Disclosed herein is a neuromorphic percolating network (100). The network comprises a substrate (102) having at least two electrical contacts (104A, 104B); a plurality of nanoparticles (106, 108, 100) distributed on the substrate (102), at least some of the nanoparticles positioned between at least two of the at least two electrical contacts, the surface coverage of the nanoparticles within a tolerance of a percolation threshold; and at least one memristive element (116) located at least partially in a gap between nanoparticles, or groups of nanoparticles, that are not otherwise directly connected to each other, the memristive element(s) at least partially providing at least one persistent pathway (118,120) of increased activity. Disclosed herein are methods for fabricating a neuromorphic percolating network or component thereof, and neuromorphic percolating networks formed by such methods.
Please help me write a proper abstract based on the patent claims. CLAIM: 1. A neuromorphic percolating network comprising: a substrate having at least two electrical contacts; a plurality of nanoparticles distributed on the substrate between at least two of the at least two electrical contacts, at least some of the nanoparticles directly connected to each other to form groups of nanoparticles, the surface coverage of the nanoparticles within a tolerance of a percolation threshold; a plurality of gaps separating the nanoparticles and groups of nanoparticles; and a plurality of memristive elements located at least partially in gaps between nanoparticles, or groups of nanoparticles, that are not otherwise directly connected to each other, the memristive elements, nanoparticles and groups of nanoparticles providing at least one persistent pathway of increased activity. 2. (canceled) 3. The network of claim 1 wherein the at least one persistent pathway of increased activity comprises at least one persistent pathway of increased conductivity. 4. The network of claim 1 wherein the at least one persistent pathway of increased activity comprises at least one persistent pathway that includes a plurality of memristive elements whose switching rate or likelihood of switching is increased. 5. The network of claim 1 wherein the at least one persistent pathway of increased activity is between two of the at least two electrical contacts. 6. The network of claim 1 at least some of the nanoparticles are at least partially oxidised so as to limit the extent of coalescence of the nanoparticles. 7. The network of claim 1 at least some of the nanoparticles are conducting. 8. The network of claim 1 wherein at least some of the nanoparticles have resultant diameters in the range 5 nm to 50 nm. 9. The network of claim 1 wherein the nanoparticles comprise one or more of the group comprising Sn, Bi, Au, Pb, Ag, Cu and an alloy of one of more of the foregoing. 10. The network of claim 1 wherein the percolation threshold comprises a surface coverage of 0.68, the tolerance for the surface coverage of the nanoparticles comprising a range of 0.40 to 0.70. 11. The network of claim 10 wherein the tolerance for the distribution of the nanoparticles comprises a range of 0.5 to 0.68. 12. The network of claim 10 wherein the tolerance for the surface coverage of the nanoparticles comprises a range of 0.55 to 0.68. 13. The network of claim 1 wherein the percolation threshold comprises 0.68, the tolerance for the surface coverage of the nanoparticles comprising a range of 0.62 to 0.72. 14. The network of claim 1 wherein the memristive elements comprise gaps which are tunnel gaps providing a low conductance state in an off state and atomic scale wires in the tunnel gaps providing a high conductance state in an on state. 15. The network of claim 14 wherein the atomic wires are formed in response to a voltage applied between the at least two electrical contacts, the voltage comprising a voltage ramp, a voltage pulse, or a series of voltage pulses. 16. The network of claim 14 wherein the atomic wires are formed in response to a current applied between the at least two electrical contacts. 17. The network of claim 14 wherein the atomic wires are formed in response to electric field driven migration, electric field driven evaporation, electrochemical reduction, and/or electrochemical oxidation. 18. The network of claim 1 wherein the substrate is non-conducting, insulating, or semi-conducting. 19. The network of any claim 1 wherein at least part of the substrate comprises a substantially planar surface. 20. The network of claim 1 wherein at least part of the substrate comprises a substantially curved surface. 21. The network of claim 1 wherein at least part of the substrate has an RMS surface roughness of less than 1 nm. 22. (canceled) 23. The network of claim 1 wherein the at least one memristive element comprises one or more of the group comprising: Ag/AgS electrochemical switches, switching molecules, and standard metal oxide memristor switching elements devices. 24. The network of claim 1 wherein the nanoparticles are functionalised with molecules. 25. The network of claim 1 wherein the molecules are able to switch between two states with well defined and distinct resistances. 26. The network of claim 25 wherein the molecules comprise one or more of the group comprising: azobenzenes, rotaxanes, and other molecular switches. 27. The network of claim 1 wherein at least some of the nanoparticles comprise Ag or Cu particles and are at least partially sulphidised. 28. The network of claim 27 wherein at least some of the atomic scale conducting wires comprise atomic scale silver or copper wires. 29. A method of fabricating a neuromorphic percolating network, or component thereof, the method comprising: providing a substrate having at least two electrical contacts; locating the substrate in a vacuum chamber, the vacuum chamber having a controlled partial pressure of air or oxygen and controlled relative humidity; and depositing a plurality of nanoparticles on the substrate between at least two of the at least two electrical contacts, at least some of the nanoparticles directly connected to each other to form groups of nanoparticles, the surface coverage of the nanoparticles within a tolerance of a percolation threshold, a plurality of gaps separating the nanoparticles and groups of nanoparticles, a plurality of memristive elements located at least partially in respective gaps between nanoparticles, or groups of nanoparticles, that are not otherwise directly connected to each other, the memristive elements, nanoparticles and groups of nanoparticles providing at least one persistent pathway of increased activity. 30. The method of claim 29 wherein the pressure of air in the vacuum chamber is in the range 1×10−6 Torr to 1×10−3 Torr. 31. The method of claim 29 wherein the pressure of air in the vacuum chamber is in the range 5×10−6 to 100×10−6 Torr. 32. The method of claim 29 wherein the pressure of air in the vacuum chamber is in the range 10×10−6 to 50×10−6 Torr. 33. The method of claim 29 wherein relative humidity of the air in the vacuum chamber is greater than 30%. 34. The method of claim 29 wherein relative humidity of the air in the vacuum chamber is greater than 60%. 35. The method of claim 29 wherein the nanoparticles are deposited onto the substrate from a vapour or a beam. 36. The method of claim 35 wherein the nanoparticles are formed by inert gas aggregation and are entrained in a beam that is directed at the substrate. 37. The method of claim 35 wherein the deposited nanoparticles have diameters in the size range 5 to 50 nm. 38. The method of claim 35 wherein the deposited nanoparticles have diameters in the size range 5 to 12 nm. 39. The method of claim 35 wherein the resultant particle size is in the range 15-50 nm. 40. The method of claim 29 further comprising monitoring the electrical conductance of the device so as to achieve the required surface coverage of the nanoparticles. 41. The method of claim 29 further comprising controlling the surface coverage to be within a tolerance of a percolation threshold. 42. The method of claim 41 wherein the tolerance comprises 10% of the percolation threshold. 43. The method of claim 29 wherein the morphology of the nanoparticle network is such that it provides a resistance in series with and/or in parallel with the sites at which switching occurs. 44. The method of claim 43 wherein the series resistance is smaller than 12 kΩ. 45. The method of claim 43 wherein the series resistance is in the range 2 to 6 kΩ. 46. The method of claim 43 wherein the parallel resistance is greater than 1 kΩ. 47. The method of claim 29 further comprising connecting at least part of the neuromorphic network to an electrical circuit that includes a current limiting device. 48. The method of claim 47 wherein the current limiting device comprises a series resistor. 49. The method of claim 48 wherein the series resistor is in the range 0.5 to 10 kΩ. 50. The method of claim 29 further comprising at least partially covering at least some of the particles with an inert material so as to stabilise the particles and/or the network of particles. 51. The method of claim 50 wherein the inert material comprises a metal oxide. 52. The method of claim 51 wherein the metal oxide comprises Al3O3. 53. The method of claim 29 further comprising controlling the width of the memristive elements by the voltage pulse. 54. The method of claim 29 further comprising controlling the width of the memristive elements by the voltage pulse so as to achieve quantised conductance 55. The method of claim 29 further comprising forming the memristive elements in response to at least one voltage ramp or at least one voltage pulse. 56. The method of claim 29 further comprising forming the memristive elements in response to a series of voltage pulses. 57. The method of claim 29 further comprising forming the atomic scale wires by controlling the amplitude of the voltage pulses and/or the time between pulses. 58. The method of claim 29 wherein the applied voltage is in the range 0.5 to 10 V. 59. The method of claim 58 wherein the applied voltage is in the range 1 to 5 V. 60. The method of claim 29 wherein the applied voltage is a voltage pulse having a width smaller than 30 s. 61. The method of claim 60 wherein the applied voltage is a voltage pulse having a width in the range 1 to 10 s. 62. A neuromorphic percolating network formed by the method of claim 29. 63. The method of claim 29 wherein the nanoparticles comprise one or more of the group comprising Sn, Bi, Au, Pb, Ag, Cu, or an alloy of one or more of the foregoing.