In this paper, a purely mechanical model for the thermoelastic behavior of a bimorph microbeam is presented. The thermoelastic coupling problem of the microbeam is converted to a mechanical problem by simply replacing...In this paper, a purely mechanical model for the thermoelastic behavior of a bimorph microbeam is presented. The thermoelastic coupling problem of the microbeam is converted to a mechanical problem by simply replacing the thermal stress in the beam with a bulk force and a surface force. Thermoelastic deformation of the bimorph microbeams with constraints frequently used in micro-electro-mechanical systems (MEMS) devices has been derived based on this model and is characterized by FEA simulation. Coincidence of the results from theory and simulation demonstrates the validity of the model. The analysis shows that a bimorph microbeam with a soft constraint and a uniform temperature field has a larger thermoelastic deformation than that with a hard constraint and a linear temperature field. In addition to the adoption of materials with large CTE mismatch,thickness ratio and length ratio of the two layers need to be optimized to get a large thermoelastic deformation.展开更多
Wrinkling and buckling of nano-films on the compliant substrate are always induced due to thermal deformation mismatch.This paper proposes effective means to control the surface wrinkling of thin film on the compliant...Wrinkling and buckling of nano-films on the compliant substrate are always induced due to thermal deformation mismatch.This paper proposes effective means to control the surface wrinkling of thin film on the compliant substrate,which exploits the curvatures of the curve cracks designed on the stiff film.The procedures of the method are summarized as:1)curve patterns are fabricated on the surface of PDMS(Polydimethylsiloxane)substrate and then the aluminum film with the thickness of several hundred nano-meters is deposited on the substrate;2)the curve patterns are transferred onto the aluminum film and lead to cracking of the film along the curves.The cracking redistributes the stress in the compressed film on the substrate;3)on the concave side of the curve,the wrinkling of the film surface is suppressed to be identified as shielding effect and on the convex side the wrinkling of the film surface is induced to be identified as inductive effect.The shielding and inductive effects make the dis-ordered wrinkling and buckling controllable.This phenomenon provides a potential application in the fabrication of flexible electronic devices.展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 91023027)
文摘In this paper, a purely mechanical model for the thermoelastic behavior of a bimorph microbeam is presented. The thermoelastic coupling problem of the microbeam is converted to a mechanical problem by simply replacing the thermal stress in the beam with a bulk force and a surface force. Thermoelastic deformation of the bimorph microbeams with constraints frequently used in micro-electro-mechanical systems (MEMS) devices has been derived based on this model and is characterized by FEA simulation. Coincidence of the results from theory and simulation demonstrates the validity of the model. The analysis shows that a bimorph microbeam with a soft constraint and a uniform temperature field has a larger thermoelastic deformation than that with a hard constraint and a linear temperature field. In addition to the adoption of materials with large CTE mismatch,thickness ratio and length ratio of the two layers need to be optimized to get a large thermoelastic deformation.
基金supported by the National Basic Research Program of China(Grant Nos.2010CB631005 and 2011CB606105)the National Natural Science Foundation of China(Grant Nos.11232008,91216301,11072125 and 11272175)Tsinghua University Initiative Scientific Research Program
文摘Wrinkling and buckling of nano-films on the compliant substrate are always induced due to thermal deformation mismatch.This paper proposes effective means to control the surface wrinkling of thin film on the compliant substrate,which exploits the curvatures of the curve cracks designed on the stiff film.The procedures of the method are summarized as:1)curve patterns are fabricated on the surface of PDMS(Polydimethylsiloxane)substrate and then the aluminum film with the thickness of several hundred nano-meters is deposited on the substrate;2)the curve patterns are transferred onto the aluminum film and lead to cracking of the film along the curves.The cracking redistributes the stress in the compressed film on the substrate;3)on the concave side of the curve,the wrinkling of the film surface is suppressed to be identified as shielding effect and on the convex side the wrinkling of the film surface is induced to be identified as inductive effect.The shielding and inductive effects make the dis-ordered wrinkling and buckling controllable.This phenomenon provides a potential application in the fabrication of flexible electronic devices.
