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Fundamentals of low-transmissibility aerostatic pads
Air bearings are known for their low friction losses, constant viscosity and cleanliness, making them favourable in numerous high-tech applications. The relatively low aerostatic bearing stiffness is the major topic in state-of-the-art research and some recently proposed concepts are able to create infinite stiffness. This results in a strong coupling between the base and flying mass, enabling unwanted propagation of base vibrations. Why not integrate the vibration-isolation and bearing function? To reduce the out of plane vibrations of a flying mass.
A previous study shows the possibility of creating a zero-stiffness bearing with the use of multiple aerostatic pads. However, the effect of the dynamic- thin-film stiffness and damping on the transmission of base vibrations is still unknown. The aim of this research is to optimise and validate the zero-stiffness concept and to study the effect of the static and dynamic pad characteristics on the transmissibility function. It is shown that both the stiffness and damping need to be minimised at equal operating fly height to create a stable system. A stable design is found with the use of a parametric optimisation procedure. The design shows a lower transmissibility when compared to a standard aerostatic bearing, although there are some challenges regarding high design sensitivities and displacement non-linearity. Different manufacturing methods are investigated to build a prototype to validate the concept. The measurements prove the validity of the model, although a clear low-stiffness operating point is not found, due to a combination of manufacturing difficulties and high design sensitivities.
The presentation will be given in English.
13h20 Debate
13h30 End
Attending colloquia is an obligatory part of the curriculum of PME.
The presence of other people who are interested will be appreciated.
10h00 Chuqian Zhang, specialisation: MNE
Coaches: Dr.ir. M. Tichem, Dr. M.K. Ghatkesar
Title: Design and fabrication of a dielectric elastomer actuator for
Organ-on-Chips platforms
Cell behaviour in vitro can be regulated by mechanical stimulation. Cytostretch is an Organ-on-Chip (OOC) platform that allows cyclic stretching tissue in culture. Its pneumatic actuation can hinder it from microfluidic systems integration. A dielectric elastomer actuator (DEA) was developed and fabricated in this thesis for Cytostretch as an alternative actuation method. The DEA consists of a suspended polymer membrane sandwiched between electrodes, which can induce out-of-plane motion when a voltage is applied. The functionality of the design was proved in numerical analysis. A complete process flow was developed and partly implemented for the wafer-scale microfabrication of this innovative actuator. The top electrodes of the device were fabricated by depositing and patterning titanium nitride with stress buffering layers. The quality of the electrodes was examined and wrinkles were found at corners of certain etching patterns. The angle of the corner and spacing between corners are proposed to be two factors influencing the wrinkle formation. This work paves the way to the successful integration of DEAs for mechanical stimulation of cell tissues within OOC platforms.
The presentation will be given in English.
10h20 Debate
10h30 End
Attending colloquia is an obligatory part of the curriculum of PME.
The presence of other people who are interested will be appreciated.
Thursday 26 September 2019, 14h00
Lecture hall B (Isaac Newton)
Mekelweg 2
2628 CD DELFT
14h00 Jan van Willigen, specialisation: MSD
Coaches: Dr.ir. R.A.J. van Ostayen, Ir. J.P.A. Nijssen
Title: Modeling of a compliant force distribution mechanism for
deformable hydrostatic bearings
Hydrostatic bearings are well known for having low friction and low wear in combination with high loading capacity. Traditionally, the running surfaces for a hydrostatic bearing are plane, rigid and smooth, ensuring a parallel lubricating film in the full range of movement. In this research, we consider a new type of compliant, hydrostatic bearing where the running surfaces have a surface waviness with a large amplitude resulting in a varying, curvature for the hydrostatic bearing to follow in its range of movement. Design choices and subsequent modeling of these types of bearings are presented in this work. The introduced bearing concept is based on a compliant whiffletree mechanism able to distribute load over multiple hydrostatic slippers. This increases deformability of the complete bearing system. In a case study the limitations of a large deforming hydrostatic bearing are modeled to understand the impacts on performance and implications.
Location: 3mE-CZ B (Isaac Newton), Leeghwaterstraat, 2628 CA Delft, Nederland
Description:
Thursday 26 September 2019, 15h00
Lecture hall B (Isaac Newton)
Mekelweg 2
2628 CD DELFT
15h00 Alok Bharadwaj, specialisation: MNE
Coaches: Dr.ir. M. Tichem, Dr. M.K. Ghatkesar
Title: Measurement of low contact angle droplet topography using
optical interferometry
Production and manipulation of microdroplets is an active are of research. The demand for finding new ways to produce microdroplets has resulted in a challenge to characterize these droplets. The problem becomes especially difficult for microdroplets which are placed on a transparent hydrophilic substrate. Ink-jet printing, Digital microfluidics, DNA synthesis are some of the applications which need topography measurements of low contact angle microdroplets. One application which is of interest is the sample preparation for Cryo Electron Microscopy (cryo-EM).
A recent development in the search for efficient sample preparation for cryo-EM is to use hollow microcantilevers (HMC). HMCs can isolate a single sub-cellular component to prepare samples confined in a femtoliter droplet. These droplets are dispensed on a hydrophilic Electron Microscopy grid (EM-grid). By controlling the thickness of the water layer on the EM-grid through evaporation, it is possible to reduce sample wastage, which is one of the biggest issues facing scientists. However, such a control loop is not possible at present due to the absent of any form of feedback. A solution is proposed to use the real-time topography measurement of such droplets as a feedback to the control loop.
The objective of this project is to investigate the feasibility of optical methods to measure the topography information of a low contact angle microdroplet. The scope of this project is limited to develop a tool for a droplet which is supported by a glass slide (droplet-on-glass). In a subsequent study, the tool will be tested for droplets supported on grid (droplet-on-grid).
An optical interferometry setup is proposed as a suitable strategy. A Mach-Zehnder interferometer is built to obtain the experimental fringes. A Single Frame Fourier Transform technique was used to analyze the data and obtain the results. Droplets of glycerol were dispensed on a glow discharged glass slide. The initial height and contact angle of such droplets were found to be around 2 microns and 4 degrees respectively. Topography of the droplet was obtained until complete evaporation and a detection limit of 165nm was achieved. The accuracy of the method was found by comparing the results obtained with a Bruker White Light Interferometer (Bruker-WLI) in PSI mode. An accuracy of 23% was observed when comparing the height of the droplet with the height obtained using Bruker-WLI. The setup had a repeatability of 14.7nm. Simulations were performed to analyze the effect of filter shape, filter width and the carrier frequency. Based on these findings, steps to measure a droplet-on-grid system with the proposed setup is explained.
We are pleased to invite you to attend the PME-Final MSc presentation on:
Friday 27 September 2019, 13h00
Instruction room I
Mekelweg 2
2628 CD DELFT
13h00 Anirudh Narayanan, specialisation: SOM
Coaches: Dr.ir. J.F.L. Goosen, Prof.dr.ir. A. van Keulen
Title: Design of a flapping wing for application in Micro Air Vehicles
Micro Air Vehicles are becoming a more prominent research area and have many promising applications in search and rescue, topographical scanning, and many other fields. A subcategory of this, Flapping Wing Micro Air Vehicles, is of particular interest as flapping wing flight is known to posses some characteristics that make it favourable over fixed wing flight in certain conditions. The goal of this study is to understand the processes and wing characteristics that influence lift generation of a flapping wing, and apply the acquired knowledge in an optimization setting to obtain an optimal wing thickness distribution which maximizes effective wing lift. To achieve this, an extensive literature survey was conducted to identify geometrical characteristics of the wing that are known to help maximize wing lift, and loading conditions under which a given wing design must be numerically studied. Using some of the identified parameters and load cases, an optimization problem was formulated and thickness distributions were obtained for two wing planform shapes. The results were compared and discussed, and general patterns were identified which give insight on flapping wing design.
The presentation will be given in English.
13h20 Debate
13h30 End
Attending colloquia is an obligatory part of the curriculum of PME.
The presence of other people who are interested will be appreciated.
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