Hard stamps

Figure 10.18 schematically illustrates the process. It uses elastomeric stamps similar those of pCP. or hard stamps formed using the etching procedures outlined in Fig. 10.10. Depositing a thin layer of solid material on to the raised features of the stamp constitutes the inking step. All of the examples described here use electron beam evaporation of a thin layer of Au (20-50 nm) or a bilayer of Au (20-50 nm)/Ti (2-5 nm).

Figure 10.20 shows a printed pattern that has nanometer resolution [11]. In this case a hard stamp of GaAs, formed by electron beam lithography and etching, was used. The metal coating consisted of a bilayer of Au (20 nm) and Ti (5 nm). The... 

FIGURE 5.5.14 Optical micrographs of gold patterns printed by nTP. (a) 100-nm holes printed with a GaAs hard stamp on a plastic substrate coated with PDMS gold patterns printed with a PDMS stamp on (b) a PDMS substrate (c) a silicon/silicon dioxide substrate and (d) an ITO-coated plastic substrate. (From Y.-L. Loo, et al., J. Vac. Set TechnoL, B, 20, 2853, 2002.)... 

While rigid hard stamps are successfully used to print submicron features, elastomeric stamps remain attractive because they can be easily fabricated and they readily conform to rigid substrates at ambient pressures. The low elastic modulus and high compressibility of elastomeric PDMS stamps can be overcome with composite PDMS stamps (/t-PDMS) [22,23]. As discussed in Section 5.5.2, /t-PDMS stamps consist of a Sylgard 184 PDMS layer that provides conformal contact with... 

For production volumes greater than otherwise might be practical with hand-operated equipment and yet less than would be economically feasible based on the costs of hard stamping or rollforming tooling, these nontraditional systems may be appropriate. 

It is applied along with traditional methods to test strength properties, hardness, to determine standardized characteristics of stamping, grain size and other structural-sensitive characteristics. 

Cladding may be less expensive than selective electro deposition when coatings greater than 1 p.m of a noble metal are required, but may be more expensive than electro deposition for thinner coatings. Selective techniques are most easily used for sheet metal substrates that are to be machine stamped and formed into contacts. Clad noble metals are considerably more ductile (and less hard) than comparable electro deposits and, therefore, are better suited to forming operations. Contacts that are made into separate parts from rod by screw machining are usually coated on all exposed surfaces by barrel electroplating. 

Discs Discs of nickel electroformed on to mandrels bearing grooves modulated with recorded sound have been used for many years for stamping sound recording discs. This process has been adapted and refined for the manufacture of digital records, including video discs . Video disc stampers must be hard, stress-free, and flat to within 0.1 m results of a short investigation directed towards these requirements have been reported ". 

Figure 4.11 (left). Tablet hardness found for the sequence of 120 tablets. On the suspicion that there is a dependency by stamp, the data are grouped by stamp (Fig. 4.12 left), (right). Correlation between tablet hardness and weight. For the residual.s that are obtained after correction for the tablet weight, see Fig. 4.12 right. 

Results The hardness and the weight are measured (for 10 tablets from each of the 12 stamps, see HARDNESS.dat, use programs XYZ, XYZCELL, LINREG) and are graphed (Fig. 4.11, left). 

Figure 4.12 (left). The hardness data is grouped by stamp, (right). By subtracting the weight-dependent portion of the hardness, the residuals are seen to cluster much more closely, particularly for those stamps marked with arrows. Because of the limited hardness resolution (0.1 kg), the symbols for two or more data points can overlap. The vertical bar indicates sfj. 

The stamp associated with the extreme hardness values (number 7, Fig. 4.12, left use STAMP.dat with program MULTI) is the next suspect It is identified and inspected on disassembly of the tablet press Due to mechanical wear, the movement of the stamp assembly is such that an above-average amount of granulate drops into cavity number 7, and is thus compressed to the limiting hardness supported by the granulate. The hardness for stamps 4, 8, and 11 tends to be low, and high for 12, but the data is insufficient to come to definite conclusions for these tools. The tablets from these stamps contaminated what would otherwise been a fairly acceptable product. Because... 

HARDNESS.dat Section 4.9 One-hundred-twenty tablets were taken off a press in the order they emerged, and hardness and weight were individually determined one column features the stamp number (cf. STAMP.dat) another column gives the weight-corrected hardness values. N = 120, M = 5 use with programs LINREG, XYZ, and XYZCELL. 

Also, electronic SOPs and protocols must be available to staff at all test sites for multisite studies. If the electronic documents are to be available at several sites, the validation phase of the system must include functionality testing at each site. Documentation of system validation needs to be available at each test site as well. Electronic SOPs must have a limited life span when printed to avoid the use of an outdated document. This may be achieved by stamping each SOP hard copy Printout not valid after date xx/xx/xx . This practice helps to ensure that system users will not retain printed SOPs long after the electronic SOP is revised. For company SOPs that are to be followed by an outside contractor who has no access to the electronic system, an alternative stamp may be used on the hard-copy SOPs that will be provided to the contractor that defines the date printed or indicates that the SOP is valid for use in a particular study. Whatever procedure is used, it must be clearly documented in an SOP. 

Rutherford s attitude toward chemistry was stereotyped by his jokes and barbs occasionally directed at his chemical colleagues. The later Manchester physicist P. M. S. Blackett recounted the famous crack, "All science is either physics or stamp collecting, "63 and it was said that Rutherford chafed at receiving the 1908 Nobel Prize in chemistry, rather than in Physics. In a lecture in which he described his theory of the nuclear atom, he joked that the "nucleus is a round, hard objectjust like Professor Perkins head."64 However, Rutherford expressed great respect for his chemist collaborator Frederick Soddy and for other chemists, as well. 

But no one who is a chemist at heart can resist the elements, and that includes me. It includes Oliver Sacks too, who as a boy set about collecting the elements as most other boys collected stamps or coins. He wanted to own them all. In the 1940s it was not so hard to add to one s collection Sacks could go to Griffin Tatlock in Finchley, north London, and spend his pocket money on a lump of sodium, which he would then send fizzing over the surface of Highgate Ponds near his home. I envy him the best I could do was to smuggle lumps of sulphur and bottles of mercury out of the school laboratory. 

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