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scars on electroformed Ni revealed two zones whose characteristic features are significantly different from those of the bulk microstructure. Bending of columns in the direction of sliding, breakdown of columnar grains into equiaxed fine grain structure, and formation of low angle grain boundaries have been revealed. 5.6 References 5.1 Rigney DA, Hirth JP. Wear 1979;53:345-70. 5.2 Rice SL, Nowotny H, Wayne SF. Wear 1981;74:131-42. 5.3 Bill RC, Wisander D. Wear 1977;41:351-63. 5.4 Rigney DA, Hammerberg JE. MRS Bulletin 1998;23(6): 32-36. 5.5 Liu J. in Bryant PJ, Lavik, M, Salomon, G (eds.), Mechanisms of solid friction. Elsevier, 1964. p.163. 5.6 Kuhlmann-Wilsdorf D. in Rigeny DA. (ed.) Fundamentals of friction and wear. ASM, 1981. p.119. 5.7 Heilmann P, Rigney DA. Metallurgical Transactions 1981;12A:686. 5.8 Heilmann P, Clark, WAT, Rigney DA. Acta Metall. 1983;31:1293. 5.9 Rainforth WM, Stevens R, Nutting J. Phil. Mag. 1992;66:621. 5.10 Rainforth WM. Wear 2000;245:162. 5.11 Farhat ZN. Wear 2001;250:401. 5.12 Reyntjens S, Puers R. J. Micromech. Microeng. 2001;11:287. 5.13 Schwartz AJ, Kumar M, Adams BL. Electron backscatter diffraction in materials science. Kluwer Academic/Plenum Publishers; 2000. 5.14 Christenson TR. in Mohammed Gad-el-Hak (ed.) MEMS handbook. CRC Press. 2001. 5.15 Hruby J. MRS Bulletin 2001;26:337. 5.16 Prasad SV, Christenson TR, Dugger MT. Advanced Materials and Processes, 2002; in press. 5.17 Humphreys FJ. J. Mater. Sci. 2001;36;3833. 5.18 Buchheit TE, LaVan DA, Michael JR, Christenson TR, Leith SD. Metallurgical and Materials Transations A 2002;33A:539-53. 5.19 Phaneuf MW. Micron 1999;39:277. 52
6 Novel Techniques for Measurement of Adhesion in LIGA Contacts 6.1 Introduction Real surfaces--however flat they may be-- are rough on an atomic scale, and contact occurs where the asperities of one surface touch the other. It is in these regions that adhesional and tribological action takes place. When the size scale of structures approach microscopic dimensions (~ 0.1 to 100 µm), adhesion between contacting surfaces becomes a critical issue. A consequence of this is that adhesion becomes a major concern for the performance and reliability of microelectromachnical systems, MEMS. Since the surface area to volume ratio of a mechanical element varies as the reciprocal of its characteristic length, the surface area to volume ratio in microsystems is several orders of magnitude larger than in macroscale mechanical systems. Combined with the fact that available motive forces via electrostatics, differential thermal expansion, fluid pressure, etc. are small, this leads to the result that adhesive forces, which are typically uncontrolled and ignored in macrosystems, play a major role in the behavior of microsystems. Further, due to the planar nature of these fabrication methods, forces tend to be transmitted between structural elements in the plane of the device, leading to the result that sliding interactions are predominantly between sidewalls. For example, see the gear train and rack mechanism, assembled from parts fabricated by LIGA, in Fig. 6.1. LIGA processing produces unique sidewall morphologies [6.1,6.2], and the existing analytical models (Derjaguin- Muller-Toporov, DMT and Johnson-Kendall-Roberts, JKR) do not account for the effect of unique morphology found on LIGA sidewalls on adhesion. The objective of this study was to develop an experimental technique to measure adhesive pull-off forces between LIGA fabricated structures in micro- and milli-newton load regimes. Fig. 6.1. A fully assembled LIGA gear train and track, showing several sidewall-to-sidewall sliding contacts. The aluminum substrate was machined conventionally to accept pressfit steel gage pins on which the keyed bushings and gears were assembled. 53
Page 1 and 2: SANDIA REPORT SAND2004-1319 Unlimit
Page 3 and 4: SAND2004-1319 Unlimited Release Pri
Page 5 and 6: Contents ACKNOWLEDGEMENTS..........
Page 7 and 8: 6.5 Summary........................
Page 9 and 10: List of Figures Figure 1.1 SEM micr
Page 11 and 12: Figure 6.2 Contact between an elast
Page 13 and 14: Preface Our team was involved in a
Page 15 and 16: strength. The subsequent chapter di
Page 17 and 18: Fig. 1.3. SEM image of cylindrical
Page 19 and 20: Fig. 1.5. Schematic of primary feat
Page 21 and 22: Fig 1.7 Double-hinged pull-tab tens
Page 23 and 24: Fig 1.10. SEM image of optical forc
Page 25 and 26: 2 Strength Distributions in SUMMiT
Page 27 and 28: 2.2 Critical Flaw Size Evaluation T
Page 29 and 30: Fig. 2.5. SEM micrograph of pull-ta
Page 31 and 32: (1) Differences in surface roughnes
Page 33 and 34: 3 The Role Of Microstructure In SUM
Page 35 and 36: crystallographic orientation of a g
Page 37 and 38: direction. Also, maximum stress loc
Page 39 and 40: 3.4 References 3.1 Randle, V., Micr
Page 41 and 42: has the advantage of distributing t
Page 43 and 44: and servovalve at a strain rate of
Page 45 and 46: 4.6 References 4.1. TJ Garino, AM M
Page 47 and 48: microscopy studies. As a first step
Page 49 and 50: Fig. 5.2. Orientation imaging of a
Page 51: Fig. 5.5. Orientation imaging of a
Page 55 and 56: of adhesion, and, (iv) a smaller co
Page 57 and 58: Force (mN) Fig. 6.5. Typical load-d
Page 59 and 60: 7 Impact of Silane Degradation Due
Page 61 and 62: All samples were coated with alkyls
Page 63 and 64: the friction structure and the cali
Page 65 and 66: 7.4 RESULTS 7.4.1 Simulation of dos
Page 67 and 68: Dose (MeV/g) Fig. 7.4. Results of X
Page 69 and 70: heating on contact angle for PFTS.
Page 71 and 72: the C-C backbone of the PFTS molecu
Page 73 and 74: The increase in static friction for
Page 75 and 76: 8 Friction and Wear of Selective Tu
Page 77 and 78: During processing of microelectrome
Page 79 and 80: actuator. After unloading, the devi
Page 81 and 82: 9 Conclusions and Recommendations T
Page 83: 10 Distribution 3 MS 0889 M.T. Dugg

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