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Many papers have been published on methods to determine the normal spring constant, kz, of atomic force microscope (AFM) cantilevers. This is necessary to calibrate force measurements in the AFM, which then lead to a wide variety of applications from measuring the rupture force of protein bonds to determining the Young’s modulus of materials such as polymers at surfaces. Manufacturers’ nominal values of kz have been found to be up a factor of two in error, therefore practical methods to calibrate kz are required. There are three main categories of methods, with some overlap, which we call: (1) dimensional, (2) static experimental and (3) dynamic experimental. Here, we consider the dimensional aspects of these methods involving the cantilever material properties and geometry. We do this via reviewing the analytical equations of seven publications and comparing them with finite element analysis (FEA) calculations. It is shown that the best analytical equations are those of Neumeister and Ducker but that these need a revision for the bending of the triangular portion of the V-shaped cantilever. This is done and the correlation with FEA is then excellent. Equations are also provided for the effect of a metallized layer and the imaging tip not being at the cantilever apex; these also agree with FEA. We evaluate the relevant uncertainties and provide recommendations as to the best equations to use together with relevant correction parameters based on the assumption that the FEA calculations are valid. We test this assumption elsewhere.

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The development of tough adhesive hydrogels has enabled unprecedented adhesion to wet and moving tissue surfaces throughout the body, but they are typically composed of nondegradable components. Here, a family of degradable tough adhesive hydrogels containing ≈90% water by incorporating covalently networked degradable crosslinkers and hydrolyzable ionically crosslinked main-chain polymers is developed. Mechanical toughness, adhesion, and degradation of these new formulations are tested in both accelerated in vitro conditions and up to 16 weeks in vivo. These degradable tough adhesives are engineered with equivalent mechanical and adhesive properties to nondegradable tough adhesives, capable of achieving stretches >20 times their initial length, fracture energies >6 kJ m −2 , and adhesion energies >1000 J m −2 . All degradable systems show complete degradation within 2 weeks under accelerated aging conditions in vitro and weeks to months in vivo depending on the degradable crosslinker selected. Excellent biocompatibility is observed for all groups after 1, 2, 4, 8, and 16 weeks of implantation, with minimal fibrous encapsulation and no signs of organ toxicity. On-demand removal of the adhesive is achieved with treatment of chemical agents which do not cause damage to underlying skin tissue in mice. The broad versatility of this family of adhesives provides the foundation for numerous in vivo indications.

An analysis has been made of the historical data for argon ion sputtering yields of 28 mono-elemental solids in the energy range 250-10 000 eV to develop an improved semi-empirical formula based on Matsunami et al.'s and Yamamura and Tawara's formulations. The best result is found if an essential component involving the target density is included in Matsunami et al.'s approach. The scatter between the predictions and the experimental data is reduced to 9.0% by generating an analytical expression for the term Q that requires none of the target-specific numbers from special look-up tables of the type used by Matsunami et al. and Yamamura and Tawara. For elements other than the 34 elements for which Q values are tabulated, the new Q values range up to a factor of 5 from the default value that they recommend.The predictions are tested by a new method for determining sputtering yields using atomic force microscopy to measure very small crater volumes sputtered in ultrahigh vacuum. Here, 26 mono-elemental targets were studied using a 5 keV argon ion beam set at 45• to the surface normal. The effect of the angle of incidence is evaluated best using Yamamura et al.'s angular equations for this contribution. Results for Sb, Te and Bi indicate a significantly higher sputtering yield than expected. This is thought to arise from the high content of polyatomic groups associated with the low sublimation energies for such clusters in the pure elements of groups V-B and VI-B of the Periodic