Metal oxide based micro supercapacitor preparation equipment and preparation method thereof
Technical Field
The invention belongs to the technical field of capacitor preparation equipment, and particularly relates to metal oxide based micro supercapacitor preparation equipment and a preparation method thereof.
Background
With the rapid development of nanotechnology, the market demand for new miniature electronic devices is increasing, and a highly integrated electronic system may be used for thousands of electronic devices, such as resistance-capacitance inductors used in notebook computers, various signal generators in the communication field, various sensors in robots, and the like. Nowadays, these portable intelligent electronic devices profoundly affect people's work and life, and people will also move to intelligent society. For portable intelligent electronic devices such as these, there is a need for an energy storage system that can correspond to the portable intelligent electronic devices with superior performance and long lifetime. The micro super capacitor has the advantages of high power density, long service life, wide operating temperature range, good safety performance, simple maintenance, environmental friendliness and the like, so the micro super capacitor has increasingly wide application prospect in the field of energy systems of small portable electronic devices.
At present, the research of the micro-super capacitor is still mostly in the development stage of the laboratory, and the complex manufacturing process and the lower energy density seriously restrict the wide application of the micro-super capacitor in the practical commercialization. Therefore, a new manufacturing process for producing a high-energy-density micro supercapacitor with a simple process and low cost in a large scale is urgently needed, and the new manufacturing process also becomes a bottleneck problem for restricting the further development of the micro supercapacitor.
Among them, the early micro super capacitor is mainly designed as a sandwich structure, but the sandwich structure is difficult to be miniaturized due to the structural design problem, and the distance between two electrodes is large, the ion transfer distance is too long and the impedance is increased, thereby causing the power density and the energy density of the device to be reduced. In contrast, the coplanar micro supercapacitor has the advantages of short ion transmission distance, difficulty in short circuit, capability of maintaining good compatibility and integration with other micro functional electronic devices, and the like, and thus becomes a research hotspot of a miniaturized energy storage unit. In the past decade, researchers at home and abroad have conducted a lot of research on coplanar micro supercapacitors, but a manufacturing process and a manufacturing method which can meet the requirements of industrial application of the coplanar micro supercapacitors have not been found yet.
At present, the manufacturing method of the coplanar micro supercapacitor mainly comprises a photoetching method, a plasma etching method, a stamping method, a screen printing method, an ink-jet printing method, a 3D printing method and a laser direct writing method.
Photolithography, which is widely used to manufacture micro-supercapacitors due to its advantages of mature manufacturing process and high manufacturing precision, is used to pattern gold current collectors on silicon wafers spin-coated with graphene oxide by photolithographyThe research result of the graphene-based interdigital micro supercapacitor manufactured by combining the oxygen plasma etching technology shows that the electrochemical performance of the interdigital micro supercapacitor is remarkably enhanced along with the increase of the number of microelectrodes and the reduction of the width of the microelectrodes, and the obtained area specific capacitance is 116 muF/cm 2 The energy density is 3.6mWh/cm 2 。
The plasma etching method is a fast and efficient technology with high cost, and the multi-wall carbon nanotube-based micro supercapacitor is etched by a composite process combining the plasma etching method and a vacuum filtration method. Research results show that the introduction of the silver nanowires effectively improves the electrochemical performance of the multi-walled carbon nanotube micro supercapacitor, and the obtained area specific capacitance, energy density and power density are 274.8 mu F/cm respectively 2 、0.17mWh/cm 3 And 1.2W/cm 3 。
The stamping method is a simple and low-cost manufacturing process of the miniature super capacitor which is designed by means of patterning of a template. Firstly, engraving a three-dimensional stamping stamp template by laser, then stamping a patterned ink pattern by adopting the three-dimensional stamping stamp, and finally, combining electroplating and electrodeposition technology to manufacture MnO taking nickel as a current collector 2 A pseudocapacitive micro-supercapacitor obtained with an area specific capacitance of 4.15mF/cm2 (scan rate of 20 mV/s) and an energy density of 0.47. Mu. Wh/cm 2 。
The screen printing method has the advantages of low cost, high efficiency, simple process and the like, and can print the micro super capacitors with different shapes on different substrates. Firstly, a patterned copper current collector is manufactured by a screen printing technology, and then Cu (OH) is deposited on the current collector in situ 2 The pseudocapacitance coplanar micro super capacitor is manufactured with FeOOH, and the obtained area specific capacitance is 58mF/cm 2 (discharge Current Density of 0.1mA/cm 2 ) The energy density is 18.07 mu Wh/cm 2 。
The ink-jet printing method has the advantages of high precision, non-contact, digital control and the like, and can print the microelectrode with the current collector integrated with the electrode active material by a one-step method. Directly manufacturing a current collector and electrode active material graphene integrated miniature through an ink-jet printing technologyA supercapacitor obtained with an area specific capacitance and an energy density of 313 μ F/cm respectively 2 And 4mW/cm 3 。
The 3D printing method is an advanced manufacturing technique through computer aided design, and has the advantages of high digitization degree and simple structural design. The 3D printing technology is used for successfully realizing the optimization of structural parameters such as the width, the height and the like of the carbon nanotube-based interdigital microelectrode through a printing nozzle with the diameter of 60 mu m, and the obtained area specific capacitance, the power density and the energy density of the manufactured high-performance three-dimensional micro supercapacitor are respectively 4.25mF/cm 2 (at a scan rate of 100 mV/s), 3.72W/cm 3 And 0.12mWh/cm 3 。
The laser direct writing method is considered to be a simple, quick and very promising manufacturing process of a miniature super capacitor, and in order to further improve the energy density of the laser direct writing graphene interdigital miniature super capacitor, a pseudo-capacitance material, such as MnO (manganese oxide), is further deposited on the surface of the patterned graphene by combining an electrochemical deposition technology or an electrochemical polymerization technology 2 FeOOH and polyaniline, mnO produced by the compounding technology 2 The-graphene// FeOOH-graphene miniature super capacitor is at 0.25mA/cm 2 The area specific capacitance obtained under the extremely small discharge current density is only 21.9mF/cm 2 。
Although the photoetching method can manufacture high-precision patterned microelectrodes, the development prospect of the method in the manufacturing of the micro-supercapacitor is severely restricted by the problems of complex and time-consuming manufacturing process, strict requirements on manufacturing environment, high price of manufacturing equipment, large pollution of photoresist and the like;
the plasma etching method is a fast and efficient technology with high cost, and simultaneously needs the assistance of manufacturing processes such as a vacuum filtration method, a sputtering method, a spin-coating method and the like to complete the manufacturing of the miniature super capacitor, and the manufacturing process is complex and needs to consume template materials;
although the stamping method can simply and conveniently stamp the microelectrodes with different patterns, the manufacturing process of the stamping stamp template is complex and time-consuming, the manufacturing precision is not high, the bonding force between materials is weak, and the energy density of the manufactured micro supercapacitor is low;
the screen printing technology is severely limited in development due to the dependence on the assistance of a patterned template and the over dependence on high-quality printing ink, and the problems of poor manufacturing precision, low loading capacity of active materials, poor direct adhesion of materials and the like of microelectrodes;
the ink-jet printing can realize template-free manufacturing, but the development of the ink-jet printing is limited due to the problems of expensive manufacturing equipment, high requirement on the quality of the ink, weak bonding force between materials and the like;
the three-dimensional pseudocapacitance microelectrode structural design of 3D printing can effectively enhance the energy density of a micro supercapacitor, but because the support of a three-dimensional high-conductivity current collector and the 3D printing technology are lack of, the support and the 3D printing technology depend on high-quality ink and the use of inactive materials such as an adhesive, a surfactant and the like, the printing precision of the microelectrode is low, and the bonding force between the materials is weak, the high-performance micro supercapacitor cannot be manufactured industrially;
the complexity of the laser direct writing method and the low capacity of the microelectrode active material limit the further improvement of the energy density of the laser direct writing micro super capacitor, and the laser equipment is expensive, the processing efficiency is low and the like limit the large-scale production of the super capacitor.
Therefore, we propose a metal oxide based micro supercapacitor manufacturing device and a manufacturing method thereof to solve the above mentioned problems in the background art.
Disclosure of Invention
The invention aims to provide a metal oxide based micro supercapacitor preparation device and a preparation method thereof, so as to solve the problems in the background technology.
In order to achieve the purpose, the invention provides the following technical scheme: a metal oxide base micro supercapacitor preparation device comprises a machine tool, a wire conveying system, a cooling liquid circulating system, a pulse power supply system and a control computer, wherein an X coordinate workbench for clamping a metal sheet workpiece is arranged on the right side of the upper end of the machine tool, a Y coordinate workbench is arranged on the left side of the upper end of the machine tool, and an adjusting lifting mechanism for adjusting the height of a nozzle is arranged inside the Y coordinate workbench;
the wire conveying system comprises a wire conveying mechanism and guide wheels, the output end of the wire conveying mechanism drives the wire electrodes, and the wire electrodes are connected to a plurality of groups of guide wheels;
the cooling liquid circulating system comprises a cooling liquid tank, a filter element and a filter screen in the cooling liquid tank, a cooling liquid circulating pump, a nozzle passing through an electrode wire and a processing tank for receiving cooling liquid, the bottom of the X coordinate worktable is fixed in the processing tank, and the cooling liquid circulating pump is used for spraying the cooling liquid in the cooling liquid tank through the nozzle;
the cooling liquid circulating pump works, the cooling liquid is filtered by the filter element, so that the cooling liquid in the cooling liquid box is sprayed out by the nozzle and is used for cooling the electrode wire and the metal sheet workpiece when the electrode wire and the metal sheet workpiece are cut, then the cooling liquid falls to the processing tank, finally the cooling liquid box is returned to the cooling liquid box after being filtered by the filter screen, and the cooling liquid is recycled.
The pulse power supply system comprises a pulse power supply and a conductive block, the conductive block is arranged at the lower end of the right side of the Y-coordinate workbench, the pulse power supply is respectively and electrically connected to the conductive block and the metal sheet workpiece, and the conductive block is electrically connected to the electrode wire;
the control computer is electrically connected with the Y-coordinate workbench, the X-coordinate workbench, the line control box, the pulse power supply, the machine tool control cabinet and the cooling liquid circulating pump, and the line control box is electrically connected with the Y-coordinate workbench and the X-coordinate workbench.
Firstly, performing electric spark etching on each surface of a metal substrate by an electric spark wire cutting processing means, then etching a criss-cross interdigital pattern on the substrate by utilizing electric spark discharge, then gluing and fixing the relative position of an electrode by using an acrylic plate, and finally immersing the prepared electrode into an electrolyte solution to obtain the three-dimensional microstructure metal oxide based high-performance supercapacitor, wherein the electrode material can be selected from metal materials such as Fe, ni, co, ti and the like and conductive materials. In addition, the method can also be used for manufacturing micro super capacitors with different structural shapes, can also be used for etching other non-metal conductive materials to prepare functional materials suitable for different application scenes, and can be used for manufacturing electronic devices such as batteries and sensors quickly.
The manufacturing method of the coplanar micro supercapacitor mainly comprises a photoetching method, a plasma etching method, a stamping method, a screen printing method, an ink-jet printing method, a 3D printing method and a laser direct writing method. The photoetching method, the plasma etching method and the stamping method have the problems of complex process, time consumption, high cost, pollution and the like, and the screen printing method and the ink-jet printing method are not suitable for the mass production of the electrodes of the miniature super capacitor because of the problem of depending on high-quality ink. In contrast, laser direct writing is considered to be a simple, fast and very promising manufacturing process for micro-supercapacitors.
The laser direct writing method is to directly process the electrode material through laser to directly manufacture the controllable patterned micro super capacitor, and the wire electrical discharge machining method is to etch through spark discharge between a tool electrode and the electrode material to obtain the micro super capacitor with a controllable structure. The device required by the laser direct writing method is expensive, the efficiency and the cost performance of the device are low when the device is used for large-scale machining and manufacturing, and compared with a laser device, the wire cut electrical discharge machining machine is cheaper, can machine a high-performance supercapacitor electrode, is suitable for machining and manufacturing the large-scale high-performance supercapacitor electrode, and is high in efficiency and cost performance.
The invention also provides a preparation method of the metal oxide based micro supercapacitor preparation equipment, which comprises the following steps:
s1, drawing a feed path: drawing a rectangular substrate pattern and a preset electrode pattern of a micro supercapacitor by using automatic programming software EAPT (easy action platform) carried by a control computer, determining a feed path, setting processing parameters, and converting the feed path pattern into an ISO code for processing a linear cutting numerical control machine;
s2, processing the substrate: clamping the sheet metal workpiece on an X-coordinate workbench, and starting an adjusting lifting mechanism to keep a distance between a nozzle and the sheet metal workpiece;
then, carrying out tool setting operation, moving a Y-coordinate workbench and an X-coordinate workbench through an automatic tool setting function of a wire control box to enable a wire electrode and a metal sheet workpiece to be in mutual contact and generate short circuit, then automatically regulating and controlling a tool setting distance between the metal sheet workpiece and the wire electrode by a machine tool control cabinet, executing an ISO code of the rectangular substrate preset in the step S1 after an original point is set, and then, operating a wire conveying system, a cooling liquid circulating system and a pulse power supply system to obtain a rectangular substrate after a program is executed;
s3, processing the side surface of the substrate: vertically clamping the rectangular substrate obtained in the step S2 on an X-coordinate workbench of a machine tool, operating a set original point in the same way as in the step S2, moving a wire electrode to a specified position, setting processing parameters, and performing electric spark etching on two larger side surfaces of the rectangular substrate;
s4, processing the interdigital: horizontally clamping the rectangular substrate with the side surface subjected to electric spark etching treatment obtained in the step S3 on an X coordinate workbench of a machine tool, starting the machine tool to operate a set original point, moving a wire electrode to a specified position, executing a preset ISO code, and obtaining interdigital electrodes which are mutually staggered along the longitudinal direction through electric spark etching, namely the electrodes of the miniature supercapacitor;
s5, immersing the obtained electrode of the micro super capacitor into 1mol/L KOH solution to obtain an assembled high-performance micro super capacitor;
and S6, carrying out electrochemical test on the high-performance micro supercapacitor assembled in the step S5 by using a cyclic voltammetry, and testing to be qualified.
Through the discharge between the molybdenum wire (namely the electrode wire) and the metal base material, the metal is locally melted or gasified by the high temperature generated instantly, a part of the metal is re-attached to the surface of the current collector after being cooled, the three-dimensional metal base current collector with a controllable structure is generated, and meanwhile, the heat effect generated in the electric spark discharge processing causes the surface of the three-dimensional metal base current collector to be thermally oxidized to synthesize the metal oxide base pseudocapacitance electrode active material, so that the rapid manufacture of the metal oxide base super capacitor is realized.
1. The high-performance supercapacitor electrode can be manufactured in a large scale with high efficiency and high cost performance; 2. the processing process is simple, and the high-performance super capacitor is manufactured by a one-step method; 3. additives such as adhesives, conductive agents and the like and toxic substances are not used in the preparation process of the electrode; 4. the processed supercapacitor electrode has excellent performance; 5. different conductive materials can be processed; 6. can be used for manufacturing electronic devices such as super capacitors, batteries, sensors and the like.
Compared with the prior art, the invention has the beneficial effects that: according to the preparation equipment and the preparation method of the metal oxide based micro super capacitor, provided by the invention, the material is subjected to controllable processing by combining drawing software, the repeatability is high, the processing energy is lower, the precision of the prepared interdigital structure micro capacitor is high, the electrochemical performance is excellent, the electrode shape of the super capacitor is controllable, the manufacturing process is simple and flexible, processing conditions such as a mask or vacuum are not required, and the number of defective products is small.
Drawings
FIG. 1 is a schematic view of a wire electric discharge machine according to the present invention;
FIG. 2 is a schematic diagram of an electrode of a miniature supercapacitor prepared by an electrospark wire-electrode cutting method according to the present invention;
FIG. 3 is a schematic view of a process flow diagram of the present invention;
FIG. 4 is a schematic diagram of a CV curve of the interdigitated cobalt-based micro supercapacitor of the present invention over a voltage window of 0-0.6V;
FIG. 5 is a schematic diagram of the area specific capacitance of the interdigital cobalt-based micro supercapacitor of the invention in a voltage window of 0-0.6V.
In the figure: 1. a control computer; 2. a line control box; 3. a pulse power supply; 4. a lifting mechanism; 5. a Y-coordinate table; 6. a wire conveying mechanism; 7. a machine tool control cabinet; 8. a coolant tank; 9. a filter element; 10. a coolant circulation pump; 11. filtering with a screen; 12. processing a tank; 13. an X coordinate table; 14. a sheet metal workpiece; 15. an electrode wire; 16. a conductive block; 17. a guide wheel; 18. a nozzle; 19. an oxide layer; 20. cooling liquid; 21. and a discharge channel.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention provides a metal oxide base micro supercapacitor preparation device as shown in figures 1-5, which comprises a machine tool, a wire conveying system, a cooling liquid circulating system, a pulse power supply system and a control computer 1, wherein an X coordinate worktable 13 for clamping a metal sheet workpiece 14 is arranged on the right side of the upper end of the machine tool, a Y coordinate worktable 5 is arranged on the left side of the upper end of the machine tool, and an adjusting lifting mechanism 4 for adjusting the height of a nozzle 18 is arranged in the Y coordinate worktable 5;
the wire conveying system comprises a wire conveying mechanism 6 and guide wheels 17, the output end of the wire conveying mechanism 6 drives the wire electrodes 15, and the wire electrodes 15 are connected to a plurality of groups of guide wheels 17;
the cooling liquid circulating system comprises a cooling liquid tank 8, a filter element 9 and a filter screen 11 in the cooling liquid tank 8, a cooling liquid circulating pump 10, a nozzle 18 penetrating through an electrode wire 15 and a processing tank 12 for receiving the cooling liquid, wherein the bottom of the X coordinate worktable 13 is fixed in the processing tank 12, and the cooling liquid circulating pump 10 is used for spraying cooling liquid 20 in the cooling liquid tank 8 through the nozzle 18;
the pulse power supply system comprises a pulse power supply 3 and a conductive block 16, the conductive block 16 is arranged at the lower end of the right side of the Y-coordinate workbench 5, the pulse power supply 3 is respectively and electrically connected to the conductive block 16 and the metal sheet workpiece 14, and the conductive block 16 is electrically connected to the electrode wire 15;
the control computer 1 is electrically connected to the Y-coordinate workbench 5, the X-coordinate workbench 13, the line control box 2, the pulse power supply 3, the machine tool control cabinet 7 and the cooling liquid circulating pump 10, and the line control box 2 is electrically connected to the Y-coordinate workbench 5 and the X-coordinate workbench 13.
Fortune silk mechanism 6 installs in the upper end of lathe, and fortune silk mechanism 6 is located the left side of Y coordinate workstation 5, and a plurality of groups of guide pulley 17 all set up the inside at Y coordinate workstation 5.
Nozzle 18 is located the top of processing groove 12, coolant liquid circulating pump 10's liquid inlet department is connected in filter core 9 top through pipeline I, and coolant liquid circulating pump 10's liquid outlet department connects in nozzle 18 through pipeline II, processing groove 12's bottom is passed through pipeline III and is connected in filter screen 11.
The invention also provides a preparation method of the metal oxide based micro supercapacitor preparation equipment, which comprises the following steps:
s1, drawing a feed path: drawing a rectangular substrate pattern and a preset electrode pattern of a micro supercapacitor by using automatic programming software EAPT (easy initial programming) or other drawing software carried by a control computer 1 of a Suzhou three-photoelectric spark wire cutting machine (shown in figure 1), determining a feed path, and converting the feed path pattern into an ISO code for machining a linear cutting numerical control machine by setting appropriate machining parameters;
s2, processing the substrate: clamping a sheet metal workpiece 14 on an X-coordinate workbench 13 of a machine tool, and starting the machine tool to adjust a lifting mechanism 4 to keep a proper distance between a nozzle 18 and the sheet metal workpiece 14;
then, carrying out tool setting operation, moving the Y coordinate worktable 5 and the X coordinate worktable 13 through the automatic tool setting function of the wire control box 2 to enable the wire electrode 15 and the sheet metal workpiece 14 to be in mutual contact and generate short circuit, and then automatically regulating and controlling the tool setting distance between the sheet metal workpiece 14 and the wire electrode 15 by the machine tool control cabinet 7;
after the origin point is determined, executing the ISO codes of the rectangular substrate preset in the step S1, wherein the wire conveying system, the cooling liquid circulating system and the pulse power supply system work at the moment, and a rectangular substrate is obtained after the program is executed;
s3, processing the side surface of the substrate: vertically clamping the rectangular substrate obtained in the step S2 on an X coordinate worktable 13 of a machine tool, operating a set original point in the same way as the step S2, moving an electrode wire 15 to a specified position, setting processing parameters, and performing electric spark etching on two larger side surfaces of the rectangular substrate;
s4, processing interdigital: horizontally clamping the rectangular substrate with the side surface subjected to electric spark etching treatment obtained in the step S3 on an X coordinate workbench 13 of a machine tool, starting the machine tool to operate the set original point, moving the wire electrode 15 to a specified position, executing a preset ISO code, and obtaining interdigital electrodes which are mutually staggered along the longitudinal direction through electric spark etching, namely the electrodes of the miniature supercapacitor;
s5, immersing the obtained electrode of the micro super capacitor into 1mol/L KOH solution to obtain an assembled high-performance micro super capacitor;
and S6, performing electrochemical test on the high-performance micro supercapacitor assembled in the step S5 by using a cyclic voltammetry, wherein the test is qualified, the used instrument is a Shanghai Hua electrochemical workstation, and the software is chi660e.
By discharging between the wire electrode 15 and the metal sheet workpiece, taking a metal-based workpiece as an example (the workpiece may be other conductive materials), the metal is melted or gasified by the high temperature instantaneously generated in the discharging channel 21, and then the metal is washed away by the cooling liquid 20 to generate a three-dimensional metal-based current collector with a controllable shape structure, and meanwhile, the surface of the three-dimensional metal-based current collector is thermally oxidized by the thermal effect generated in the electric spark discharging process to synthesize an oxide layer 19 composed of a metal oxide-based pseudocapacitance electrode active material, thereby realizing the rapid manufacturing of the metal oxide-based supercapacitor (as shown in fig. 2).
For example, fe grows in situ on the current collector after the metal such as iron, nickel, cobalt, titanium and the like is subjected to wire cut electrical discharge machining and etching treatment x O y 、Ni x O y 、Co x O y 、TiO 2 And the like metal oxides and partial carbides. Firstly, a rectangular substrate is cut by using a wire-cut electrical discharge machine, then the two larger side surfaces of the rectangular substrate are subjected to electrical discharge etching, then interdigital electrodes which are mutually staggered are processed on the substrate along the longitudinal direction by a wire-cut electrical discharge machining method, and then the miniature super capacitor is manufactured (as shown in figure 3).
Taking an electric spark direct-writing cobalt sheet as an example, the cobalt-based metal oxide micro super capacitor is manufactured, and the test result shows that the CV curve of the cobalt-based metal oxide micro super capacitor is in a rectangle-like shape (as shown in FIG. 4) under the scanning speed of 10mV/s-200mV/s, which shows that the micro super capacitor manufactured by the method has good capacitance characteristic and is used for manufacturing the cobalt-based metal oxide micro super capacitorThe high area ratio capacitance 24.19339mF/cm is obtained 2 (at a scan rate of 10mV/s, as in FIG. 5).
Compared with the prior art, the method is convenient and quick, has few steps, strong adhesion between the active substance and the current collector, no need of using toxic solvent and abundant manufacturing materials. The performance of the miniature super capacitor manufactured by the novel method provided by the invention is superior. In addition, the wire cut electrical discharge machining numerical control machine can regulate and control three-dimensional structure parameters of the microelectrode with high precision, so that micro super capacitors with different shapes and structures can be manufactured, and the wire cut electrical discharge machining numerical control machine is suitable for large-scale production. In addition, the method can also be used for etching other non-metallic conductive materials to prepare functional materials suitable for different application scenes, and can be used for manufacturing batteries, sensors and other electronic devices quickly.
The method combines drawing software to carry out controllable processing on the material, has high repeatability and lower processing energy, and the prepared interdigital structure micro capacitor has high precision and excellent electrochemical performance, the electrode shape of the super capacitor is controllable, the manufacturing process is simple and flexible, processing conditions such as masks or vacuum and the like are not needed, and defective products are few.
Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that modifications may be made to the embodiments or portions thereof without departing from the spirit and scope of the invention.