WO2022129270A1

WO2022129270A1 - Self-powered device and method for measuring a parameter of a sensing power cell

Info

Publication number: WO2022129270A1
Application number: PCT/EP2021/086069
Authority: WO
Inventors: Albert ÁLVAREZ CARULLA; Yaiza MONTES CEBRIÁN; Pedro Luis MIRIBEL CATALÀ; Jordi COLOMER FARRARONS; Manuel Puig Vidal
Original assignee: Universitat De Barcelona
Priority date: 2020-12-17
Filing date: 2021-12-16
Publication date: 2022-06-23

Abstract

A self-powered device and a method for measuring a parameter of a sensing power cell are disclosed. The device comprises an electronic unit to be connected to a sensing power cell; a parameter associated to the sensing power cell being measurable via the electronic unit. The electronic unit includes a storage element to be charged by the sensing power cell via a charging voltage; a sensing module to measure a generated electrical current during the charging of the storage element, and to generate a voltage as a result; a data interface module connected to the sensing module to receive the generated voltage; and a detection module to monitor the charging voltage, and, when the latter has reached a pre-configured polarization voltage, to indicate to the data interface module to convert the received voltage to a readable result. A Point-of-care device is also disclosed.

Description

Self-powered device and method for measuring a parameter of a sensing power cell

TECHNICAL FIELD

The present invention is directed, in general, to the field of self-powered devices. In particular, the invention relates to a self-powered device (or system), and to a method, for measuring a parameter of a sensing power cell. The invention also relates to the use of the self-powered device as a Point-of-Care (POC) device.

BACKGROUND ART

In the field of self-powered devices, and in particular POC devices, there are different approaches that are conditioned by the use or particular scenarios of the devices, with particular interest in approaches of very low power.

Within the different proposed solutions there is a great interest in the area of the most ideal scenario where no power supply to the device would be required. In this ideal scenario, the device containing the sample, a parameter of which is to be measured/detected, generates an output in an autonomous way. In particular, these solutions have problems in controlling the sample, such as the control of the measurement itself, i.e. at which point in the measurement process the measured value can be obtained, and how this measured value can be extracted.

Different approaches are oriented to use solutions on paper (pPADS) (cf. G. G. Morbioli, et al., «Technical aspects and challenges of colorimetric detection with microfluidic paper-based analytical devices (pPADs) - A review», Anal. Chim. Acta, vol. 970, pp. 1-22, 2017) or screen printed devices (cf. Y. Xia, J. Si, and Z. Li, «Fabrication techniques for microfluidic paper-based analytical devices and their applications for biological testing: A review», Biosensors and Bioelectronics, vol. 77. pp. 774-789, 2016; and G. Jenkins et al., «Printed electronics integrated with paper-based microfluidics: new methodologies for next-generation health care», Microfluid Nanofluid 19, pp. 251-261 , 2015).

Within the so-called self-powered approaches (cf. M. Grattieri and S. D. Minteer, «Self- Powered Biosensors®, ACS Sensors 3(1), pp. 44-53, 2018), the power supply element or power generation, and the measurement, are based on the fuel cell itself. In these cases, an electronic interface based on a potentiostat would not be necessary. There are approximations of the latter, the so-called chromatic ones, among which the most typical approach is the lateral flow.

These solutions in which the reading is simply based on a visual response need a means to be able to extract the reading from the measurement; usually an optical medium such as the use of a mobile phone.

In some examples (cf. A. C. Sun, et al, «An efficient power harvesting mobile phonebased electrochemical biosensor for point-of-care health monitoring», Sensors and Actuators, B Chem., vol. 235, pp. 126-135, 2016), the mobile phone itself has a role as an element to power a particular Plug-and-Play system of the sensor and the electronics itself, and also has the role of being able to extract and process the measurements.

Within these self-powered typologies there are different approaches defined as qualitative (the classic example of a urine test strip), semi-quantitative and quantitative (seeking to draw a readout from them). In the present invention, the reading level of the measurement is done visually, as if it were a ruler. It would correspond to a chromatic case (cf. M. A. Pellitero et al., «Quantitative self-powered electrochromic biosensors®, Chem. Sci., vol. 8, n.o 3, pp. 1995-2002, 2017; and M. Aller Pellitero, et al, «iR Drop Effects in Self- Powered and Electrochromic Biosensors®, J. Phys. Chem. C, vol. 122, n.o 5, pp. 2596- 2607, 2018).

Other solutions seek an approach where the self-powered device is smarter, in the sense that it has greater capacity and functionality. Although in the previous chromatic cases it is not of great interest to know what energy can be extracted from the sensor element, in these approaches it is wanted that the sensor element also has the role of energy generating element. There are known different references regarding lactate, cholesterol, ethanol and glucose generators, among others (cf. A. Baingane and G. Slaughter, «Self- Powered Electrochemical Lactate Biosensing®, Energies, vol. 10, n.o 10, p. 1582, 2017;

A. N. Sekretaryova, et al, «Cholesterol self-powered biosensor®, Anal. Chem., vol. 86, n.o 19, pp. 9540-9547, 2014; and A. Ruff, et al, «A Self-Powered Ethanol Biosensor®, ChemElectroChem, vol. 4, n.o 4, pp. 890-897, 2017).

Another approach is disclosed by Koji Sode et al. «BioCapacitor: A novel principle for biosensors®, Biosensors and Bioelectronics, Elsevier Science LTD, vol 76. pp. 20-28, 2015. In the review, the authors disclose a novel biodevice that is based on an enzyme fuel cell that generates sufficient stable power to operate electric devices, designated "BioCapacitor." To increase voltage, the enzyme fuel cell is connected to a charge pump, and to obtain a sufficient power and voltage to operate an electric device a capacitor is used to store the potential generated by the charge pump. By using the combination of a charge pump and capacitor with an enzyme fuel cell, the author claim that high voltages with sufficient temporary currents to operate an electric device can be generated without changing the design and construction of the enzyme fuel cell.

Therefore, the different state-of-the-art self-powered approaches have some major drawbacks: 1) they use a non-self-powered external device or instrument to output the measurement, e.g., oscilloscope, smartphone, etc.; 2) they provide a continuous measurement without a criteria and an indication about when the measurement has ended; and 3) In the chromatic cases, when they do not use non-self-powered external devices, its output is generally unquantified and subjective.

New low-power easy-to-use and low-complex (i.e. with reduced electronics and resources) self-powered devices are therefore needed.

SUMMARY OF INVENTION

To that end, embodiments of the present invention provide according to a first aspect a self-powered device for measuring a parameter of a sensing power cell. The self- powered device comprises a single sensing power cell and an electronic unit configured to be electrically connected to the single sensing power cell. The electronic unit is configured to measure a parameter related to the sensing power cell, and the sensing power cell is configured to generate an electrical current \_CELL and a voltage \/_CELL which depend on said parameter.

The electronic unit includes: a storage element configured to be charged by the sensing power cell via a charging voltage \/_CAP ', a sensing module configured to measure the generated electrical current \_CELL during the charging of the storage element, and to generate a voltage \/ SENSE as a result; a data interface module electrically connected to the sensing module to receive the generated voltage V SENSE ', and a detection module configured to monitor the charging voltage \/_CAP , and, when the charging voltage \/_CAP has reached a pre-configured polarization voltage V_P of the sensing power cell, to indicate to the data interface module to convert the received voltage \/ SENSE to a readable/legible result (or simply result or outcome); that is. a result that is able to be read easily, either by a human eye or by electronic means. The sensing power cell can be a galvanic cell, such as a fuel cell, among others. In this particular embodiment, the parameter can comprise the concentration of a sample included in or added to the sensing power cell. In other embodiments, the sensing power cell can be a thermoelectric generator. Thus, a parameter related to the thermoelectric generator, for example the temperature gradient, can be monitored and measured.

In the proposed self-powered device the sensing power cell acts as power source and sensor at the same time. Likewise, the proposed self-powered device can provide the criterion of when the parameter measurement should be performed and when the measurement process has ended, without the need for a complex programming or without using microprocessors, timers, etc. In addition, it determines when the measurement should take place in a controlled manner.

Thus, the present invention allows determining a working point of the sensing power cell, without having to use a potentiostat; therefore avoiding the use of complex electronics and equipment. In addition it allows performing the measurement autonomously, with the own energy of the sensing power cell.

In an embodiment, the sensing power cell is a removable element. In another embodiment, the sensing power cell is a disposable element.

In some embodiments, the electronic unit can be reused, extending its cycle of use.

In an embodiment, the data interface module comprises a display.

In an embodiment, the storage element comprises a capacitive load that is connected to the sensing power cell and to the detection module. The capacitive load in some embodiments can be a supercapacitor.

In an embodiment, the sensing module comprises an instrumentation amplifier and a metal-oxide-semiconductor field-effect transistor (MOSFET), which is connected to the sensing power cell via a first resistor R_sand via a second resistor R_G, the first resistor R_s being arranged in a path followed by the electrical current from the sensing power cell to the capacitive load.

Embodiments of the present invention also provide a method for measuring a parameter of a sensing power cell, comprising: generating, by a sensing power cell, an electrical current \_CELL and a voltage \/_CELL , the generated electrical current \_CELL and the voltage VCELL being associated to a parameter associated to the sensing power cell; as a result of said generating step, charging a storage element of an electronic unit via a charging voltage \/_CAP ', generating a voltage \/ SENSE from the generated electrical current \_CELL by means of a sensing module of the electronic unit measuring the generated electrical current \_CELL during the charging of the storage element; providing, by the sensing module, the generated voltage \/SENSE to a data interface module; monitoring, by a detection module of the electronic unit, the charging voltage \/_CAP , and, when the charging voltage \/_CAP reaches a pre-configured polarization voltage V_P, further indicating to the data interface module that it can convert the voltage \/SENSE to a readable result; and as a result of the indication, the data interface module showing a result of the parameter measurement.

In an embodiment, the generation of the electrical current starts once the sensing power cell has been plugged to the electronic unit. In another embodiment, the generation of the electrical current starts once a sample is added to the sensing power cell.

In an embodiment, the capacitive load is charged via a non-linear sweep voltammetry (NLSV) method. That is, the electronic unit implements a capacitive load-based method to perform a NLSV to the sensing power cell.

In an embodiment, the parameter comprises a concentration of a sample, the sensing power cell comprising a galvanic cell. In another embodiment, the parameter comprises a gradient temperature, the sensing power cell comprising a thermoelectric generator.

In an embodiment, the storage element comprises a capacitive load and the method further comprises using the capacitive load for powering the electronic unit.

Embodiments of the present invention also provide the use of the device of the first aspect as a POC device. Other embodiments also provide the self-powered device as a POC device.

Therefore, present invention provides a solution that overcomes the prior art drawbacks by providing a criteria and an indicator for the end of the measurement and an interface to provide/show/display the result, particularly to a user, without external non-self- powered devices involved.

The power consumption of the electronic unit is less than 6 pW. Moreover, the power extracted from the power sensing cell for its polarization is not wasted but can remain stored in the storage module to increase the display’s autonomy or to increase device’s functionality. Furthermore, the low complexity of the invention, mainly consisted of passive components, allows the solution to be translated in other eco-friendly state-of- the-art technologies where different materials are used to implement electronic circuits, like paper or Molded Interconnect Devices (MID).

The details of one or more embodiments of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF DRAWINGS

The previous and other advantages and features will be more fully understood from the following detailed description of embodiments, with reference to the attached figures, which must be considered in an illustrative and non-limiting manner, in which:

Fig.1 schematically illustrates a block diagram of the proposed self-powered device, according to an embodiment of the present invention. In the figure, R = Result.

Fig. 2 schematically illustrates another block diagram of the proposed self-powered device, according to another embodiment of the present invention.

Fig. 3 is a flow chart of a method for measuring a parameter of a sensing power cell, according to an embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

The present invention provides a novel electrochemical characterization approach intended for self-powered applications. The invention consists of a sensing power cell and an electronic unit (e.g. an electronic reader), and allows to characterize a parameter related to the sensing power cell. The versatility of the present invention for being adapted to different sensing power cells, its performance, cost effective implementation and low power consumption make this solution suitable for self-powered Point-of-Care (POC) devices in scenarios with extreme low power availability.

Fig. 1 illustrates an embodiment of the proposed low-power easy-to-use and low- complex self-powered device (or system) 100, hereinafter referred as device, comprising a single sensing power cell 101 , for example a galvanic cell or a thermoelectric generator (TEG), among others, and a very simple electronic unit 110, which is powered thanks to the sensing power cell 101. The sensing power cell 101 empowers the device 100, which can combine microfluidic resources for the pre-manipulation and conditioning of a sample, and acts as a sensor at the same time.

The sensing power cell output characteristics depend on a parameter thereof, like the sample concentration used as electrolyte, the enzyme levels in a fuel cell, the bacterial levels in a micro-bial fuel cell, the temperature level of a TEG, or even the light level in a room for smart buildings, in the case of an indoor solar cell.

The electronic unit 110 is formed by a sensing module 111 , a detection module 112, a storage module 113 comprising a capacitive load, and a data interface module 114.

The device 100 starts its operation disconnected from the sensing power cell 101 or without the sample, for example used as electrolyte, deposited, and with the storage module 113 initially discharged. The device 100 is intended to start its operation once the sensing power cell 101 is plugged or the sample is added. Then, the sensing power cell 101 starts to charge the storage module 113. Thus, the polarization voltage V_P applied to the sensing power cell 101 corresponds to the charging voltage V_CAP of the storage module 113. This method provides a way to perform a Non-Linear Sweep Voltammetry (NLSV) from 0V to sensing power cell’s 101 Open Circuit Potential (OCP). As in Linear Sweep Voltammetry (LSV), from this method, polarization curves can be measured to distinguish between parameters, for example between concentrations. The parameter measurement, for example the concentration measurement, is usually extracted from current measurement at a given polarization voltage V_P which usually is selected in terms related to the sensing power cell’s characteristics like sensitivity, repeatability, reproducibility, among others.

The sensing module 111 is the responsible to measure the sensing power cell output electrical current \_CELL during the proposed capacitive load-based LSV method. In some embodiments, the sensing module 111 can be configured to perform the measure of the electrical current \_CELL continuously. Alternatively, in other embodiments, said measuring is performed when indicated by the detection module 112.

The sensing module 111 particularly provides an analog signal VSENSE as indicator of the electrical current \_CELL outputted by the sensing power cell 101. In order to provide a result, VSENSE is sourced to the data interface module 114. While the sensing module 111 provides a measurement, one critical aspect is when the measurement is taken to generate a result and provide/show/display it to a user, for example. The detection module 112 is intended for this task. The detection module 112 monitors the charging voltage V_CAP of the storage module 113. When the charging voltage V_CAP reaches a pre-configured desired polarization voltage V_P, the detection module 112 indicates to the data interface module 114 the occurrence of the event through a signal V_LATCH- Then, the data interface module 114 captures VSENSE and converts it to a (user)-readable result and holds its value independently of VSENSE evolution, without the need of any non-self-powered external device such as an oscilloscope, a mobile phone, etc.

With regard to Fig. 2, therein another embodiment of the proposed device 100 is illustrated. In this particular embodiment, in order to stay as close as possible to a real- world application, the sensing power cell 101 comprises a galvanic cell, in particular a sodium chloride (NaCI) cell. A stack of two galvanic cells in series is used in this case, each one with a cell diagram

where the following electrochemical reaction takes place

Zn(s) 4- 2 Hat) (1) - Zii(OHk qj 4- Hg

The potential provided by each cell corresponds to the Zn(s) oxidation, which has an electromotive force potential E° of 0:761V, and the H+ reduction. The Cu(s) electrode acts as an inert electrode in the sensing power cell 101. Different NaCI solutions with different concentrations as electrolyte were used. During sensing power cell’s operation, measured potential can vary as a result of electrodes polarization. The distance between electrodes was 2:2 cm and the active area of each electrode was 2:5 cm x 2:5 cm.

To implement the cell, Zn(s) and Cu(s) electrode strips were used. For the electrolyte, NaCI solutions with different concentrations using sodium chloride (NaCI, ACS grade, 99:5%) were used. De-ionized water was also used experiments.

The electronic unit 110 in this case is implemented on a Printed Circuit Board (PCB) with flexible substrate (not limitative as more compact and eco-friendly solutions, like a Molded Interconnect Device (MID), which is based on a thermoplastic body with an integrated conductive pattern, can be also used). To sense the cell output current ICELL, a high-side current-sensing circuit is used as sensing module 111. A shunt resistor R_s is placed in the current path from the sensing power cell 101 to the storage module 113. Using an Operational Amplifier 121 and a P-channel MOSFET (PMOS) 122, the voltage drop V_s at R_s, originated by the electrical current flow across the resistor R_s, is replicated across the resistor R_G. Thus, a proportional replicated current l_G passes through the resistor R_B and an output voltage SENSE is generated. The relationship between the electrical current outputted by the sensing power cell 101 and the voltage level of SENSE is

In this particular embodiment, a TS12011 from Silicon Labs has been used to implement the Operational Amplifier 121. A PMN70XPX has been used for the PMOS 122.

For the storage module 113, a 4:7 mF supercapacitor is used as capacitive load and storage element.

The detection module 112 has to detect when its input voltage V_CAP is higher than the desired polarization voltage V_P; an Under-Voltage Lockout (UVLO) is particularly used to perform such task. This was implemented using a TS12001 , annotated as 123 in Fig. 2. When the voltage V_CAP reaches the desired polarization voltage V_P, the signal V_TRI_GG goes high indicating the end of the measurement.

The unit 123 generates a complementary signal V_LATCH that is used to latch the result outputted by the data interface module 114. This module 114, which in this embodiment particularly comprises a display 126, converts the analog signal VSENSE to a result readable by a user. In the embodiment of Fig. 2, a latched comparator 125 with a voltage reference 124 is used for this purpose. The circuit operates as a 1 bit Flash Analog-to- Digital Converter (ADC). The signal VSENSE is connected to the positive input of the comparator 125 while the voltage V_REp outputted by the voltage reference 124 is connected to the negative input. The comparator’s output V_COMP toggles normally when the incoming signal VLATCH remains high. When VLATCH goes low, V_COMP remains latched holding the result of the measurement. V_COMP, in conjunction with V_TRI_GG, are connected to the display 126, where V_TRI_GG indicates the end of the measurement and V_COMP its result. For the characterization of the NaCI-based galvanic cell, electrochemical experiments were carried out for a concentration range with an equivalent conductivity in the range of interest for cystic fibrosis screening defined by the Diagnostic Sweat Testing Guidelines from the Cystic Fibrosis Foundation. NaCI solutions with a concentration of 5 mM, 30 mM, 60 mM and 160 mM were used. For a given concentration, an LSV was performed from cell’s OCP to 0V with a scan rate of 10 mVs'¹. LSV measurements were carried out using a potentiostat. This characterization serves to validate the construction of the implemented galvanic cell 101 and its performance. However, to select the proper values for the electronic unit’s passive components, a characterization using the method used by the electronic unit 110 was also carried out. I.e., a discharged 4:5 mF supercapacitor was connected to the galvanic cell 101 using NaCI solutions with a concentration of 5 mM, 30 mM, 60 mM and 160 mM. Simultaneously, its voltage and output electrical current were logged using a Source Meter Unit (SMU).

The electronic unit 110 was plugged in the galvanic cell 101 with sample concentrations from 5 mM to 160 mM. During the characterization, the analog signals were logged with two oscilloscopes in common triggered configuration. The power consumption was also characterized using a SMU.

During the experiments, the implemented NaCI-based galvanic cell 101 exhibited an OCP of 1:715 V and a maximum output current of 0:780 mA at a polarization voltage of 0:9V over the concentration range from 5 to 160 mM. The electronic unit 110 measured electrical current with a transfer function gain of 1 :012V mA'¹. The overall device exhibited a maximum coefficient of variation of 6:1%. All this was achieved in less than 12 seconds with a maximum power consumption of 5:8 pW and Commercial-off-the- Shelf parts.

With regard now to Fig. 3, therein an embodiment of the proposed method is illustrated. At step 301, the method comprises generating an electrical current ICELL and a voltage VCELL via the sensing power cell 101 comprising a sample a parameter of which is to be measured, the generated electrical current ICELL and the voltage V_CELL being associated with the parameter. At step 302, and as a result of the previous step, the storage element 113 such as a capacitive load or a supercapacitor is charged via a charging voltage V_CAP- At step 303, a voltage VSENSE, which is derived from the generated electrical current ICELL during the charging of the storage element 113, is generated by the sensing module 111 ; the latter, at step 304, further providing the generated voltage VSENSE to the data interface module 114, for example a user-interface module having a display or a database. At step 305, the method comprises monitoring the charging voltage V_CAP through the detection module 112; the latter, at step 306, and when the charging voltage V_CAP reaches a preconfigured polarization voltage V_P, further indicating to the data interface module 114 that it can convert the voltage VSENSE to a readable result. Finally, at step 307, as a result of the indication, the data interface module 114 shows the result of the parameter measurement.

The foregoing describes embodiments of the present invention and modifications, obvious to those skilled in the art can be made thereto, without departing from the scope of the present invention.

Claims

1. A self-powered device for measuring a parameter of a sensing power cell, comprising:

- a sensing power cell (101); and

- an electronic unit (110) electrically connected to the sensing power cell (101), the electronic unit (110) being configured to measure a parameter associated to the sensing power cell (101), the sensing power cell (101) being configured to generate an electrical current \_CELL and a voltage \/_CELL which depend on said parameter, the electronic unit (110) including:

- a storage element (113) configured to be charged by the sensing power cell (101) via a charging voltage \/_CAP ',

- a sensing module (111) configured to measure the generated electrical current \_CELL during the charging of the storage element (113), and to generate a voltage \/SENSE as a result;

- a data interface module (114) electrically connected to the sensing module (111) to receive the generated voltage \/ SENSE ; and

- a detection module (112) configured to monitor the charging voltage \/_CAP, and, when the charging voltage \/_CAP has reached a pre-configured polarization voltage V_P of the sensing power cell (101), to indicate to the data interface module (114) to convert the received voltage V_SEWSE to a readable result.

2. The device of claim 1, wherein the sensing power cell (101) comprises a galvanic cell including a sample, and the parameter comprises a concentration of the sample.

3. The device of claim 1, wherein the sensing power cell (101) comprises a thermoelectric generator, and the parameter comprises a temperature gradient.

4. The device of any one of the previous claims, wherein the sensing power cell (101) is a removable element.

5. The device of any one of the previous claims 1-3, wherein the sensing power cell (101) is a disposable element.

6. The device of any one of the previous claims, wherein the data interface module (114) comprises a display (126).

7. The device of any one of the previous claims, wherein the storage element (113) comprises a capacitive load that is connected to the sensing power cell (101) and to the detection module (112).

8. The device of claim 7, wherein the capacitive load is a supercapacitor.

9. The device of any one of the previous claims, wherein the sensing module (111) comprises an instrumentation amplifier and a metal-oxide-semiconductor field-effect transistor, MOSFET, and is connected to the sensing power cell via a first resistor R_sand via a second resistor R_G, wherein the first resistor R_s is arranged in a path followed by the electrical current from the sensing power cell to the capacitive load.

10. A method for measuring a parameter of a sensing power cell, comprising:

- generating, by a sensing power cell, an electrical current \_CELL and a voltage \/_CELL, the generated electrical current \_CELL and the voltage \/_CELL being associated to a parameter associated to the sensing power cell;

- as a result of said generating step, charging a storage element of an electronic unit via a charging voltage \/_CAP ',

- generating a voltage \/SENSE from the generated electrical current \_CELL by means of a sensing module of the electronic unit measuring the generated electrical current \_CELL during the charging of the storage element;

- providing, by the sensing module, the generated voltage \/ SENSE to a data interface module;

- monitoring, by a detection module of the electronic unit, the charging voltage \/_CAP, and, when the charging voltage \/_CAP reaches a pre-configured polarization voltage V_P, further indicating to the data interface module that it can convert the voltage V_SEWSE to a readable result; and

- as a result of the indication, the data interface module showing a result of the parameter measurement.

11. The method of claim 10, wherein:

- a sample is further included to the sensing power cell, the parameter comprising a concentration of the sample and the sensing power cell comprising a galvanic cell; or

- the parameter comprising a gradient temperature, the sensing power cell comprising a thermoelectric generator. 14

12. The method of claim 10, wherein the generation of the electrical current starts once the sensing power cell has been plugged to the electronic unit or once a sample is added to the sensing power cell.

13. The method of any one of the claims 10-12, wherein the capacitive load is charged via a non-linear sweep voltammetry, NLSV, method.

14. The method of any one of the claims 10-13, wherein the storage element comprises a capacitive load and the method further comprises using the capacitive load for powering the electronic unit.

15. A point-of-care device comprising the self-powered device according to any one of claims 1 to 9.