fig. 9, on the surface of the metal electrode (6) schematic outlines of four disk-shaped cells in an independent arrangement are visible. These cells are covered by the metal electrode layer (6), the piezoelectric layer (7), and the membrane (1). On the left side of each disk, the first electrical contact (9) is disposed on the metal electrode layer (6), and on the right side, an etching is visible penetrating down the structure through the metal electrode layer (6) and the piezoelectric layer (7), of the bottom of which is the membrane (1). The second electrical contact (10) is visible in the centre of the etching, on the surface of the membrane (1).

[0086] Fig. 10 shows the SOI membrane bulging upwards that is subjected to tensile strain. At the very top of the membrane, a SiN layer responsible for generating this strain is indicated. This effect is known and generally treated as a parasitic effect, and it pertains to the stress in silicon nitride (SiN) which can be modulated from strongly compressive to strongly tensile by adjusting appropriate thermal parameters during the SiN deposition process. In the context of the present invention, such controlled stress is desirable because it ensures the desired curvature of the membrane. The production of such system components is known in the art and will not be further described herein.

[0087] Fig. 11 depicts the realisation of the metallic membrane using the so-called "resist flossing" technique so far employed in the production of lenses. This method involves using convex templates as original moulds for producing convex elements, e.g., optical lenses. The production of such components is known in the art and will not be further described herein. In the present invention, the obtained convex forms are coated with a metal layer, which is a corresponding counterpart of the convex SOI membrane and simultaneously of the bottom electrode under the piezoelectric layer. Figs. 12 a), b), and c) show a possible method for production a bistable membrane using the LOCOS (Local Oxidation of Silicon) technology, which is used before applying the STI (Shallow Trench Isolation) technology for lateral isolation in the production process of LSI components. LOCOS is a technique which relies on local oxidation of silicon to create an insulating layer that separates individual components on a chip. This insulating layer prevents current flow between neighbouring components, which is key for ensuring proper operation of semiconductor devices. Performing such LOCOS oxidation is known in the art and will not be further described herein. In the present invention, the LOCOS-type oxidation is not intended for lateral isolation, but is used to achieve the desired membrane shape, i.e., the convex dome shape, by leveraging the characteristic edge shape of the LOCOS region. These edges do not have a rectangular outline, but gradually taper, forming a bird's beaklike shape. Performing three LOCOS-type oxidations on the SOI membrane, as shown in Figure (a), produces the desired silicon membrane shape, as in Figure (b), which is then released from the LOCOS oxide via an SiO? etching process. The final membrane shape is shown in Figure (c).

[0088] Use of the Invention

[0089] The pressure-to-electric energy transducer according to the invention may be particularly useful for applications associated with powering electronic systems with particularly low power (LP, low power) consumption. In practice, these are most often integrated circuits made using the VLSI (Very -Large-Scale of Integration) technology. Due to significant advancements in the degree of integration, based on the so-called Moore's Laws, today's LP VLSI circuits can perform 1 million logical operations per second (so- called MIPS - million instructions per second) using up just 2.4 pj, in other words using the power of 2.4 microJoules / s. Because of these achievements, loT network nodes are now being developed that measure a particular physical parameter (e.g., temperature, pressure, CO2 concentration, etc.), analyse the acquired data, and transmit the results of the analysis via an integrated radio transmitter, consuming no more than 90 pJ of energy for the entire operation cycle. Moreover, loT sensor networks do not operate continuously; on the contrary, they perform such a measurement-analysis-radio transmission cycle every few seconds, minutes, hours, or even once every few days, depending on the application. For these reasons, the invention appears to be particularly suitable for powering loT network nodes. Reference Signs List

[0090] 1 - Heavily doped silicon membrane, also serving as the positive electrode

[0091] 2 - BOX (Buried Oxide)

[0092] 3 - Substrate silicon of the SOI plate 4 - Hermetic sealing lid

[0093] 5 - Chamber

[0094] 6 - Metal electrode

[0095] 7 - Piezoelectric layer

[0096] 9 - First electrical contact 10 - Second electrical contact

[0097] 11 - Cavity space filled with the fluid substance, part of which undergoes the liquid-gas phase transition during module operation

[0098] 12 - Saturated vapour of the fluid substance, part of which undergoes the liquid-gas phase transition during module operation

Claims

Claims1. An energy generation module comprising a pressure or temperature transducer, characterized in that it comprises a hermetic chamber (5) comprising a bottom and walls, wherein the walls of the chamber (5) are constituted by a substrate silicon layer (3) on which a buried oxide layer (2) is disposed, and the bottom constitutes a hermetic sealing lid (4) on which a fluid layer of a substance undergoing phase transition during operation of the module (12) is present, furthermore, the cavity is closed from above by a bistable membrane (1) that is susceptible to deformation due to the pressure difference between the inside and outside of the chamber (5), on the membrane a piezoelectric layer (7) is disposed, on which a metal electrode (6) is disposed, simultaneously a first electrical contact (9) is disposed on the metal electrode (6), while a second electrical contact (10) is disposed on the silicon membrane (1), simultaneously, inside the chamber (5), the fluid substance is present, part of which undergoes the liquid-gas phase transition during operation of the module (11).

2. The generation module according to claims 1 or 2 characterised in that the substance which undergoes the phase transition during operation of the module (11) is a compound selected from the group including chloroethane, isopropanol or ethanol, acetone, methanol, diethyl ether, chloroform, isopropanol, ethylene, gasoline, freons, liquid nitrogen.

3. The generation module according to claims 1 or 2 characterised in that the membrane (1) is a silicon layer of an n-type or a p-type doped at a level of at least 1019atoms3 per cm .

4. The generation module according to any of claims 1-3 characterised in that the silicon membrane (1) is made using the SOI technology.

5. The generation module according to any of claims 1-4 characterised in that the membrane (1) is coated with a thin metal layer on which there is the piezoelectric layer (7).

6. The generation module according to claim 3, characterised in that the membrane (1) is made of a metal selected from the group including aluminium, titanium, tungsten, copper, or a highly conductive material selected from the group including TiN (titanium nitride), TaN (tantalum nitride).

7. The generation module according to claim 5, characterised in that the piezoelectric layer (7) is made of a material selected from the group including ZnO, PZT (lead zirconate titanate), PVDF (polyvinylidene fluoride) and its copolymers, barium titanate (BaTiCh), lithium niobate (LiNbOs), quartz silicate, or aluminium oxide.

8. A set of modules according to claims 1 to 7 connected in parallel or in series in a modules matrix, or in a mixed manner using MESA-type isolation of each module individually or groups of modules.

9. Use of the set of modules according to claim 8 for powering loT network nodes.

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