Date of Award

Spring 5-5-2023

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science in Mechanical Engineering (MSME)

Department

Mechanical Engineering

Advisor

Bashir Khoda

Second Committee Member

Khalid Jawed

Third Committee Member

William Gramlich

Additional Committee Members

Yingchao Yang

Abstract

The demand for particle transfer is increasing in various industries, such as manufacturing, metal joining, microfluidics, roller lubrication process, fuel cells, super-capacitors, hybrid coating, and protective layer applications. As a result, the importance of efficient transfer of solid micron-size particles is becoming more crucial. Submicron-sized particles can easily adhere to solid substrates due to negligible gravitational force, while micron-sized or larger particles require a binder to overcome the gravitational effects. This thesis aims to investigate the interactions between microparticles and polymer thin film on cylindrical substrates using particle transfer methods. The process parameters are optimized and demonstrated two applications of this process: sorting particles based on their size from poly-disperse particle mixtures and controlling the friction force of the rods.

To transfer particles into a substrate, a density-mismatching heterogeneous suspension is utilized, where kinetic energy is supplied by a magnetic stirrer’s rotation to keep the particles suspended during transfer. Initially, the effect of magnetic stirrer rotation and binder concentration on the optimal particle transfer was investigated. As a result of optimizing process parameters, a novel technique was developed for filtering poly-disperse particles from density mismatching heterogeneous mixtures at the solid-liquid interface (submerged condition) using entrapment instead of the conventional entrainment approach used in dip-coating processes. The polymer layer thickness formed over the substrate is controlled by controlling the binder concentration in the suspension. The binder concentration is varied from ϕb = 1% to ϕb = 13% at different intervals and the particle concentration is kept fixed ϕp = 10%. The viscosity is measured at room temperature (25 ºC) to observe the behavior of the suspension using a rotational rheometer. The variation in the polymer layer thickness controls the size of the entrapped particles. This work successfully showed the size-based separation of particles from a poly-disperse particle mixture.

Another aspect of this thesis involved the systematic control of frictional forces between elastic rods in contact by transferring particles via dip-coating. Non-spherical particles adhere to the rods using a polymeric binder. A custom continuous dip-coating setup was constructed in the laboratory to coat the elastic rods. The particle delivery over the rods is regulated by controlling the concentration of particles in the suspension. Particle concentration in the suspension is varied from ϕp = 1% to ϕp = 13% at different intervals to observe the effect of variation of particle concentration keeping the binder concentration fixed (ϕb = 5%). The coated rods are dried in the oven to overcome the effect of the solvent during the friction force measurement. Table-top experimental setup with a push-pull digital force gauge is used to measure the variation friction force at different pulling lengths of overhand knots with a variety of unknotting numbers. This work successfully demonstrates a novel method of controlling the friction force of elastic rods by controlling the particle concentration in the suspension.

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