Measurements over the past 30 years have indicated that surface stress can significantly affect the stiffness of microcantilever plates. Several one-dimensional models based on beam theory have been proposed to explain this phenomenon, but are found to be in violation of Newton's third law, in spite of their good agreement with measurements. In this Letter, we review this work and rigorously examine the effect of surface stress on the stiffness of cantilever plates using a full three-dimensional model. This study establishes the relationship between surface stress and cantilever stiffness, and in so doing elucidates its scaling behavior with cantilever dimensions. The use of short nanoscale cantilevers thus presents the most promising avenue for future investigations.

Nanomechanical doubly-clamped beams and cantilever plates are often used to sense a host of environmental effects, including biomolecular interations, mass measurements, and responses to chemical stimuli. Understanding the effects of surface stress on the stiffness of such nanoscale devices is essential for rigorous analysis of experimental data. Recently, we explored the effects of surface stress on cantilever plates and presented a theoretical framework valid for thin plate structures. Here, we generalize this framework and apply it to cantilever plates and doubly-clamped beams, exploring in detail the relative physical mechanisms causing a stiffness change in each case. Specifically, Poisson's ratio is found to exert a dramatically different effect in cantilevers than in doubly-clamped beams, and here we explain why. The relative change in effective spring constant is also examined, and its connection to the relative frequency shift is discussed. Interestingly, this differs from what is naively expected from elementary mechanics. Finally, a discussion of the practical implications of our theoretical findings is presented, which includes an assessment of available experimental results and potential future measurements on nanoscale devices.

Numerous measurements have indicated that surface stress can significantly modify the stiffness of cantilever sensors. In contrast, theoretical calculations using classical beam theory predict that stiffness is independent of surface stress. Using a three-dimensional analysis, we recently showed that surface stress does indeed have an effect within the framework of linear elasticity. However, only cantilevers of rectangular geometry were explored. Here, we vary cantilever geometry and find that it plays a critical role, with V-shaped cantilevers displaying greatly enhanced sensitivity in comparison to rectangular cantilevers. Tuning cantilever geometry therefore provides a sensitive route to controlling the effects of surface stress.

Sn and Nb modified ultrafine Ti-based bulk alloys with high-strength and enhanced ductility Appl. Phys. Lett. 102, 061908 (2013) A comparative study of two molecular mechanics models based on harmonic potentials J. Appl. Phys. 113, 063509 (2013) Viscoplastic analysis of cyclic indentation behavior of thin metallic films J. Appl. Phys. 113, 063510 (2013) The increase in conductance of a gold single atom chain during elastic elongation J. Appl. Phys. 113, 054316 (2013) Additional information on J. Appl. Phys. Buckling of elastic structures can occur for loads well within the proportionality limit of their constituent materials. Given the ubiquity of beams and plates in engineering design and application, their buckling behavior has been widely studied. However, buckling of a cantilever plate is yet to be investigated, despite the widespread use of cantilevers in modern technological developments. Here, we address this issue and theoretically study the buckling behavior of a cantilever plate that is uniformly loaded in its plane. Applications of this fundamental problem include loading due to uniform temperature and surface stress changes. This is achieved using a scaling analysis and full three-dimensional numerical solution, leading to explicit formulas for the buckling loads. Unusually, we observe buckling for both tensile and compressive loads, the physical mechanisms for which are explored. We also examine the practical implications of these findings to modern developments in ultra sensitive micro-and nano-cantilever sensors, such as those composed of silicon nitride and graphene. V C 2013 American Institute of Physics.

The thermal storage and insulation properties of garments enhanced with phase change material (PCM) will be investigated using a finite difference procedure. A diver dry suit embedded with microencapsulated PCM will be shown to enhance thermal protection under extreme temperature conditions. Under conditions of high body heat production a garment embedded with Macro-encapsulated PCM is shown to absorb excess heat while maintaining a relatively constant temperature.