Browsing by Author "Vlassak, Joost"

Now showing items 1-20 of 53

    • 3D Printing of Transparent and Conductive Heterogeneous Hydrogel-Elastomer Systems 

      Tian, Kevin; Bae, Jinhye; Bakarich, Shannon E.; Yang, Canhui; Gately, Reece D.; Spinks, Geoffrey M.; in het Panhuis, Marc; Suo, Zhigang; Vlassak, Joost J. (Wiley-Blackwell, 2017)
      Hydrogel-based ionic devices represent an alternative approach to stretchable electronics through use of soft ionic conductors that are both highly stretchable and transparent. However, these devices require the integration ...

    • Adhesion Degradation and Water Diffusion in Nanoporous Organosilicate Glass Thin Film Stacks 

      Lin, Youbo; Tsui, Ting Y.; Vlassak, Joost (The Electrochemical Society, 2010)
      The diffusion of water in nanoporous organosilicate glass (NPOSG) film stacks causes significant adhesion degradation of the capping layer on top of the NPOSG. We have used this adhesion degradation to estimate the diffusivity ...

    • Analysis of Ti–Ni–Hf shape memory alloys by combinatorial nanocalorimetry 

      Vlassak, Joost; Motemani Sharabiani, Yahya; McCluskey, Patrick; Zhao, Chunwang; Tan, Ming J.; Tan, Ming (Elsevier BV, 2011-12)
      The martensitic transformation in Ti-Ni-Hf thin films with ultra-fine grain structure has been analyzed as a function of composition using a high-throughput array of nanocalorimeters. The martensite-austenite transformation ...

    • An Apparatus for Performing Microtensile Tests at Elevated Temperatures inside a Scanning Electron Microscope 

      Sim, Gi-Dong; Park, Jun-Hyub; Uchic, Michael D.; Shade, Paul A.; Lee, Soon-Bok; Vlassak, Joost J. (Elsevier, 2013)
      In this paper, we introduce an apparatus to perform microtensile tests at elevated temperatures inside a scanning electron microscope. The apparatus has a stroke of 250 μm with a displacement resolution of 10 nm and a load ...

    • Application of in-situ nano-scanning calorimetry and X-ray diffraction to characterize Ni–Ti–Hf high-temperature shape memory alloys 

      McCluskey, Patrick; Xiao, Kechao; Gregoire, John M.; Dale, Darren; Vlassak, Joost J. (Elsevier BV, 2015)
      Combinatorial nanocalorimetry and synchrotron x-ray diffraction were combined to study the martensite-austenite (M-A) phase transformation behavior of Ni-Ti-Hf shape memory alloys. A thin-film library of Ni-Ti-Hf samples ...

    • Bauschinger effect in thin metal films: Discrete dislocation dynamics study 

      Davoudi, Kamyar M.; Nicola, Lucia; Vlassak, Joost J. (American Institute of Physics (AIP), 2014)
      The effects of dislocation climb on plastic deformation during loading and unloading are studied using a two-dimensional discrete dislocation dynamics model. Simulations are performed for polycrystalline thin films ...

    • Debonding and fracture of ceramic islands on polymer substrates 

      Vlassak, Joost; Sun, Jeong-Yun; Lu, Nanshu; Yoon, Juil; Oh, Kyu-Hwan; Suo, Zhigang (AIP Publishing, 2012-01)
      We perform in-situ uniaxial tensile tests on polyimide substrates with patterned ceramic islands. The islands fail by either channel cracking or debonding from the substrate, depending on island size and thickness. To ...

    • Determining the Elastic Modulus and Hardness of an Ultrathin Film on a Substrate Using Nanoindentation 

      Li, Han; Vlassak, Joost J. (Materials Research Society, 2009)
      A data analysis procedure has been developed to estimate the contact area in an elasto-plastic indentation of a thin film bonded to a substrate. The procedure can be used to derive the elastic modulus and hardness of the ...

    • Diffusion, Deformation, and Damage in Lithium-Ion Batteries and Microelectronics 

      Pharr, Matt Mathews (2014-06-06)
      This thesis explores mechanical behavior of microelectronic devices and lithium-ion batteries. We first examine electromigration-induced void formation in solder bumps by constructing a theory that couples electromigration ...

    • Discoveries in Phononic Crystals and Acoustic Metamaterials 

      Wang, Pai (2015-10-13)
      Phononic crystals and acoustic metamaterials are heterogeneous materials that enable manipulation of elastic waves. An important characteristic of these heterogeneous systems is their ability to tailor the propagation of ...

    • Dislocation climb in two-dimensional discrete dislocation dynamics 

      Vlassak, Joost; Davoudi, Kamyar M.; Nicola, Lucia (AIP Publishing, 2012-05-15)
      In this paper, dislocation climb is incorporated in a two-dimensional discrete dislocation dynamics model. Calculations are carried out for polycrystalline thin films, passivated on one or both surfaces. Climb allows ...

    • Dislocation evolution during plastic deformation: Equations vs. discrete dislocation dynamics study 

      Davoudi, Kamyar M.; Vlassak, Joost (AIP Publishing, 2018-02-28)
      Equations for dislocation evolution bridge the gap between dislocation properties and continuum descriptions of plastic behavior of crystalline materials. Computer simulations can help us verify these evolution equations ...

    • The Effect of Porogen Loading on the Stiffness and Fracture Energy of Brittle Organosilicates 

      Li, Han; Lin, Youbo; Tsui, Ting Y.; Vlassak, Joost J. (Materials Research Society, 2009)
      Integrating porous low-permittivity dielectrics into Cu metallization is one of the strategies to reduce power consumption, signal propagation delays, and crosstalk between interconnects for the next generation of integrated ...

    • Failure by Simultaneous Grain Growth, Strain Localization, and Interface Debonding in Metal Films on Polymer Substrates 

      Lu, Nanshu; Wang, Xi; Suo, Zhigang; Vlassak, Joost J. (Materials Research Society, 2009)
      In a previous paper, we have demonstrated that a microcrystalline copper film well bonded to a polymer substrate can be stretched beyond 50% without cracking. The film eventually fails through the co-evolution of necking ...

    • Fatigue fracture of tough hydrogels 

      Bai, Ruobing; Yang, Quansan; Tang, Jingda; Morelle, Xavier P.; Vlassak, Joost J.; Suo, Zhigang (Elsevier BV, 2017)
      Tough hydrogels of many chemical compositions have been developed in recent years, but their fatigue fracture has not been studied. The lack of study hinders further development of hydrogels for applications that require ...

    • Fiber-reinforced tough hydrogels 

      Illeperuma, Widusha Ruwangi Kaushalya; Sun, Jeong-Yun; Suo, Zhigang; Vlassak, Joost J. (Elsevier BV, 2014)
      Using strong fibers to reinforce a hydrogel is highly desirable but difficult. Such a composite would combine the attributes of a solid that provides strength and a liquid that transports matter. Most hydrogels, however, ...

    • Focused Ion Beam Induced Deflections of Freestanding Thin Films 

      Kim, Young-Rok; Chen, Peng-Chieh; Aziz, Michael; Branton, Daniel; Vlassak, Joost (American Institute of Physics, 2006)
      Prominent deflections are shown to occur in freestanding silicon nitride thin membranes when exposed to a 50 keV gallium focused ion beam for ion doses between 10<sup>14</sup> and 10<sup>17</sup> ions/cm<sup>2</sup>. Atomic ...

    • Force and stroke of a hydrogel actuator 

      Illeperuma, Widusha Ruwangi Kaushalya; Sun, Jeong-Yun; Suo, Zhigang; Vlassak, Joost J. (Royal Society of Chemistry (RSC), 2013)
      Hydrogels that undergo a volume phase transition in response to an external stimulus are of great interest because of their possible use as actuator materials. The performance of an actuator material is normally characterized ...

    • High-temperature tensile behavior of freestanding Au thin films 

      Sim, Gi-dong; Vlassak, Joost J. (Elsevier BV, 2014)
      The mechanical behavior of freestanding thin sputter-deposited films of Au is studied at temperatures up to 340 °C, using tensile testing. Films tested at elevated temperatures exhibit a significant decrease in flow stress ...

    • High-throughput analysis of thin-film stresses using arrays of micromachined cantilever beams 

      Kim, Hyun-Jong; Han, Jun-Hyun; Kaiser, Roy; Oh, Kyu Hwan; Vlassak, Joost (AIP Publishing, 2008-04)
      We report on a technique for making high-throughput residual stress measurements on thin films by means of micromachined cantilever beams and an array of parallel laser beams. In this technique, the film of interest is ...