BilMech distinguishes itself from most other engineering departments via a strong emphasis on undergraduate research activities. Starting from the first year of their studies at the Mechanical Engineering Department, successful undergraduates have the opportunity to join a research group the activities of which are of interest to them. Efficiently advised by the particular faculty member leading the research group, undergraduates take an active part in research, by helping graduate students with their projects or even conducting projects of their own via the 2209/A program of TUBITAK. As of Fall 2015, fourteen undergraduates at BilMech have received TUBITAK 2209/A awards and the number is expected to increase even more in the coming years.
Some examples of undergraduate research projects conducted in our department are presented below.
Homogenization in Hydrodynamic Lubrication: Microscopic Regimes and Re-Entrant Textures
İbrahim Nasuh Yıldıran (ME ’16, now @ Koç University)
During his undergraduate research with Dr. Barbaros Çetin and Dr. İlker Temizer, İbrahim Nasuh Yıldıran has investigated the microscopic mechanisms which influence the macroscopic response of hydrodynamically lubricated micro-textured interfaces. The form of the Reynolds-type equation which governs the macroscopic mechanics of such interfaces is well-accepted. The central role of the ratio of the mean film thickness to the texture period in determining the flow factor tensors that appear in this equation had also been highlighted in a pioneering theoretical study through a rigorous two-scale derivation. However, the resulting homogenization theory still remained to be numerically investigated. İbrahim numerically studied three microscopic regimes of lubrication and extensively demonstrated the factors which influence the transition between these regimes. In addition to conventional textures which typically appear in the literature, he additionally considered representative re-entrant textures which are amenable to manufacturing through recently developed techniques.
The results of İbrahim’s research have been published as an article in a leading tribology journal.
Tuning macroscopic sliding friction at soft contact interfaces: Interaction of bulk and surface heterogeneities
Karsu İpek Kılıç (ME ’16, now @ Stanford University)
During her undergraduate research with Dr. İlker Temizer, Karsu İpek Kılıç has studied the macroscopic frictional response of soft interfaces, which is strongly governed by the interaction of surface heterogeneities such as micro-texture features with bulk heterogeneities such as voids or inclusions beneath the highly deformable surface. This microscopic interaction manifests itself on the macroscale as an interface response that is reminiscent of stick-slip. Consequently, the accompanying macroscopic friction signal exhibits strong oscillations around a mean value, which itself significantly differs from its microscopic value due to finite deformations. Karsu identified a mechanism which enables the tuning of the macroscopic friction signal of soft interfaces. Specifically, she demonstrated that positioning subsurface particles in the vicinity of micro-texture features can significantly reduce observed oscillations, thereby allowing control of macroscopic sliding friction.
The results of Karsu’s research have been published as an article in a leading tribology journal.
Development and experimental verification of a numerical model for a micro- fluidic polymerase chain reactor
İlbey Karakurt (ME ’15, now @ UC Berkeley)
Polymerase-chain-reaction (PCR) is a thermal cycling process (repeated heating and cooling of PCR solution) for amplifying DNA. PCR devices have many biomedical applications. One of the most important aspects for the success of PCR is to control the temperature of the solution precisely at the desired temperature levels required for PCR in a cyclic manner. Microfluidics offers a great advantage over conventional techniques since very small amounts of PCR solution is needed for the process to occur at the desired temperature levels. In this project, İlbey Karakurt worked on develoing a multiphysics-based computational model under the guidance of Dr. Barbaros Çetin to assess the thermal performance of a microfluidics platform for continuous-flow PCR. With the computational model, the effects of design parameter on the performance of PCR cycle were aimed to be understood and utilized for the optimization of a microfluidic PCR device. The results of the computational model have been verified by the experimental results in the second phase of the project. The computational model will have the potential to be implemented for a general design tool for the design of efficient microfluidics based thermal reactors which can extend the boundaries of microfluidics technologies in biomedical and bioengineering fields.
Investigating the Effect of Tip Structure and Elasticity on Atomic-Resolution Scanning Probe Microscopy
Berkin Uluutku (ME ’15, now @ George Washington University)
Atomic-resolution scanning probe microscopy experiments suffer from various problems including thermal drift, piezo nonlinearities, variability in tip apex chemistry, structural asymmetry of the tip apex, as well as tip elasticity. In this project conducted under the guidance of Dr. Mehmet Z. Baykara, Berkin Uluutku performed numerical simulations utilizing analytic potentials and simple tip apex models to study the effects of tip elasticity and asymmetry on atomic-resolution scanning probe microscopy experiments. It is projected that a better understanding of the role of the tip in scanning probe microscopy will allow more meaningful comparisons between experimental results obtained by different research groups.
Homogenization of Soft Interfaces in Time-Dependent Hydrodynamic Lubrication
Gökberk Kabacaoğlu (ME ’14, now @ UT Austin)
During his undergraduate research with Dr. İlker Temizer, Gökberk Kabacaoğlu has studied the thin film lubrication problem with highly deformable surfaces which are both rough and moving. In order to understand the physics of the fluid film at the interface, the problem has been modeled by means of the Reynolds equation. However, the common assumption of microscopically smooth surfaces was not invoked since real surfaces are inevitably rough or textured by design. Based on the motion and the topology of the interface, the problem was considered in three regimes: stationary, quasi-stationary, and unsteady. Furthermore, most biological and synthetic interfaces are soft. Hence, Gökberk’s research focused on the study of the microscale lubrication problem where the deformation and the surface roughness effects are taken into account. The macroscopic response was then predicted through a numerically efficient homogenization-based scale transition theory that unifies all soft hydrodynamic lubrication regimes in a single framework.
The results of Gökberk’s research have been published as an article in a high-ranking computational mechanics journal.