Removing material from surfaces and related articles and systems

Abstract

Methods, articles, and systems involving the removal of material from surfaces are generally described.

Description

[0001]Attorney Docket No. M0925.70966WO00 REMOVING MATERIAL FROM SURFACES AND RELATED ARTICLES AND SYSTEMS RELATED APPLICATIONS This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application No.63 / 560,594, filed March 1, 2024, and entitled “Removing Material From Surfaces And Related Articles And Systems,” which is incorporated herein by reference in its entirety for all purposes. TECHNICAL FIELD Methods, articles, and systems involving the removal of material from surfaces are generally described. SUMMARY The present disclosure is generally related to methods, articles, and systems in which material is removed from surfaces. The material removal can be accomplished, for example, via bubble generation and / or pH adjustment. In certain embodiments, the methods, articles, and systems described herein can be used to remove material from surfaces while preserving the non-toxicity of the material and / or while preserving the viability of biological cells that form all or a part of the material. The subject matter of the present disclosure involves, in some cases, interrelated products, alternative solutions to a particular problem, and / or a plurality of different uses of one or more systems and / or articles. In one aspect, systems for removing material from surfaces are provided. In some embodiments, the system comprises: a primary electrode; and a counter electrode in electrochemical communication with the primary electrode, wherein: the primary electrode is in contact with an aqueous primary electrolyte, the counter electrode is in contact with an aqueous counter electrolyte, the counter electrolyte is fluidically separated from the primary electrolyte, and the system is configured to remove material from a surface of the primary electrode under at least some conditions under which electrolysis of water from the primary electrolyte and / or the counter electrolyte is performed. In another aspect, methods for removing material from a surface of a primary electrode are provided. In some embodiments, the method comprises: applying a voltage between the primary electrode comprising the surface and a counter electrode such that hydrogen gas bubbles are Attorney Docket No. M0925.70966WO00 formed and / or pH is altered by electrolysis at the primary electrode and material is removed from the surface of the primary electrode, wherein: the primary electrode is in contact with an aqueous primary electrolyte, optionally, the counter electrode is in contact with an aqueous counter electrolyte, and the counter electrolyte is fluidically separated from the primary electrolyte. In some embodiments, the method comprises: applying a voltage between the primary electrode comprising the surface and a counter electrode such that hydrogen gas bubbles are formed and / or pH is altered by electrolysis at the primary electrode and material is removed from the surface of the primary electrode. In some such embodiments, the material on the surface of the primary electrode comprise biological cells, and the biological cells remain viable after removal from the surface of the primary electrode; and / or the material on the surface of the primary electrode comprise an ingestible food product, and the ingestible food product remains non-toxic after removal from the surface of the primary electrode; and / or the material on the surface of the primary electrode comprise an ingestible drug product, and the ingestible drug product remains non-toxic after removal from the surface of the primary electrode; and / or the material on the surface of the primary electrode comprise a non-toxic organic material, and the non-toxic organic material remains non-toxic during removal from the surface of the primary electrode. Other advantages and novel features of the present disclosure will become apparent from the following detailed description of various non-limiting embodiments of the disclosure when considered in conjunction with the accompanying figures. In cases where the present specification and a document incorporated by reference include conflicting and / or inconsistent disclosure, the present specification shall control. BRIEF DESCRIPTION OF THE DRAWINGS Non-limiting embodiments of the present disclosure will be described by way of example with reference to the accompanying figures, which are schematic and are not intended to be drawn to scale unless otherwise indicated. In the figures, each identical or nearly identical component illustrated is typically represented by a single numeral. For purposes of clarity, not every component is labeled in every figure, nor is every component of each embodiment of the disclosure shown where illustration is not necessary to allow those of ordinary skill in the art to understand the disclosure. Attorney Docket No. M0925.70966WO00 FIG.1 is a cross-sectional schematic diagram of a system, in accordance with certain embodiments. FIG.2 is, in accordance with some embodiments, a cross-sectional schematic diagram of a system in which material is being removed from an electrode. FIG.3 is a cross-sectional schematic diagram of a system in which a counter electrode moves relative to a primary electrode, in accordance with some embodiments. FIG.4 is, in accordance with some embodiments, a cross-sectional schematic diagram of a system comprising an electrode and a sensor. FIGS.5A and 5B show, in accordance with some embodiments, fluorescent microscope images (FIG.5A) and measured surface coverage (FIG.5B) of Chlorella vulgaris adhesion on polycarbonate at different times. FIG.5C shows, in accordance with some embodiments, a schematic of an algae removal system using electrochemical bubble generation. Here, the anode (oxygen evolving) and cathode (hydrogen evolving) streams are separated to prevent toxic chlorine ions and other generated biocides at the anode from affecting algae in the cathodic region of interest. FIGS.5D-5E show, in accordance with some embodiments, fluorescent microscope images before (FIG.5D) and after (FIG.5E) bubbling. FIG.5F shows, in accordance with certain embodiments, a plot of algae coverage before and after bubbling. FIGS.6A-6B show, in accordance with some embodiments, an experimental system to measure algae removal by bubble generation. FIG.6A shows a schematic of the experimental setup comprising a transparent gold electrode, a PDMS mini-fluidic channel, and an optical microscope. Brightfield imaging was used to image the bubble activity, and fluorescence was used to image the algae on the surface. FIG.6B shows a two-fingered electrode design to minimize ohmic losses and to separate the anodic and cathodic activity. FIGS.7A-7C show, in accordance with some embodiments, experimental algae detachment results from surface micro bubble generation. FIG.7A shows Brightfield (top) and fluorescence (bottom) microscope images of bubbling at three different current densities. Scale bar is 200 µm. Measured bubble radius distribution (shown in FIG.7B) and algae coverage (shown in FIG.7C) as a function of current density. The line in FIG.7B indicates average bubble radius. FIGS.8A-8D show, in accordance with some embodiments, a theoretical model to estimate the shear stress induced by bubble departure. FIG.8A shows a schematic of fluid flow Attorney Docket No. M0925.70966WO00 beneath departing bubble. FIG.8B shows calculated wall shear stress beneath a departing bubble as a function of distance from nucleation site at multiple times for a bubble with 30 µm radius. FIG.8C shows predicted maximum wall shear stress as a function of non-dimensional distance from the nucleation site for multiple bubble radii. FIG.8D shows the probability of algae removal as a function of non-dimensional distance from nucleation site for multiple bubble radii. FIGS.9A-9C show, in accordance with some embodiments, the comparison of experimental and theoretical results for bubble departure. FIG.9A shows a schematic of single bubble departing a fouled surface and leaving a removal radius of detached algae of radius Rr. Removal radius is defined as radius at which 50% of the algae are removed post-departure. FIG. 9B shows fluorescent (left and right) and brightfield (middle) microscope images of a single bubble departing a surface covered in algae. Scale bar is 100 µm. FIG.9C shows measured and theoretically predicted removal radius versus bubble departure radius. FIG.10A shows, in accordance with some embodiments, a schematic of a centimetric scale prototype benchtop scale algae de-fouling system in which robotics are used to detach cells using electrolyte bubbles, with separated analyte and catholyte streams through a Proton Exchange Membrane (PEM). A linear actuator is used to move the secondary electrode over the surface and minimize Ohmic losses. FIG.10B shows, in accordance with some embodiments, algae coverage before bubbling, and after every sweep. After sweep 3, the medium is replaced with fresh algae-free medium to show effect of detached algae. Scale bar is 1 cm. FIG.10C shows, in accordance with some embodiments, images of algae medium with growing algae on day 0, 6, and 10. FIG.10D shows, in accordance with some embodiments, cell density of a diluted sample taken from a 1-hour long bubbling experiment to indicate viability remains through separating the streams. FIG.11A shows, in accordance with some embodiments, a schematic of a microfluidic cell adhesion platform. FIG.11B shows, in accordance with some embodiments, normalized algae coverage versus applied shear stress on the wall. FIG.11C shows, in accordance with some embodiments, fluorescence images of algae coverage after different applied wall shear stresses. Attorney Docket No. M0925.70966WO00 FIG.12A shows, in accordance with some embodiments, a systematic study of colloidal adhesion against applied shear for a 5.09 µm diameter Carboxyl-coated polystyrene bead and a 6.05 µm diameter un-coated polystyrene bead performed in 1M potassium Bicarbonate. FIGS.12B-12C show, in accordance with some embodiments, colloidal coverage (FIG. 12B) and microscope images (FIG.12C) as a function of current density. FIG.13A shows, in accordance with some embodiments, height versus time for a 30 µm radius bubble. FIG.13B shows, in accordance with some embodiments, water velocity beneath the bubble as a function distance from nucleation site for a 30 µm bubble. FIG.13C shows, in accordance with some embodiments, calculated Reynold’s number for the water flow beneath the bubble, taking the gap height as characteristic distance. FIG.14A shows a schematic of a bubble contacting a wall before departure. FIG.14B shows an estimate of bubble contact line radius versus bubble departure radius. FIGS.15A-15B show a gold electrode surface with confluent MG-63 cells before (FIG. 15A) and after (FIG.15B) bubbling. Scale bar is 100 µm. FIG.15C shows the viability of MG-63 human cells after detachment using standard trypsin enzyme approach and surface bubble generation approach. FIGS.16A shows an image of a bubble growing on an untreated gold surface with no visible contact line (scale bar is 100 micrometers), according to some embodiments. FIG.16B shows an image of a bubble growing on a thiol treat hydrophobic gold surface with a visible contact line (scale bar is 200 micrometers), according to some embodiments FIG.17A is a schematic of bubble growth and detachment, and algae removal from the surface, according to some embodiments. FIG.17B is a plot depicting the calculated wall shear stress beneath departing bubble as a function of distance from nucleation site at various times for a bubble with 30 µm radius, according to some embodiments. FIG.17C is a plot depicting the predicted maximum wall shear stress as a function of non-dimensional distance from the nucleation site for multiple bubble radii, according to some embodiments. Dashed horizontal line indicates shear stress of 9.5 Pa, which is the experimentally measured applied shear strength leading to 50% algae coverage. Attorney Docket No. M0925.70966WO00 DETAILED DESCRIPTION Certain aspects of the present disclosure involve systems and methods for removing materials from a surface of a primary electrode without damaging the removed materials and / or rendering the removed materials toxic. In accordance with certain embodiments, this can be realized by forming hydrogen gas bubbles at the primary electrode, wherein the hydrogen gas bubbles are dislodged from the surface resulting in the removal of the material from the surface. In some embodiments, the system comprises a vessel comprising the primary electrode, a counter electrode, a primary electrolyte, and a counter electrolyte. The hydrogen gas bubbles can, in some embodiments, be formed by electrolysis between the primary electrode and a counter electrode. The primary electrode may be in electrochemical communication with the counter electrode via a primary electrolyte in contact with the primary electrode and a counter electrolyte in contact with the counter electrode. During electrolysis, oxygen gas and chloride ions may be generated in the counter electrolyte, the latter of which may negatively impact the viability and / or non-toxicity of the material on the surface of the primary electrode. In some embodiments, the counter electrolyte can be fluidically separated from the primary electrolyte to advantageously prevent chloride ions generated at the counter electrode to interfere with the material at the primary electrolyte. In some embodiments, electrolysis of the water in a primary electrolyte and / or a counter electrolyte may alter the pH of the primary electrolyte to facilitate the removal of the material from the surface of the primary electrode. With advancements related to cell growth and proliferation techniques, various industries, including the pharmaceutical, biomedicine, implant, food processing, and biofuel industries are becoming increasingly dependent on bioreactors. These industries, among others, may use bioreactors to grow cells and / or process material (e.g., fuel, cosmetics, food, or drugs), but bioreactors often have limited efficiency due to downtime associated with fouling of the bioreactor surfaces. Historically, enzymatic approaches were utilized and rely on the use of trypsin to detach cells from surfaces. This is generally a slow process and has limited throughput. Accordingly, the present disclosure describes systems and methods for removing materials from a surface that can exhibit any one or more of a number of advantages, in certain cases. The systems and methods described herein may, in some embodiments, advantageously remove material from a surface such that the removed material remains viable, non-toxic, or is otherwise suitable for its intended use. As another advantage, the systems and methods described herein, in some embodiments, may remove material from the surface at a relatively high rate. Attorney Docket No. M0925.70966WO00 As noted above, certain embodiments are related to systems and the use of such systems to remove materials from electrodes. Accordingly, in some embodiments, the system comprises one or more electrodes. In some embodiments, the system comprises a primary electrode. For example, as shown in FIG.1, system 100 comprises primary electrode 102. In some embodiments, the system comprises a counter electrode. For example, as shown in FIG.1, system 100 comprises counter electrode 104. In some embodiments, the primary electrode and the counter electrode can be in electrochemical communication with each other when in the presence of one or more electrolytes. As an example, FIG.2 shows system 100 comprising primary electrode 102 and counter electrode 104. Primary electrode 102 and counter electrode 104 are in electrochemical communication with each other via primary electrolyte 206 and counter electrolyte 208. In some embodiments, the primary electrode is in contact with the primary electrolyte. For example, as shown in FIG.2, primary electrode 102 is in contact with primary electrolyte 206. During electrolysis, the primary electrode may serve as the cathode in an electrochemical reaction (e.g., electrolysis). That is, when the primary electrode is in contact with an electrolyte, a reduction reaction may occur at the primary electrode, thereby reducing water in the primary electrolyte to produce bubbles (e.g., hydrogen gas bubbles). For example, in FIG.2, electrolysis at primary electrode 102 forms bubbles 204B on surface 103 while primary electrode 102 is in contact with primary electrolyte 206. Bubbles 204B may dislodge to form dislodged bubbles 204A and remove material 110 from surface 103. In some embodiments, the primary electrode is conductive. The primary electrode may comprise any of a myriad of electrically conductive materials including but not limited to metals (e.g., gold, silver, platinum, copper, aluminum, zinc, and or combinations of these and / or other metals, such as are present in metal alloys (e.g., bronze, stainless steel)), conductive nanoparticles, carbon-based compounds (e.g., graphite, graphene, carbon black) and / or conductive polymers. The primary electrode may have any of a variety of form factors. In some embodiments, the primary electrode is a wire, a sheet, a foil, a layer, and / or a conductive network. In some embodiments, the primary electrode comprises a surface. In some embodiments, the primary electrode further comprises material (e.g., one or more solids) on the surface of the primary electrode. In some embodiments, the surface of the primary electrode can have sufficient adhesion to biological cells to allow for growth and proliferation of the biological cells. During electrolysis, hydrogen bubbles may be formed and dislodged at the surface of the Attorney Docket No. M0925.70966WO00 primary electrode thereby removing material on the surface. In some embodiments, the material removed from the surface of the primary electrode can be suspended in the primary electrolyte. For example, in FIG.2, system 100 comprises primary electrode 102 with material 110 on surface 103 of primary electrode 102. Upon the application of a voltage, hydrogen bubbles 204B form on surface 103 of primary electrode 102. As further shown in FIG.2, dislodged hydrogen bubbles 204A remove material 110 from surface 103 and form suspended material 202 in primary electrolyte 206. In some embodiments, the material on the surface of the primary electrode may be removed without the assistance of surfactants and / or other chemical compounds. In some embodiments, the surface can be patterned and / or roughened. That is, the surface of the primary electrode can be subjected to patterning and / or roughening processes including but not limited laser engraving, laser ablation, and / or photolithography. A patterned and / or roughened surface of the primary electrode may increase the number of nucleation sites on the surface thereby increasing the nucleation and / or formation of bubbles compared to a surface of a primary electrode that is otherwise identical conditions having a relatively smooth surface. Increased and / or improved hydrogen bubble formation may advantageously facilitate the removal of material from the surface of the primary electrode. In some embodiments, the surface of the primary electrode can include features (e.g., milliscale, microscale, and / or nanoscale features). In some embodiments, the features comprise protrusions. According to certain embodiments, the features comprise ridges, pores, spikes and / or posts. The milliscale features can have, for example, a maximum height of greater than 100 micrometers and up to 10 millimeters. The microscale features can have, for example, a maximum height of from 1 micrometer to 100 micrometers, from 1 micrometer to 10 micrometers, from 10 micrometers to 20 micrometers, from 20 micrometers to 30 micrometers, from 30 micrometers to 50 micrometers, from 50 micrometers to 70 micrometers, or from 70 micrometers to 100 micrometers. Combinations of the above cited ranges are also possible (e.g., 30 micrometers to 70 micrometers, or 20 micrometers to 100 micrometers). The nanoscale features can have, for example, a maximum height of from 1 nm to 1 micrometer. According to some embodiments, the maximum height of the nanoscale features is from 1 nm to 100 nm, from 100 nm to 200 nm, from 200 nm to 300 nm, from 300 nm to 500 nm, from 500 nm to 700 nm, or from 700 nm to 1 micrometer. Combinations of the above cited ranges are also possible (e.g., 300 nm to 700 nm, or 200 nm to 1 micrometer). Attorney Docket No. M0925.70966WO00 In some embodiments, the primary electrode is associated with a sensor. For example, in FIG.4, primary electrode 102 is associated with sensor 402. In some embodiments, the primary electrode is or is part of the sensor or is a surface on the sensor. Many commercial and / or industrial processes rely on sensors to provide feedback on the status of various conditions in a particular process. However, these sensors may foul over time with any of a myriad of material that may be in and / or around the local environment of the sensor. In some embodiments, the reduction reaction occurring at the primary electrode may produce hydrogen gas bubbles that remove the material on a surface of the sensor and / or alter the pH of the primary electrolyte to facilitate the removal of the material from the electrode and / or the sensor. In some embodiments, the primary electrode is or is part of a surface on the vessel. Fouling of surfaces within bioreactors, fermenters, cell culture flasks, and / or cell culture plates can compromise product quality, increase labor costs, and / or increase downtime of the aforementioned systems. In certain embodiments, the primary electrode can reduce fouling on the surfaces of the vessel thereby reducing the need for frequent maintenance and / or cleaning of the vessel surfaces. In some embodiments, the primary electrode can be optically transparent. In some embodiments, the primary electrode can be translucent. An optically transparent and / or translucent primary electrode may advantageously allow for visual and / or optical monitoring of fouling on the primary electrode surface. In some embodiments, the counter electrode is in contact with the counter electrolyte. For example, in FIG.2, counter electrode 104 is in contact with counter electrolyte 208. During electrolysis, the counter electrode may serve as the anode in an electrochemical reaction. That is, when the counter electrode is in contact with an electrolyte, an oxidation reaction may occur at the counter electrode, thereby oxidizing water to produce oxygen gas, in some embodiments. For example, in FIG.2, counter electrode 104 is oxidizing water in the counter electrolyte 208 while bubbles 204B are forming on primary electrode 102. In some embodiments, biocides can be generated at the counter electrode. In some embodiments, the biocides may include but are not limited to chlorine gas, chlorine ions, hypochlorite, among others. In some embodiments, the biocides may negatively affect the material being removed from the surface of the primary electrode. The counter electrode may comprise any of a myriad of electrically conductive materials including but not limited to metals (e.g., gold, silver, platinum, copper, aluminum, zinc, and or combinations of these and / or other metals, such as are present in metal alloys (e.g., bronze, Attorney Docket No. M0925.70966WO00 stainless steel)), conductive nanoparticles, carbon-based compounds (e.g., graphite, graphene, carbon black) and / or conductive polymers. The counter electrode may have any of a variety of form factors. In some embodiments, the primary electrode is a wire, a sheet, a foil, a layer, and / or a conductive network. In some embodiments, the primary electrode and the counter electrode are in electrical communication with a voltage source. For example, as shown in FIG.1, primary electrode 102 is in electrical communication with counter electrode 104 via voltage source 106. Upon the application of a voltage between the primary electrode and the counter electrode, an electrolysis reaction may occur thereby produce hydrogen bubbles at the surface of the primary electrode. In some embodiments, the counter electrode and the primary electrode can be moved relative to each other. In some embodiments, the primary electrode and counter electrode can be moved relative to each other while remaining in electrochemical communication. For example, as shown in FIG.3, counter electrode 100 within movable container 302 can vary its position with respect to primary electrode 102. Without wishing to be bound by any particular theory, by varying the position of the counter electrode with respect to the primary electrode, the distance between the counter electrode and the position of material on the surface may be reduced. Accordingly, the ohmic losses between the primary and counter electrode may be reduced thereby allowing for greater bubble generation and material removal. In some embodiments, the counter electrode and the primary electrode are in relative motion in a lateral direction (e.g. by moving the counter electrode laterally relative to the primary electrode). In some embodiments, the counter electrode moves along a first geometric plane that is substantially parallel to (e.g., within 5°, within 3°, within 1°, or within 0.1° of parallel to) a second geometric plane defined by the surface of the primary electrode. In some embodiments, the counter electrode moves along a third geometric plane that intersects the second geometric plane defined by the surface of the primary electrode. In some embodiments, the distance between the primary electrode and the counter electrode is relatively small. The uses of “primary” and “counter” with respect to the any electrodes or other components (e.g., electrolytes) disclosed herein are simply used for convenience of referring to these two electrodes, and these terms are not being used in a way that is intended to be otherwise limiting. As noted above, in some embodiments, the system comprises a primary electrolyte. In some embodiments, the primary electrolyte is an aqueous primary electrolyte. In some embodiments, the primary electrode is in contact with the primary electrode. For example, in Attorney Docket No. M0925.70966WO00 FIG.2, primary electrolyte 206 is in contact with primary electrode 102. The primary electrolyte can, in some embodiments, comprise any of a myriad of electrolyte solutions including but not limited to potassium bicarbonate, sodium chloride, sodium nitrate, calcium chloride, magnesium sulfate, or dipotassium phosphate. In some embodiments, the primary electrolyte comprises algal culture media (e.g., Modified Bold 3N Medium by UTEX). In some embodiments, the primary electrolyte is chloride-free (e.g., substantially free of chlorine ions) and / or free of chlorine gas during electrolysis. In some embodiments, the primary electrolyte is substantially free of biocides. Biocides formed during electrolysis, such as chlorine ions and / or chlorine gas, may harm the growth of biological compounds, such as algae and / or cells, and / or contaminate ingestible food and / or drug products. In certain embodiments, the primary electrolyte does not form chlorine ions and / or chlorine gas during electrolysis thereby removing the material on the surface of the primary electrode without harming and / or contaminating the material. As noted above, in some embodiments, the system comprises a counter electrolyte. In some embodiments, the counter electrolyte is an aqueous counter electrolyte. In some embodiments, the counter electrolyte is in contact with the counter electrode. For example, in FIG.2, counter electrolyte 208 is in contact with counter electrode 104. The counter electrolyte can, in some embodiments, comprise any of a myriad of electrolyte solutions including but not limited to potassium bicarbonate, sodium chloride, sodium nitrate, calcium chloride, magnesium sulfate, or dipotassium phosphate. In some embodiments, the counter electrolyte comprises algal culture media (e.g., Modified Bold 3N Medium by UTEX). In some embodiments, the counter electrolyte is chloride-free (e.g., substantially free of chlorine ions) and / or chlorine gas during electrolysis. In some embodiments, the counter electrolyte is substantially free of biocides. As described elsewhere in this disclosure, biocides formed during electrolysis may harm the growth of biological compounds, such as algae and / or cells, and / or contaminate ingestible food and / or drug products. In certain embodiments, the counter electrolyte does not form chlorine ions and / or chlorine gas during electrolysis such that the system can remove material on the surface of the primary electrode without harming and / or contaminating the material. In some embodiments, the counter electrolyte comprises chloride (e.g., chlorine ions) and / or chlorine gas during electrolysis. In some embodiments, the counter electrolyte comprises biocides and / or other contaminants that may harm and / or otherwise damage the material on the surface of the primary electrode. Advantageously, the system described herein may remove Attorney Docket No. M0925.70966WO00 material from the surface of the primary electrode without having biocides and / or other contaminants in the counter electrolyte to harm or damage the material. In some embodiments, the counter electrolyte is fluidically separated from the primary electrolyte. For example, in FIG.2, counter electrode 104 and counter electrolyte are positioned within container 113 such that counter electrolyte 208 is fluidically separated from primary electrolyte 206. In some embodiments, the system comprises an ion-conductive medium that allows the primary electrode and the counter electrode to maintain electrochemical communication while being fluidically separated. For example, in FIG.2, ion-conductive medium 108 separates counter electrolyte 208 and counter electrode 104 from primary electrode 102 and primary electrolyte 206. In some embodiments, biocides (e.g., chlorine ions, chlorine gas) can be generated at or near the counter electrode, and these biocides may negatively affect the material being removed from the surface of the primary electrode. By separating the counter electrode from the primary electrode, the biocides (e.g., chlorine ions and / or chlorine gas) may not interact with the material on the surface of the primary electrode or the material suspended in the primary electrolyte. In some embodiments, fluid separation between the counter electrolyte and the primary electrode is maintained by the ion-conductive medium. In some embodiments, the ion- conductive medium is an ion-conductive membrane. In some embodiments, the ion-conductive medium is a charge-selective membrane. In some embodiments, the ion-conductive medium is a proton exchange membrane. Without wishing to be bound by any particular theory, the ion conductive medium may selectively allow for the passage of species (e.g., charged species, protons) through the medium while inhibiting the migration of biocides from the counter electrode and counter electrolyte to the primary electrode and primary electrolyte. Accordingly, the ion conductive medium facilitates and maintains the separation between the primary electrolyte and counter electrolyte while maintaining electrochemical communication between the primary electrode and counter electrode. In some embodiments, the system is configured to remove material from the surface of the primary electrode. In some embodiments, removal of the material can be at least partially derived from bubble generation. In some embodiments, removal of the material can be at least partially derived from pH variation within the primary electrolyte. In some embodiments, removal of the material can be at least partially derived from both bubble generation and pH variation within the primary electrolyte. For example, as shown in FIG.2, material 110 on surface 103 of primary electrode 102 can be removed by forming bubbles 204B on surface 103. Attorney Docket No. M0925.70966WO00 In some embodiments, the bubbles comprise hydrogen gas bubbles. As dislodged bubbles 204A detach from surface 103, removed material 202 may be suspended in primary electrolyte 206. In some embodiments, the material suspended in the primary electrolyte can be collected for use for its intended application. In some embodiments, the removal of the material from the surface of the primary electrode is not due to physical, chemical, or biological alteration of the material itself. Without wishing to be bound by any particular theory, the removal of the material from the surface of the primary electrode may be a result of the hydrodynamic properties associated with the formation and / or dislodgment of bubbles rather than the alteration of the material itself. In some embodiments, electrolysis of the water in the primary electrolyte and / or the counter electrolyte can occur under any of a variety of conditions. In some embodiments, a voltage of at least 0.5 V, at least 1V, at least 3V, at least 5V, at least 10V, and / or at least 15V is applied between the primary electrode and the counter electrode. In some embodiments, a current density is applied across the primary electrode and the counter electrode. In some embodiments, the current density applied between the primary electrode and the counter electrode is greater than or equal to 10 mA / cm2, greater than or equal to 25 mA / cm2, greater than or equal to 50 mA / cm2, greater than or equal to 100 mA / cm2, greater than or equal to 150 mA / cm2, and / or greater than or equal to 200 mA / cm2. In some embodiments, the current density applied between the primary electrode and the counter electrode is less than or equal to 200 mA / cm2, less than or equal to 150 mA / cm2, less than or equal to 100 mA / cm2, less than or equal to 50 mA / cm2, less than or equal to 25 mA / cm2, or less than or equal to 10 mA / cm2. Combinations of these ranges are also possible (e.g., greater than or equal to 10 mA / cm2and less than or equal to 200 mA / cm2). Other ranges are also possible. In some embodiments, the bubbles each have a radius. Without wishing to be bound by any particular theory, bubbles having larger radii may be more effective at removing material from the surface of the primary electrode. In some embodiments, at least 50 vol%, at least 75 vol%, at least 90 vol%, at least 95 vol%, at least 98 vol%, at least 99 vol%, or at least 99.9 vol% of the total volume of the bubbles generated in the system have a radius of greater than or equal to 5 micrometers, greater than or equal to 10 micrometers, greater than or equal to 15 micrometers, greater than or equal to 20 micrometers, greater than or equal to 30 micrometers, greater than or equal to 40 micrometers, greater than or equal to 50 micrometers, greater than or equal to 75 micrometers, or greater than or equal to 100 micrometers. In some embodiments, at least 50 vol%, at least 75 vol%, at least 90 vol%, at least 95 vol%, at least 98 vol%, at least 99 vol%, or at least 99.9 vol% of the total volume of the bubbles generated in the system have a Attorney Docket No. M0925.70966WO00 radius of less than or equal to 100 micrometers, less than or equal to 75 micrometers, less than or equal to 50 micrometers, less than or equal to 40 micrometers, less than or equal to 30 micrometers, less than or equal to 20 micrometers, less than or equal to 15 micrometers, less than or equal to 10 micrometers, or less than or equal to 5 micrometers. Combinations of these ranges are possible (e.g., greater than or equal to 5 micrometers and less than or equal to 100 micrometers). Other ranges are possible. In some embodiments, the material on the surface of the primary electrode comprises one or more solids. In some embodiments, the material comprises a non-homogeneous mixture of phases (e.g., materials comprising phases of solids and / or liquids, biological cells). That is, the material may comprise one or more phases of matter. In some embodiments, the material comprises one or more solids. In some embodiments, the solids comprise biological cells, ingestible food products, ingestible drug products, and / or non-toxic organic matter. The material may comprise, for example, nutritional fiber, nutritional fat, nutritional carbohydrates, and / or nutritional protein. In some embodiments, the material comprises at least some solid. In some embodiments, the material comprises solid in combination with a liquid and / or a gas. In certain embodiments, the material is not a homogeneous gas. In some embodiments, the material is not a homogeneous liquid. In some embodiments, the material removed by the system may remain suitable for its intended purpose after removal. Without wishing to be bound by any particular theory, the application of a voltage between the primary electrode and the counter electrode may induce electrolysis of water in the electrolytes in the system, and the resulting pH alteration and / or the formation of hydrogen gas bubbles on the primary electrode may remove material on the surface of the primary electrode without damaging, contaminating, or otherwise harming the material rendering it less suitable for its intended purpose. In some embodiments, the dislodgement of hydrogen gas bubbles can advantageously allow for the material to be removed in a relatively gentle manner without imparting significant damage to the material. In some embodiments, the material comprises biological cells and / or proteins. In some embodiments, the system is configured to remove the biological cells and / or the proteins from the surface of the primary electrode. In some embodiments, the biological cells and / or the proteins remain viable after removal from the surface of the primary electrode. That is, the biological cells and / or the proteins, during removal from the surface, have not been altered in a manner that renders them less suitable for their intended purpose. In some embodiments, the biological cells comprise MG-63 cells. In some embodiments, the biological cells and / or the Attorney Docket No. M0925.70966WO00 proteins comprise any of a myriad of cells and / or proteins including but not limited to cells and / or proteins derived from bacterial, fungal, mammalian, and / or plantae origin. In some embodiments, the biological cells comprise algae. In some embodiments, the material comprises a polypeptide. In some embodiments, the removal of biological cells and / or the proteins from the surface of the primary electrode is not associated with the alteration of the biological cell and / or the protein and / or the viability of the biological cell and / or the protein. Without wishing to be bound by any particular theory, the biological cells and / or the proteins may be removed from the surface of the primary electrode as a result of the hydrodynamic properties associated with the formation and / or dislodgment of bubbles rather than biological cell death and / or alteration. Generally, viable biological cells are those that may be re-cultured in an appropriate cell culture medium. Thus, in accordance with certain embodiments, the viability of the biological cells removed from the surface can be determined by re-culturing the biological cells in an appropriate cell medium. Viability of biologicals cells can be determined using a cell counter (e.g., CellDrop FL cell counter). In some embodiments, the biological cells and / or the proteins can retain their respective function (e.g., catalytic function) after removal from the surface. In some embodiments, the material removed from the surface is a non-toxic material and remains so after removal from the surface. In certain embodiments, the material removed from the surface includes substantially no materials other than those included on the FDA’s “Generally Recognized as Safe” Substances database and / or listed in 21 C.F.R. § 182. The term “toxic” generally refers to a substance showing detrimental, deleterious, harmful, or otherwise negative effects on a subject, tissue, or cell when or after administering the substance to the subject or contacting the tissue or cell with the substance, compared to the subject, tissue, or cell prior to administering the substance to the subject or contacting the tissue or cell with the substance. In certain embodiments, the effect is death or destruction of the subject, tissue, or cell. In certain embodiments, the effect is a detrimental effect on the metabolism of the subject, tissue, or cell. In certain embodiments, a toxic substance is a substance that has a median lethal dose (LD50) of not more than 500 milligrams per kilogram of body weight when administered orally to an albino rat weighing between 200 and 300 grams, inclusive. In certain embodiments, a toxic substance is a substance that has an LD50 of not more than 1,000 milligrams per kilogram of body weight when administered by continuous contact for 24 hours (or less if death occurs within 24 hours) with the bare skin of an albino rabbit weighing between two and three kilograms, inclusive. In some embodiments, a toxic substance is a substance that has a LD50 Attorney Docket No. M0925.70966WO00 less than or equal to the LD50 of bleach, chlorine gas, and / or hypochlorous acid. For instance, in some embodiments, a toxic substance having an LD50 less than or equal to the LD50 of bleach will have a LD50 less than or equal to 8200 milligrams per kilogram of body weight. The term “non-toxic” refers to a substance that is not toxic. In some embodiments, the material comprises an ingestible food product. In some embodiments, the system is configured to remove the ingestible food product from the surface of the primary electrode. In some embodiments, the ingestible food product remains non-toxic after removal from the surface of the primary electrode. That is, the ingestible food product after removal may be suitable for safe consumption by the intended subject (e.g., a human subject and / or a non-human animal subject). In some embodiments, the ingestible food product is substantially free of any of the biocides or other toxins generated by the system. In some embodiments, bleach, chlorine gas, and / or hypochlorous acid is not present in the ingestible food product. In some embodiments, the material comprises an ingestible drug product. In some embodiments, the system is configured to remove the ingestible drug product from the surface of the primary electrode. In some embodiments, the ingestible drug product remains non-toxic after removal from the surface of the primary electrode. That is, the ingestible drug product after removal may be suitable for safe consumption by the intended subject (e.g., a human subject and / or a non-human animal subject) at the intended dosage. In some embodiments, the ingestible drug product is substantially free of any of the biocides or other toxins generated by the system. In some embodiments, bleach, chlorine gas, and / or hypochlorous acid is not present in the ingestible drug product. In some embodiments, the material comprises a non-food, non-drug, non-toxic organic material. In some embodiments, the system is configured to remove the non-food, non-drug, non-toxic organic material from the surface of the primary electrode. In some embodiments, the non-toxic organic material remains non-toxic after removal from the surface of the primary electrode. In some embodiments, bleach, chlorine gas, and / or hypochlorous acid is not present in the remove the non-food, non-drug, non-toxic organic material. In some embodiments, material is removed from the surface of the primary electrode under at least some conditions under which electrolysis of water in the primary and / or counter electrolyte can be performed. In some embodiments, electrolysis of water in the primary electrolyte and / or the counter electrolyte may be initiated by applying a voltage between the primary electrode and the counter electrode. Attorney Docket No. M0925.70966WO00 In some embodiments, the system comprises a vessel. In some embodiments, the vessel comprises the primary electrode, the primary electrolyte, the counter electrode, the counter electrolyte, the ion conductive medium, and / or the container. In some embodiments, the vessel is configured to hold the primary electrolyte and the counter electrolyte. For example, in FIG.2, system 100 comprises vessel 112 holding primary electrolyte 206. In some embodiments, the vessel is configured such that the primary electrolyte and / or the counter electrolyte may be introduced and / or removed via an inlet and / or outlet. In some embodiments, the material removed from the surface of the primary electrode and suspended in the primary electrolyte can be collected via an outlet on the vessel. In some embodiments, the vessels can be configured to agitate the primary electrolyte to further facilitate the removal of material from the surface of the primary electrode. In some embodiments, the vessel is configured to support a biologically active environment. That is, the vessel may impart, maintain, or be subjected to conditions that facilitate the growth and proliferation of biological compounds (e.g., biological cells). Such conditions include but are not limited to pH, temperature, pressure, electromagnetic radiation, and / or mechanical agitation. In some embodiments, the vessel is or is part of a bioreactor. In some embodiments, the vessel is or is a part of a fermenter. In some embodiments, the vessel is or is a part of a cell culture plate. In some embodiments, the vessel is or is a part of a cell culture plate. In some embodiments, the vessel is or is a part of a photobioreactor. The vessel described herein may comprise any of a myriad of materials. In some embodiments, the vessel comprises a polymeric material. In some embodiments, the vessel comprises a ceramic. In some embodiments, the vessel comprises a metal. In some embodiments, a surface of the vessel comprises the primary and / or the counter electrode. In some embodiments, material can be removed from a relatively large percentage of the surface area of the surface (e.g., the surface of the primary electrode). For example, in some cases, material can be removed from at least 25%, at least 50%, at least 75%, at least 90%, at least 95%, at least 99%, at least 99.9%, or from 100% of the surface area of the surface (e.g., the surface of the primary electrode). In some cases, at least 25%, at least 50%, at least 75%, at least 90%, at least 95%, at least 99%, at least 99.9%, or 100% of the surface area of the surface that was originally covered by the material is no longer covered by the material after removal of material from the surface. In some embodiments, material can cover a surface area of the surface that is at least 1 cm2, at least 10 cm2, at least 50 cm2, at least 100 cm2, at least 500 cm2, at least 1000 cm2, at least Attorney Docket No. M0925.70966WO00 5000 cm2, at least 1 m2, at least 10 m2, or more. In some such embodiments, the material can be removed from a relatively large percentage of such covered surface area (e.g., from at least 25%, at least 50%, at least 75%, at least 90%, at least 95%, at least 99%, at least 99.9%, or from 100% of the covered surface area of the surface). In some embodiments, a relatively large percentage of the material that is removed from the surface can remain non-toxic and / or viable. For example, in some embodiments, at least 25%, at least 50%, at least 75%, at least 90%, at least 95%, at least 99%, at least 99.9%, or 100% of the biological cells removed from the surface can remain viable. In certain embodiments, at least 25%, at least 50%, at least 75%, at least 90%, at least 95%, at least 99%, at least 99.9%, or 100% of the material removed from the surface can remain non-toxic. The following examples are intended to illustrate certain embodiments of the present invention, but do not exemplify the full scope of the invention. EXAMPLE 1 Biofouling and uncontrolled cell-adhesion are an important challenge for a wide range of industries and applications with bio-sensitive media (e.g., biosensitive environments) such as pharmaceuticals, biomedicine, biosensors and other implants, food processing, energy, biofuel production as well as many others. Moreover, on-demand cell detachment is of great importance in the aforementioned application. Existing methods such as enzymatic treatments and mechanical scraping are often time-consuming, labor-intensive, and harmful to cells. In two- dimensional cell culturing, for example, passaging requires the viable removal of adherent cells from the surface for subsequent re-culturing. Current cell detachment strategies for mammalian cell cultures rely heavily on enzymatic approaches, a time intensive method which harms cell viability and generates large volumes of liquid waste; a process largely unchanged for over 100 years. Another example is algae-fouling in photobioreactors (e.g., algae adhesion to walls of photobioreactors). Photobioreactors are a common tool used to cultivate algae for applications such as cosmetics, biofuel, dietary supplements, and medical drugs among others. Currently their operation is limited due to fouling leading to large downtimes for cleaning, thereby increasing operational costs. To illustrate this, an accelerated in-lab fouling study that simulated photobioreactor conditions on a lab-scale and found that algae coverage increased rapidly over time as shown in FIGS.5A-5B (see the Additional Details section below for experimental procedures) was performed. This experiment was performed on polycarbonate, a material commonly used in photobioreactors. Attorney Docket No. M0925.70966WO00 Over the last several decades, several technologies have emerged as potential solutions for fouling in bio-sensitive environments, such as surface coatings with biocidal compounds or functionalization inhibiting protein adsorption or electrostatically active surfaces. However, the fast depletion of molecules in such coatings and the ability to only slow down but not eliminate fouling has limited their practical implementation. Recently, electrochemical gas-evolving surfaces have been used to actively remove foulants. These pass a current and split water, and generate bubbles at the interface through an applied voltage. However, the rapid depletion of molecules in such coatings have limited their practical implementation. Some anti-fouling and cell-detachment strategies have employed active and on-demand methods of local biocide formation, such as sodium hypochlorite (bleach) and hypochlorous acid generated on the fouled surface through electrochemical means. Highly effective in detaching cells and foulants, the formation of biocides limits its application to applications where the survival of detached cells and surrounding environment are not critical concerns, such as with underwater sensors or desalination membranes. Interestingly, this electrochemical process also generates bubbles directly on surfaces, but these bubbles have been viewed as byproducts that merely enhance the function of the biocide. It has been stipulated that anti-fouling occurs on these surfaces through a combination of biocide formation through electrochlorination, triple-contact-line movement, and fluid flows generated by the growing bubble. Without wishing to be bound by any particular theory, when the departing bubble departs from the fouled surface, the bubble may efficiently detach foulants (e.g., cells) and provides a physical mechanism for cell detachment that allows for on-demand, repeatable, and viable detachment. However, other foulant release mechanisms from the surface remain unclear. Furthermore, the potential of biocide generation to negatively impact sensitive applications remains uninvestigated. Narrowing down the exact method of detachment is of importance, especially for applications with sensitive media. Namely, if triple contact line movement or mechanical effects of bubble growth or departure are responsible for detaching the cells, there is an opportunity to use surface level bubble generation with sensitive cells or in chemically sensitive media. If the detachment method is mainly due to biocide formation and inactivation of the cells, then this method is not applicable for these applications. To investigate if bubble generation can be a successful cell removal strategy without affecting viability, first electrochlorination needs to be eliminated. To illustrate that bubble generation without local electrochlorination can still remove foulant, the set-up as shown in FIG. 5C is used (see the Additional Details section below for experimental procedures). As biocides Attorney Docket No. M0925.70966WO00 such as chlorine ions and hypochlorite are generated at the anode, the anode and cathode are separated in this setup. By focusing on the hydrogen evolving surface (cathode) and separating toxic biocides generated at the oxygen evolving surface (anode) from the region of interest, it can be shown that fouling can be detached solely using local bubble generation. Chlorella vulgaris micro-algae are used as a model cell. Chlorella vulgaris is a fresh- water algae commonly grown for dietary supplements, biofuel, and cosmetics. It has a diameter of 2 to 10 µm. Bubbles are electrochemically generated on a bio-fouled surface composed of 10 nm transparent gold film on glass, which constitutes the biofouled electroactive surface. In FIGS.5D-5F, it is shown that algae foulant is successfully detached through hydrogen bubble generation on the cathode surface at the region of interest. To show that viability remained, detached algae were captured and successfully re-cultured. In this work surface-level (e.g., electrochemical) bubble generation was demonstrated as a method of gently detaching cells from surfaces without biocide formation and hence without affecting the biological viability. Unlike previous strategies to prevent adhesion that are either chemistry specific or solution specific, a strategy that physically removes the foulant and does not depend on the chemical details of the material is implemented. A milli-fluidic imaging platform with a chloride-free electrolyte is created to study the interactions between departing bubbles and fouled algae on the surface in a chlorine-free medium to underscore the significance of hydrodynamic factors in both bubble and cell detachment processes. An inverted fluorescence microscopy setup to allow for the imaging of both the bubble dynamics and the attached algae on the surface was also used. Experiments were conducted using individual bubble departures on surfaces populated with adhered cells to ascertain the effective radius of action of within which a departing bubble. Quantification of the influence of algae influences on its surroundings was also explored. Using single bubble departures on fouled surfaces, the radius of action of a departing bubble was measured. The algae adhesion strength to the gold surface was independent quantified using a tunable shear flow in a micro-fluidic chip. Based on the observations, it may be hypothesized that a new mechanism of foulant removal, namely shear stress on the wall generated beneath departing bubbles, without biocide generation is possible. This hypothesis is supported with an analytical model that can predict the shear stress generated by fluid flow beneath a departing bubble. The model is validated using a micro-fluidic adhesion experiment, and through experiments using single bubble departure on fouled surfaces. Finally, a lab-scale de-fouling set-up was built where robust and low-power fouling removal was shown in algae medium while maintaining Attorney Docket No. M0925.70966WO00 high viability. The on-demand prototype detachment approach with partitioned electrodes that allowed for biocide-free operation even in media containing chloride ions. The same set-up is used to detach mammalian cells (MG-63 cultured human cells ) with high viability for further culturing. Therefore, unlike existing strategies that prevent adhesion through toxic coatings, this technique physically removes already adhered cells on demand. Moreover, the primary mechanism of cell detachment presented in this work relies solely on hydrodynamic flows beneath rising bubbles, hence does not depend on the chemical details of the material, foulant, or solution. Mini-fluidic algae detachment platform with chloride-free electrolyte To investigate the mechanism of cell de-adhesion further, a platform was developed that was capable of imaging both the electrochemically induced micro-bubbles and the cells adhered to the surface. Freshwater algae chlorella vulgaris algae have a diameter of 2 to 10 µm. Chlorella vulgaris autofluoresce which allows for separate imaging from the micro-bubbles. For this, an inverted microscope is equipped with both transmission brightfield and reflective fluorescence imaging to image the bubbles and micro-algae respectively. For fluorescence, the beamsplitter has a 475 nm with 40 nm bandpass exciter, 500 nm splitter, and 650 nm longpass receiver lenses. Algae autofluoresce at these wavelengths. Transmission brightfield microscopy allows for the highspeed imaging of evolving bubbles, while reflective fluorescence microscopy allows for the visualization of cells’ adherence to and detachment from the surface without interference of the bubbles above (e.g., unaffected by any overlaying bubbles). For the electrode surface, a transparent gold electrode with film-thickness of 10 nm on glass was used and purchased from Platypus Technologies LLC. Gold was chosen as a catalyst due to its high stability and resistance to corrosion. At 10 nm, the gold electrode on glass is transparent to both visible and fluorescent light at the wavelengths of interest. A mini-fluidic channel is created out of polydimethylsiloxane (PDMS) and attached to the electroactive gold surface. A mold was 3D printed using a Formlabs SLA printer to cast the PDMS channel. The resulting channel has a height of 3 mm, width of 4 mm, and length of 2 cm. The resulting mini-fluidic detachment platform is shown in FIG.6A. To prevent electrochlorination, a chloride free electrolyte is necessary to avoid negatively affecting cell viability. For this purpose, 1M of potassium bicarbonate is used as electrolyte. The resulting electrolyte has a pH of 8.2, within the range of growth conditions for freshwater algae. The 1M potassium bicarbonate electrolyte furthermore acts as a buffer, meaning it will act to dampen pH Attorney Docket No. M0925.70966WO00 responses near the electrode. For the electrode, a two-fingered design as seen in FIG.6B was chosen. Each electrode has a width of 10 mm and a height of 1 mm, leading to an active electrode area of 10 mm2for the anode and cathode. The spacing between the two electrodes is 1 mm, and strategically chosen to reduce Ohmic losses while allowing for ample separation to prevent mixing between the two streams. Freshwater algae Chlorella vulgaris were used as model cells. Chlorella vulgaris algae are cultured for 5-9 days (see the Additional Details section below for further details). The resulting algae solution is then introduced in the mini-fluidic channel and allowed to settle for 2 hours. After 2 hours, the algae media is flushed out and replaced with the potassium bicarbonate electrolyte by flowing at 1 ml per minute for 5 minutes. At this point, the channel was filled with chloride-free electrolyte, with cells attached on the wall. To start the experiment, bubbling was then induced by applying a set current density across the two electrodes using a DC power supply. To emulate conditions found in photobioreactors and to remove detached algae, a low electrolyte flowrate of 1 ml per minute is applied to the channel with a syringe pump. This leads to an applied shear stress on the wall of around 3 mPa, well below the required shear stress to remove attached algae. This leads to a flow velocity of 0.1 m / s, similar to those found in photobioreactors. To quantify the adhesion strength of chlorella vulgaris onto the electrode substrate and to validate that the chloride-free potassium bicarbonate electrolyte is not harmful to the algae cells in this time, an adhesion experiment in a microfluidic chip was performed (see the Additional Details section below). An S-shape curve (e.g., an algae adhesion curve as a function of increasing wall shear stress) for remaining algae coverage versus applied wall shear stress is found. At 9.6 Pa of wall shear stress, 50% of the algae attached to the surface are removed. This indicates that algae adhesion remains when switching solution from culturing media to the potassium bicarbonate electrolyte solution, and such a switch does not compromise the algae’s ability to adhere within the time window of the experiments. Detaching algae using interfacial micro-bubble generation. In FIG.7A microscope images of the algae surface at multiple applied current densities can be seen. At each step, 10 seconds of bubbling is applied. See the Additional Details section below for the full experimental procedure. With increasing current density an increase in bubbling can be seen. This is expected as current density is directly related to the volumetric gas flux. The increase in the surface bubble coverage with increasing current density coincides with Attorney Docket No. M0925.70966WO00 a slight decrease in average size and a decrease in the variance of the bubble radii, as seen by the bubble radius distribution in FIG.7B. An average bubble radius of around 30 µm is found for the three higher current densities. Increasing current density also results in a steep decrease in algae coverage, as shown in FIG.7C. At the highest current density tested, the remaining algae coverage is less than 15% of the original coverage. This shows the efficacy of surface level bubble generation in detaching cells. It is important to note that the salinity of the solution is high, higher than that of seawater. This experiment shows that micro-bubble generation at the interface can remove foulant even for high salinity applications, such as those found with oceanic sensors or desalination membranes. To further demonstrate fouling detachment is not a result of the biological properties of algae but indeed a purely hydrodynamic phenomenon, bubbling experiments were repeated using polystyrene colloids, a non-living foulant of similar diameters (5-6 µm) and density as micro-algae. Information on the adhesion and bubbling experiments using polystyrene colloids can be found in the Additional Details section below. Adhesion and bubbling detachment results for polystyrene colloids are in line with the results found with Chlorella vulgaris are seen when the colloidal media is switched to polymer colloids (FIGS.12A-12C). This indicates that the process of detachment is not related to biological effects of the cells, such as cell death or membrane rupture, but due to mechanical effects brought about by the bubbles. Theoretical model predicting wall shear stress beneath departing bubbles. The two potential physical mechanisms that could explain algae detachment from surface level bubble generation are the movement of the triple contact line before departure and the flows induced by the bubbles after departure. Triple contact line movement can be discarded because the extension of the contact line remains well below 1 micrometer, which is less than the size of a single algae, for bubbles with radii ranging from 5 to 200 microns. It may be hypothesized that flows beneath departing bubbles are leading to algae detachment from the surface. As a bubble departs the surface driven by buoyancy, a flow is generated beneath the bubble as indicated in FIG.8A. The motion of the contact line as a detachment mechanism is implausible, as no contact line is visible for the experiments performed, as described elsewhere in this example. This is in agreement with recent observations made on electrochemically generated bubbles on a platinum electrode. The extension of the contact line is expected to be only a fraction of the size of a single algae cell. Attorney Docket No. M0925.70966WO00 An estimate for the expected wall shear stress for a departing bubble can be made through volume conservation and Newton’s law. The dynamics of a rising bubble departing from the surface was calculated first. For this, the acceleration term was balanced including an ^^ added mass term, with gravity, the buoyancy force and the drag force as (ρb+ CAMρw)3^ Rb= FB + Fg – 6πηRbVb. Here, ρb and ρw are the densities of the bubble (hydrogen) and water respectively, Rbis the radius of the bubble, FBand Fgare the buoyancy and gravitational force respectively, η is the viscosity of water, Vbis the rise velocity of the bubble, and CAMis the added mass coefficient. A value of ½ for added mass coefficient CAM is used. This is the added mass for a free rising bubble. The derivation for the added mass, the solution to this first order differential equation, can be found in the Additional Details section below. The solution to this first order differential equation and the full derivation of the shear stress on the wall can be found in the Additional Details section below. First, the velocity of the rising bubble is solved for. Assuming a spherical shape, it can be derived by integrating this equation twice that the height of the bubble as a function of time and radius. Here, h(r) is the vertical distance between the bottom of the bubble to the location on the bubble at radius r, while h(t) is the distance between the wall and the bottom of the bubble as indicated in FIG.8A. A plot for h(t) for a 30 µm radius bubble can be found in FIG.13A. Through volume conservation and assuming incompressibility of both media, the following solution is found for the average horizontal velocity of water beneath the bubble as a function of time and radius: Finally, by assuming a laminar flow, a no-slip boundary condition on the wall, and a slip boundary condition on the bubble surface, the shear stress on the wall can be estimated at all points beneath the bubble as ηvw / h. This leads to the following relation for shear stress on the wall: The velocity and Reynolds number of the flow beneath a 30 µm radius bubble are plotted in FIGS.13B-13C as a function of distance from the nucleation site and different time stamps. The gap height was used as a characteristic distance. Reynolds numbers well below 1 are found, Attorney Docket No. M0925.70966WO00 indicating that the viscous assumption is correct. In FIG.8B the calculated shear stress for a 30 µm radius bubble as a function of distance from the nucleation site can be seen plotted for multiple timestamps. The maximum shear calculated at every point it also plotted. The predicted shear stress is of the same magnitude as the adhesion strength of the algae measured in FIG.11B. From the micro-fluidic adhesion experiments, a shear stress of 9.6 Pa was found to be able to remove 50% of the algae covering the surface. It may also be noted that due to mass conservation the predicted shear stress goes to zero at r = 0. In FIG.8B, the calculated shear stress for a 30 mm radius bubble as a function of the distance from the nucleation site at multiple timestamps was plotted. The maximum shear calculated at every point over the entire dynamic of bubble rise was plotted (black line). When comparing that value to the predicted maximum shear stress in FIG.8B, it was found that for a 30 µm bubble, the average bubble size in the experiment, induces a shear flow of 9.6 Pa in at all points below 7 µm distance from the nucleation site. Alternatively, one could speculate that algae detachment can be due to the movement of the triple contact line. Even though triple contact line movement has been shown to be a strong de-fouler, it can be shown that the extension of the contact line for bubbles of these sizes is of negligible size. In the Additional Details section below it is shown that for bubble diameters of interest in this paper (5 to 200 µm in radius), the contact line radius remains well below 1 µm, which is less than the size of a single algae. The distribution of bubble sizes generated by electrolysis in FIGS.7A-7C go from around 5 µm to 100 µm in radius. In FIG.8C, the maximum calculated shear stress as a function of non-dimensional distance from the nucleation site is plotted for different bubble radii. The non-dimensional distance (x / R) is defined as the distance x from the nucleation site divided by the bubble departure radius. Here, the impact of bubble radius can be seen. Larger bubbles are shown to be more effective in removing foulant. From the combination of the theoretical model and the relation between wall shear stress and experimentally measured algae coverage in FIG. 11B, the plot in FIG.8D is constructed. This plot indicates the probability of algae being removed as a function of non-dimensional distance from the nucleation site. Going further, this calculation was used to predict the probability of algae being removed as a function of distance from the nucleation site for all bubble radii. An estimate of the wall shear stress at every point beneath the departing bubble from the model was obtained. Furthermore, previous experiments have established the probability of algae removal versus applied shear stress using our microfluidic adhesion platform. Combining the two, the Attorney Docket No. M0925.70966WO00 probability of algae being removed by the bubble as a function of non-dimensional distance from the nucleation site was obtained and plotted in FIG.8D. To validate the proposed model further, the predicted effect of bubble departure radius on algae detachment efficiency can be experimentally investigated. For this, the impact of a single bubble departing on a fouled surface is investigated. To achieve single bubble departures, the same mini-fluidic experiment as before is performed, however the duration of bubbling is decreased from 10 seconds to 1 second, reducing the probability that two bubbles nucleate sequentially from the same nucleation site, and allows for single nucleation events on our fouled electrode surfaces. Furthermore, only the lower current density of 8 mA / cm2is applied as lower current densities lead to lower bubble growth rates. The bubble removal radius Rr is defined as the radius from the point of nucleation at which 50% of all algae are removed after bubble departure. This is illustrated in FIG.9A. In FIG.9B, microscope images of a single bubble departure event are shown. Here, around the nucleation site, a clear radial decrease in algae coverage is visible after departure. In FIG.9C, the removal radius, Rr, versus bubble departure radius for the single bubble experiments can be seen. Similarly, the predicted removal radius found from the combination of the model and the adhesion experiments is plotted. Great overlap between the model and the experiments can be seen without any fitting parameter. Taken together, these results show that shear flow beneath bubbles detaches foulant. The model leads to a slight underestimate in the removal radius. It is hypothesized that the underestimation is due to the added mass coefficient. It could be due to some simplifying assumptions made in the model, such as using the added mass coefficient of a free rising bubble or assuming the bubble stays perfectly spherical. The former would lead to an increase in the added mass, while the latter a decrease. Additional modeling was also carried out. The dynamics and shape of a bubble rising in an unbounded liquid is generally known, and a phase diagram can be established as a function oftwo non-dimensional numbers, the Bond and Galileo numbers, ,- = . 01 *500 ! / 2 and 34 = .! , with hwand ρwthe viscosity and density of water respectively, g the gravitational acceleration, R the bubble radius, and 8 the surface tension of water. ,- and 34compare the gravitational force to the surface tension force and the gravitational force to the viscous force respectively. In this example, the bubble radius ranges from 5 μm to 100 μm, yielding ,- smaller than 10-3and 34in a range from 0.03 to 3. This means that surface tension forces impose that the bubbles stay spherical. Attorney Docket No. M0925.70966WO00 Knowing this, a proposed mechanism of cell detachment is illustrated in FIG.17A. Namely, spherical bubbles detach and rise from the surface, initiating a water flow beneath them. The generated water flow creates a sufficiently large shear stress on the adhered cells to detach them. To validate this mechanism, the wall shear stress was analytically estimated and induced by a departing bubble which was then compare to the experimentally derived stress necessary to detach algae. The complete derivation of the wall shear calculation can be found elsewhere in this example. First the dynamics of bubble rise are derived, solving for the velocity of the rising bubble as a function of time from departure to the terminal velocity. Through volume conservation beneath the rising bubble, an average velocity vw(x,t) of the water flow beneath the bubble is found which is a function of both time t and lateral distance x from the nucleation site of the bubble. Finally, assuming a no-slip boundary condition on the wall and a slip boundary condition on the bubble, the following shear stress on the wall is found: Here vb(t) is the rise velocity of the bubble, and h(x,t) is the height of the water film beneath the bubble as a function lateral distance x from the nucleation site and of time t. In FIG.17B, the calculated shear stress was plotted for a 30 mm radius bubble, the average bubble radius found in the experiments, as a function of the distance from the nucleation site at multiple time intervals. The maximum shear calculated at each position over the entire time interval of bubble rise was plotted. Using the microfluidic adhesion experiments, it was established that an applied shear stress of ~9.5 Pa is required to dislodge 50% of the attached algae on gold samples. From this model it is found that for a 30 mm radius bubble, a shear stress of ~9.5 Pa is induced within 7 mm distance from the nucleation site. It is also noted that the bubbles generated in the experiments have a broad size distribution. Next, the role of the bubble departure size on the detachment of cells was investigated. In FIG. 17C, the maximum calculated shear stress as a function of the non-dimensional distance (x / R) from the nucleation site is plotted for different bubble radii. Lab-scale prototype of non-toxic cell detachment. Last, a practical lab-scale prototype of a cell detachment system was designed to show robust cell detachment for both algae and mammalian cells while maintaining viability. As Attorney Docket No. M0925.70966WO00 fouled wall and primary electrode, a 1 inch by 3 inch substrate (e.g., a glass slide) coated with a 2 nm titanium adhesion layer and a 10 nm gold catalyst layer is used. The secondary electrode (which can be the counter electrode) is a 4 cm long platinum wire. As medium, a 7-day old algae chlorella vulgaris solution inside its respective medium. The composition of the algae medium can be found elsewhere in this example. Unlike the previous electrolyte, the freshwater culture media of chlorella vulgaris contains NaCl and other chloride compounds. Hence, if the anode is in direct contact with the medium, it will generate toxic chemicals, such as chlorine gas, and negatively affect the viability of the biological medium. Furthermore, the electrode will degrade rapidly due to the formation of chloride-complexes, limiting its practical application. To prevent these negative effects, the anode, is separated from the primary electrode through a Proton Exchange Membrane (PEM) as indicated in FIG.10A. The PEM is an Aquivion® membrane purchased from the Fuelcell Store. The PEM only allows the passage of protons through the membrane, in essence separating the two electrolytic streams. This is to limit toxic chemicals generated at the anode (the platinum wire) from migrating to the primary electrolyte (the algae medium) and negatively affecting the viability of the biological medium. To further limit toxic chemical generation (e.g., chloride complexes) from forming at the isolated anode, which would rapidly degrade the electrode, a chloride-free electrolyte consisting of 1M potassium bicarbonate is chosen for the secondary electrolyte (the anolyte). The anolyte and catholyte are prevented from mixing due to the PEM separating the two. To minimize ohmic losses, which are especially important in fresh-water media due to the low conductivity, it is desirable to reduce the distance between the secondary electrode and the active surface. However, it is also desirable to ensure that the secondary electrode does not obstruct light entering the medium. To obtain a balance, the platinum electrode is attached to (e.g., mounted to) a motorized linear actuator. This setup allows precision movement of the platinum electrode over the surface, lowering the distance between the two electrodes and consequently lowering Ohmic losses. This setup is advantageous because it is desirable for the system to be transparent, precluding the option to make the secondary electrode larger. Finally, the catalyst surface is fouled through settling (e.g., gravitational settling) using concentrated (e.g., via a centrifuge) 7-day old chlorella vulgaris solutions. The dense algae medium is allowed to settle for 24 hours. Afterwards, the system is flushed twice to remove unadhered algae and left filled with algae-free freshwater culturing-medium (UTEX Bold 3N medium) to remove non-attached algae. An image of the surface after flushing can be seen in FIG.10B at t = 0. Attorney Docket No. M0925.70966WO00 To perform the experiment, 15V is applied across the two electrodes and the actuator sweeps the surface 3 times at a velocity of 1cm / s. A relatively high voltage is necessary due to the low conductivity of the freshwater medium. A picture of the fouled surface taken after every sweep can be seen in FIG.10B. After the third sweep, the medium is replaced with new culture medium to remove detached algae in the solution. As can be seen in FIG.10B, most of the adhered cells was successfully removed. To investigate the impact of bubbling on viability, this experiment was performed again. In this separate experiment, the voltage was applied for an hour with a stationary electrode in 7- day old algae medium using the PEM separated secondary electrode. After an hour, 5 ml of the treated algae medium was taken and diluted with 15 ml of algae-free culture media. This solution can be seen in the leftmost image in FIG.10C. This solution is then placed in a light- controlled incubator and allowed to grow. As can be seen in FIG.10C, the bubbled algae medium remains viable and algae growth through day 0, 6, and 10 and is seen through the increasing green color. The cell density of this solution was also measured every two days with a NanoDrop UV-Vis Spectrophotometer and is plotted in FIG.10D. This indicates that the algae remained viable and had no visible impact from bubbling. The algae growth curve has an S-shape curve that saturates (e.g., levels off) after 1 week, as the high-density solution runs out of nutrients. To further show that viability remains with the proposed technique even for more sensitive cells, a similar experiment with a PEM separated electrode was used to detach confluent human MG-63 cells. Here, MG-63 human cells were cultured for 3 days on the transparent gold electrode. Once the cells are fully grown and confluent, they are detached from the surface through bubble generation using the same PEM separated secondary electrode used above. Full experimental details can be found in the Additional Details section below. The electrode surface depleted of cells after bubbling is shown in FIG.15B. After 3 days, the cells were detached from the surface using bubbling with a PEM separated electrode. The viability of these cells was measured using a cell counter and were found to not differ from cells detached from the surface using a standard trypsin enzymatic cell detachment approach, as can be seen in FIGS.15A-15C, indicating the wide applicability of this mechanical detachment method for a range of applications with sensitive media. FIGS.15A-15B show a gold electrode surface with confluent MG-63 cells before (FIG.15A) and after (FIG.15B) bubbling. FIG.15C shows the viability of MG-63 human cells after detachment using a standard trypsin enzyme approach and surface bubble generation approach. The benefits of this Attorney Docket No. M0925.70966WO00 technique compared to the trypsin protocol are the amount of time and the quantity of material needed to detach cells. In this example, it was demonstrated that bubbles departing from a substrate are capable of detaching adhered cells from the surface without affecting their viability. It was shown with experiments and theory that flows generated beneath departing bubbles generates sufficient shear to remove attached cells gently from the surface. The above strategy relies solely on hydrodynamic flows, hence does not depend on the physicochemical characteristics of the cells, surface, or culture media. Moreover, unlike conventional strategies to prevent adhesion that are either chemistry specific or solution specific and that avoid contact between the surface and the cells, a strategy that physically removes the foulant in a time-controlled manner and therefore does not depend on the chemical details of the material was implemented. In the experiments, bubbles were generated by water splitting through electrolysis on transparent metallic electrodes. It was verified that this method works for non-living and living organisms without affecting the viability of cells negatively. Finally, a practical lab-scale prototype of a de-fouling system is made to show robust cell detachment while maintaining viability. This system is successfully implemented in detaching and maintaining viability for both chlorella vulgaris micro-algae as well as MG-63 human cells. The approach proposed in this paper can work for both seawater and fresh-water algae, mammalian cell culturing, sensors in the food industry, and other applications with sensitive media. Additional Details Algae culturing Chlorella vulgaris cells and MB3N medium were purchased from UTEX. All samples of algae were incubated in a humidity-saturated chamber with 5% CO2at 25°C with light cycle of 12 h day and 12 h night and light intensity of 100 μmol m2s−1. The cultures were constantly shaken on a rotating platform to prevent settling. Settling experiments of 2h were conducted with algae cultures of age 5 to 9 days. Experimental procedures of illustrative biofouling experiment The experiment shown in FIG.5A was performed by placing a polycarbonate square of 1 inch by 1 inch in a vessel of 7-day old Chlorella vulgaris algae. Polycarbonate was used as it is a common material used for photobioreactor walls. Algae were allowed to settle through gravity, accelerating fouling. Attorney Docket No. M0925.70966WO00 Experimental procedures of illustrative bubbling experiment For the illustrative bubbling experiment shown in FIGS.5C-5F, a 4-inch silicon wafer coated with 100nm of gold is purchased from Sigma-Aldrich. A 100 µm thick polycarbonate sheet is attached to the wafer with an opening at the region of interest. This opening will be the cathodic surface at which hydrogen is generated. A mini-fluidic T-shaped channel is attached to the wafer. The channel has a width of 1 cm, every arm has a length of 2.5 cm, and height of 1 cm. The anode is separated from the algae-covered cathode surface by a separate channel. The anode is a platinum wire purchased from Sigma-Aldrich. The anode and cathode are separated to avoid toxic side reactions, such as the evolution of chlorine gas or hypochlorite, from reaching the region of interest, the exposed cathode surface. A 7-day old chlorella vulgaris solution in culturing medium is introduced in the system and allowed to settle for 2 hours. After 2 hours, all the non-adhered algae are flushed out the system with culturing medium, and a low flow rate is applied of 5 ml / min during the experiment to flush out detached algae. Hydrogen is generated on the surface by applying 300V using a DC power supply to the anode and cathode. This leads to a significant decrease in algae coverage as shown in FIGS.5D- 5F. Images taken using an optical microscope. High voltage is required due to the low conductivity of fresh water media and the large distance between the anode and cathode, required to separate the streams. Algae Adhesion Experiment Microfluidic chips were constructed using 100 µm thick double-sided tape from Nitto Denko Corporation. Microfluidic channels of 6 mm width and 3 cm length were cut out of the tape using a razor blade or a CO2laser. Thus, the overall microfluidic channel geometry for shear experiments was 3 cm, 6 mm, and 100 µm in length, width, and height, respectively. The double-sided tape was carefully attached to transparent gold slides. A ¼ inch thick top plate of polycarbonate was placed on the other side of the tape with holes drilled for an inlet and outlet. The completed chip was connected to a syringe pump, which controlled the shear rate in the chip. The completed chip was then flushed with 1M potassium bicarbonate for 5 minutes at a low flow rate of 0.1 ml per minute. Once this is completed, the adhesion experiments are performed. A schematic of the microfluidic cell adhesion platform is shown in FIG.11A. Attorney Docket No. M0925.70966WO00 The imposed shear stress on the wall in this microfluidic chip can be calculated from the viscous limit of the Navier-Stokes equation. This leads to an estimate of shear on the wall as follows: Here, τwis the shear stress on the wall, h is the channel height, η is the viscosity of water, and ^!is the average velocity of water, calculated from the known applied volume flux. The fluid flow, and hence the shear stress on the wall, is applied for 30 seconds at each step. In FIG.11B the normalized algae coverage versus applied shear stress on the wall can be seen. It is shown that above 9.6 Pa of wall shear, 50% of algae are removed. In FIG.11C, fluorescent images of algae coverage after different applied wall shear stresses that were taken during the experiments are shown. Experimental process bubbling experiments For the electrode surface, a transparent gold electrode with film-thickness of 10 nm on glass is purchased from Platypus Technologies. To create the electrode design seen in FIG.6B, a 150W continuous output Nd:YAG laser scriber is used to create the pattern by removing the 10 nm gold metal layer between the electrodes. After scribing, the samples are cleaned by rinsing with acetone, ethanol, and isopropyl alcohol before plasma cleaning in O2plasma for 5 minutes. The mini fluidic chip was assembled through covalent bonding of the PDMS. For the bubbling experiments, the minifluidic chip as shown in FIG.6A is used. To prepare for the experiments, 5 to 9 day old algae media is introduced into the chip and allowed to settle in the incubator for 2 hours. After 2 hours, the algae media is replaced with the chlorideless 1M potassium bicarbonate electrolyte by flowing at 1 ml per minute for 5 minutes. After, the flow rate is adjusted to 1 ml / min to flush detached algae and emulate conditions found in photobioreactors. A set voltage is applied for 10 seconds at a time and ramped up from low to high current density. After every step, a fluorescent reflected microscopy image and a brightfield transmitted microscopy image is taken. Colloidal bubbling detachment experiments To further support that bubble detachment of foulant is not due to the biological nature of algae, the experiments were repeated with polystyrene beads as foulant. Uncoated polystyrene beads and polystyrene beads coated with carboxyl with a diameter of 6.04 µm and 5.09 µm Attorney Docket No. M0925.70966WO00 respectively were purchased from Spherotech. The beads fluoresce Nile Red (559 nm excitation, 635 nm emission). The concentrated bead solution was 100X diluted in a 0.1M potassium bicarbonate solution. A lower salinity than for the algae experiments was chosen to decrease charge screening and hence increase surface charge effects of the spheres with the surface, increasing the adhesion strength of the particles to the surface to mimic that of algae. In FIG.12A the adhesion strength of the beads is shown, measured using the microfluidic adhesion platform. This indicates that the polystyrene beads adhere well to the surface with similar adhesion strength as Chlorella Vulgaris micro-algae. For the bubbling experiment, the diluted solution was allowed to settle for 2 hours. Afterwards, it was flushed at 1 ml / min for 5 minutes with a 1M Potassium Bicarbonate electrolyte. A low flow rate of 1 ml / min is applied during bubbling to remove detached beads, and bubbling is induced for 10 seconds at every current step. In FIG.12B the algae coverage versus current density is shown. Similar performance as seen with microalgae is found, indicating that the detachment mechanism is physical and not biological. In FIG.12C microscope images of the experiments as a function of current density can be seen. Derivation of wall shear stress beneath a departing bubble Velocity of rising bubble The wall shear stress induced by a departing bubble through volume conservation and Newton’s second law was estimated. The dynamics of a rising bubble departing from the surface was first calculated. For this, we balance the acceleration term including an added mass term, with gravity, the buoyancy force and the drag force as: Here, ρgand ρware the densities of the bubble (hydrogen) and water respectively, R is the radius of the bubble, FBand Fgare the buoyancy and gravitational force respectively, η is the viscosity of water, vbis the rise velocity of the bubble, and CAMis the added mass coefficient. A value of ½ for added mass coefficient CAMis used, which can be shown is the added mass coefficient of a free rising bubble. Attorney Docket No. M0925.70966WO00 This equation is a first order differential equation and the resulting solution for the bubble velocity is: Here ^^is the steady state velocity and tc is the characteristic time to reach steady state: 2^. − . ^ / ^)^ = ! 5^ 9 % Height as a function of time From the bubble velocity correlation, the height of the bubble as a function of time can be calculated. I^ ^ = 0 , ℎ^^ = 0^ = 0, ℎ^0^ = ^^^D + =, / K^KL / = = −^^^DThis gives: The height versus time for a 30 µm bubble is plotted in S4a. Estimation of water velocity beneath departing sphere Attorney Docket No. M0925.70966WO00 It is assumed that the bubble is a sphere of radius R. The bubble touches the surface at r = 0. It is defined that h(x,t) is the height of the sphere as a function of lateral distance x. Therefore h(x = 0, t = 0) = 0 and h(x = R,t = 0) = R. By volume conservation assuming incompressibility of the media, in the volume delimited case by the radius x + dx and x and the height h(x,t), it follows that: Note that h(x = 0, t = 0) = 0. Rewriting the equation above, it is possible to obtain the following equation: Integrating the equation, it is found that: :^^!^:, ^^ = ^^^^⋅1 2ℎ^:, ^^One can verify that this meets the boundary condition requirement on x = 0 and x = R. The water velocity at different time stamps as a function of distance from the nucleation site for a 30 µm radius bubble is plotted in FIGS.13A-13C. Estimation of wall shear stress beneath departing sphere The Reynolds number for the flow beneath the bubble is plotted in FIG.13C for a 30 µm diameter bubble. Here, the gap between the wall and the bubble is taken as characteristic height. The flow is in the viscous dominated regime. Now the shear stress on the wall is: Attorney Docket No. M0925.70966WO00 Finally, h(x,t=0) for a sphere can be written as: Hence, the shear stress on the wall can be written as: Triple contact line diameter estimation To understand the role of the contact line, imaging was performed on the gold electrode surface covered with algae. When focusing on a single bubble, as shown in FIG.16A, no visible contact line can be seen. The microscope image resolution is ~2 μm. For the contact line to have an appreciable impact, the pinned length of the contact line must be larger than the diameter of a single cell, which is ~5 μm and clearly visible in the images. Given that the contact patch diameter is smaller than the cell dimensions, wit can be assumed that the triple contact line does not contribute to cell detachment. In contrast to the untreated gold surface, a clear contact line is visible when a hydrophobic surface is used. To illustrate this, the gold electrode was functionalized using 1H,1H,2H,2H perfluorodecylthiol. A single bubble generated on the hydophobized surface is shown in FIGS.16A-16B. As can be seen, the contact line is not visible for the untreated gold surface (ie., the electrode used), while for the thiol treated surface a clear contact line is visible. To estimate the size of the contact line of a bubble right before departing the surface, a force balance is made. If the most conservative estimate is taken, this will be a force balance between buoyancy and the surface tension force: X2 = XYIf the contact line radius is defined as rsas indicated in FIG.14A, by making a conservative estimate the following is found: Here, σ is the surface tension of water (72 mN / m). In FIG.14A, a schematic of a bubble contacting a wall before departure is shown, and the contact radius as a function of bubble radius Attorney Docket No. M0925.70966WO00 can be seen. This indicates that for the bubble sizes of interest in this work, the bubble contact line radius is negligible compared to the size of the micro-algae (5 µm in diameter). FIG.14B is an estimate of bubble contact line radius versus bubble departure radius. Detaching Human MG-63 cells To further show that the proposed technique does not affect the viability, the experiment was performed using very sensitive human cells. Specifically, MG-63 human osteosarcoma cancer cell line was used. As electrode surface, a 1 inch by 1-inch transparent gold slide was glued to a 60 mm polystyrene petri dish. This electrode assembly was then plasma cleaned in O2 plasma for 5 minutes, sprayed with ethanol, and left to dry in a biohood for an hour to prevent contamination and enhance cell adhesion. The electrode assembly was then seeded with 1:5 diluted MG-63 cells and left to grow in an incubator at 35°C and 5% CO2 for 3 days until confluent. Once confluent, bubbling was initiated at 4V for 20s with the same PEM separated electrode as discussed in FIGS.10A-10C. Removed cells were then pipetted up and let to rest in the incubator for 10 minutes. Viability was measures using a CellDrop FL cell counter and a AO / PI (Acridine Orange and Propidium Iodide) stain. Algae Culture Media Composition – Bold 3N Medium Freshwater algae medium was purchased from The Culture Collection of Algae at the University of Texas at Austin, UTEX. The composition of the aqueous media, as given by UTEX, can be found in the table below. While several embodiments of the present invention have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and / or structures for performing the functions and / or obtaining the results and / or one or more of the Attorney Docket No. M0925.70966WO00 advantages described herein, and each of such variations and / or modifications is deemed to be within the scope of the present invention. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and / or configurations will depend upon the specific application or applications for which the teachings of the present invention is / are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, the invention may be practiced otherwise than as specifically described and claimed. The present invention is directed to each individual feature, system, article, material, and / or method described herein. In addition, any combination of two or more such features, systems, articles, materials, and / or methods, if such features, systems, articles, materials, and / or methods are not mutually inconsistent, is included within the scope of the present invention. The indefinite articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.” The phrase “and / or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Other elements may optionally be present other than the elements specifically identified by the “and / or” clause, whether related or unrelated to those elements specifically identified unless clearly indicated to the contrary. Thus, as a non-limiting example, a reference to “A and / or B,” when used in conjunction with open-ended language such as “comprising” can refer, in one embodiment, to A without B (optionally including elements other than B); in another embodiment, to B without A (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); etc. As used herein in the specification and in the claims, “or” should be understood to have the same meaning as “and / or” as defined above. For example, when separating items in a list, “or” or “and / or” shall be interpreted as being inclusive, i.e., the inclusion of at least one, but also including more than one, of a number or list of elements, and, optionally, additional unlisted items. Only terms clearly indicated to the contrary, such as “only one of” or “exactly one of,” or, when used in the claims, “consisting of,” will refer to the inclusion of exactly one element of Attorney Docket No. M0925.70966WO00 a number or list of elements. In general, the term “or” as used herein shall only be interpreted as indicating exclusive alternatives (i.e., “one or the other but not both”) when preceded by terms of exclusivity, such as “either,” “one of,” “only one of,” or “exactly one of.” “Consisting essentially of,” when used in the claims, shall have its ordinary meaning as used in the field of patent law. As used herein in the specification and in the claims, the phrase “at least one,” in reference to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elements and not excluding any combinations of elements in the list of elements. This definition also allows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase “at least one” refers, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, “at least one of A and B” (or, equivalently, “at least one of A or B,” or, equivalently “at least one of A and / or B”) can refer, in one embodiment, to at least one, optionally including more than one, A, with no B present (and optionally including elements other than B); in another embodiment, to at least one, optionally including more than one, B, with no A present (and optionally including elements other than A); in yet another embodiment, to at least one, optionally including more than one, A, and at least one, optionally including more than one, B (and optionally including other elements); etc. As used herein, “wt%” is an abbreviation of weight percentage. As used herein, “at%” is an abbreviation of atomic percentage. Some embodiments may be embodied as a method, of which various examples have been described. The acts performed as part of the methods may be ordered in any suitable way. Accordingly, embodiments may be constructed in which acts are performed in an order different than illustrated, which may include different (e.g., more or less) acts than those that are described, and / or that may involve performing some acts simultaneously, even though the acts are shown as being performed sequentially in the embodiments specifically described above. Use of ordinal terms such as “first,” “second,” “third,” etc., in the claims to modify a claim element does not by itself connote any priority, precedence, or order of one claim element over another or the temporal order in which acts of a method are performed, but are used merely as labels to distinguish one claim element having a certain name from another element having a same name (but for use of the ordinal term) to distinguish the claim elements. Attorney Docket No. M0925.70966WO00 In the claims, as well as in the specification above, all transitional phrases such as “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” “holding,” and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases “consisting of” and “consisting essentially of” shall be closed or semi-closed transitional phrases, respectively, as set forth in the United States Patent Office Manual of Patent Examining Procedures, Section 2111.03.

Claims

Attorney Docket No. M0925.70966WO00 CLAIMS What is claimed is:

1. A system, comprising: a primary electrode; and a counter electrode in electrochemical communication with the primary electrode, wherein: the primary electrode is in contact with an aqueous primary electrolyte, the counter electrode is in contact with an aqueous counter electrolyte, the counter electrolyte is fluidically separated from the primary electrolyte, and the system is configured to remove material from a surface of the primary electrode under at least some conditions under which electrolysis of water from the primary electrolyte and / or the counter electrolyte is performed.

2. The system of claim 1, wherein the material comprises one or more solids.

3. The system of any one of claims 1-2, wherein the material comprises a biological cell and / or a protein.

4. The system of any one of claims 1-3, wherein the primary electrode is or is part of a surface of a vessel configured to support a biologically active environment.

5. The system of claim 4, wherein the vessel is or is part of a bioreactor, a fermenter, a cell culture plate, and / or a cell culture flask.

6. The system of any one of claims 1-5, wherein the surface of the primary electrode is associated with a sensor.

7. The system of any one of claims 1-6, wherein the fluidic separation between the counter electrolyte and the primary electrode is maintained by an ion-conductive medium.Attorney Docket No. M0925.70966WO00 8. The system of claim 7, wherein the ion-conductive medium is a charge-selective membrane.

9. The system of any one of claims 7-8, wherein the ion-conductive medium is a proton exchange membrane.

10. The system of any one of claims 1-9, wherein the system is configured such that the counter electrode and the primary electrode can be moved relative to each other while remaining in electrochemical communication with each other.

11. The system of any one of claims 1-10, wherein the material on the surface of the primary electrode comprises biological cells, ingestible food or drug products, and / or non-toxic organic material.

12. The system of any one of claims 1-11, further comprising the material on the surface of the primary electrode.

13. The system of any one of claims 1-12, wherein the primary electrode is patterned and / or roughened.

14. The system of any one of claims 1-13, wherein the aqueous counter electrolyte is substantially chloride-free.

15. A method for removing material from a surface of a primary electrode, comprising: applying a voltage between the primary electrode comprising the surface and a counter electrode such that hydrogen gas bubbles are formed and / or pH is altered by electrolysis at the primary electrode and material is removed from the surface of the primary electrode, wherein: the primary electrode is in contact with an aqueous primary electrolyte,Attorney Docket No. M0925.70966WO00 optionally, the counter electrode is in contact with an aqueous counter electrolyte, and the counter electrolyte is fluidically separated from the primary electrolyte.

16. The method of claim 15, wherein the material comprises a biological cell and / or a protein.

17. The method of any one of claims 15-16, wherein the hydrogen gas bubbles are dislodged from the surface of the primary electrode such that the dislodgement of the hydrogen gas bubbles results in the removal of material from the surface.

18. The method of any one of claims 15-17, further comprising moving the counter electrode and the primary electrode relative to each other.

19. The method of any one of claims 15-18, wherein the material on the surface of the primary electrode comprises biological cells, and the biological cells remain viable after removal from the surface of the primary electrode.

20. The method of any one of claims 15-19, wherein: the material on the surface of the primary electrode comprises an ingestible food product, and the ingestible food product remains non-toxic after removal from the surface of the primary electrode; and / or the material on the surface of the primary electrode comprises an ingestible drug product, and the ingestible drug product remains non-toxic after removal from the surface of the primary electrode; and / or the material on the surface of the primary electrode comprises a non-toxic organic material, and the non-toxic organic material remains non-toxic during removal from the surface of the primary electrode.

21. The method of any one of claims 15-20, wherein the aqueous primary electrolyte remains substantially free of chlorine ions and / or chlorine gas during electrolysis.Attorney Docket No. M0925.70966WO00 22. The method of any one of claims 15-21, wherein the material removed from the surface of the primary electrode are then suspended in the aqueous primary electrolyte.

23. A method for removing material from a surface of a primary electrode, comprising: applying a voltage between the primary electrode comprising the surface and a counter electrode such that hydrogen gas bubbles are formed and / or pH is altered by electrolysis at the primary electrode and material is removed from the surface of the primary electrode.

24. The method of claim 23, wherein: the material on the surface of the primary electrode comprises biological cells, and the biological cells remain viable after removal from the surface of the primary electrode; and / or the material on the surface of the primary electrode comprises an ingestible food product, and the ingestible food product remains non-toxic after removal from the surface of the primary electrode; and / or the material on the surface of the primary electrode comprises an ingestible drug product, and the ingestible drug product remains non-toxic after removal from the surface of the primary electrode; and / or the material on the surface of the primary electrode comprises a non-toxic organic material, and the non-toxic organic material remains non-toxic during removal from the surface of the primary electrode.

25. The method of any one of claims 23-24, wherein the material comprises a biological cell and / or a protein.

26. The method of any one of claims 23-25, wherein the hydrogen gas bubbles are dislodged from the surface of the primary electrode such that the dislodgement of the hydrogen gas bubbles results in the removal of material from the surface.Attorney Docket No. M0925.70966WO00 27. The method of any one of claims 23-26, further comprising moving the secondary electrode and the primary electrode relative to each other.

28. The method of any one of claims 23-27, wherein the material on the surface of the primary electrode comprises biological cells, and the biological cells remain viable after removal from the surface of the primary electrode.

29. The method of any one of claims 23-28, wherein the material on the surface of the primary electrode comprises an ingestible food product, and the ingestible food product remains non-toxic after removal from the surface of the primary electrode.

30. The method of any one of claims 23-29, wherein the material on the surface of the primary electrode comprises an ingestible drug product, and the ingestible drug product remains non-toxic after removal from the surface of the primary electrode.

31. The method of any one of claims 23-30, wherein the material on the surface of the primary electrode comprises a non-toxic organic material, and the non-toxic organic material remains non-toxic during removal from the surface of the primary electrode.

32. The method of any one of claims 23-31, further comprising an aqueous primary electrolyte associated with the primary electrode, wherein the aqueous primary electrolyte remains substantially free of chlorine ions and / or chlorine gas during electrolysis.

33. The method of any one of claims 23-32, further comprising an aqueous primary electrolyte associated with the primary electrode, wherein the material removed from the surface of the primary electrode are then suspended in the aqueous primary electrolyte.

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