Description:FORM 2
THE PATENT ACT, 1970
(39 of 1970)
COMPLETE SPECIFICATION
(See section 10, rule 13)

TITLE: MACROALGAE BASED SURFACE CHARGE INDUCED HYDRO-VOLTAIC DEVICE AND METHOD THEREOF

INVENTORS
CHATTERJEE, Anamika, Indian Citizen
Department of Sciences, Amrita School of Physical Sciences, Coimbatore, Amrita Vishwa Vidyapeetham, India

LAL, Sujith, Indian Citizen
Department of Sciences, Amrita School of Physical Sciences, Coimbatore, Amrita Vishwa Vidyapeetham, India

THIRUGNASAMBANDAM, Manivasagam G, Indian Citizen
Center of Excellence in Advanced Materials and Green Technologies, Amrita School of Engineering, Coimbatore, Amrita Vishwa Vidyapeetham, India

BATABYAL, Sudip, Indian Citizen
Department of Sciences, Amrita School of Physical Sciences, Coimbatore, Amrita Vishwa Vidyapeetham, India

APPLICANT
Amrita Vishwa Vidyapeetham
Coimbatore, Tamil Nadu- 641112, India

THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED

MACROALGAE BASED SURFACE CHARGE INDUCED HYDRO-VOLTAIC DEVICE AND METHOD THEREOF
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] None.
FIELD OF THE INVENTION
[0002] The present invention generally relates to electricitygenerating devicesand more particularly relates to surface charge induced bioelectricity generationdevices and methods thereof.
BACKGROUND OF THE RELATED ART
[0003] Energy demand for growing population is increasing day by day. The technology associated with production of energy depends on decreasing reserve fossil fuel thereby creating a problem of CO2 emission and global warming. Hydro-voltaic is a recently developed technique to generate electricity using water flow inside charged porous medium induced by water evaporation. Activated carbon and other carbon based materials have been used as hosts for water molecules that flow by capillary action. Several attempts have been made, and many reports have been published to conclude the overall mechanism of HV generation. Among these, water evaporation induced HV (WEI-HV) generation has garnered attention due to its unique characteristics such as being a natural process, eco-friendly and simple to fabricate. According to reports, an HV device generates power when water molecules interact with porous carbon with enormous functional groups. The interaction between the functional groups and H+ ions in water creates an EDL, along its length and diameter of a porous medium, leading to the formation a potential difference. The EDL changes along the water flow and diminishes when the gradient stops. Additionally the potential variation along its length due to the linear gradient of ions. WEI-HV devices mostly required some external energy such as light or heat to raise the water wicking ability through the device, which can enhance the interaction of water with carbon surface.
[0004] Biobased energy generation is one of the promising technologies for continuous and sustainable development of green energy. Researchers have developed various designs of hydro voltaic devices using various microbes as an active material. DOI: 10.1126/sciadv.abm8047 titled “Water evaporation induced electricity with Geobacter sulfurreducens biofilms” discloses a bacterial biofilm based WEG device. The developed device generates continuous electric power with a maximum output power density of ~685.12 µW/cm2. Another research “Hydro-voltaic effect of microbial films enables highly efficient and sustainable electricity generation from ambient humidity” (https://doi.org/10.1016/j.cej.2022.135921) discloses use of microbial films from the cells of three types of electroactive active bacteria including G. sulfurreducens (strains KN400 and PCA) and Shewanellaoneidensis MR-1, and one non-electroactive bacterium Escherichia coli BW25113 for hygroelectricity generation. However, the above mentioned devices generate power but the current produced is in the range of few µA.
[0005] Further, there is no previously reported work on HV power generation from algaedespite of algal feedstock being capable and preferable to produce bioelectricity, biofuel, bio hydrogen and some other form of bioenergy without requiring any agricultural land and potable water for cultivation. The electrostatic charges present on the algal surface plays an important role in their life activities. It is believed that most of the algae having the negative surface charges due to the presence of some negative functional group like carboxylic (-COOH) and amino (-NH2) on the cytomembrane. However, energy harvesting by using the surface properties of algae are not at all explored.
[0006] Furthermore, none of the above mentioned bio-based material and devices harvest energy by using the surface properties of algae.Accordingly, there is a need for easy to fabricate hydro voltaic device integrated with electrostatic surface charges for power generation generating high voltage values and current values. A macro alga based hydro voltaic device is disclosed that is capable of generating voltage and current.
SUMMARY OF THE INVENTION
[0007] According to one embodiment of the present subject matter, a hydro-voltaic device for surface charge induced bioelectricity generation is disclosed. The device includes a substrate having a top end and a bottom end, the substrate is configured to hold a macroalgae film to form a biofilm deposited substrate. In various embodiments, the macroalgae is Pithophoraroettleri. The device further includes a first electrode affixed to the top end of the deposited substrate. A second electrode is affixed to the bottom end of the deposited substrate and is configured to immerse in an aqueous solution located at an optimized spacing from the first electrode. In various embodiments, the spacing between the first and second electrode ranges from 1 to 5 cm. The device also includes a reservoir comprising the aqueous solution with the deposited substrate in contact therewithin, wherein capillary action is configured to form an electric double layer formed at the macroalgae surface - aqueous solution interfaces, thereby generating voltage and current flow between the first electrode and the second electrode. In various embodiments, the generated voltage is in the range of 0.3 to 0.8 V.In various embodiments, the device generates currentintherangeof 4 to 32 µA/ sq. cm.
[0008] According to another embodiment of the present subject matter, a method for hydro-voltaic power generation integrated with electrostatic charges on macroalgae surface. The method involves providing pre-treated and fragmented macroalgae. The pre-treatment of macroalgae includes washing with deionized water followed by fragmentation into small pieces. Next step includes depositing macroalgae uniformly on a substrate to form a biofilm deposited substratefollowed by overnight drying the biofilm deposited substrate. In various embodiments, the predetermined conditions include relative humidity of 50-60% and a temperature ranging from 25-28°C.Further the method includes the step of punching electrodes along the length of biofilm deposited substrate to form a hydro-voltaic (PHV) devicefollowed by placing the PHV device in a reservoir comprising an aqueous solutionto an angle of contact to enhance the voltage generated. This is followed by allowing the water to flow through the PHV device by capillary action and forming an electric double layer at soil- aqueous solution interfaces, thereby generating voltage and causing flow of current across the ends of the PHV device. The method further includes the step of exposing the device to reduced relative humidity to enhance the voltage generated.

BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The invention has other advantages and features which will be more readily apparent from the following detailed description of the invention and the appended claims, when taken in conjunction with the accompanying drawings, in which:
[0010] FIG.1A: a schematic representation of a macroalgae based hydro-voltaic (PHV) device and EDL formation from the water on the surface of the biofilm.
[0011] FIG. 1B: a photographic image of PHVdevice.
[0012] FIG. 2: a flow diagram of a method of fabricating a macroalgae based hydro-voltaic (PHV) device to generate voltage and current.
[0013] FIG. 3A: a photographic image of filamentous green algae.
[0014] FIG. 3B: an optical microscopic image of filamentous green algae.
[0015] FIG. 3C: a low resolution scanning electron microscopic image of algal bunch.
[0016] FIG. 3D: a high resolution scanning electron microscopic image of a single fiber of Pithophoraroettleri.
[0017] FIG. 4: FTIR spectra of fresh water macroalgaePithophoraroettleri.
[0018] FIG.5A:image showing electrical measurement of PHV device- current generation with time
[0019] FIG. 5B: image showing electrical measurement of PHV device- voltage generation with time for the optimized PHV device.
[0020] FIG. 5C: image showing electrical measurement- power generation in a single PHV device over a long period using carbon and aluminium electrodes- current generation with time (over 10,000 min).
[0021] FIG. 5D: image showing electrical measurement- power generation in a single PHV device over a long period using carbon and aluminium electrodes- voltage generation with time (over 12,000 min).
[0022] FIG. 5E: image showing electrical measurement- power generation in two PHV devices connected in series over a long period using carbon and aluminium electrodes- voltage generation with time (over 1,800 min).
[0023] FIG. 5F: image showing stable out voltage of a single PHV device.
[0024] FIG.6A: a schematic representation of PHV device with length and width variation.
[0025] FIG. 6B: image showing voltage generation with time for different electrode distance.
[0026] FIG. 6C: image showing current generation with time for different electrode distance.
[0027] FIG. 6D: image showing voltage generation with time for different width of the device.
[0028] FIG. 6E: image showing systematic current and voltage generation in 16 PHV devices
[0029] FIG.7A: image showing voltage generation of PHV under the light ON-FF condition.
[0030] FIG.7B: image showing voltage generation with time for different dry conditions.
[0031] FIG.7C: a photographic image of wet algal film.
[0032] FIG.7D: a photographic image of dry algal film.
[0033] FIG.8A: a schematic representation of 7 PHV devices connected in series.
[0034] FIG.8B: a photographic image of total voltage generation from series connected 7 PHV devices.
[0035] FIG.8C: a photographic image of charging capacitor from total voltage generation from series connected 7 PHV devices
[0036] FIG.8D: a photographic image of LED light glowing for a demonstration of practical application.
[0037] FIG. 9: image showing contact angle of water droplet on algal film surface to confirm the hydrophilic test: a) at t=0 second and b) at t=4 seconds.
[0038] FIG. 10:image showing zeta potential of water dispersed mashed Pithophora.
[0039] FIG. 11A: image showing voltage and current output of sealed PHV device.
[0040] FIG.11B: image showingopen and sealed condition of 5 PHV devices.
[0041] FIG. 12: image showing effect of varying humidity on the device performance and corresponding voltage generation.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0042] While the invention has been disclosed with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the invention. In addition, many modifications may be made to adapt to a particular situation or material to the teachings of the invention without departing from its scope.
[0043] Throughout the specification and claims, the following terms take the meanings explicitly associated herein unless the context clearly dictates otherwise. The meaning of "a", "an", and "the" include plural references. The meaning of "in" includes "in" and "on." Referring to the drawings, like numbers indicate like parts throughout the views. Additionally, a reference to the singular includes a reference to the plural unless otherwise stated or inconsistent with the disclosure herein.
[0044] The present subject matter discloses a macroalgae based hydro-voltaicdevice (PHV)that is capable of enhanced power generation, as further disclosed with reference to the drawings. In various embodiments, a method of fabricating a macroalgae based hydro-voltaic device to generate voltage and current is disclosed.
[0045] A schematic representation of macroalgae based hydro-voltaic device (PHV) is illustrated in FIG. 1A, according to one embodiment of the present subject matter. The macroalgae based hydro-voltaic device 100 includes a substrate 104, a first electrode 108, a second electrode 110 and a reservoir 114. In various embodiments, the PHV device 100 is primarily configured to hold a macroalgae film 102.
[0046] In various embodiments, the macroalgae based hydro-voltaic device 100 includes the substrate 104 having a top end and a bottom end. In various embodiments, the substrate 104 is configured to hold macroalgae film 102 to form a biofilm deposited substrate 106. In one embodiment, the macroalga is green alga. In one embodiment, the macroalga is Pithophoraroettleri. In various embodiments, the substrate 104 includes the first electrode 108 affixed to the top end of the deposited substrate106. In various embodiments, the substrate 104 includes the second electrode 110 affixed to the bottom end of the deposited substrate 106. In various embodiments, the second electrode110 is configured to immerse in an aqueous solution112. In various embodiments, the second electrode110 is located at an optimized spacing from the first electrode108.
[0047] In various embodiments, the biofilm deposited substrate106 is immersed in the reservoir 114 comprising the aqueous solution 112 with the biofilm deposited substrate in contact therewithin. In various embodiments, the device 100 produces high voltage and high current under ambient temperature and related humidity without any external energy such as light, heat or wind, between the electrodes 108 and 110. In various embodiments, immersing the PHV device 100 in the reservoir of aqueous solution 112 allows capillary flow of the aqueous solution 112. In various embodiments, the interaction of aqueous solution 112 with the macroalgae biofilm 102 deposited on the substrate 104 with evaporation and phase changes are believed to cause a potential across the biofilm deposited substrate 106.
[0048] In various embodiments, the aqueous solution 109 may be water or other polar fluid. In various embodiments, the electrodes 108, 110 are located at an optimized spacingin the range of 1 to 5 cm.
[0049] In various embodiments, an electrical double layer (EDL) is formed due to interaction of the macroalgae biofilm 102 with the aqueous solution 112, at the biofilm-aqueous solution interfaces as illustrated in FIG. 1A. The filament of macroalgae has one or more functional groups, especially hydroxyl, amide and oxygen-rich functional groups. In various embodiments, the one or more functional groups attach with H+ in aqueous solution, and create the EDL layer, thereby generating voltage and current flow between the first electrode 108 and the second electrode 110.The EDL layer and the movement of charges are illustrated in FIG. 1Adepicting a specific double layer formation occurring around macroalgae biofilm102 when aqueous solution 112 flows through it.In one embodiment, the gradient of the functional group along the direction of the solution flow generates the voltage across the device.
[0050] In various embodiments, the macroalgae- aqueous solution interaction and thereby the voltage of the macroalgae based hydro-voltaic device 100 is proportional to the surface charge on the macroalgae-biofilm 102 present on the substrate104, up to an optimum value. This means as the quantity of macroalgae102 decreases from this optimum value, the macroalgae- aqueous solution interaction reduces, thereby leading to reduction in the output voltage.
[0051] In various embodiments, the PHV device 100 is configured to produce voltages in the range of 0.3V to 0.8V. In various embodiments, the PHV device100 is configured to generate currents in a range of 4- 32µA from single PHV device 100 without applying any voltage. In various embodiments, power generation capacity of the PHV varies with type of electrode used. In various embodiments, the electrodes may include aluminium tape, carbon or aluminium electrodes.
[0052] In one embodiment, the PHV device 100 is configured to generate enhanced voltage on reducing relative humidity. In various embodiments, two or more PHV devices 100 are connected in series and parallel arrangements to get a combined output voltage.
[0053] In another embodiment, a method 200 of fabricating macroalgae based hydro-voltaic device to generate voltage and current is disclosed. A flow diagram of a method of fabricating the macroalgae based hydro-voltaic device to generate voltage and current is illustrated in FIG. 2, according to one embodiment of the present subject matter. The method in step 201 includes providing pre-treated and fragmented macroalgae. Step 202 includes depositingmacroalgae uniformly on a substrate. In various embodiments, step 203includes drying biofilm overnight under ambient conditions to form biofilm deposited substrate. In various embodiments, the predetermined condition for drying in step 203 comprises relative humidity of 50-60% at 25-28°C. This is followed by step 204 of punching electrodes along the length of biofilm to form a macroalgae based hydro-voltaic device. Step 205 includes placing the tubular structure in a reservoir comprising an aqueous solution. In various embodiments, the step of placing the PHV in the reservoir includes placing in an angle of contact for enhanced wicking ability. In step 206, the aqueous solution is allowed to flow through the PHV deviceby capillary action. Finally, the method includes step 207of forming an electric double layer (EDL)between macroalgae filaments- aqueous solution interfaces, thereby generating voltage and causing flow of current across the ends of the biofilm deposited substrate of the PHV device. The EDL is formed by attachment of functional groups in macroalgae filament, especially surface hydroxyl, carbon, hydrogen, amide groups and oxygen containing functional groups, with H+ in the aqueous solution. This leads to the generation of voltage and causing flow of current across the ends of thePHV device. In some embodiments, the method may include additional step of exposing the biofilm deposited substrate 106 of PHV device to reduced relative humidity, thereby enhancing the voltage and current drawn from the device.
[0054] In various embodiments, the macroalga is pre-treated by washing several times with deionized water. In various embodiments, the washing of macroalga is followed by fragmentation into small pieces.
[0055] The voltage generation in the PHV device 100 of the present invention largely depends on the surface charge on the macroalgae. The living algal cell generates large voltage and currents compared to the dried dead cell wherein the surface charge on the dead cellbiofilm reduces largely.The change in the relative humidity of the surrounding of the fabricated PHV device 100of the present invention affectsthe power generation as relative humidity value controls the water evaporation rate. The main reason for the voltage generation in the PHV device 100 of the present invention is the surface charge on the macroalgae and the ionization of the water. The macroalgaePithophoraused in present invention has sufficient amount of surface charge owing to the presence of functional group on the cell membrane, which act as charge centre, and enable electro-flocculation and electrophoretic deposition of biofilm. These surface charges enable the formation of the spheres and ultimate electrical double layers on the surface of the cell membrane. Because of the EDL formation some gradient of hydrogen ions is formed in between two algal filaments from the surface of the filaments to the centre. The formed EDL potential along with the streaming potential of the hydrogen ions from bottom (water storage) to the top develops the final voltage and currents. The FIG. 1A shows the schematic diagram of the EDL formation from the water on the surface of the cell membrane. The surface charge on the Pithophorais further confirmed by the zeta potential measurement of the algal cells.
[0056] The PHV device 100 may generate power in a simple, efficient way with negligible external energy support. The method 200 brings in use the macroalgae as an active material, hence improving the practical usage of readily available natural resource. The method 200 has been experimentally validated and has demonstrated production of an extremely low cost PHV device. The intrinsic properties of the Pithophoramacroalgal biofilms are believed to be responsible for this performance.Thus the device of the present invention is configured to be lightweight and cost efficient. Besides, the PHV device of the present invention is an eco-friendly alternative to disposable energy generating devices that are of complex design, expensive to manufacture and thus may have higher environmental impact. Also, the PHV device generates current and voltage irrespective of the position of the light source and anytime of the day.Moreover, the PHV device and method of the present invention is of low cost, chemical free, recyclable and of compact nature.
[0057] Although the detailed description contains many specifics, these should not be construed as limiting the scope of the invention but merely as illustrating different examples and aspects of the invention. It should be appreciated that the scope of the invention includes other embodiments not discussed herein. Various other modifications, changes and variations which will be apparent to those skilled in the art may be made in the arrangement, operation and details of the system and method of the present invention disclosed herein without departing from the scope of the invention as described here and as set forth in the claims attached herewith.
EXAMPLES:
[0058] EXAMPLE 1: FABRICATION OF MACROALGA BASED HYDRO-VOLTAIC (PHV) DEVICE:
[0059] Material:A macroalgae based hydro-voltaic device (PHV) was fabricated to analyse the significance of water and functional group incorporated substrate.The PHV device was fabricated using macroalgae wherein naturally grown filamentous green algae was collected from the water body of Amrita VishwaVidyapeetham campus, Coimbatore, Tamil Nadu, India. Microscopic glass slide was used as substrate. Commercial aluminium tape, carbon and aluminium electrodes were used to determine power generation capacity of the device.
[0060] Isolation and identification of algal species- Morphological analysis: Morphological features of the algae were investigated by macroscopic and microscopic (Olympus Magnus microscope model Ch20i) observation. The filaments of collected algae were green to dark brown in colour, freely but sparsely branched, and containing terminal and intercalary akinetes. It is clearly depicted from the microscopic view (FIG. 3B) of algae that the filamentous or bundle of crisscross thread like structure can be used to enhance the water wicking ability than the vertical structure. Also, it can boost the interaction between algae surface and water molecules. Usually, cells of Pithophorawere slender and cylindrical shape, the length was in the order of 1100-1450 µm and width of 50-120 µm. These algae comprised of very thin cell wall devoid of layers. A single cell possesses one reticulated chloroplast along with profuse pyrenoids. According to microscopic images the terminal cells were cone shaped and rounded. Under the 10× magnification the algae were showing irregular branched filaments containing numerous spores like reproductive cells, called akinets, which were lime green to dark greenish brown in colour. Microscopic features confirmed that the alga belonged to the family of Pithophoraceae and the genus is Pithophora.
[0061] Phylogenetic analysis:DNA sequence analysis and phylogenetic analysis were performed to identify the algal species. The species identification were carried out in YaazhXenomics, coimbatore, Tamil Nadu, India. For the species identification, DNA sequencing by Sanger sequence method was performed and partial sequences of 18S rDNA were amplified using the primers. DNA isolation from algae samples was done by using the EXpure DNA isolation kit developed by Bogar Bio Bee stores Pvt. Ltd., then polymerase chain reaction (PCR) were performed to amplify specific cloned or genomic DNA sequences with the help of specific enzyme and then the PCR product was sequenced by using the ABI PRISM® BigDyeTM terminator cycle sequencing kits with AmpliTaq® DNA polymerase (FS enzyme) (Applied Biosystems). From this study it was confirmed that the species is green filamentous macro algae Pithophoraroettleri.
[0062] Pre-Treatment of Macroalgae:The collected algae wasfilamentous green macroalgae that were branched, rough to touch and looked like interlaced mass of green thread or wool- like growth. Naturally collected algae was separated by hand screening process then washed with tap water at least 20 times, after that the algae were washed in de-ionized (DI) water by immersing in DI water for several times and at last on the flow of DI water. Finally, clean algae were centrifuged for 10 min, and separated algae were washed with DI water again.
[0063] Fabrication ofthe Macroalgae Based PHV Device:Green algae-based hydro-voltaic devices were fabricated using thin film algal deposition technique. The stepwise fabrication procedure is shown in FIG. 2, the real image in FIG. 1B clearly indicates that the entire algae were uniformly distributed through the area, to enhance the water up-taking ability for a better capillary action.The algae deposited devices were dried by keeping the devices overnight at room temperature under ambient condition ofrelative humidity of 50-60% at 25-28°C.The purpose of drying the devices is to build the strong adhesion of algae to the glass substrate.
[0064] The real camera image of collected wet algae was shown in FIG. 3A.Algae based hydro-voltaic devices (PHV-1 and PHV-2) with different set of electrodes were fabricated and their performances were further analysed.
[0065] PHV-1: Aluminium film (tape) was attached at the two end of the PHV device as electrode as shown in FIG. 1B. On the time of current and voltage measurement one side of the device were kept under water and other side were kept outside the water and finally the two terminals connected with the source meter.
[0066] PHV-2:PHV-2 device was fabricated by attaching the different electrodes-carbon and aluminiumalong the thickness of the device.While assessing the performance of the device/ devicesone side was immersed in water reservoir and other side was kept outside water and the two terminals were connected with the source meter.
[0067] EXAMPLE 2:STRUCTURAL AND FUNCTIONAL GROUP CHARACTERIZATION:To confirm the EDL formation, structural and functional group analysis of the macroalgae was performed to further use in a practical application.
[0068] Field Emission Scanning Electron Microscope (FE-SEM) Analysis:To understand the morphology of the fabricated device, the surface morphology was confirmed with Field emission scanning electron microscope (FESEM) using Carl Zeiss. The FE-SEM images of the algal film in FIG. 3C indicate the thread like structure which can increase the interaction of algal filaments with water. The higher magnified image (FIG. 3D) shows the high surface area for interaction with the water molecules.
[0069] Fourier Transformation Infrared Spectroscopy (FTIR) Analysis:To study the presence of functional groups on the macroalgae, Fourier transformation infrared spectroscopy (FTIR) was performed using Thermo-fisher, USA. FIG. 4 shows the obtained FTIR spectra of the Pithophora algae. As shown in FIG. 4, there are many vibration peaks obtained from the hydrophilic functional groups, such as surface hydroxyl groups at 3701 cm-1 and 3345 cm-1. The stretching vibration of carbon and hydrogen obtained at 2931 cm-1.The sharp peak at 1650 cm-1 and 1034 cm-1 obtained due to presence of amide groups because of the cell proteins in algae. Thus, from this study it was found that Pithophora algae have large number of functional groups which results to a better capillary action.
[0070] Effect of Contact Angle On Hydrophilic Nature Of Algae:To obtain perfect water evaporation induced hydro-voltaic device, water wicking ability is an inevitable property of the material. To confirm that, hydrophilicity was measured by contact angle measurement and the image was shown in the FIG. 9. The Data physics OCA 50 equipment was used to measure the contact angle in order to determine the hydrophilic nature of the algae. FIG. 9(A) shown that a single drop of water was dropped, and the angle of contact was 138? whereas the FIG. 9(B) was showing the water was absorbed by the algae layer, within 4 s the angle reduced to 29? signifying the excellent hydrophilic nature. Thus, this could be very advantageous for a better capillary action. The reason for the good hydrophilic nature in algae due to the presence of high hydroxyl functional groups
[0071] Surface Charge Analysis Using Zeta Potential:To confirm the surface charge analysis of algae, zeta potential experiment was conducted, and it was shown in the supporting information FIG. 10. The Fig. clearly indicating the negatively charged surface of algae which can uplift the cations during the water wicking. Due to water pumping, a drift current was created along the plane.
[0072] EXAMPLE 3: PERFORMANCE ANALYSIS OF THE FABRICATED PHV:
[0073] After fabrication the PHV device (PHV-1, PHV-2), the output performance of macroalgae material based PHV was tested thoroughly using electrical source meter. During the experiments, the device’s bottom portion was submerged in water and the top portion was left outside. The current and voltage measurements of the PHV device were carried out using the Tektronix source meter (model no: 2450 SMU).
[0074] Experiment-1: The PHV-1 device generated a constant voltage nearly 0.28 V-0.335 V and current in the range of 4.3 µA at ambient temperature and humidity which was shown in FIG. 5. The stability of the PHV-1 device under ambient condition (80 % RH) was measured and shown in FIG. 5F, wherein the output was nearly same for almost 1400 min indicating this alga based PHV-1 devices having sufficient stability for practical applications.
[0075] Experiment-2:To show the practical application from this environmentally friendlyhydro-voltaic device PHV-1, seven PHV-1 deviceswere fabricated and connected in series and it was shown in FIG. 8A. Keithley source meter was used to measure the resultant generated voltage from the PHV-1 device, and it was shown in FIG. 8B. In the FIG. 8B, all the PHV-1 devices were connected in series and the resultant voltage was nearly 1.425 V. Hence, two individual capacitors were connected with the capacity of 1000 µF (25 V) for 5 min to store the charge, and it was shown in the FIG. 8C. The charged capacitors were connected in series using bread board, and a red LED bulb was attached, the LED light was lightened with very high intensity and it was further reduced after 10 s but not to zero and it was attached in the FIG. 8D.
[0076] Experiment-3:FIG. 5C is the graphical representation of the outputs from the PHV-2 device under sameelectrodes. Additional experiments to ensure the practical application of the device by attaching the different electrodes along the thickness were performed. Remarkably, the device shows excellent power generation in a single PHV-2 device over a long period using carbon and aluminium electrodes. FIG. 5C gives a stable current of 32 µA over 10,000 min. Also, the device shown a high voltage of more than 0.8 V over 12,000 min in FIG. 5D. These figures imply that this method might be useful to generate electricity from bio-based materials.
[0077] To ensure the device's practical applications, two PHV-2 devices were connected in series and the overall voltage from the device was measured. The obtained data is shown in FIG. 5E. It is clearly visible that the voltage was doubled during the series connection and shown more than 1.5 V. This enhancement in voltage is useful for low energy electronic devices.
[0078] Example- 4: PERFORMANCE ASSESSMENT OF PHV DEVICE UNDER VARIOUS CONDITIONS:
[0079] Confirmation ofPower Generation by Capillary Action: To confirm the power generation by capillary action through algae, several controlled experiments were carried out. It is significant to note that the output power was investigated while varying the spacing between the top and bottom electrodes. Hence, the device with various gaps between the electrodes such as 1.5 cm, 2 cm, 2,5 cm, 3.5 cm, and 4 cm were fabricated with same mass of algae and its output data was shown in FIG. 6A. Notably, 3.5 cm device giving the best output voltage of 0.33 V and 4.3 µA current. Thus, the 3.5 cm gap is the optimized device for water pumping whereas, the less gap device having high water pumping, but the interaction with water is less, whereas the high gap device like 4 cm having high interaction surface area but the capillary action may be less due to the extreme height. After the alteration of height, the width of the surface was changed with same gap (3.5 cm) between the electrodes. We varied the width of the plane like 1 cm, 1.5cm, and 3 cm and kept the quantity of algae same. For a good hydro-voltaic device, a capillary action should also be high, and the EDL surface also should be a considerable one. Hence, the 1 cm width sample having a better capillary action, though the EDL interaction area is less, where the 3 cm width device having a high surface EDL property, but due to the wide space, water uptake may be reducing. Thus, 1.5 cm width device maintains the equal benefits in water uptake and EDL interaction. The output data of the different width was shown in FIG.6B, FIG.6C and FIG. 6D. Basis on understanding, nearly 16 devices were fabricated and their output voltage and current is given in the supporting data FIG. 6E.
[0080] Effect of Sealing the Device on Power Generation: To confirm the factors influencing the power generation from fabricated device, several experimental were carried out. First, a major proof in hydro-voltaic device to confirm the necessity of external energy, so we have analysed the PHV device output by sealing the entire device with a polythene tape. No external energy was provided to the device to ensure the source of the power generation from the device. Interestingly, even in a sealed condition, the device given an output of voltage 0.1 V and nearly 1 µA current and it was shown in FIG. 11A. This is contradicting the widely reported basic phenomena of water evaporation induced hydro-voltaic devices. Moreover, systematic data of 5 open/ sealed devices was carried out and shown in FIG. 11B.From the obtained results, all sealed PHV devices still giving an output without any external energy supports (to carry out the evaporation). Only 20-30 mV was reduced during sealed condition. From this observation, we can conclude that impact of evaporation is independent of power generation.
[0081] Validation of Source for Power Generation:To validate the source of power generated from the device, we have done some optical analysis with the algae to understand the possible way of induced bioelectricity. For that, artificial solar simulator was used to illuminate the light on the algae and measured the output voltage. Interestingly, during light off condition the algae are giving high voltage whereas during light ON condition, the voltage is reducing, andit was shown in FIG. 7A. This is just opposite of the hydro-voltaic mechanism, where evaporation induced the electricity generation that conveys the other novel way of power generation. This may be due to the surface charge of living algae and did not dependmuch on the evaporation induced by light. Also, the reduction of voltage may be because of electrolysis of water by photosynthetic process in the presence of light.
[0082] Effect of Algal Cell Viability On Power Generation:To understand further the surface charge induced voltage generation, comparison was done using living algae and dead algae. Initially, we have measured the dry PHV device, and it was showing 0 A current, whereas during addition of water, the induction of current was initiated and continuing nearly 6 µA to 10 µA. To compare, we kept the device in a hot air oven at 70 ?C for 2 h. The colour of the PHV device was slightly changed from green colour (FIG. 7C) to light brown colour (FIG. 7D), this is a sign that algae’s live cells eventually die. The output current of PHV after 2 h of drying treatment is showing 2 µA-4 µA. After, the same PHV device was kept in hot air oven for 15 h at 70 ?C, its output current was reduced to 1 µA (FIG. 7B). The colour of the algae was changed to whitish green colour indicating almost whole algae content was totally dead. These two controlled experiments resulted strong evidence that the power was generated in PHV device is due to surface charges of living cells. From all observed behaviour of the device, the voltage generation was due to the interaction between the surface charge of live algae and the water molecules.
[0083] Effect of Relative Humidity on Power Generation: To alter the flow rate of water through the algae surface for measure the change in voltage generation, we have varied the surrounding relative humidity (RH) and measured the voltage. The obtained result is shown in FIG. 12. It is clear from the measured data, that, voltage is increasing when the relative humidity is decreasing. Therefore, more water molecules can pump to the top, which increases the voltage generation along the length. FIG. 12 tells the voltage is dropping from 320 mV to 150 mV when the RH changes from 62 % to 96 %.
[0084] Comparison of other HVs with PHV (this work):Though there is no previously reported work on HV power generation from algae, here some comparisons were tabulated with previously reported HV power generation data from different inorganic and bio materials. The comparison data is shown in Table 1.
Table 1 Comparison Of Other HV Reports With This Work.
Material used References Obtained voltage
Carbon nanotube In: Sustainable Energy & Fuels Carbon Nanotubes
(https://doi.org/ 10.1039/d1se01996a) 0.370 V/7 µA
Al2O3 TLC plates All-weathercompatible hydrovoltaic cells based on Al2O3 TLC plates. (https://doi.org/10.1021/acsomega.1c04751)
Towards Watt-scale hydroelectric energy harvesting by Ti3C2TXbased transpiration-driven electrokinetic power generators. Energy Environ
(https://doi.org/10.1039/d1ee00859e) 0.33 V/0.85 µA
Geobactersulfurreducens biofilms Water evaporation–induced electricity
withGeobactersulfurreducens biofilms. (https://doi.org/10.1126/ sciadv.abm8047) ~0.53 V/~2.28 µA at 90 % RH
ZnO nanoarray Self-powered wearable biosensor in a baby diaper for monitoring neonatal jaundice through ahydrovoltaic-biosensing coupling effect of ZnO nanoarray.
(https://doi.org/10.3390/ bios12030164) 0.03 V
BCP-RGO Efficient moistureinduced energy harvesting from water-soluble conjugated block copolymerfunctionalized reduced graphene oxide.
(https://doi.org/10.1021/acsomega.0c03717) 18 mV
Ni-Al layered double hydroxide Electricity generation from a Ni-Al layered double hydroxide-based flexible generator driven by natural water evaporation. (https://doi.org/10.1016/j.nanoen.2018.12.042) 0.7/1.3 µA
Milk protein nanofibrils Moisture-enabled hydrovoltaic power generation with milk protein nanofibrils.(https://doi.org/10.1016/j.nanoen.2022.107709) 0.65 V/ 2.9 µA
Present work -- 0.32 V/4.4 µA

, Claims:[0086] We claim:
1. A hydro-voltaic device (100) for surface charge induced bioelectricity generation, comprising:
a substrate (104) having a top end and a bottom end, the substrate configured to hold a macroalgae film (102) to form a biofilm deposited substrate (106);
a first electrode (108) affixed to the top end of the deposited substrate (106);
a second electrode (110) affixed to the bottom end of the deposited substrate (106), configured to immerse in an aqueous solution (112) located at an optimized spacing from the first electrode; and
a reservoir (114) comprising the aqueous solution (112) with the deposited substrate (106) in contact therewithin, wherein capillary action is configured to form an electric double layer formed at the macroalgae surface - aqueous solution interfaces, thereby generating voltage and current flow between the first electrode (108) and the second electrode (110).

2. The hydro-voltaic device (100) as claimed in claim 1, wherein the macroalgae is Pithophoraroettleri.

3. The hydro-voltaic device (100) as claimed in claim 1, wherein the generated voltage is in the range of 0.3 to 0.8 V.

4. The hydro-voltaic device (100) as claimed in claim 1, wherein the device (100) generates current in the range of 4 to 32 µA/ sq. cm.

5. The hydro-voltaic device (100) as claimed in claim 1, wherein the spacing between the first and second electrode ranges from 1 to 5 cm.
6. A method (200) for hydro-voltaic power generation integrated with electrostatic charges on macroalgae surface, the method comprising the steps of:
providing (201) pre-treated and fragmented macroalgae;
depositing (202) macroalgae uniformly on a substrate to form a biofilm deposited substrate;
drying (203) the biofilm deposited substrate overnight under predetermined conditions;
punching electrodes (204) along the length of biofilm deposited substrate to form a hydro-voltaic (PHV) device;
placing the PHV device in a reservoir (205) comprising an aqueous solution;
allowing the water to flow through the PHV device (206) by capillary action; and
forming an electric double layer (207) at soil- aqueous solution interfaces, thereby generating voltage and causing flow of current across the ends of the PHV device.

7. The method as claimed in claim 5, wherein pre-treatment of macroalgae includes washing with deionized water followed by fragmentation into small pieces.

8. The method as claimed in claim 5, wherein the predetermined conditions for drying in step 203 comprises relative humidity of 50-60% and a temperature ranging from 25-28°C.

9. The method as claimed in claim 5, comprising the step of placing the PHV device to an angle of contact to enhance the voltage generated.

10. The method as claimed in claim 5,comprising the step of exposing the device to reduced relative humidity to enhance the voltage generated.

Dr V. SHANKAR
IN/PA-1733
For and on behalf of the Applicants