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Full-Text Articles in Engineering Science and Materials

Influence Of Flow Rate, Nozzle Speed, Pitch And The Number Of Passes On The Thickness Of S1805 Photoresist In Suss Microtec As8 Spray Coater, Rohan Sanghvi, Gyuseok Kim Oct 2019

Influence Of Flow Rate, Nozzle Speed, Pitch And The Number Of Passes On The Thickness Of S1805 Photoresist In Suss Microtec As8 Spray Coater, Rohan Sanghvi, Gyuseok Kim

Tool Data

S1805 positive photoresist has been deposited on single crystalline Si wafers using a Suss MicroTec Alta Spray. The influence of flow rate, nozzle speed, pitch and number of passes on the thickness of the photoresist was studied. Results show that the thickness of S1805 is linearly proportional to the flow rate and number of passes, and inversely proportional to the nozzle speed and pitch.


Correction Of Pattern Size Deviations In The Fabrication Of Photomasks Made With A Laser Direct-Writer, Ningzhi Xie, George Patrick Watson Oct 2019

Correction Of Pattern Size Deviations In The Fabrication Of Photomasks Made With A Laser Direct-Writer, Ningzhi Xie, George Patrick Watson

Protocols and Reports

When using Heidelberg DWL66+ laser writer to fabricate the photomask, the pattern feature dimensions may have deviations. These deviations can be caused by the lithography process and the undercut in the metal etch process. The same deviation value of 0.8µm was found to appear in all the patterns independent of the pattern original size and local pattern density. To overcome this universal deviation, a universal bias is suggested to be applied to the original patterns during the data preparation for the lithography process. In order to ensure this pre-exposure bias method can work, both the laser direct-write exposure conditions ...


The Role Of Sliding Contact In Nanoscale Tribochemistry, Zachary Banks Milne Jan 2018

The Role Of Sliding Contact In Nanoscale Tribochemistry, Zachary Banks Milne

Publicly Accessible Penn Dissertations

In this dissertation, the results of experimental and theoretical studies exploring friction

and adhesion at the nanoscale are presented. Using a customized in situ transmission

electron microscopy nanoindentation methodology, it is observed that cohesion of silicon and

adhesion of silicon and diamond are strongly modied by the sliding speed and the normal

stress applied during sliding. This indicates that shear stress modulates the reactivity of the

surfaces. This is the rst time that tunable adhesion of hard contacts has been demonstrated

in situ.

If sliding experiments are performed in ultra-high vacuum and the interfacial shear stress

is low enough to ...


Mechanics Of Fluctuating Elastic Plates And Fiber Networks, Xiaojun Liang Jan 2017

Mechanics Of Fluctuating Elastic Plates And Fiber Networks, Xiaojun Liang

Publicly Accessible Penn Dissertations

Lipid membranes and fiber networks in biological systems perform important mechanical functions at the cellular and tissue levels. In this thesis I delve into two detailed problems -- thermal fluctuation of membranes and non-linear compression response of fiber networks. Typically, membrane fluctuations are analysed by decomposing into normal modes or by molecular simulations. In the first part of my thesis, I propose a new semi-analytic method to calculate the partition function of a membrane. The membrane is viewed as a fluctuating von Karman plate and discretized into triangular elements. Its energy is expressed as a function of nodal displacements, and then ...


Phase Boundary Propagation In Mass Spring Chains And Long Molecules, Qingze Zhao Jan 2016

Phase Boundary Propagation In Mass Spring Chains And Long Molecules, Qingze Zhao

Publicly Accessible Penn Dissertations

Martensitic phase transitions in crystalline solids have been studied and utilized for many technological applications, including biomedical devices. These transitions typically proceed by the nucleation and propagation of interfaces, or phase boundaries. Over the last few decades, a continuum theory of phase transitions has emerged under the framework of thermoelasticity to study the propagation of these phase boundaries. It is now well-established that classical mechanical and thermodynamic principles are not sufficient to describe their motion within a continuum theory, and a kinetic relation must be supplied to complete the constitutive description. A few theoretical techniques that have been used to ...


Continuum And Computational Modeling Of Flexoelectricity, Sheng Mao Jan 2016

Continuum And Computational Modeling Of Flexoelectricity, Sheng Mao

Publicly Accessible Penn Dissertations

Flexoelectricity refers to the linear coupling of strain gradient and electric polarization. Early studies of this subject mostly look at liquid crystals and biomembranes. Recently, the advent of nanotechnology revealed its importance also in solid structures, such as flexible electronics, thin films, energy harvesters, etc. The energy storage function of a flexoelectric solid depends not only on polarization and strain, but also strain-gradient. This is our basis to formulate a consistent model of flexoelectric solids under small deformation. We derive a higher-order Navier equation for linear isotropic flexoelectric materials which resembles that of Mindlin in gradient elasticity. Closed-form solutions can ...


Dielectric Elastomer Composites: Macroscopic Behavior And Instabilities, Morteza Hakimi Siboni Jan 2014

Dielectric Elastomer Composites: Macroscopic Behavior And Instabilities, Morteza Hakimi Siboni

Publicly Accessible Penn Dissertations

Dielectric Elastomers (DEs) are an interesting class of active materials that can exhibit coupled electrical and mechanical behaviors, for example they can respond to an external electric field by changing their shape or size. This unique property is known as electrostriction, and makes such materials promising candidates for a wide range of practical applications, and therefore there is a need for the design of DEs with enhanced electromechanical couplings. In this work we investigate the possibility of enhancing the electrostriction by making composites consisting of one or more family of filler phases in a soft dielectric host.

We use homogenization ...


Overall Mechanical Response Of Soft Composite Materials With Particulate Microstructure At Finite Strains, Reza Avazmohammadi Jan 2014

Overall Mechanical Response Of Soft Composite Materials With Particulate Microstructure At Finite Strains, Reza Avazmohammadi

Publicly Accessible Penn Dissertations

Many soft, composite materials manufactured or found in nature consist of a homogeneous matrix phase and a random distribution of micron-sized particles in the matrix. Examples among engineering materials include reinforced elastomers, microgel suspensions and polymer-matrix composites, whereas biological tissues and fluids, such as intervertebral disc and blood, provide examples of natural materials. In this thesis, we present homogenization-based models for the overall constitutive behavior of such composite materials when subjected to mechanical loadings. These models account for the constitutive nonlinearities associated with the local behavior of the matrix and particle phases, as well as for the nonlinearities associated with ...


Mechanics Of Micro-Structured Soft Materials And Their Applications In Adhesion And Wetting, Chi-Mon Chen Jan 2013

Mechanics Of Micro-Structured Soft Materials And Their Applications In Adhesion And Wetting, Chi-Mon Chen

Publicly Accessible Penn Dissertations

Mechanical instability and large deformation are pervasive occurrences on stressed soft material surface patterns, which are normally detrimental to device performance. In this dissertation we show that these phenomena can be harnessed on structured polymeric thin films for surface patterning, strong dry adhesion and guided wettability. On dyed SU-8 photoresist films with graded depth-wise crosslinking density, we study the swelling-induced wrinkling. We demonstrate that isotropic surface wrinkles can be aligned with low aspect ratio 1-D channel-type pre-patterns. By varying the pitch and height ratios, defined as the pre-pattern pitch and height of the channels to the wrinkle wavelength and amplitude ...


Complex Fluids In Microchannel Flows At Low Reynolds Number: Elastic Instabilities And Rheology, Lichao Pan Jan 2013

Complex Fluids In Microchannel Flows At Low Reynolds Number: Elastic Instabilities And Rheology, Lichao Pan

Publicly Accessible Penn Dissertations

Complex fluids, especially fluids containing polymer molecules, are frequently encountered in everyday life from foods, paints, to cosmetics. Polymeric fluids are usually viscoelastic and do not flow like water. As a result, these fluids can exhibit flow instabilities even at low Reynolds number (Re) where viscous forces dominate inertial forces, and a new type of turbulence - purely elastic turbulence. It has been demonstrated that these nonlinear behaviors are arised from elastic stresses and have been observed in flows with curved streamlines.

The first part of this work investigates flow instabilities of viscoelastic fluids in microchannel system. Experiments are performed in ...


Patterning Of Alloy Precipitation Through External Pressure, Jack A. Franklin Dec 2010

Patterning Of Alloy Precipitation Through External Pressure, Jack A. Franklin

Publicly Accessible Penn Dissertations

Due to the nature of their microstructure, alloyed components have the benefit of meeting specific design goals across a wide range of electrical, thermal, and mechanical properties. In general by selecting the correct alloy system and applying a proper heat treatment it is possible to create a metallic sample whose properties achieve a unique set of design requirements. This dissertation presents an innovative processing technique intended to control both the location of formation and the growth rates of precipitates within metallic alloys in order to create multiple patterned areas of unique microstructure within a single sample. Specific experimental results for ...