Patent Publication Number: US-9905389-B2

Title: Method of manufacturing an article with integral active electronic component

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This is a divisional of U.S. application Ser. No. 14/658,797, filed Mar. 16, 2015, which claims priority to EP Application No. 14 250 050.3, filed 21 Mar. 2014, the entire contents of each of which are hereby incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to the manufacture of active electronic components. In particular it relates to the manufacture of a 3D printed article including a 3D printed thermionic electronic component integral with a fabric of the article. 
     BACKGROUND OF THE INVENTION 
     Additive manufacturing, also known as three dimensional (3D) printing, is a process of manufacturing a three dimensional solid object from a model such as a digital model by an additive process in which material is layered, adhered, bonded or otherwise deposited successively until the solid object is formed. Such an approach is in contrast to traditional manufacturing techniques where articles are formed from the assembly of parts which themselves may be machined, cast or moulded. 
     There are many benefits to additive manufacturing over traditional manufacturing techniques, including technical benefits and commercial benefits. Technically, additive manufacturing allows virtually any arrangement of a three dimensional object to be created from a growing number of materials, including plastics, metals and ceramics. The arrangement can include complex features, even internally, since the additive approach to manufacturing is capable of generating complex structure. Additive approaches generate less waste compared to traditional approaches, provide increased consistency between articles of manufacture, improved speed of manufacture from initial design with minimal setup required, the advantages of novel structures and shapes and new combinations of materials. 
     Commercially, additive manufacturing provides considerable cost-savings over traditional manufacturing techniques, especially where a number of articles for manufacture is relatively small. For example, prototypes, proof-of-concepts, spare-parts and articles manufactured in isolated or remote locations, such as in orbit or space, are readily produced at low cost using additive manufacturing. The speed of manufacturing is also a benefit since a three dimensional article can be produced from a three dimensional design relatively rapidly. 
     Additive manufacturing covers a number of approaches. Extrusion deposition is an approach to additive manufacturing in which beads of material are extruded in a controlled manner either by way of a moveable extruder (“print-head”); a moveable table or support; or both. The extruded beads harden rapidly to form a layer or part of an article onto which further extrusion can take place. In this way the article is built-up additively. 
     An alternative approach is the selective fusing of granular materials such as a selective sintering or melting of metals or polymers. Using such an approach granular material is deposited in layers and selectively sintered, melted or bonded using, for example, convection heat, laser or electron beam. The selection is made based on a three dimensional model of the article in a layered manner. In this way the article is built-up additively. 
     Use of additive manufacturing to produce electrical or electronic devices has been severely constrained since additive manufacturing is not suitable for manufacturing complex modern electronic components from many disparate materials. While additive manufacturing has found applications in the printing of planar circuit board layouts with component sockets and interconnects in combination with trenches or routes for electrical connections, there is currently a requirement for placement, installation and/or assembly of electrical and electronic components following the additive manufacturing process. This requirement for post-manufacture assembly and/or installation has the considerable disadvantage that component locations, sockets and routes must be accessible in an additively-manufactured product. Accordingly, the hugely beneficial characteristics of additive-manufacturing of accurately producing complex, internalised and potentially inaccessible structures are entirely lost in the electronic field. Furthermore, the requirement for post-manufacture assembly and/or installation imposes burdens of additional manufacturing steps that considerably erode the benefits of additive manufacturing. 
     Thus it would be beneficial to produce electronic devices using additive manufacturing approaches without the aforementioned disadvantages. 
     SUMMARY OF THE INVENTION 
     The present invention accordingly provides, in a first aspect, a method of manufacturing an article with integral active electronic component comprising: using an additive manufacturing process to: a) form a non-electrically conductive substrate; b) form a non-electrically conductive perforated layer having an aperture; c) form electrically conductive anode and cathode elements spaced in the aperture; d) deposit a conductive electrical connection to each of the elements suitable for imparting an electrical potential difference between the elements; e) form a non-electrically conductive sealing layer atop the perforated layer so as to retain and seal the aperture in the perforated layer. 
     Thus, embodiments of the present invention provide for the production of a three dimensional article by way of the additive manufacturing process. The use of such a manufacturing process allows for the production of a three dimensional article having potentially complex internal characteristics with the integration of active electronic components such as diodes and triodes within the fabric of the article. Due to the production and integration of active electronic components as part of the article manufacturing process, there is no requirement for post-production assembly or installation of electronic components. Thus, manufacture of articles with installed electronic components can occur contemporaneous with the manufacture of the substantive three dimensional structure of the article. This relieves the manufacturing process from considerations of post-production assembly and installation of electronic components, such as burden approaches of the prior art that require multi-part manufacture with accessible integration interfaces and the like. Further, the cost of manufacture is dramatically reduced due to the use of additive manufacturing process, especially where small numbers of articles are required such as in prototyping or proof-of-concept manufacture, or in remote or inaccessible locations such as in orbit or space. 
     The inclusion of active electronics within the fabric of a three dimensional article will reduce the overall weight of the article due to the absence of additional components, appendages. Furthermore, articles can be made more streamlined, with electronic componentry embedded within the article, such as internally in an imperceivable, undetectable and/or unobtrusive location within the article. Where the active electronic component is embedded in the article, the component can be protected from exposure to fluids such as moisture or air. The ability of additive manufacturing to produce articles on the micro-scale provides for potentially ‘intelligent’ (in the sense of including electronic componentry) articles in all manner of applications, including: electronics embedded within cellular telephone cases or covers; electronics embedded within cable sheaths; electronics embedded within fabric or clothing; electronics embedded within cases, covers, walls or other structural elements of other devices such as consumer or entertainment devices; electronics in spare-parts; and the like. 
     The removal of the requirement for accessibility of an electrical circuit and component locations for post-manufacturing assembly or installation dramatically redefines how electrical circuits and electronic devices can be designed and implemented in articles of manufacture. Embodiments of the present invention provide for true three-dimensional arrangements of active electronic components and the connections therebetween without a requirement for accessibility of individual components or connections. This provides for an increase in the efficient use of space or volume of an article, and potentially for the reuse of active electronic components where appropriate by circuits of the same device under control. Vertical interconnects can provide for three dimensional processing elements such as cubic or other three dimensional arrangements of electronic components and circuits. A layered architecture of electronic components can be produced with layers of active electronic components within a single three dimensional article. Common services such as provision of power, dissipation of power, dissipation of thermal energy and the like can be provided by strata of service layers included as part of the additive manufacturing process, such as metal layers for power supply or layers of thermally efficient conducting materials for heat dissipation or transfer. Conceivably, channels and conduits can be provided, manufactured as part of the additive manufacturing process, for the communication of fluids such as coolants or gases to further provide services to electronic components such as the transfer of heat from within the article, such as heat generated by the active electronic components. 
     A particular advantage of the use of thermionic electronic components is the benefits of such components over silicon equivalents such as silicon transistors. Thermionic components have considerable robustness and provide improved analogue signal transfer properties. For example, thermionic components are highly resistant to electromagnetic pulses and solar flare activity providing particular benefits on application to satellites technology or critical infrastructure systems. 
     While the use of thermionic electronic components has been largely superseded by semiconductor equivalents, the inventors have realised the surprising benefits of such components in the field of additive manufacturing based on the simplicity of manufacturing such components, capabilities for which now exist in the field of additive manufacturing, the effectiveness of such components and their reliability. 
     Preferably, forming one or more of: the substrate; perforated layer; and sealing layer includes forming a channel providing fluid communication between the aperture and an evacuation port of the article, wherein the evacuation port is suitable for evacuating the aperture of gas so as to generate vacuum-like conditions in the aperture. 
     Preferably the additive manufacturing process takes place within a sealed atmosphere constituted substantially of an inert gas so as to encase the inert gas in the aperture on formation of the sealing layer. 
     Preferably the anode and cathode are positioned at opposing sides of the aperture. 
     Preferably the cathode is located centrally in the aperture and the anode occupies at least part of a wall of the aperture. 
     Preferably the additive manufacturing process includes an extrusion deposition process. 
     Preferably the additive manufacturing process includes a granular material binding process. 
     Preferably the method further comprises: using the additive manufacturing process to form a filament element in thermal proximity with the cathode so as to, in use, induce thermionic emission by the cathode. 
     Preferably the method further comprises using the additive manufacturing process to: form a conductive grid element spaced from, and positioned between, the anode and cathode elements; and deposit a conductive electrical connection to the grid for providing an electrical signal to the grid, such that the grid regulates the transmission of electrons from the cathode to the anode. 
     Preferably at least one of the: non-electrically conductive substrate; perforated layer; and sealing layer are formed in ceramic. 
     Preferably at least one of the: anode; the grid; and the conducive electrical connections are formed from a gallium alloy. 
     Preferably the gallium alloy is a binary eutectic alloy of gallium and indium. 
     Preferably the cathode includes tungsten. 
     The present invention accordingly provides, in a second aspect, an article with integral active electronic component manufactured by the process of any preceding claim. 
     The present invention accordingly provides, in a third aspect, a 3D printed apparatus comprising a 3D printed thermionic electronic component integral with a fabric of the apparatus. 
     Preferably the thermionic electronic component is a diode comprising a cathode and an anode. 
     Preferably the thermionic electronic component is a triode comprising a cathode, an anode and a grid to regulate the passage of electrons from the cathode to the anode. 
     Preferably the apparatus further comprises a 3D printed circuit. 
     The present invention accordingly provides, in a fourth aspect, an additive manufacturing apparatus for manufacturing an article with integral active electronic component, the apparatus comprising: a computer system; a first additive manufacturing component adapted to form non-electrically conductive three dimensional structures; a second additive manufacturing component adapted to form electrically conductive three dimensional structures; wherein the first and second additive manufacturing components are operable under control of the computer system, the computer system being adapted to control the components to: a) form a non-electrically conductive substrate; b) form a non-electrically conductive perforated layer having an aperture; c) form electrically conductive anode and cathode elements spaced in the aperture; d) deposit a conductive electrical connection to each of the elements suitable for imparting an electrical potential difference between the elements; e) form a non-electrically conductive sealing layer atop the perforated layer so as to retain and seal the aperture in the perforated layer. 
     The present invention accordingly provides, in a fifth aspect, a computer system for controlling an additive manufacturing apparatus, the additive manufacturing apparatus being adapted to manufacture three dimensional structures from both non-electrically conductive and electrically conductive materials simultaneously, the computer system being operable to control the additive manufacturing apparatus to perform the method described above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: 
         FIG. 1  depicts an exemplary three dimensional article with integral diode electronic component produced in accordance with embodiments of the present invention; 
         FIG. 2  depicts an exemplary three dimensional article with integral triode electronic component produced in accordance with embodiments of the present invention; 
         FIG. 3  depicts an arrangement of a non-electrically conductive substrate having a non-electrically conductive perforated layer atop in accordance with embodiments of the present invention; 
         FIG. 4  depicts the arrangement of  FIG. 3  having electrically conductive anode, cathode and grid elements formed in an aperture in accordance with embodiments of the present invention; 
         FIG. 5  depicts the arrangement of  FIG. 4  having conductive electrical connections to each of the elements formed in the aperture in accordance with embodiments of the present invention; 
         FIG. 6  depicts the arrangement of  FIG. 5  having a non-electrically conductive sealing layer formed atop the perforated layer in accordance with embodiments of the present invention; 
         FIG. 7  depicts an exemplary three dimensional article with integral active electronic components and having a channel to an evacuation port of the article in accordance with embodiments of the present invention; 
         FIG. 8  depicts an exemplary three dimensional article with integrated active electronic components disposed in a layers in accordance with embodiments of the present invention; 
         FIG. 9  is a block diagram of a computer system suitable for controlling the operation of an additive manufacturing machine in accordance with embodiments of the present invention; 
         FIG. 10  is a component diagram of an additive manufacturing apparatus in accordance with embodiments of the present invention; 
         FIG. 11  is a flowchart of a method of manufacturing an article with integral active electronic component in accordance with embodiments of the present invention; and 
         FIG. 12  depicts an arrangement of an active electronic component disposed in an aperture of an article in accordance with embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       FIG. 1  depicts an exemplary three dimensional article  100  with integral diode  120  electronic component produced in accordance with embodiments of the present invention. The article  100  is constructed using an additive manufacturing approach including one or more techniques such as, inter alia: an extrusion deposition process; a material binding process such as selective laser sintering, direct metal laser sintering, selective laser melting or electron beam melting; and/or a stereolithographic approach such as photopolymerisation. Such techniques are also known as 3D printing, and a product or resulting article of such techniques is known as a 3D printed article or apparatus. The article  100  is comprised of a substantive structure  102  such as a body, framework, lattice, arrangement or other structure substantially constituting the article, otherwise referred to as the fabric of the article. For example, the article  100  can be, inter alia: a part; prototype; component; appliance; tool; cover; case; model; or any other conceivable three dimensional article. The substantive structure  102  is formed from a non-electrically conductive material by the additive manufacturing process. For example, the substantive structure  102  is a plastic such as a polymer, and preferably a plastic able to tolerate high temperatures. Alternatively, the substantive structure  102  can be formed of a ceramic or similar material. Other non-electrically conductive materials suitable for forming the substantive structure  102  will be apparent to those skilled in the art. 
     The article  100  has formed within, and integral to, the substantive structure  102 , an active electronic component as a diode  120 . The diode  120  is integral to the fabric of the article  100  and is at least partly constituted by the substantive structure  102  of the article  100 . It will be appreciated by those skilled in the art that an active electronic component, such as a diode, rectifier, triode and the like, is an electronic component that requires a power source for one or more of its functions, as distinct from a passive electronic component such as a resistor or capacitor, which requires no power source for operation. The diode  120  is formed in an aperture in the substantive structure  102  of the article  100 . At one end of the aperture a cathode  106  is formed as an electrically conductive element. At the other end of the aperture, and spaced from the cathode  106 , an anode  108  is formed as a second electrically conductive element. The cathode  106  and anode  108  are formed by an additive manufacturing process. In one embodiment the anode is formed by the 3D printing technique for liquid metal structures described by Ladd et al in “3D Printing of Free Standing Liquid Metal Microstructures” (Collin Ladd et al, Advanced Materials, Volume 25, Issue 36, pages 5081-5085, Sep. 25, 2013). Ladd et al describe an approach to extruding conductive metal wires at room temperature. Such an approach is particularly suited to combination with extruding of other materials such as polymer extrusion. For example, the anode  108  can be constituted of a gallium alloy such as a binary eutectic alloy of gallium and indium which can be extruded in an additive manufacturing process at room temperature as described by Ladd et al. Additionally or alternatively, the cathode  106  and/or anode  108  are formed by a material binding process such as sintering. For example, direct metal laser sintering in which a laser is used to precisely and selectively sinter metal powder, can be employed for anode  108  and/or cathode  106  formation. 
     The cathode  106  is a hot cathode that heats to cause thermionic emission of electrons from the cathode  106 . In one embodiment the cathode  106  also acts as a filament to achieve the required heating. Alternatively, a separate filament  104  is provided in thermal proximity with the cathode  106  so as to heat the cathode  106  to induce thermionic emission by the cathode  106 . Preferably, cathode  106  is formed from an electrical conductor with a high heat resistance, such as tungsten or a tungsten alloy. Such materials are known to be formable by an additive manufacturing process such as a bonded tungsten 3D printing process as is available from ExOne Company (eg. ExOne&#39;s M-Flex 3D printer). 
     Each of the anode  108  and cathode  106  are electrically connected to a conductive electrical connection  114 ,  112 . The electrical connections  114 ,  112  are suitable for imparting an electrical potential difference between the anode  108  and cathode  106 . For example, the anode  108  electrical connection  114  is connected to a source of positive electrical potential such as a positive voltage, while the cathode  106  electrical connection  112  is connected to a source of relatively less electrical potential such as ground. Where provided, the filament  104  also has an electrical connection  110  for powering the filament to generate heat. The electrical connections  110 ,  112 ,  114  are formed as part of an additive manufacturing process such as the approach of Ladd et al described above, or any suitable approach to depositing conductive electrical connections by additive manufacturing while manufacturing the article  100 . 
     Most preferably, the aperture formed for the diode  120  is a sealed vacuum, such as can be achieved by a manner described later. Alternatively, the aperture is sealed store of an inert gas such as a noble gas or nitrogen, the reactivity and effect of which on thermionic emission and transfer of electrons by and from the cathode is predictable and known. To ensure the provision of an inert gas in the aperture of the article  100 , the additive manufacturing process for the article  100  can be performed in a sealed atmosphere constituted substantially, preferably entirely, of the inert gas so as to encase the inert gas in the aperture on sealing of the aperture. 
     Thus the article  100  includes an active electronic component as a diode  120 . When a potential difference is imparted between the hot cathode  106  and the anode  108 , electrons will travel from the cathode  106  to the anode  108  in the manner known from vacuum tube diodes. 
       FIG. 2  depicts an exemplary three dimensional article  200  with integral triode  240  electronic component produced in accordance with embodiments of the present invention. Many of the features of  FIG. 2  are identical to those described above with respect to  FIG. 1  and these will not be repeated here.  FIG. 2  further includes a grid  220  element as an electrically conductive element spaced from, and positioned between, the cathode  106  and the anode  108 , with an associated deposited electrical connection  224  for providing an electrical signal to the grid  220 . The grid  220  is traversable by electrons arising from thermionic emission of the cathode  106  and the grid  220  regulates the transmission of electrons from the cathode  206  to the anode  108  depending on the electrical potential of the grid  220  determined by the electrical signal. Such a grid  220  is formed as part of the additive manufacturing process for the article  200 , such as by the approach of Ladd et al described above which is particularly suited to creating a grid, lattice or array arrangement of electrically conductive elements. 
     Thus the article  200  includes an active electronic component as a triode  240 . When a potential difference is imparted between the hot cathode  106  and the anode  108 , electrons will travel from the cathode  106  to the anode  108  regulated by an electrical potential at the grid  220  determined by an electrical signal for the grid  220 , in the manner known from vacuum tube triodes or valves. 
     Thus embodiments of the present invention arranged according to  FIG. 1  or  FIG. 2  provide a 3D printed article or apparatus  100 ,  200  comprising a 3D printed thermionic electronic component  120 ,  240  integral with a fabric  102  of the apparatus  100 ,  200 . The thermionic electronic component  120 ,  240  is a diode comprising a cathode  106  and an anode  108 , or a triode comprising a cathode  106 , an anode  108  and a grid  220  to regulate the passage of electrons from the cathode to the anode. The apparatus  100 ,  200  can further include a 3D printed circuit by way of electrically conductive connections  110 ,  112 ,  114 ,  224  connecting external to the apparatus or, conceivably, to other active electronic components elsewhere in the apparatus  100 ,  200 . 
     An exemplary method of additive manufacture of an article such as article  100  or article  200  will now be described.  FIG. 3  depicts an arrangement of a non-electrically conductive substrate  302  having a non-electrically conductive perforated layer  304  atop in accordance with embodiments of the present invention. The substrate  302  is initially formed from a non-electrically conductive material such as a plastic, polymer or ceramic using an additive manufacturing process such as hereinbefore described. Subsequently, the perforated layer  304  is formed atop the substrate using a similar manufacturing process to that of the substrate except that one or more apertures  306  are formed in the perforated layer  304 . The apertures  306  are illustrated as rectangular in shape though it will be appreciated that any shape can be used. In one embodiment, the formation of the apertures  306  is achieved by defining a digital model of the perforated layer  304 , including definitions of the apertures  306 , and interpretation of the digital model by a control apparatus or process of an additive manufacturing process so as to control the additive manufacturing process to create the apertures  306  such as by way of omitting to extrude or bond non-conductive material in the locations of the apertures  306 . 
       FIG. 4  depicts the arrangement of  FIG. 3  having electrically conductive cathode  402 , anode  406  and grid  404  elements formed in an aperture in accordance with embodiments of the present invention. An additive manufacturing process is used to form the cathode  402 , anode  406  and (optionally) grid  404  as electrically conductive elements described above. For example, the approach of Ladd et al is used to provide the anode  406  and grid  404 . The cathode  402  can be provided by bonded tungsten 3D printing using a sintering technique such as direct metal laser sintering. While  FIG. 4  is illustrated with a grid  404  element, it will be appreciated that the production of a diode active electronic component would not require the grid  404  element. Further, it will be appreciated that a separate filament could additionally be provided in the aperture in thermal proximity with the cathode  402 .  FIG. 5  depicts the arrangement of  FIG. 4  having conductive electrical connections  502 ,  504 ,  506  to each of the elements  402 ,  404 ,  406  formed in the aperture  306  in accordance with embodiments of the present invention. The conductive electrical connections  502 ,  504 ,  506  are preferably provided by the approach of Ladd et al described above. 
       FIG. 6  depicts the arrangement of  FIG. 5  having a non-electrically conductive sealing layer  602  formed atop the perforated layer  304  in accordance with embodiments of the present invention. The non-electrically conductive sealing layer  602  is formed in a similar manner, and using similar or identical materials, to the substrate  302  and perforated layer  304 . The sealing layer  602  serves to retain and seal the apertures  306  in the perforated layer  304 . In one embodiment, at least the sealing layer  602  is formed while the article of manufacture is enclosed within in a sealed atmosphere constituted of a noble gas and the sealing of the apertures  306  is hermetic so that there is no fluid communication into or out of the apertures  306 . 
     In an alternative embodiment, the sealing layer  602  does not hermetically seal the apertures, as will be described with respect to  FIG. 7 .  FIG. 7  depicts an exemplary three dimensional article  700  with integral active electronic components and having a channel  706  to an evacuation port  702  of the article in accordance with embodiments of the present invention. The article  700  is manufactured by an additive manufacturing process as hereinbefore described such that the integral active electronic components are integral with a fabric of the apparatus  700 . Additionally, the additive manufacturing process is adapted to form the channel  706  for fluid communication between an aperture of (potentially multiple) active electronic components and the evacuation port  702 . The channel  706  can be formed in any, or multiple, of the substrate  302 , the perforated layer  304  or the sealing layer  602 , and a direction, path or route of the channel  706  is not limited except that the channel  706  cannot interrupt any conductive electrical connection in the article  700 . The channel  706  interfaces with each electronic component via an opening  704  into the aperture of the electronic component. The evacuation port  702  is provided at one end of the channel  706 , or at a point along the channel  706 , in order to effect the evacuation of gas from the channel  706  and the apertures of active electronic components in the article  700 . The evacuation can be achieved by use of a vacuum pump or the like, and is followed by sealing the evacuation port  702  in order to maintain vacuum-like conditions in the apertures of the active electronic devices. Preferably, the apertures contain a vacuum in order to improve the transmission of electrons arising from the thermionic emission at the cathode  402 . 
       FIG. 8  depicts an exemplary three dimensional article  800  with integrated active electronic components disposed in a layers  802 ,  804  in accordance with embodiments of the present invention. Due to the additive manufacturing process employed to manufacture articles in accordance with embodiments of the present invention, the scope for novel, efficient and effective arrangements of active electronic components is increased.  FIG. 8  illustrates how such components can be arranged in layers  802 ,  804  so as to stratify the article  800 , with potentially electrical connection between electronic components occurring intra-layer and inter-layer, and potentially spanning many layers. Such connections can be modelled by a 3D model of the article  800  and can be generated as part of the additive manufacturing process irrespective of the direction in which such connections occur. Similarly, the orientation, shape and dimensions of the active electronic components themselves can be adapted, varied, configured and/or tailored depending on the requirements of the article  800 . 
     It will be appreciated that passive electronic components can also be formed as part of an additive manufacturing process, such as resistors and capacitors. Such passive components are relatively straightforward to manufacture. For example, a resistor can be formed as a solid printed blocks of ceramic material. A means of insulation of the passive component from the substantive body of the article may be required and can be achieved by enclosing such components in apertures within an article, suspended or held in place by electrical connections. Similarly, capacitors can be created using a structure similar to the active electronic devices except with 2 parallel metallic plates deposited within the aperture. Thus active and passive components required for substantially all electronic and logic requirements of an electronic apparatus can be formed integrally within a three dimensional article using the additive manufacturing approach. 
       FIG. 9  is a block diagram of a computer system suitable for controlling the operation of an additive manufacturing machine in accordance with embodiments of the present invention. A central processor unit (CPU)  902  is communicatively connected to a storage  904  and an input/output (I/O) interface  906  via a data bus  908 . The storage  904  can be any read/write storage device such as a random access memory (RAM) or a non-volatile storage device. An example of a non-volatile storage device includes a disk or tape storage device. The I/O interface  906  is an interface to devices for the input or output of data, or for both input and output of data. Examples of I/O devices connectable to I/O interface  906  include a keyboard, a mouse, a display (such as a monitor) and a network connection. 
       FIG. 10  is a component diagram of an additive manufacturing apparatus  1006  in accordance with embodiments of the present invention. The additive manufacturing apparatus  1006  is a combination apparatus including a conductive additive manufacturer  1008  for forming three dimensional structures from electrically conductive material, and a non-conductive additive manufacturer  1010  for forming three dimensional structures from non-electrically conductive material. Manufacturers  1008  and  1010  are arranged so as to operate on the same subject article during manufacture such that the article can be subject to either or both the manufacture of conductive content or non-conductive content. It will be appreciated by those skilled in the art that the two manufacturers  1008  and  1010  can be combined or integrated into a single component capable of operating in multiple modes of capable of accommodating both conductive and non-conductive materials. The two manufacturers  1008  and  1010  operate in synchronisation and/or contemporaneously or a mixture of both synchronised and contemporaneous modes. For example, where a conductive additive manufacturing process occurs such that a non-conductive process could occur at the same time, then a contemporaneous mode of operation can be employed (though not necessarily). The operation of the manufacturers  1008  and  1010  is preferably computer controlled. In the embodiment of  FIG. 10 , a computer system  1012  is communicatively connected to the conductive additive manufacturer  1008  and the non-conductive additive manufacturer  1010  for instructing each of the manufacturers  1008  and  1010  as to additive manufacturing operations that are to be undertaken. The computer system  1012  is responsive to a specification  1004  for an article for manufacture. In one embodiment the specification  1004  is a digital representation of a three dimensional specification of an article for manufacture. For example, for an extrusion-based manufacturing process, the specification can include a definition of the materials for extrusion and the locations, positions, arrangements or configurations of one or more extruding heads, heads for a binder, setter, epoxy or the like and/or a table, workpiece or article holder. The manufacturing process can be defined using vector definitions specifying the discrete or relative movement or relocation etc. Alternatively, in a granular fusing based additive manufacturing approach, a location of fusing, binding, heating or the like can be specified by the specification  1004 , such as by way of control instructions for a laser or similar fusion mechanism. In embodiments of the present invention, the specification  1004  is in the form of the Additive Manufacturing File format (AMF) or a Stereolithography file format (STL). 
     The specification  1004  is provided by a specification definition system  1002  such as a 3D modelling system, a computer aided design (CAD) or computer aided manufacturing (CAM) system as are known in the art. Such systems can be adapted to generate the specification  1004  in an AMF or STL format. Such formats can be adapted to include additional information relating to electronic circuit elements such as active and passive components and electrical connections therebetween. 
       FIG. 11  is a flowchart of a method of manufacturing an article with integral active electronic component in accordance with embodiments of the present invention. Initially, at step  1102 , a layer of non-conducting material is deposited by an additive manufacturing process as a substrate  302 , such as a plastic or ceramic layer. At step  1104  a layer of non-conducting material with one or more apertures  306  is deposited by an additive manufacturing process as a perforated layer  304 . The configuration of the apertures  306  are defined by a circuit design included in a specification  1004  of an article for manufacture. At step  1106  a set of metal elements are deposited in the aperture  306  by an additive manufacturing process arranged as a cathode, anode and, as required, a filament and grid (triode). At step  1108  conductive connections for the elements in the aperture  306  are deposited by an additive manufacturing process. At step  1110  a sealing layer  602  is deposited atop the perforated layer  304 . 
       FIG. 12  depicts an arrangement of an active electronic component disposed in an aperture of an article in accordance with embodiments of the present invention. Previously, the apertures  306  have been illustrated as generally rectangular in shape.  FIG. 12  illustrates one alternative configuration of an aperture having a generally circular cross section and being generally cylindrical in shape. In the arrangement of  FIG. 12  a cathode  1206  is arranged centrally in the aperture and an anode  1202  is arranged to occupy at least part of, and potentially all of, a wall of the aperture. The cathode  1206  can be further provided with a filament disposed about a central longitudinal axis of the cathode  1206 . The arrangement of  FIG. 12  is preferable where the non-electrically conductive substrate  302 , perforated layer  304  and/or sealing layer  602  are less able to tolerate high temperatures, such as certain plastics and polymers, since a filament can be disposed away from the walls of the aperture and, if configured appropriately and supported such as by electrical connection means, also away from the substrate and sealing layer  602 , by being substantially centrally disposed in the centrally positioned cathode  1206 . Additionally, in a triode arrangement, a grid  1204  is provided in a concentric arrangement about the cathode  1206  to regulate a flow of electrons arising due to thermionic emission from the hot cathode  1206  to the anode  1202 . 
     Insofar as embodiments of the invention described are implementable, at least in part, using a software-controlled programmable processing device, such as a microprocessor, digital signal processor or other processing device, data processing apparatus or system, it will be appreciated that a computer program for configuring a programmable device, apparatus or system to implement the foregoing described methods is envisaged as an aspect of the present invention. The computer program may be embodied as source code or undergo compilation for implementation on a processing device, apparatus or system or may be embodied as object code, for example. 
     Suitably, the computer program is stored on a carrier medium in machine or device readable form, for example in solid-state memory, magnetic memory such as disk or tape, optically or magneto-optically readable memory such as compact disk or digital versatile disk etc., and the processing device utilises the program or a part thereof to configure it for operation. The computer program may be supplied from a remote source embodied in a communications medium such as an electronic signal, radio frequency carrier wave or optical carrier wave. Such carrier media are also envisaged as aspects of the present invention. 
     It will be understood by those skilled in the art that, although the present invention has been described in relation to the above described example embodiments, the invention is not limited thereto and that there are many possible variations and modifications which fall within the scope of the invention. 
     The scope of the present invention includes any novel features or combination of features disclosed herein. The applicant hereby gives notice that new claims may be formulated to such features or combination of features during prosecution of this application or of any such further applications derived therefrom. In particular, with reference to the appended claims, features from dependent claims may be combined with those of the independent claims and features from respective independent claims may be combined in any appropriate manner and not merely in the specific combinations enumerated in the claims.