Patent Publication Number: US-11396710-B2

Title: Reactor for layer deposition by controllable anode array

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. patent application Ser. No. 17/227,726, entitled “Electrochemical Layer Deposition,” filed on Apr. 12, 2021, which claims priority to U.S. patent application Ser. No. 16/432,857, entitled “Electrochemical Layer Deposition By Controllable Anode Array,” filed Jun. 5, 2019, now U.S. Pat. No. 10,975,485 B2. This application also claims priority to U.S. patent application Ser. No. 15/356,210, entitled “Apparatus for Electrochemical Additive Manufacturing,” filed on Nov. 18, 2016, and now U.S. Pat. No. 10,465,307 B2. Which claims priority to U.S. Provisional Patent Application No. 62/257,333, entitled “Apparatus for Production of Three-Dimensional Metal Objects by Stereo-Electrochemical Deposition”, filed on Nov. 19, 2015, fully incorporated by reference herein. This application is also related to U.S. patent application Ser. No. 15/415,246, entitled “Three Dimensional Additive Manufacturing Of Metal Objects By Stereo-Electrochemical Deposition,” filed on Jan. 25, 2017, now U.S. Pat. No. 9,777,385 B2, which also claims priority to U.S. Provisional Patent Application No. 62/257,333, entitled “Apparatus for Production of Three-Dimensional Metal Objects by Stereo-Electrochemical Deposition”, filed on Nov. 19, 2015. 
     TECHNICAL FIELD 
     The present disclosure relates to an apparatus, a system and a method for electrically depositing conductive material from a metal salt solution (hereinafter referred to as an electrolyte or ionic solution) on the cathode to form multiple layers using a two-dimensional array of anodes to fabricate large three dimensional metal structures. 
     BACKGROUND 
     Additive manufacturing, also known as 3D Printing, is used for the production of complex structural and functional parts via a layer-by-layer process, directly from computer generated CAD (computer aided drafting) models. Additive manufacturing processes are considered additive because conductive materials are selectively deposited on a substrate to construct the product. Additive manufacturing processes are also considered layered meaning that each surface of the product to be produced is fabricated sequentially. 
     Together, these two properties mean that additive manufacturing processes are subject to very different constraints than traditional material removal-based manufacturing. Multiple materials can be combined, allowing functionally graded material properties. Complicated product geometries are achievable, and mating parts and fully assembled mechanisms can be fabricated in a single step. New features, parts, and even assembled components can be “grown” directly on already completed objects, suggesting the possibility of using additive manufacturing processes for the repair and physical adaptation of existing products. Structural and functional parts created by additive manufacturing processes have numerous applications in several fields including the biomedical and aerospace industries. Traditional milling and welding techniques do not have the spatial resolution to create complex structural parts that can be achieved through additive manufacturing 
     However, electrochemical additive manufacturing (ECAM) techniques in general have several limitations such as choice of material, porosity, strength, scalability, part errors, and internal stresses. A deposition process must be developed and tuned for each material, and multiple material and process interactions must be understood. Resulting products may be limited by the ability of the deposited material to support itself and by the (often poor) resolution and accuracy of the process, Widespread use of additive manufacturing techniques may be limited due to the high cost associated with selective laser melting (SLM) and electron beam melting (EBM) systems. Further, most additive manufacturing devices currently in the industry use powdered metals which are thermally fused together to produce a part, but due to most metals&#39; high thermal conductivity this approach leaves a rough surface finish because unmelted metal powder is often sintered to the outer edges of the finished product. 
     Challenges associated with the use of the ECAM processes in commercial systems also include the slow speed of deposition with a single anode, and small (micrometer) size of parts producible by a conventional ECAM method. Microstructures such as metal pillars have been produced using localized electrochemical deposition (LECD) process with a single anode, which is similar to ECAM, but is limited in scope to the fabrication of simple continuous features. 
     The stereo-electrochemical deposition (SED) process, an extension of the ECAM process, combines two technologies: stereo-lithography and electroplating. By inducing an electric field between the anode and the cathode, and passing metal salts between the electrodes, it is possible to produce metal parts at the cathode rapidly at room temperature. Since the path of the electric field is dependent on the geometry of the part being built, printing of extreme overhang angles approaching 90 degrees without the need for a support structure, is possible. 
     The SED process is capable of depositing most conductive materials including metals, metal alloys, conducting polymers, semiconductors, as well as metal matrix composites and nanoparticle-impregnated materials. Electroplating and electroforming techniques have established the capability of electrochemical processes to deposit metals over large areas, but localizing the deposition to a controlled area has presented a challenge. 
     The SED process has the potential to cheaply and quickly produce both metals and composite metal/polymer systems because it is a non-thermal process requiring relatively few moving parts and no expensive optical or high vacuum components. Additionally, the material is deposited atom by atom resulting in good micro-structural properties (such as porosity, grain size, and surface finish) which can be controlled electronically. These characteristics allow the SED process to create certain three dimensional geometries much faster, and with higher quality than conventional methods. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Advantages of the subject matter claimed will become apparent to those skilled in the art upon reading this description in conjunction with the accompanying drawings, in which like reference numerals have been used to designate like elements, and in which: 
         FIG. 1  is a perspective view of the reactor for stereo-electrochemical deposition of layers of metallic material to fabricate a structure. 
         FIG. 2  is a front view of the reactor for stereo-electrochemical deposition of layers of metallic material to fabricate a structure. 
         FIG. 3  is a perspective view of the anode array and the controller board of the reactor for stereo-electrochemical deposition of layers of metallic material to fabricate a structure. 
         FIG. 4  is a block diagram of the components of the process of stereo-electrochemical deposition of layers of metallic material to fabricate a structure. 
         FIG. 5  is a block diagram of the process flow for stereo-electrochemical deposition of layers of metallic material to fabricate a structure. 
         FIG. 6  is a block diagram of the chemical pumping and handling system for stereo-electrochemical deposition of layers of metallic material to fabricate a structure. 
         FIG. 7A  is a 3D model of a structure to be fabricated by stereo-electrochemical deposition of layers of metallic material. 
         FIG. 7B  is a top view of a structure fabricated by stereo-electrochemical deposition of layers of metallic material. 
         FIG. 7C  is a side view of a structure fabricated by stereo-electrochemical deposition of layers of metallic material. 
         FIG. 8A  is a 3D model of a structure to be fabricated by stereo-electrochemical deposition of layers of metallic material. 
         FIG. 8B  is a side view of a structure fabricated by stereo-electrochemical deposition of layers of metallic material. 
         FIG. 8C  is a top view of a structure fabricated by stereo-electrochemical deposition of layers of metallic material. 
         FIG. 9A  is a 3D model of a structure to be fabricated by stereo-electrochemical deposition of layers of metallic material. 
         FIG. 9B  is a side view of a structure fabricated by stereo-electrochemical deposition of layers of metallic material. 
         FIG. 9C  is a top view of a structure fabricated by stereo-electrochemical deposition of layers of metallic material. 
         FIG. 10A  is a 3D model of a structure to be fabricated by stereo-electrochemical deposition of layers of metallic material. 
         FIG. 10B  is a side view of a structure fabricated by stereo-electrochemical deposition of layers of metallic material. 
         FIG. 10C  is a top view of a structure fabricated by stereo-electrochemical deposition of layers of metallic material. 
         FIG. 11A  is a 3D model of a structure to be fabricated by stereo-electrochemical deposition of layers of metallic material. 
         FIG. 11B  is a side view of a structure fabricated by stereo-electrochemical deposition of layers of metallic material. 
         FIG. 11C  is a side view of a structure fabricated by stereo-electrochemical deposition of layers of metallic material. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiments of the present invention relate to a controlled stereo-electrochemical deposition (SED) reactor and process performed upon a cathode to create centimeter-scale three dimensional metal objects via electrodeposition of multiple layers using an array of computer controlled anodes and a cathode. The materials are deposited layer by layer in “slices” on the cathode to produce the desired three-dimensional structures. In some embodiments the plurality of anodes are selectively movable, in other embodiments, the cathode is selectively moveable, and in other embodiments, both are moveable relative to each other. 
     The system for stereo-electrochemical deposition of metal objects comprises a chemical reactor, a chemical pumping and handling system, and an electrical control system. Each of these systems is described in detail below. 
       FIGS. 1 and 2  illustrate an embodiment of the chemical reactor for SED of metal objects. Reactor  100  generally includes a chemical reaction chamber  14  configured to contain an electrolyte, or ionic solution, that is used for the stereo-electrochemical deposition of layers of metal to fabricate a structure. During the deposition process, electrolyte is continuously supplied to chamber  14 . The electrolyte flows through chamber  14  and is collected for disposal or recycling. Chamber  14  is disposed on a structural support  38 , which may be made of metal or plastic or other suitable materials known to those of ordinary skill in the art. In an embodiment, a linear actuator  30  to control the movement of cathode  26  is disposed on chamber  14  on the side opposite to where structural support  38  is located. 
     In one embodiment, chamber  14  is rectangular in cross-section and is made of a chemical resistant polymer material, glass, or other chemically-resistant metal, plastic or ceramic material capable of containing the solution. In an alternate embodiment, chamber  14  may be circular or another geometry in cross-section, composed of glass or an alternate chemical resistant polymer, metal or ceramic material capable of containing the solution. Persons of ordinary skill in the art would understand however that chamber  14  may have be configured according to many different designs suitable to carry out the SED process according to the invention. Conventional reactor design considerations would apply to the geometry, size and materials of construction. 
     Chamber  14  is provided with an inflow fluid port  20   a  to allow fresh electrolyte from the chemical pumping and handling system to enter chamber  14 . Chamber  14  is also fitted with an outflow fluid port  20   b  to allow the used electrolyte to exit chamber  14  into a waste handling or recycling system (not shown). In other embodiments, chamber  14  may be fitted with a plurality of inflow fluid ports and outflow fluid ports. The inflow and outflow ports may be positioned on the same side wall of chamber  14 , or they may be positioned on different side walls of chamber  14 , or may be included as part of the design of the anode or the cathode assemblies. 
     Electrolyte from tank  59  is pumped into chamber  14  by fluid pump  52  ( FIG. 6 ) through the inflow fluid port  20   a . Fluid port  20   a  is disposed on a fluid flow guide  22   a . In an embodiment, fluid ports connect the chamber to the rest of the chemical pumping and handling system components (pump, quick disconnect fittings, valves, tank, etc.). In an embodiment, fluid flow guide  22  is disposed on the side walls of chamber  14  to direct the flow of the electrolyte to the fluid guide vanes  34  and anode array  10 . 
     As illustrated in  FIG. 3 , anode array  10  is disposed on fluid guide vanes  34 . Anode array  10  is completely submerged in the electrolyte during the operation of the SED process. Fluid guide vanes  34  provide compressive force between the anode array  10 , the gasket  12 , and the anode flange  32 . Fluid guide vanes  34  also direct the flow of the electrolyte over anode array  10 , laminarizing the flow over the anodes to provide for even deposition of metal layers according to the invention. During the operation of the system, electrolyte is pumped into the chamber as described above, and pumped out of chamber  14  through flow guides  22   b  and the outflow fluid port  20   b  into a waste or recycling system. 
     As illustrated in  FIG. 3 , anode array  10  is positioned within fluid guide vanes  34  of chamber  14  of the reactor  100 . In an embodiment, anode array  10  may have a rectangular shape with a plurality of elements that define a pattern of arrangement of the individual anode elements responsible for depositing metal layers in desired shapes. Anode array  10  may be made of a combination of plastic, ceramic, polymer, refractory or transition metal, semiconductor, carbon, and/or dielectric material. In other embodiments, array  10  may have different geometric designs to connect individual anodes in different patterns such as rectangular, circular, hexagonal, or oval. Within the anode array, multiple insulated anode conductive elements made of platinum or another conductive substance are generally disposed on and secured to the overall anode array  10 . In an embodiment, each individual exposed anode element of anode array  10  is made of platinum wire. 
     In  FIG. 3 , an anode array interface board  16  is electrically coupled to array  10  to provide electrical power to array  10  through conventional ribbon cables or other suitable connection means known in the art. Anode array interface board  16  also receives current and voltage information from cathode  26  through the current sensor  46  and the voltage controller  63  both embedded in the control board  400  ( FIG. 4 ). Board  16  accepts electronic information as well as electrodeposition power (current) in a corresponding fashion to the anode array patterns dictated by addressing system  57  and current controller  64  respectively ( FIG. 4 ). In other embodiments, some or all of the functions of the control board  400  may be integrated into the anode interface board  16 . 
     In other embodiments, a printed circuit board with the same pattern of openings as anode array  10  may be used to connect each of the anode elements to a power source. In an embodiment, array  10  comprises 64 dimensionally stable platinum anodes made from 24-gauge (0.5 mm diameter) 3 mm long platinum wire, such as, for example, 95% Pt 5% Ru wire. Anode elements of the anode array  10  are secured into fitted vias in anode array interface board  16 . In an embodiment, anode array interface board  16  is built on a FR4 2.0 mm thick double-sided PCB Board fabricated with 0.3 mm trace width. 
     As illustrated in  FIGS. 1-3 , gasket  12  is disposed between array  10  and fluid guide vanes  34 , to contain the electrolyte in the chemical reactor and prevent leaks. In an embodiment, gasket  12  is made from a chemically resistant elastomeric polymer. In an embodiment, an anode flange  32  is disposed underneath the anode array  10 . In an embodiment, anode array  10  is secured by screws on the bottom to chamber  14 , and these screws are tightened to provide clamping force to compress gasket  12 . In another embodiment, the clamping force is provided by other mechanical devices, such as spring tension, or a full-length threaded rod which exert force on the chamber  14  downward towards the anode array  10  to compress gasket  12  between the anode array  10  and the bottom of chamber  14 . In other embodiments not shown in  FIGS. 1-3 , the anode array may be coupled to an electro-mechanical positioning system so that the position of the anode array relative to the cathode may be changed according to the desired position for the metal layer deposition step of the fabrication. 
     Referring again to  FIGS. 1-3 , a cathode  26  comprising one or more cathodic conductive materials is disposed within chamber  14  and is spaced from anode array  10 . In an embodiment, cathode  26  may be disposed above anode array  10 . In an embodiment, cathode  26  comprises a 9×9 mm square graphite rod with a polished anode-facing end. Cathode  26  is attached to the anode-facing surface of cathode slider  24 . Cathode slider  24  mechanically fixes the position of cathode element  26  within chamber  14  during operation of the system and deposition method and houses a chemically resistant electrical connection between the cathode and control board  400 . In an embodiment, cathode slider  24  is made of plastic, for example, polypropylene with an electrical contact made of chemically resistant conductive material, for example titanium, chromium-alloy, stainless steel, or carbon. A cathode slider linkage  28  connects the cathode slider  24  to the linear actuator  30  which controls the movement of cathode slider  24  within chamber  14 . 
     In an embodiment, in which the cathode can be selectively positioned relative to the anode array, the distance between cathode  26  and anode array  10  is controlled by movement of the cathode slider  24 . In an embodiment, cathode slider  24  is driven by a position actuator  30 , which is controlled by a position controller  56  located on the control board  400  ( FIG. 4 ). In an embodiment, position actuator  30  may be a non-captive leadscrew stepper motor such as, for example, Haydon Kerk Motion Solutions, Inc.&#39;s switch and instrument stepper motor. In an embodiment, position controller  56  may be a stepper motor driver such as, for example, a Pololu Corporation&#39;s A4988 stepper motor driver. The position of cathode  26  within chamber  14  is detected through a cathode position sensor  62  (not shown) located near the top of chamber  14 , and is communicated to microcontroller  50  ( FIG. 4 .) In an embodiment, cathode position sensor  62  may be a mechanical waterproof micro-switch such as, for example, a Yueqing Dongnan Electronics Co., Ltd. WS1 Waterproof Micro Switch 5A 
       FIG. 4  illustrates the level of chemical exposure of various components of the SED system  1000 . SED system  1000  comprises chemically exposed components module  500 , chemically immersed components module  600 , and a control module  400 . Chemically immersed components of module  600  should be composed of engineered plastics (such as PET, PP, FEP, PTFE, certain epoxies, etc.), noble metals, certain carbon compounds, or other highly chemical resistant materials. Chemically exposed components of module  500  should be waterproof and have no exposed solder or metal parts except stainless steel. Components of the control module  400  are not exposed to chemicals and do not need to be made of chemical resistant materials. 
       FIG. 4  also illustrates the operation of the electrical control system  1000  which enables stereo-electrochemical deposition of layers of metallic material according to an embodiment of the invention. Control board  400  provides regulated power to all electromechanical components of the reactor for the SED process (such as the pump, the stepper motor and the stepper motor driver), as required by the software configuration of the system and the Multiple Independently Controlled Anode (MICA) algorithm. 
     As illustrated in  FIG. 4 , microcontroller  50  interfaces with a storage module  42  to receive machine configuration information and layer slice data. Storage module  42  may be a personal computer or any device capable of storing and passing layer slice data to the microcontroller  50 . In an embodiment, the storage module  42  is composed of a Secure Digital card reader and card. In another embodiment, the storage module  42  is composed of a serial interface to a personal computer which delivers layer files to the microcontroller  50 . 
     Some example computer devices include desktop computers, portable electronic devices (e.g., mobile communication devices, smartphones, tablet computers, laptops) such as the Samsung Galaxy Tab®, Google Nexus devices, Amazon Kindle®, Kindle Fire®, Apple iPhone®, the Apple iPad®, Microsoft Surface®, the Palm Pre™, or any device running the Apple iOS®, Android® OS, Google Chrome® OS, Symbian OS®, Windows Mobile® OS, Windows Phone, BlackBerry® OS, Embedded Linux, Tizen, Sailfish, webOS, Palm OS® or Palm Web OS®. 
     In an embodiment, microcontroller  50  may be an Arduino Mega microcontroller board. Microcontroller  50  receives electronic input corresponding to the position of cathode  26  from cathode position sensor  62 . Microcontroller  50  receives electronic input from current sensor  46  corresponding to the total deposition current flowing through the cathode element. Using this electronic input, microcontroller  50  determines through computations whether to move the cathode, increase or decrease voltage to the anode elements, or turn various anode elements on or off in order to facilitate accurate and speedy deposition of the current layer slice. 
     Microcontroller  50 , in an embodiment, directs the operation of the cathode z-axis position controller  56  based on information received from the current sensor  46 , from the position sensor  62 , and based on the active/inactive state of each anode in the addressing system  57 . This information is used by the MICA software algorithm running on microcontroller  50  to determine the appropriate cathode z-axis position of cathode  26 . Cathode position controller  56  controls the movement of linear actuator  30  which is mechanically linked to, and moves, cathode  26  via cathode slider linkage  28  and cathode slider  24  inside chamber  14 , as was described above. ( FIGS. 1 and 2 ). 
     Microcontroller  50  controls the operation of fluid pump  52  and valves  54  to direct the flow of the electrolyte solution through chamber  14  of the reactor  100 . In an embodiment, valves  54  comprise electrically actuated, chemically resistant solenoid valves. In an embodiment, the fluid pumping speed may be varied at regular intervals to clear out bubbles which may have formed on the anode after a length of time of steady state deposition. In another embodiment, the fluid pumping speed may be kept at a steady rate and ultrasonic agitation may be provided into the reaction chamber  14  in order to clear out bubbles. 
     Anode array  10  is controlled by microcontroller  50  through an addressing system  57 , which in turn supplies data to the current controller  64 . The source voltage to the current controller  64  is also adjusted continuously by microcontroller  50  through a voltage controller  63  which receives an analog signal from the microcontroller  50  through the Digital-to-Analog converter (DAC)  61 . According to embodiments of the invention, current controller  64  may be a NPN or PNP transistor, a Sziklai Pair compound transistor comprising one NPN transistor and one PNP transistor, a n/p-channel Field Effect Transistor (FET), or any device which has the ability to deactivate or limit the current flowing to individual anodes in the anode array when the current exceed a certain threshold limit. 
     In an embodiment, the addressing system  57  may be a shift register or latching circuit composed of one or more transistors, serial-in/parallel-out (SIPO), parallel-in/serial-out (PISO) or other addressing components which convert a multiplexed digital signal into a de-multiplexed digital or analog signal. In an embodiment, the voltage controller  63  may be a Linear Technologies LM317 adjustable linear voltage controller, buck, boost or single-ended primary-inductor converter (SEPIC) converter, or any adjustable voltage power supply of sufficient current capacity to supply all anode elements of anode array  10 . In an embodiment, DAC  61  is composed of a LC or RC filter circuit intended to convert digital PWM signals from the microcontroller into an analog input for the voltage controller  63 . In other embodiments, DAC  61  may be omitted if a digital voltage controller  63  is used. 
     The metal deposition model according to the present invention is derived from Faraday&#39;s first and second laws of electrolysis. The amount of chemical change produced by current at an electrode-electrolyte boundary is proportional to the quantity of electricity used. The amounts of chemical changes produced by the same quantity of electricity in different substances are proportional to their equivalent weights. 
     These laws can be expressed as the following formula: 
     
       
         
           
             m 
             = 
             
               
                 ( 
                 
                   Q 
                   F 
                 
                 ) 
               
               ⁢ 
               
                 ( 
                 
                   M 
                   z 
                 
                 ) 
               
             
           
         
       
     
     Where m is the mass of the substance liberated at an electrode in grams; Q is the total electric charge passed through the substance; F is Faraday&#39;s constant (96485 C/mol −1 ); M is the molar mass of the substance in AMU (for example, for copper this value is 63.55); z is the valence of the ions of the substance (for example, for copper (II) sulfate this value is 2). 
     For variable electric current deposition (as utilized by SED) Q can be defined as:
 
 Q=∫   0   t   I (τ) dτ 
 
where t is the total electrolysis time, and I(τ) is the electric current as a function of the instantaneous time tau τ. d(τ) is the computation time for each iteration of the algorithm.
 
     Substituting mass for volume times density, and adding the integral charge for Q produces: 
               ρ   ⁢           ⁢   V     =       ρ   ⁢           ⁢   Ad     =         ∫   0   t     ⁢     Idt   *   M         z   *   F               
Where ρ is the density of the material (8.96 g/cm 3 {circumflex over ( )}3 for copper); A is the area of a single deposit on the cathode (note: this is NOT the same as the anode area) d is the distance (z-height) of the deposited column of material.
 
     Rearranging the equation and expanding the area term results in the following equation: 
     
       
         
           
             d 
             = 
             
               
                 
                   ∫ 
                   0 
                   t 
                 
                 ⁢ 
                 
                   Idt 
                   * 
                   M 
                 
               
               
                 zF 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 
                   
                     ρπ 
                     ⁡ 
                     
                       ( 
                       
                         r 
                         eq 
                       
                       ) 
                     
                   
                   2 
                 
               
             
           
         
       
     
     This equation gives a model for the z-height produced at a single circular anode pin as a function of deposition current, equivalent radius of the cathode deposit, and known physical and chemical constants. 
     The equivalent radius of a deposit produced on the cathode, R eq  is modeled as a function of the “throw angle” (λ), the working distance (dw) and the anode radius (r) which is approximated by the following function:
 
 r   eq   =r+d   w *tan(λ)
 
     According to an embodiment, the throw angle (λ) was empirically determined to best fit with observed results at 28° for a standard acid copper solution consisting of 900 g distilled water, 250 g copper sulfate pentahydrate, and 80 g sulfuric acid by weight. Those of ordinary skill will be able to determine the throw angle (λ) for other electrolytes and reactor configurations, if required. 
     Microcontroller  50  uses the above mathematical model to produce an overall process flow which compares the expected deposition rate on anode array  10  with the actual rate of deposition as detected by the cathode position sensor. In one embodiment, the expected deposition rate on anode array  10  is compared with the actual deposit height by “shorting” successive anodes in anode array  10  and raising the cathode to the next layer only when all anodes have been shorted. In an embodiment, the microcontroller  50  attempts to have the system for stereo-electrochemical deposition of layers of metallic materials to fabricate a structure by creating an even layer of metal deposits across each of the active anodes of anode array  10  by allowing the metal deposited material to grow from the cathode element  26  until the metal deposited material reaches anode array  10 . When the metal material deposited on the cathode element contacts the anode element, the metal material will short circuit cathode to anode. The current controller  64  detects the short circuit on each individual anode of anode array  10  and limits that individual anode&#39;s current to a predetermined value, or cuts off current to that individual anode element altogether. This information is detected by microcontroller  50  through the MICA algorithm by analyzing input from the current sensor  46 . 
     In an embodiment, the Multiple Independently Controlled Anodes (MICA) software performs the following steps: 
     1. Detect deposit layer height (zero the cathode); 
     2. Detect uneven deposits, adjust individual anode pulse-width modulation (PWM) to compensate; 
     3. Raise cathode to appropriate working distance; 
     4. Recalculate constants for new working distance and the of active anodes in the anode array; 
     5. Begin printing layer with n active anodes; 
     6. Sense total current; 
     7. If current is below desired amperage as predicted by model, raise voltage; 
     8. If current is above desired amperage, lower voltage; 
     9. If current derivative is above threshold (possible short), return to step 2, above; 
     10. If predicted deposit height exceeds threshold, return to step 1, above; 
     11. Otherwise, run the Ziegler-Nichols method of tuning a proportional integral derivative controller (PID controller) to maintain anode deposition current at appropriate level—return to step 6. 
       FIG. 5  illustrates the logic flow process of the controlled stereo-electrochemical deposition according to the mathematical model described above. The overall process may be described as “deposit, verify, adjust, and repeat.” 
     Typical process parameters for the SED process, in an embodiment, are listed below: 
     
       
         
           
               
               
             
               
                   
               
               
                 Parameter 
                 Value 
               
               
                   
               
             
            
               
                 Voltage 
                 Dynamically adjusted via Zieglar-Nichols 
               
               
                   
                 PID (1.8-3.8 V) 
               
               
                 Pulse period 
                 DC 
               
               
                 Electrolyte 
                 Copper sulfate hexahydrate (250 g), 
               
               
                   
                 Sulfuric acid (80 g), water (900 g) 
               
               
                 Anode 
                 64 Pt-Ru (95/5) pins (0.5 mm diameter) 
               
               
                 Cathode 
                 9 mm × 9 mm graphite block 
               
               
                 Working distance 
                 0.6-0.9 mm 
               
               
                 Target deposition current 
                 1.38-6.0 mA/pin (65-285 A/dm 2 ) 
               
               
                   
               
            
           
         
       
     
     The process described above functions well for electrodeposition of two-dimensional objects and can be accomplished without any CAD, stereolithography modeling or slicing software. 
     However, in order to accomplish true three-dimensional (stereo)-electro deposition (SED) of functional parts, additional steps are required. 
       FIG. 5  depicts the process for SED of multiple layers to fabricate three dimensional structures according to an embodiment. In step  500 , a CAD model of the desired product is exported to a stereolithography (STL) file. In step  501 , the STL file is exported to an open source digital light projection (DLP)-based stereo-lithography (SLA) 3D printer controller (slicing) software application, to produce layer slices. In an embodiment, the slicing software may be Creation Workshop v1.0.0.13 from Envision Labs. In step  502 , layer slice information is processed into anode array signals by the slicing software. Layer slice information may be output as PNG files along with a descriptive G-code file with information regarding layer width and number of slices. In step  503 , anode array signals are sent to microcontroller  50 . A machine configuration file (.mcf) may be created for microcontroller  50  to allow microcontroller  50  to determine the physical parameters of the controlled stereo-electrochemical deposition reactor. 
     In step  504 , microcontroller  50  loads new layer information based on layer slices received in step  503 . In step  505 , microcontroller  50  detects the deposit height of cathode  26  for deposition of the new layer of metallic material. During operation of the SED process, microcontroller  50  may detect any uneven deposits of new material and adjust the overall anode bias voltage to maintain target deposition rate. 
     In step  506 , microcontroller  50  adjusts the position of cathode  26  to an appropriate working distance from anode array  10  for deposition of the new layer of material. In step  507 , microcontroller  50  computes the parameters of the operation of the SED system based upon the new position of cathode  26  determined in step  506 . In step  508 , microcontroller  50  causes a layer to be deposited. Microcontroller  50  continuously monitors the drive current, bias voltage and active anodes of anode array  10  to maintain overall system efficiency. 
     As illustrated in steps  509  and  510 , if microcontroller  50  detects that the cathode current is above the target anode element amperage times the number of active anodes, voltage to entire anode array is lowered by microcontroller  50 , or microcontroller  50  deactivates anode elements as needed to eliminate shorted anode elements. As illustrated in steps  513  and  514 , if microcontroller  50  detects that the drive current is below the desired amperage as predicted by the model, voltage to the anode array is increased. 
     As illustrated in steps  511  and  512 , if microcontroller  50  detects that all anodes of anode array  10  have been deactivated, the deposition of the layer is deemed complete. The process returns to step  504  for deposition of the next layer, and repeats until the structure is completed. 
       FIG. 6 . illustrates an embodiment of the chemical pumping and handling subsystem which enables the stereo-electrochemical deposition process. A tank  59  is connected to the system through quick disconnect fittings  60  to route the flow of electrolyte to chamber  14  through filter  58  and valves  54 . The flow of electrolyte then returns through the pump  52  and another set of quick disconnect fittings  60  and returns to the tank  59  or to a waste management system. In an embodiment, a filter  58  may be used, such as, for example, a chemical resistant polypropylene T-strainer, 200 mesh from McMaster Carr (8680T21). The electrolyte is propelled through the system by fluid pump  52  such as HYCX 10inkpump-12 VDC. The flow of the electrolyte through the system is controlled using fluid valves  54 , which may be chemically resistant valves, such as, for example, Parker Series 1 Miniature Inert PTFE Isolation Valves. Microcontroller  50  controls the operation of pumps  52  and valves  54 . Power supply  40  provides the necessary power to run the system. In an embodiment, power supply  40  may be a Toshiba 15V 3.0 mm PA3283U-1ACA adapter/charger. 
     The following is a material selection guide which sets forth expected model compatibility, chemical prices, deposition rates and material properties for the various metals which could be deposited according to the embodiments of the invention: 
     
       
         
           
               
               
               
               
               
               
               
             
               
                   
               
               
                   
                   
                   
                 Deposition 
                 Electrical 
                 Thermal 
                 Melting 
               
               
                   
                 Models 
                 Feedstock Price 
                 speed 
                 Conductivity 
                 Conductivity 
                 Point 
               
               
                   
                 supported 
                 ($/kg metal ion eq.) 
                 (% of Cu speed) 
                 (% of Cu) 
                 (% of Cu) 
                 (° C.) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Gold 
                 All 
                 Spot + 20% 
                 25% 
                 65% 
                 83% 
                 1064 
               
               
                 Silver 
                 All 
                 Spot + 30% 
                 10% 
                 106%  
                 106%  
                 962 
               
               
                 Zinc 
                 All 
                 $45 
                 150%  
                 29% 
                 29% 
                 420 
               
               
                 Zn/Fe/Co/Ni Alloys 
                 All 
                 $50 
                 10-35%       
                 10-28%       
                 5-20%     
                 300-750 
               
               
                 Copper 
                 All 
                 $50 
                 100%  
                 100%  
                 100%  
                 1085 
               
               
                 Nickel 
                 A1200-2500 
                 $50 
                 40% 
                 22% 
                 24% 
                 1455 
               
               
                 Tin 
                 All 
                 $50 
                 15% 
                 15% 
                 17% 
                 231 
               
               
                 Pure Iron 
                 All 
                 $50 
                 300%  
                 17% 
                 20% 
                 1538 
               
               
                 Stainless 316L 
                 A1200-2500 
                 $60 
                 5-10%     
                 2.5%  
                  4% 
                 1400 
               
               
                 Aluminum 
                 A1200-2500 w/Mods 
                 $120  
                 15% 
                 60% 
                 50% 
                 660 
               
               
                 Titanium 
                 A1200-2500 w/Mods 
                 $160  
                 5-20%     
                  4% 
                  5% 
                 1668 
               
               
                 Polypyrrole 
                 A1200-2500 
                 $80 
                 1-2%  
                 0.000084%     
                 0.05%     
                 150 
               
               
                 Tungsten Carbide MMC 
                 A2500 
                 $80 
                 5-10%     
                  8% 
                 28% 
                 2800 
               
               
                 BNNT Reinforced 316L 
                 A2500 
                 $850  
                 4-5%  
                  1% 
                  3% 
                 1400 
               
               
                 SGCNT/Cu Matrix 
                 A2500 
                 $550  
                 90% 
                 140%  
                 110%+ 
                 1085 
               
               
                   
               
            
           
         
       
     
     Below is a list of potentially deposited materials and ranges of allowable, and preferred, process conditions for each deposit material, identifying the metals that can be deposited and the various reagents and additives used in the SED process for each deposit material. In the chemical compositions listed below, all compounds are assumed to be soluble in an aqueous solution: 
     Copper
         Allowable chemicals/concentrations:
           Copper sulfate, hexahydrous or anhydrous (0-350 g/L).   Concentrations are for the hexahydrous case   Sulfuric acid (0-270 g/L)   Copper chloride (0-100 g/L)   Copper Fluoroborate (0-450 g/L)   Fluoroboric acid (0-30 g/L)   Boric acid (0-30 g/L)   Copper pyrophosphate (22-38 g/L) and corresponding salt: potassium or sodium pyrophosphate (150-250 g/L), as well as a source of nitrate (5-10 g/L) and ammonia ions (⅓ g/L).   Copper cyanide (15-75 g/L) and corresponding cyanide salts or Rochelle salt.   
           Allowable Additives
           benzotriazole, cadmium, casein, cobalt, dextrin, dimethylamino derivatives, disul-fides, 1,8-disulfonic acid, disodic 3,3-dithiobispropanesulfonate, 4,5-dithiaoctane-1,8 disulfonic acid, dithiothreitol, ethylene oxide, gelatin, glue, gulac, lactose benzoylhydrazone, 2-mercaptoethanol, molasses, sulfonated petroleum, o-phenanthroline, polyethoxyether, polyethylene glycol, polyethylene imine, poly N,N0-diethylsaphranin, polypropylene ether, propylene oxide, sugar, thiocarbamoyl-thio-alkane sulfonates, and thiourea.   
           Allowable Temperature range
           18° C.-60° C.   
           Allowable Voltage range
           0.2V-6V   
           Allowable Current range
           1.6 A/dm 2  to 260 A/dm 2      
           Preferred conditions for the SED process
           Electroplating solution: Copper sulfate, 250 g/L (saturated solution at room temperature). Sulfuric acid 0-40 g/L.   Additives: Sodium dodecyl sulfate (SDS) 600 mg/L   Temperature: 25° C. (room temperature)   Voltage: 2.8-3.2V   Current: 200-500 A/dm 2 , 75% duty cycle square wave   
               

     Nickel
         Allowable Chemicals/concentrations:
           Nickel sulfate, hexahydrous (225-400 g/L).   Boric acid (0-45 g/L)   Nickel Ammonium Sulfate (0-45 g/L)   Nickel Chloride (30-450 g/L)   Nickel fluoroborate (0-300 g/L)   Zinc sulfate (0-30 g/L)   Ammonium sulfate (0-35 g/L)   Sodium thiocyanate (0-15 g/L)   Zinc chloride (0-30 g/L)   Ammonium chloride (0-30 g/L)   Phosphoric or phosphorous acid (0-50 g/L)   
           Allowable Additives:
           Sulfur containing compounds and surfactants   Benzene, naphthalene and other “brighteners”   
           Allowable Temperature range:
           25° C.-80° C.   Temperature control should be controlled to within +/−2° C.   
           Allowable Voltage range:
           0.2-1.0V, 4V possible in high frequency pulsed deposition   
           Allowable Current range:
           0.5-10 A/dm 2      
           Allowable Preferred conditions for the SED process
           Electroplating solution: Nickel sulfate, 240 g/L. Nickel chloride, 45 g/L. Boric acid, 30 g/L.   Additives: Sodium dodecyl sulfate (SDS) 600 mg/L   Temperature: 25° C. (room temperature)   Voltage: 4V @ 75% duty cycle 100 ns pulse period   Current: 10 A/dm 2  (target)   
               

     Silver
         Allowable Chemicals/concentrations:
           Silver metal (0-120 g/L)   Silver cyanide (0-150 g/L)   Silver nitrate (0-450 g/L)   Potassium cyanide (45-160 g/L)   Potassium carbonate (15-90 g/L)   Potassium nitrate (0-60 g/L)   Potassium hydroxide (0-30 g/L)   
           Allowable Additives:
           Glucose, tartaric acid, Rochelle salt, ethyl alcohol, potassium nitrate, hydrazine, hydrazine sulfate, ammonia, ethylenediamine, 3,5-diiodotyrosine, Na-2-3-mercaptopropane sulfonate, and other “stabilizers”.   
           Allowable Temperature range:
           25° C.-50° C.   
           Allowable Voltage range:
           4-6V (strike voltage), 0.1-2V plating voltage, pulse deposition may be possible   
           Allowable Current range:
           0.5-10 A/dm 2      
           Preferred conditions for the SED process (process may be modified to reduce cyanides due to their toxicity)
           Electroplating solution: Silver nitrate or silver cyanide-based solution.   Additives: Sodium dodecyl sulfate (SDS) 600 mg/L, other additives TBD   Current: 10 A/dm 2  (target)   
               

     Zinc
         Allowable Chemicals/concentrations:
           Zinc cyanide (0-60 g/L)   Sodium cyanide (0-40)   Sodium hydroxide (0-80 g/L)   Sodium bicarbonate/carbonate (0-15 g/L)   Sodium sulfide (0-2 g/L), catalytic   Zinc chloride (0-130 g/L)   Nickel chloride (0-130 g/L)   Potassium chloride (0-230 g/L)   
           Allowable Additives:
           Thiosemicarbazide and their thiosemicarbazone derivatives such as Thiosemicarbazide (TSC), Acetophenone (AcP), Cinnamaldehyde (CnA), Crotonaldehyde (CrA), Furfuraldehyde (FrA), Salcylaldehyde (SaA), Acetophenonethiosemicarbazone (ApTSCN), Cinnamaldehydethiosemicarbazone (CnTSCN), Crotonaldehydethiosemicarbazone (CrTSCN), Furfuraldehydethiosemicarbazone (FrTSCN), Salcylaldehyde thiosemicarbazone (SaTSCN)   (a) poly(N-vinyl-2-pyrrolidone), and p0 (b) at least one sulfur-containing compound selected from compounds of the formulae: RS(R′O)nH (I) or S—[(R′O)nH]2 (II)   Polyvinyl alcohols, polyethyleneimine, gelatin and peptone   
           Allowable Temperature range:
           25° C.-40° C.   
           Allowable Voltage range:
           3-18V (strike voltage), pulse deposition may be possible   
           Allowable Current range:
           0.1-50 A/dm 2      
           Preferred conditions for the SED process (will not deposit pure zinc due to toxicity and difficulty of using DSA anode tech—instead will attempt deposit zinc/nickel alloys)
           Electroplating solution: Zinc chloride, 120 g/L. Nickel chloride 120 g/L. Potassium chloride, 230 g/L   Additives: Sodium dodecyl sulfate (SDS) 600 mg/L, polyvinyl alcohol MW 5 k-20 k Dalton, as well as polyethyleneimine, gelatin and peptone, 0.1-3 g/L.   Temperature: 25° C. (room temperature)   Current: 5 A/dm 2  (target)   
               

     Iron and ferrous alloys
         Allowable Chemicals/concentrations (for iron metal):
           Iron sulfate (0-300 g/L) or Iron ammonium sulfate   Ammonium sulfate (0-120 g/L)   Ferrous chloride (0-300 g/L)   Calcium chloride (0-335 g/L)   Potassium chloride (0-180 g/L)   Ammonium chloride (0-20 g/L)   Iron fluoroborate (0-226 g/L)   Sodium chloride (0-10 g/L)   
           Allowable Chemicals/concentrations (for selected stainless steel alloys),
           Iron sulfamate, Cobalt sulfamate, ammonium metavanadate, boric acid, sodium tetraborate, ascorbic acid, saccharin, SDS, potassium dichromate (˜300 g/L), nickel sulfate (˜80 g/L), Iron sulfate (˜50 g/L), Glycine (˜150 g/L)   
           Allowable Chemicals/concentrations (for selected high-toughness boron steel alloy)
           Ferrous chloride (˜200 g/L)   Malic acid (0.6 g/L)   Boric acid (40 g/L)   Dimethylamineborane (3 g/L)   
           Allowable Additives:
           SDS   1 g/L of condensate of sodium naphthalene sulfonate and formaldehyde   
           Allowable Temperature range:
           25° C.-110° C.   
           Allowable Current range:
           1-400+ A/dm 2      
           Preferred conditions for the SED process (iron chloride baths will be avoided due to the tendency for ferric chlorides to form, and due to the extremely corrosive nature of the chloride plating solutions)
           Electroplating solution: Iron fluoroborate (225 g/L), Sodium chloride (0-10 g/L). Boron-alloy and stainless solutions may be pursued at a later date   Additives: Sodium dodecyl sulfate (SDS) 600 mg/L, 1 g/L of condensate of sodium naphthalene sulfonate and formaldehyde   Temperature: &gt;50° C. (target)   Current: 10 A/dm 2  (target)   Working distance: TBD (suspected to be around the same distance as the radius/half width of the anode)   
               

     Aluminum
         May employ ionic liquids, aluminum chlorides, aluminum chloride-butylpyridinium chlorides (BPC), aluminum chloride-trimethylphenylammonium chloride (TMPAC) and/or aluminum flourobororides   Deposition potential likely ˜−0.4-1.0V       

     Polymer deposition and polymer matrix composites (PMC)
         Allowable Chemicals/concentrations (for iron metal):
           Polyaniline   Polypyrrole (monomer 3 g/L)   polythiophene   polyphenylenevinylene   Acetonitrile   Methanol   Oxcalic acid   Sodium salicylate   
           Allowable Additives:
           Lithium perchlorate (as a catalyst for deposit adhesion), Tiron (0.05 M)   
           Allowable Voltage range:
           0.4-1.0V   
           Allowable Current range:
           0.1 A/dm 2      
           Preferred conditions for the SED process
           Electroplating solution: Pyrrole, 3 g/L. Lithium perchlorate, concentration TBD. Tiron (15.7 g/L), composite materials may be added to the electroplating bath such as: single walled or multi-walled functionalized carbon nanotubes, silica fibers, aerogels, or amorphous powders, boron, boron nitride, silicon carbide, or other high strength ceramic materials, graphene or graphene oxide, etc.   Additives: Sodium dodecyl sulfate (SDS) 600 mg/L, 1 g/L of condensate of sodium naphthalene sulfonate and formaldehyde.   Dopants: Tosyl chloride, tosylic acid.   Temperature: &gt;50° C. (target), max temp will depend on chamber construction mats.   
               

     Metal matrix composites (MMC)
         Allowable Chemicals/concentrations:
           All allowable chemicals and concentrations listed in the specification. Functionalized/solvated nanomaterials or high strength ceramic fibers such as: single walled or multi-walled functionalized carbon nanotubes, silica fibers, aerogels, or amorphous powders, boron, boron nitride, silicon carbide, or other high strength ceramic materials, graphene or graphene oxide, etc.   Multi-walled carbon nanotubes (MWNTs) may be added in concentrations as high as 4 g/L   
           Allowable Additives:
           Polycyclic acid, MHT, Polyacrylic acid, SDS   
           Allowable Voltage range:
           0.4-5.0V   
           Allowable Current range:
           0.1 A/dm 2      
           Preferred conditions for the SED process
           Electroplating solution: Pyrrole, 3 g/L. Lithium perchlorate, concentration TBD. Tiron (15.7 g/L), composite materials may be added to the electroplating bath such as: single walled or multi-walled functionalized carbon nanotubes, silica fibers, aerogels, or amorphous powders, boron, boron nitride, silicon carbide, or other high strength ceramic materials, graphene or graphene oxide, etc.   Additives: Sodium dodecyl sulfate (SDS) 600 mg/L, 1 g/L of condensate of sodium naphthalene sulfonate and formaldehyde Temperature: &gt;50° C. (target), max temp will depend on chamber construction mats.   
               

     Below is a list of electrolytes which may be used to carry the metal, semimetal and electroconductive monomer ions:
         Water
           Allowable temperatures: 18° C.-95° C.   Allowable voltage range: 0.2-7.2V   Allowable current range: 0.1-1000 A/dm 2      Potentially deposited materials: All potentially deposited materials listed in the specification, in addition to Al, Pd, In, Sb, Te, Ga, Si, Ta, and Ti, as well as Metal Matrix Composites (MMC) and codeposited Polymer Matrix Composites (PMC).   
           Ionic liquids
           Based on: Ethyl ammonium nitrate, alkyl-pyridinium chloride, 2-hydroxy-N,N,N-trimethylethanaminium, dimethylsulfoxide, or alkyl-arylimidazolium.   Containing an anion group such as: Hexafluorophosphate, Bis(trifluoromethylsulfonyl) amide, Trispentafluoroethyltrifluorophosphate, Trifluoroacetate, Trifluoromethylsulfonate, Dicyanoamide, Tricyanomethide, Tetracyanoborate, Tetraphenylborate, Tris(trifluoromethylsulfonyl)methide, Thiocyanate, Chloride, Bromide, Tetrafluoroborate, Triflate, etc.   Containing a cation groups such as: Choline, Pyrrolidinium, Imidazolium, Pyridinium, Piperidinium, Phosphonium (including Tri-hexyl-tetradecylphosphonium), Pyrazolium, Ammonium, Sulfonium, etc.   Allowable temperatures: 0° C.-300° C.   Allowable voltage range: 0.2-7.2V   Allowable current range: 0.1-1200 A/dm 2      Potentially deposited materials: All listed in 0095, in addition to Al, Pd, In, Sb, Te, Ga, Si, Ta, Mg, and Ti, as well as Metal Matrix Composites (MMC) and codeposited Polymer Matrix Composites (PMC).   
               

       FIG. 7A  illustrates a 3D model of a structure to be fabricated by stereo-electrochemical deposition of layers of copper performed under the following conditions: 
     
       
         
           
               
               
             
               
                   
               
               
                 Parameter 
                 Value 
               
               
                   
               
             
            
               
                 Voltage 
                 Dynamically adjusted via Zieglar-Nichols 
               
               
                   
                 PID (1.8-3.8 V) 
               
               
                 Pulse period 
                 DC 
               
               
                 Electrolyte 
                 Copper sulfate hexahydrate (250 g), 
               
               
                   
                 Sulfuric acid (80 g), water (900 g) 
               
               
                 Anode 
                 64 Pt-Ru (95/5) pins (0.5 mm diameter) 
               
               
                 Cathode 
                 9 mm × 9 mm graphite block 
               
               
                 Working distance 
                 0.65 mm 
               
               
                 Target deposition current 
                 5.0 mA per pin 
               
               
                   
               
            
           
         
       
     
       FIG. 7B  is a top view of a structure fabricated by stereo-electrochemical deposition of layers of copper for 6 hours under the conditions described above. 
       FIG. 7C  is a side view of a structure fabricated by stereo-electrochemical deposition of layers of copper for 6 hours under the conditions described above. 
       FIG. 8A  illustrates a 3D model of a structure to be fabricated by stereo-electrochemical deposition of layers of copper performed under the following conditions: 
     
       
         
           
               
               
             
               
                   
               
               
                 Parameter 
                 Value 
               
               
                   
               
             
            
               
                 Voltage 
                 Dynamically adjusted via Zieglar-Nichols 
               
               
                   
                 PID (1.8-3.8 V) 
               
               
                 Pulse period 
                 DC 
               
               
                 Electrolyte 
                 Copper sulfate hexahydrate (250 g), 
               
               
                   
                 Sulfuric acid (80 g), water (900 g) 
               
               
                 Anode 
                 64 Pt-Ru (95/5) pins (0.5 mm diameter) 
               
               
                 Cathode 
                 9 mm × 9 mm graphite block 
               
               
                 Working distance 
                 0.7 mm 
               
               
                 Target deposition current 
                 5.2 mA per pin 
               
               
                   
               
            
           
         
       
     
       FIG. 8B  is a side view of a structure fabricated by stereo-electrochemical deposition of layers of copper for 8 hours under the conditions described above. 
       FIG. 8C  is a top view of a structure fabricated by stereo-electrochemical deposition of layers of copper for 8 hours under the conditions described above. 
       FIG. 9A  illustrates a 3D model of a structure to be fabricated by stereo-electrochemical deposition of layers of copper performed under the following conditions: 
     
       
         
           
               
               
             
               
                   
               
               
                 Parameter 
                 Value 
               
               
                   
               
             
            
               
                 Voltage 
                 Dynamically adjusted via Zieglar-Nichols 
               
               
                   
                 PID (1.8-3.8 V) 
               
               
                 Pulse period 
                 DC 
               
               
                 Electrolyte 
                 Copper sulfate hexahydrate (250 g), 
               
               
                   
                 Sulfuric acid (80 g), water (900 g) 
               
               
                 Anode 
                 64 Pt-Ru (95/5) pins (0.5 mm diameter) 
               
               
                 Cathode 
                 9 mm × 9 mm graphite block 
               
               
                 Working distance 
                 0.86 mm 
               
               
                 Target deposition current 
                 2.1 mA per pin 
               
               
                   
               
            
           
         
       
     
       FIG. 9B  is a side view of a structure fabricated by stereo-electrochemical deposition of layers of copper for 50 hours under the conditions described above. 
       FIG. 9C  is a top view of a structure fabricated by stereo-electrochemical deposition of layers of copper for 50 hours under the conditions described above. 
       FIG. 10A  illustrates a 3D model of a structure to be fabricated by stereo-electrochemical deposition of layers of copper performed under the following conditions: 
     
       
         
           
               
               
             
               
                   
               
               
                 Parameter 
                 Value 
               
               
                   
               
             
            
               
                 Voltage 
                 Dynamically adjusted via Zieglar-Nichols 
               
               
                   
                 PID (1.8-3.8 V) 
               
               
                 Pulse period 
                 DC 
               
               
                 Electrolyte 
                 Copper sulfate hexahydrate (250 g), 
               
               
                   
                 Sulfuric acid (80 g), water (900 g) 
               
               
                 Anode 
                 64 Pt-Ru (95/5) pins (0.5 mm diameter) 
               
               
                 Cathode 
                 9 mm × 9 mm graphite block 
               
               
                 Working distance 
                 1 mm 
               
               
                 Target deposition current 
                 3.1 mA per pin 
               
               
                   
               
            
           
         
       
     
       FIG. 10B  is a side view of a structure fabricated by stereo-electrochemical deposition of layers of copper for 97 hours under the conditions described above. 
       FIG. 10C  is a top view of a structure fabricated by stereo-electrochemical deposition of layers of copper for 97 hours under the conditions described above. 
       FIG. 11A  illustrates a 3D model of a structure to be fabricated by stereo-electrochemical deposition of layers of copper performed under the following conditions: 
     
       
         
           
               
               
             
               
                   
               
               
                 Parameter 
                 Value 
               
               
                   
               
             
            
               
                 Voltage 
                 Dynamically adjusted via Zieglar-Nichols 
               
               
                   
                 PID (1.8-3.8 V) 
               
               
                 Pulse period 
                 DC 
               
               
                 Electrolyte 
                 Copper sulfate hexahydrate (250 g), 
               
               
                   
                 Sulfuric acid (80 g), water (900 g) 
               
               
                 Anode 
                 64 Pt-Ru (95/5) pins (0.5 mm diameter) 
               
               
                 Cathode 
                 9 mm × 9 mm graphite block 
               
               
                 Working distance 
                 0.8 mm 
               
               
                 Target deposition current 
                 2.6 mA per pin 
               
               
                   
               
            
           
         
       
     
       FIG. 11B  is a side view of a structure fabricated by stereo-electrochemical deposition of layers of copper for 110 hours under the conditions described above. 
       FIG. 11C  is a side view of a structure fabricated by stereo-electrochemical deposition of layers of copper for 110 hours under the conditions described above. 
     In the description above and throughout, numerous specific details are set forth in order to provide a thorough understanding of an embodiment of this disclosure. It will be evident, however, to one of ordinary skill in the art, that an embodiment may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form to facilitate explanation. The description of the preferred embodiments is not intended to limit the scope of the claims appended hereto. Further, in the methods disclosed herein, various steps are disclosed illustrating some of the functions of an embodiment. These steps are merely examples, and are not meant to be limiting in any way. Other steps and functions may be contemplated without departing from this disclosure or the scope of an embodiment.