Abstract:
A life and electrical properties enhanced microelectromechanical systems (MEMS) switch apparatus in which a combined nanoparticle and ionic fluid lubricant is used to prolong switch elements operating lifetime and desirable electrical characteristics during this lifetime. Nanoparticle materials such as noble metal particles are combined with ionic corona producing liquid organic materials to achieve a desirable contact lubricant material serving to delay the onset of several disclosed classic contact failure mechanisms. Improvement over other contact lubricant materials and favorable contact testing results are included.

Description:
RIGHTS OF THE GOVERNMENT 
   The invention described herein may be manufactured and used by or for the Government of the United States for all governmental purposes without the payment of any royalty. 

   BACKGROUND OF THE INVENTION 
   The microelectromechanical systems (MEMS) switch has become an essential element in many electronic systems and would find even greater usage in integrated circuit and other electrical applications, except for its fundamentally electromechanical nature and thus excessively limited operating lifetime. The fundamental mechanical limitations of wear, stiction and thermal response as well as electrical resistance, R, increases and other mechanical related properties are clearly present in these small switches to a degree, currently precluding use of such elements except in well defined and probably mostly non-critical switching applications. MEMS lifetimes measured at 10 9  and upward operating cycle events would clearly increase the use of such switches to a significant degree. 
   Thus even though the electrical switching art reveals a considerable degree of direct approach attention to the improvement of MEMS switches over the years, there appears to exist in this art a degree of avoidance of one indirect approach to the improvement of many of the MEMS encountered fundamental mechanical limitations. This indirect approach involves the use of lubrication for the switch elements, especially lubrication with materials having more than friction related improvement capabilities, modern materials able to also contribute to a plurality of electrical characteristics of a treated switch. 
   Previous lubricant based attempts to realize increased lifetimes have included the addition of self-assembled monolayer (SAM) lubricant materials, including materials derived from diphenyl disulfide and other lubricants, to MEMS contacts. Such additions provide less than desired performance often because of carbonaceous film growth and contact resistance difficulties encountered in the range of 10 4  operating cycles with, for example, 10 microamperes of load current and from heat promoted failures incurred very early in the presence of one milliampere load currents. Improved lubrication involving nanoparticles in combination with plasma is the domain of the present invention. 
   Nanoparticles in general are considered in the World Intellectual Property Organization (WIPO) published patent application 2006/110166 of E. P. Giannelis et al. of Cornell University. This application designates the United States as one of several locations in which patent protection is sought. The application is titled “Functionalized Nanostructures with Liquid-Like Behavior” and is hereby incorporated by reference herein. The work leading to this application was also supported by the U.S. Air Force. 
   SUMMARY OF THE INVENTION 
   The present invention provides improved life and operating characteristics for an electrical switch, especially a switch of the microelectromechanical systems or MEMS type. 
   It is therefore an object of the present invention to provide nanoparticle based lubrication and electrical characteristics enhancements in plural types of MEMS related electrical switch elements. 
   It is another object of the present invention to provide metallic and ionic nonmetallic lubricant nanoparticles based electrical switch characteristic enhancements. 
   It is another object of the present invention to provide a plurality of MEMS switch nanoparticle based lubrication and contact enhancement materials. 
   It is another object of the present invention to provide increased operating life in a MEMS electrical switch apparatus. 
   It is another object of the invention to employ the combination of ionic liquid materials and metallic nanoparticle materials as a lubricant in a MEMS electrical switch. 
   It is another object of the present invention to achieve decreased electrical resistance characteristics over the useful life of a metal contact MEMS electrical switch. 
   It is another object of the present invention to limit the effects of plural failure mechanisms in a MEMS electrical switch. 
   It is another object of the present invention to provide a selectable viscosity lubricant material in a MEMS electrical switch. 
   It is another object of the present invention to provide control of use induced contact surface bonding in a MEMS electrical switch. 
   It is another object of the present invention to provide enhanced surface conformity in a MEMS electrical switch. 
   It is another object of the present invention to provide controlled volatility in a MEMS electrical switch lubricant. 
   It is another object of the present invention to provide enhanced thermal stability in the operation of a MEMS electrical switch. 
   It is another object of the present invention to provide enhanced current, i.e., conduction characteristics in a MEMS electrical switch. 
   It is another object of the present invention to reduce use-provoked friction, stiction, wear and conductivity degradations in a MEMS electrical switch apparatus. 
   These and other objects of the invention will become apparent as the description of the representative invention embodiments proceeds. 
   These and other objects of the invention are achieved by a microelectromechanical systems (MEMS) electrical switch comprising: 
   first and second selectively engageable-nano sized MEMS switch electrical contacts; and 
   an electrically conductive lubricant film material received intermediate engaging face portions of said nano-sized MEMS switch electrical contacts; 
   said lubricant film material including a plurality of metallic nanoparticles resident on a face portion of one of said nano-sized MEMS switch electrical contacts; 
   said lubricant film material also having an ionized particle inclusive liquid surrounding said metallic nanoparticles on said face portion of said nano-sized MEMS switch electrical contacts and supplementing inter contact electrical conductivity characteristics and nanoparticle migration characteristics of said metallic nanoparticles. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings incorporated in and forming a part of the specification, illustrate several aspects of the present invention and together with the description serve to explain the principles of the invention. In the drawings: 
       FIG. 1  includes the views of  FIG. 1   a  and  FIG. 1   b  and shows cross-sectional representations of two different types of microelectromechanical systems switches. 
       FIG. 2  includes the views of  FIG. 2   a ,  FIG. 2   b  and  FIG. 2   c , and shows two common failure mechanisms incurred in MEMS switches and a present invention resolution thereof. 
       FIG. 3  shows an enlarged view of adjacent MEMS switch contacts including an intervening nanoparticle lubricant material. 
       FIG. 4  shows an enlarged view of open MEMS switch contacts including nanoparticle lubricant material. 
       FIG. 5  shows a microphotograph view of nanoparticle liquid material. 
       FIG. 6  shows a diagrammatic representation of a metallic nanoparticle in combination with an ionized organic material. 
       FIG. 7  shows a synthesis sequence for one embodiment of present invention MEMS lubricant materials. 
       FIG. 8  includes the views of  FIG. 8   a  and  FIG. 8   b  and shows enlarged representations of a spin coated nanoparticle lubricant MEMS switch contact. 
       FIG. 9  includes the views of  FIG. 9   a ,  FIG. 9   b ,  FIG. 9   c ,  FIG. 9   d ,  FIG. 9   e  and  FIG. 9   f , and shows details of a MEMS contact related laboratory evaluation arrangement. 
       FIG. 10  includes the views of  FIG. 10   a  and  FIG. 10   b , and shows representative initial and degraded MEMS switch contact characteristics. 
       FIG. 11  includes the views of  FIG. 11   a ,  FIG. 11   b  and  FIG. 11   c , and shows microphotographic representations of a lubricated contact wear scar. 
       FIG. 12  includes the views of  FIG. 12   a ,  FIG. 12   b  and  FIG. 12   c , and shows additional magnifications of an enlarged portion of the  FIG. 11  lubricated contact wear scar with a non-lubricated comparison scar. 
       FIG. 13  includes the views of  FIG. 13   a ,  FIG. 13   b  and  FIG. 13   c , and shows contact wear scar physical details and wear scar chemical analysis. 
       FIG. 14  includes the views of  FIG. 14   a ,  FIG. 14   b ,  FIG. 14   c  and  FIG. 14   d , and shows physical, chemical and quantity details for a nanoparticle lubricated, wafer mounted, MEMS contact wear scar. 
       FIG. 15  includes the views of  FIG. 15   a  and  FIG. 15   b , and shows electrical performance details of a nanoparticle lubricated MEMS contact. 
       FIG. 16  shows an expanded elevation representation of a nanoparticle lubricant added surface. 
       FIG. 17  includes the views of  FIG. 17   a  and  FIG. 17   b , and shows a comparison of present invention and prior SAMS lubricant testing results. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  in the drawings includes the views of  FIG. 1   a  and  FIG. 1   b , and shows cross-sectional representations of two different types of microelectromechanical systems (MEMS) switches. In the  FIG. 1   a  drawing there appears a cross-sectional representation of a metal to metal variety MEMS contact set in which, upon deflection of a contact suspension apparatus (not shown), the faces  100  and  102  of an upper movable contact pair meet with corresponding lower contact faces  104  and  106 . This meeting can of course be accompanied by electrical spark erosion, contact buffing, contact wear and other contact life limiting mechanisms. The present invention provides assistance in achieving delayed onset of several of these limiting mechanisms. 
     FIG. 1   b  in the drawings shows details of another form of MEMS electrical switch, an enclosed switch in which capacitance coupling is used to achieve signal transfer between switch input and output electrical circuits. Notwithstanding the absence of specific metal to metal engagement in the  FIG. 1   b  switch arrangement, such switches and their “contacts” are nevertheless subject to some of the same and to additional failure mechanisms as in the  FIG. 1   a  metal to metal switch arrangement. Details of these capacitance coupled switch failure mechanisms may be appreciated in ensuing paragraphs herein. 
   In the  FIG. 1   b  drawing there is shown, for example, a substrate  110  on which is received a switch enclosure  112  having a plurality of enclosure openings  114  usable during certain switch fabrication steps. The  FIG. 1   b  MEMS switch includes a substrate  110 -held fixed position contact  120 , a movable contact  122  and an electrical insulating member  124  holding the contacts  120  and  122  in a non-touching but increased capacitance coupling physical condition when the movable contact  122  is changed from the  FIG. 1   b  illustrated “open” switch condition to a closer, contact “closed”, switch condition wherein increased capacitance coupling and signal transmission between contacts  120  and  122  occur. Distorted movement of the contact  122  and its engagement with the insulating member  114  of course contributes to some of the previously identified and other life limiting switch degradation mechanisms. Such mechanisms may include, for example, frictional and impact wearing of the insulating member  114 . 
     FIG. 2  in the drawings includes the views of  FIG. 2   a ,  FIG. 2   b  and  FIG. 2   c , and illustrates two especially significant of the common failure mechanisms incurred in MEMS switches and also represents generally a present invention approach toward alleviation of these failure mechanisms. In the  FIG. 2  drawings a movable MEMS contact  200  is shown to be engaged with a smooth surface  204  of a fixed position contact  202  at an interface  206 , while in the condition of the contacts  200  and  202  being held in low electrical current provoked contact adhesion. In the  FIG. 2   b  drawing a movable MEMS contact  210  is shown coupled to a fixed position contact  212  by an extended nanowire connection represented at  214 . This nanowire connection represents a commonly encountered degradation or failure mechanism in a MEMS switch circuit and is also found to be subject to present invention intervention. Low electrical current provoked flat contact adhesion as in the  FIG. 2   b  drawing is relieved by the nanoparticle and ionized liquid fluid of the present invention remaining with the contact faces during contact open and closed events, thus precluding a flat surface adhesion. 
   A general representation of the present invention arrangement for alleviating the degraded MEMS switch conditions represented in the  FIG. 2   a  and  FIG. 2   b  drawings is shown in the  FIG. 2   c  drawing. In this drawing the two contacts  220  and  222  are shown to be separated by an array of metallic nanoparticles  224  surrounded by a liquid  226  containing ionized nonmetallic organic material particles. Together the nanoparticles  224  and the liquid  226  comprise a present invention contact “lubricant”  223  affording a plurality of MEMS contact advantages as are described in detail in following paragraphs herein. 
   The  FIG. 2   c  lubricant  223  can be described as a monolithic hybrid nanoparticle material comprised of an inorganic nano-sized metallic core and an organic low viscosity corona. Advantages of such nanoparticle lubricants as compared to ordinary nanoparticles include (1) less agglomeration; (2) better processing; (3) controlled particle interactions; and (4) production of a solvent-free liquid. An ionic liquid may be used as a corona offering advantages such as (1) high fluidity; (2) low melting temperature; (3) high boiling temperature; (4) thermal stability; and (5) low vapor pressure. As a contact lubricant these materials appear to provide high conductivity of metallic nanoparticles and enablement for lubricant reflow to damaged areas. 
     FIG. 3  in the drawings shows an enlarged view of a closed MEMS switch including nanoparticle agglomerations  304 ,  306 ,  308  and  310  disposed between two switch contact surfaces  300  and  302 . In this closed condition the particle agglomerations  304  and  310  complete an electrical path  312  and  316  between contact surfaces  300  and  302  to allow electrical current, i, and electrical charge, Q, as indicated at  315 , to flow across the opening between contact surfaces. Additional parallel current paths exist by way of each additional touching particles (not shown) in the region between contacts. The agglomeration of particles at  308  is considered to be non-touching and to comprise an open circuit electrical path. The metal particle sizes in the  FIG. 3  agglomerations may, for example, range between five and twenty nanometers and the separation of contact surfaces  300  and  302  reside in this same dimensional range. 
     FIG. 4  in the drawings shows a view of the  FIG. 3  closed MEMS switch in an open switch condition and with a spacing of one to two micrometers present between switch contact surfaces  300  and  302 . In this open switch condition multiple desirable aspects of the present invention nanoparticle fluid become visible, as are indicated at  402  and  404 , for examples. Shortened terminations of what are often switch shorting nanowires formed during the electrical arcing of opening switch contacts are represented at  404 ,  406  and  408  in  FIG. 4 . Early termination of such shorting is a first of the desirable aspects of the combined metal nanoparticle and organic particle fluid present at  226  in the  FIG. 2 ,  FIG. 3  and  FIG. 4  drawings. This shortening of nanowires is found to improve the tendency of a MEMS switch opening event to result in an electrically shorted contact pair. 
   The nanoparticle fluid replacement mechanism identified at  402  in  FIG. 4  is another of the desirable aspects of the combined metal nanoparticle and organic particle fluid present at  304 ,  306 ,  308 , and  310  and at  226  in the  FIG. 2 ,  FIG. 3  and  FIG. 4  drawings. Since the nanoparticle fluid film exists in a liquid or near-liquid state between closed switch contacts as shown in  FIG. 3 , any evaporation or consumption of this fluid as a result of the contact opening is at least partially accommodated by a fluid replacement mechanism. The drawings of  FIG. 13  and  FIG. 14  and related discussions herein provide additional details concerning the achieved nanoparticle fluid migration mechanism. 
     FIG. 5  in the drawings shows a transmission electron microscope (TEM) microphotograph image obtained by passing an electron beam through a sample of nanoparticle liquid into a fluorescent screen. The individual metal particles appearing in  FIG. 5  are of Gold and of about 20 to 30 nanometers diameter and are immersed in an ionic liquid filling the spaces between metallic particles. Platinum particles of smaller 5 nanometers diameter provide a similar result from TEM exposure and lubrication properties of desirable advantage in selected uses. From an overall viewpoint particle sizes between about one and one hundred nanometers are of interest for use in the present invention; specific instances herein however, identify particles falling in a smaller part of this overall range. 
     FIG. 6  in the drawings shows a representation of an individual  FIG. 5  nanoparticle of, for example, Gold metal together with one arrangement of a corona of organic ionic particle fluid attending this nanoparticle. In the  FIG. 6  drawing the ionic particle corona at  600  may be of about 1.5 to 2 nanometers in thickness and may be comprised at  604  of mercaptoethanesulfonate, HSCH 2 CH 2 SO 3 , and at  602  of quartneary ammonium materials, (CH 3 )N+R 3  where R=C 10 −C 12 . Other corona materials are believed feasible. Charge polarity indicators relevant to the ionized materials at  602  and  604  appear at  606  and  608  in the  FIG. 6  drawing and indicate an attractive force between the ionic fluid and the metallic particle. This attractive force may be described as involving a negative surface charge on the nanoparticle with strong covalent bond coupling between nanoparticle and first layer corona molecules and ionic coupling of lesser strength between first layer corona molecule and second layer corona molecule. In the lubricant art quaternary ammonium is desirable at least partially because of the  FIG. 6  and  FIG. 7  illustrated long hydrocarbon chain and branch structure that promotes liquidity. The  FIG. 6  illustrated combination of metallic nanoparticles with an ionized organic plasma liquid for contact lubrication is believed novel, particularly in the MEMS art. 
     FIG. 7  in the drawings shows the salient steps in a process for synthesizing the ionic fluid portion of a gold and ionic liquid nanoparticle fluid lubricant invention embodiment. As shown in the  FIG. 7  drawing this process may include the following four major steps; other processes are of course possible:
         1. Hydrate and boil Gold (III) chloride in water.   2. Add the tribasic dihydrate Sodium Citrate, xHAuCl 4+yNaOOCC(CH   2 COONa) 2  (with an OH radical attaching vertically to the final C of the yNaOOCC), then boil to achieve 20 nanometers diameter Gold particles.   3. Cool and add Sodium 2-mercaptoethanesulfonate, (MES) HSCH 2 CH 2 SO 3 −Na+, to achieve Gold SCTD nanoparticle with MES corona.   4. Add adogen (quaternary ammonium) positive ion source to achieve CH 3 N+((CH 2 ) 8 CH 3 ) 3 Cl−, a Gold nanoparticle with negatively charged MES and positively charged quaternary ammonium corona.       
   The relative inside and outside directions of the ionic charges shown in the  FIG. 7  drawing with respect to the metallic nanoparticle are notable in the present invention. A  FIG. 7-like  process may also be used with a PtCl 4  (Platinum chloride) initial material to achieve a Platinum nanoparticle ionic liquid lubricant. Other metals including Silver, Palladium, Rhodium and Ruthenium are believed usable in the invention lubricant. 
   To reiterate the  FIG. 7  process in alternate and more detailed language, Gold nanoparticles with a 20 nanometers diameter may be synthesized following the known in the art Turkevich method and passivated with a five fold excess of the Sodium salt of mercaptoethanesulfonate (MES). The subsequent ruby-colored aqueous solution may be combined with a 2-fold equivalence of a quaternary alkyl ammonium chloride (Adogen 464). The Gold nanoparticles may be collected and purified from the resultant two-phase, blue-colored mixture by repetitive (5-times) centrifugation and re-suspension in water and ethanol. The product is insoluble in water but forms a ruby-colored solution in toluene as anticipated for dissolution of individual gold nanoparticles of this size. Total gold content varies from 10 to 80 weight percent, depending on the extent of purification in where the excess mass is attributed to the Adogen surfactant. 
   Small angle neutron scattering and transmission electron microscopy indicate the  FIG. 6  organic ionic corona is about 1.5-2 nanometers in thickness. In a similar fashion, Platinum nanoparticles may be produced via the reduction of H 2 PtCl 6  in the presence of a threefold equivalence of mercaptoethanesulfonate with the dropwise addition of a chilled solution of NaBH 4  (170 mm). The ligand exchange step for Adogen may be performed identically as in the case of Gold to yield platinum nanoparticles of about 5-10 nanometers diameter. Nanoparticles may be applied to a gold-plated GaAs wafer surface by spin coating from a toluene solution. Generally a spin coating thickness between 0.5 and 100 nanometers is preferred. 
     FIG. 8   a  in the drawings shows a microphotograph of a Gold electrode spin-coated with a Gold nanoparticle lubricant. Notably, there is no stacking up of nanoparticles on the surface in  FIG. 8   a  as a result of a strong interaction between surface and nanoparticles. Individual nanoparticle and nanoparticle aggregates provide asperity structures with larger lateral dimensions than individual nanoparticles in  FIG. 16   a . Peak-to-valley roughness is about 100 nanometers for the Gold wafers used in this microphotograph with a lateral distance between local peaks of about fifty micrometers. 
   A simplified one-dimensional schematic line scan of such nanoparticles is shown in the  FIG. 16  drawing. In  FIG. 16  the nanoparticles are represented as segments as a result of different scales in the lateral and vertical directions. For illustration purposes, let us assume that the  FIG. 16  profile comes into contact with a flat surface; without nanoparticle presence peak  1  comes into contact with the surface and considerable deformation of the profile or contact is needed before peak  2  comes into contact. This leads to large localized contact areas and an undesirable contact situation. With nanoparticle presence, however, two distinct nanocontacts are established on peak  1  and subsequent nanocontacts occur on peak  2 . In this way, multiple localized nanocontacts spread out on a surface as opposed to lesser number of larger contact spots. 
     FIG. 8  in the drawings also shows the appearance of a Gold MEMS electrical contact coated with a film of Gold nanoparticle ionic lubricant. The  FIG. 8  drawings include a microphotograph as the  FIG. 8   a  “drawing” as do several ensuing “drawings” herein; identifications as “drawing” and “microphotograph” are used interchangeably in ensuing paragraphs herein. The clustered, small, generally round, objects in the  FIG. 8   a  microphotograph are of course metallic nanoparticles in the lubricant film. The  FIG. 8   a  coating is of about 3.5 nanometers thickness, appears free of particle stacking and is generally of the profile appearing in the  FIG. 8   b  microphotograph. Lateral dimensions are indicated in the microphotograph. Multiple sized surface asperities in the lateral and vertical directions appear on the  FIG. 8   a  contact surface; as are also shown in  FIG. 8   b.    
     FIG. 9  in the drawings shows details of MEMS electrical contact laboratory ball-on-wafer experimental arrangement usable to evaluate lubricated MEMS performance. The controlled conditions disclosed in  FIG. 9  and the resulting subsequent  FIG. 10  test results drawings herein are believed to provide consistent indications of switch life and lubricant behavior under meaningful conditions. 
     FIG. 10  in the drawings includes the views of  FIG. 10   a  and  FIG. 10   b , and shows quantitatively representative initial and degraded MEMS switch contact electrical characteristics achieved with two ensuing contact use test conditions. In these drawings the left hand scale and the left hand scale-connected data curves indicate the applied contact force measured in micro Newtons and the right hand scale and right hand scale-connected data curves indicate the achieved contact resistance measured in Ohms. The time dependent periodic waveforms observed in  FIGS. 10   a  and  10   b  result from the pulsating nature of the electrical energy applied to the contact for testing described in the  FIG. 9  drawing. Generally it may be observed that achievement of low and unvarying contact resistance is desirable in a pair of tested contacts; time dependent higher resistance is an undesirable characteristic and a contact failure indication. Incurred contact cycles at current loading of one milliampere, i.e. 10 4  and 10 5  cycles, are identified in the  FIG. 10  drawings. 
     FIG. 17  in the drawings shows yet another comparison of present invention and prior lubricant assisted contact testing for Gold contacts. The  FIG. 17  data in  FIGS. 17   a  and  17   b  represents contact force and resistance measurements conducted using a constant approach and a retract speed of 320 nanometers per second and a peak contact force of 200 micro Newtons in a ball laboratory apparatus. Switching performance for the diphenyl disulfide self-assembled monolayer lubricant represented in the  FIG. 17   a  drawing leaves much to be desired in view of an immediate failure, with a developed resistance of about 20 ohms as a result of a first contact engagement using the current flow of 1 milliampere. The similar contact and conditions with present invention nanoparticle lubricant included are represented in the  FIG. 17   b  drawing, and show desirable improvement in contact life at 10 5  cycles and one ohm of developed resistance. 
     FIG. 11  in the drawings includes the microphotograph views of  FIG. 11   a ,  FIG. 11   b  and  FIG. 11   c , and shows a physical wear scar resulting from extended  FIG. 9  indicated testing of a Gold nanoparticle lubricated Gold MEMS contact.  FIG. 11   a  shows a coated wafer wear scar achieved after 10 5  cycles of 1 millampere contact opening and closing using a particular magnification as may be appreciated from the electron microscope parameters shown in the lower margin of the drawing or microphotograph. The  FIG. 11   b  and  FIG. 11   c  views of the same wear scar represent greater magnifications as may be observed from the dimensional indications appearing in each drawing view. Of particular interest in the  FIG. 11  microphotographs is the fact that 10 5  current flowing opening and closing events result in an easily visible wear pattern scar; that larger nanoparticles are displaced just outside the  FIG. 11   a  wear scar during the opening and closing cycles and that evidence of desirable nanoparticle presence and nanowire termination in the contact appears. 
     FIG. 12  includes the views of  FIG. 12   a ,  FIG. 12   b  and  FIG. 12   c , and in the first two views therein shows additional microphotograph magnifications of an enlarged portion of the  FIG. 11  lubricated contact wear scar. Thus these parts of  FIG. 12  represent another set of views of a 10 5  cycles nanoparticle film lubricated contact of the  FIG. 11  type at the same and greater lubricant film wear area magnifications. Again, the  FIG. 12  degree of magnifications is indicated by a scale representation in a portion of the each microphotograph. Of particular interest in  FIG. 12  is the nanoparticle agglomerations attending the scar, the limited size of the ball wear area in the  FIG. 12   b  microphotograph, together with the limited occurrence and size of undesired contact cycle formed nanowires of the  FIG. 2  and  FIG. 4  types. The  FIG. 12   c  drawing shows the more pronounced tendency to form the nanowire contact shorting structures in a non-lubricated or uncoated MEMS contact as is shown for comparison purposes. A summarization of the  FIG. 12  indications appears below the  FIG. 12   a  microphotograph in  FIG. 12 . 
     FIG. 13  in the drawings includes the views of  FIG. 13   a ,  FIG. 13   b  and  FIG. 13   c , and shows a contact wear scar and combined Platinum lubricant film and Gold electrode material. A gross lower magnification of the scar area appears in the  FIG. 13   a  drawing, while a diagram of the contact lubricant replenishment mechanism occurring in this  FIG. 13   a  contact appears in the  FIG. 13   b  drawing. In the  FIG. 13   c  drawing there appears a quantitative representation of the Platinum and Gold materials used in the contact of  FIG. 13 . The horizontal scale in  FIG. 13   c  represents differing levels of kinetic energy and the lowermost  FIG. 13  curve indicates the response of lubricant materials to these different kinetic energy levels while the lubricant is in the non-contacted or original virgin status; the vertical scale in  FIG. 13   c  indicates relative lubricant response to these differing energy level excitations of a sample to some arbitrary response magnitude scale. 
   The recurrent peaks in the uppermost, wear mark related area, of the  FIG. 13   c  curves are characteristic of the differing metals appearing in the contact nanoparticle lubricant and electrode, i.e., peaks relating to Gold and Platinum. As indicated by the occurrence of and the energy level location of these metal caused curve peaks the detection of Platinum metal in the Gold wear mark is significant under the represented conditions because such metal was initially present in undetectable quantities in the wear mark region of the represented contact and has migrated into the wear mark following a wear inducing event. The word “Auger” appearing in the  FIG. 13   c  data indicates the curves there to be obtained from an Auger spectrometer examination. Such examinations are known in the art and are used to determine near surface properties of a sample such as metal. The Auger process involves impingement of electrons of known energy level on an examined surface and consideration of surface displaced particle energy levels as the output data. 
     FIG. 14  in the drawings includes the views of  FIG. 14   a ,  FIG. 14   b ,  FIG. 14   c  and  FIG. 14   d , and shows both physical details and quantity details attending a Platinum nanoparticles and ionic liquids-lubricated Gold MEMS electrode contact wear scar  1400  in  FIG. 14   a .  FIG. 14   a  provides a three-dimensional microphotograph view of the contact wear scar  1400  and its surrounding area including the micrometer dimensioned overall sizes and a nanometer scaled wear scar or raised feature depth gauge  1402 . Both an ionic liquid nanoparticle suspension lubricant texture representation and wear scar details also appear in the  FIG. 14   a  microphotograph.  FIG. 14   b  shows a representative cross-sectional view of a  FIG. 14   a  type Gold metal contact having a nanoparticle and ionic liquid film lubricant layer, including a raised central region  1404 , as may arise from previous contact wear and arcing. Notably, the nanoparticle and ionic liquid lubricant regions surrounding the raised central region in  FIG. 14  are shown as being largely devoid of metallic nanoparticles as a result of the desirable metallic ionic liquid aided nanoparticle migrations toward the disturbed central region  1404 ; these migrations are represented at  1410  and  1412 , as having commenced. 
     FIGS. 14   c  and  14   d  are related drawings showing a quantitative evaluation of an ionic liquid Platinum nanoparticle lubricated Gold contact area,  1421  as in  FIG. 14   a , and inclusive of a  10   5  cycles one milliampere achieved central wear mark  1422 . A significant component of the  FIG. 14   c  and  FIG. 14   d  evaluation is the line scan trajectory  1420  across both the lubricated contact area  1421  and the central wear mark  1422 . As is indicated in the  FIG. 14   d  drawing, this line scan  1420  provides an input signal for an Auger spectrometer apparatus providing measurement of relative amounts of Gold and carbon encountered by the moving spot of the line scan trajectory  1420 . The Carbon component in the wear scar  1422  and the surrounding area  1421  is indicated by the curve  1432  and the peak  1435  in the  FIG. 14   d  drawing. This detected free Carbon arises from electrical arc induced decomposition of the ionic liquid  1407  in which the Platinum nanoparticles of the  FIG. 14  contact are suspended; this ionic liquid may be observed in the formulas relating to the  FIG. 6  drawing to include such Carbon as a component material. As indicated by the  FIG. 14   d  curve  1434 , the wear mark  1422  also is characterized by a reduced amount of Gold in the mark area; this reduced amount is indicated at  1436  in the  FIG. 1   d  drawing.  FIGS. 14   c  and  14   d  thus provide evidence of lubricant replenishment and migration into the contact zone. 
     FIG. 15  in the drawings includes the views of  FIG. 15   a  and  FIG. 15   b , and shows extended life electrical performance details, i.e., contact electrical resistance magnitudes, for MEMS contacts lubricated in accordance with the present invention. The  FIG. 15  drawings provide indications of contact life according to the present invention under both 10 microampere and 1000 microampere or 1 milliampere contact electrical loading in dry nitrogen atmospheres. The  FIG. 15  drawings indicate contact performance with ionic lubricant (IL) films and include self assembled monolayer or SAM lubricant performance for comparison purposes. Additional comparison is provided in the  FIG. 15  drawings with respect to uncoated contact life and the incorporation of both Platinum and Gold nanoparticle ionic lubricant materials. 
   Of particular interest in the  FIG. 15  drawings is the 10 6  cycles of operating life at the lower testing 10 microampere current level and the fact that this life is achieved without contact failure or resistance increase occurrences, even at the 10 6  cycles testing point. Thus since this 10 6  cycles of life can occur without failure, contact life into at least integer multiples of the 10 6  cycles, e.g. 5×10 6  cycles, or 10 7  cycles, appears reasonable. The absence of contact shorting (as from the  FIG. 12   c  nanowires) at the greater 1000 microampere test current level with a 10 5  cycles test ending is also a notable features in the  FIG. 15  drawings. 
   With respect to contact resistance related failure mechanisms, it appears significant in  FIG. 15  that relatively small contact resistance increases with the 1000 microampere testing current and 10 5  cycles testing end are experienced during use of the present invention, and that even less contact resistance is encountered at 10 6  cycles with the  FIG. 15   a  10 microampere testing current. These resistance magnitudes appear of special interest in view of the significantly higher resistances found with fewer testing cycles in instances wherein the present invention is not employed. 
   We recognize of course in connection with  FIG. 15 , that MEMS contact life in the 10 9  operating cycles and longer is desirable and will enable use of such contacts in numerous applications not possible with the  FIG. 15  characteristics. The 10 6  and 10 7  cycle life times achieved under the  FIG. 15  testing conditions are nevertheless believed to be improvements in the MEMS art and, perhaps most importantly, suggestive of evolutionary additional approaches in accordance with the present invention for achieving even longer MEMS contact lifetimes. Nanoparticle liquid lubricants may thus be appreciated as structurally engineered inorganic fluids comprised of nanoparticles with covalently attached ionic organic corona exhibiting softening temperatures between 0° and 100° C. Such nanoparticle fluids are shown herein to provide both desirable contact lubrication and electrical conduction properties and prevent switch shorting and thermal decompositions at higher milliampere switch current levels. 
   Therefore we have herein disclosed the use of novel liquid nanoparticles as lubricants for MEMS switches. The nanoparticle liquids include nanostructurally engineered inorganic fluids of nanoparticles with covalently attached ionic organic corona that exhibit softening temperatures between 0° and 100° C. The structure of liquid nanoparticle fluid enables hot (under flowing electrical current) switching, where the nanoparticle liquid is an operating component for both contact lubrication and electrical conduction, and prevents switch shorting and thermal decomposition at milliampere current levels. Liquid nanoparticles circumvent two of the primary failure mechanisms of MEMS switches at high currents, e.g. currents of greater than one milliampere, contact melting and contact adhesion or stiction. Desirable electrical conductivity of these materials, as compared to other molecular level lubricants such as organic molecular wires, is a primary contributor to enhanced performance. Gold nanoparticles of about 20 nanometers diameter and an ionic organic corona of Mercaptoethanesulfonate HSCH 2 CH 2 SO 3  and quaternary ammonium (CH 3 ) +R   3  where R=C 10 −C 12  are examples of the invention realization. The disclosure relates to the use of additional metal and metal alloy nanoparticles and additional ionic organic corona molecular species for MEMS electrical switching devices. 
   The foregoing description of the preferred embodiment of the present invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Obvious modifications or variations are possible in light of the above teachings. The identified embodiment was chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the inventions in various embodiments and with various modifications as are suited to the particular scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally and equitably entitled.