Micropillar arrays are used to measure traction forces of individual cells and of cells in tissue. For this technique single cells are placed on poly-di-methyl siloxane (PDMS) micropillar arrays...Show moreMicropillar arrays are used to measure traction forces of individual cells and of cells in tissue. For this technique single cells are placed on poly-di-methyl siloxane (PDMS) micropillar arrays and observed on an inverted high-resolution optical microscope. As of the requirements for a high-resolution inverted microscopy, the images of the micropillar array are taken through the cell.A refractive index change between the cell and cell medium results in refraction of light at their interface. Here we introduce a method to characterize astigmatism caused by this varying refractive index. We found that that astigmatism can lead to aberrations up to 400 nm. Further, based on the same method we were able to estimate the refractive index of the nucleus to be $1.366\pm0.004$. Our results demonstrate that astigmatism should be taken into account during traction force measurements, especially when measuring forces close to the nucleus.Show less
This work explores the design, synthesis and actuation of temperature sensitive hydrogel-elastomer bilayers. Following previous research we created a protocol to graft poly-N-isopropylacrylamide ...Show moreThis work explores the design, synthesis and actuation of temperature sensitive hydrogel-elastomer bilayers. Following previous research we created a protocol to graft poly-N-isopropylacrylamide (PNIPAM) on top of a rubber substrate. These bilayers can be bent by changing the temperature of the system using a heat bath. Novel bilayers are designed where a mechanical instability is introduced. None of the designed instabilities are triggered during actuation, instead the bilayers bend in a different direction.Show less
In medical imaging, model observers are used to define a new method of task based image quality assessment. In this thesis a novel search algorithm is presented that detects possible lesions in a...Show moreIn medical imaging, model observers are used to define a new method of task based image quality assessment. In this thesis a novel search algorithm is presented that detects possible lesions in a digital anthropomorphic 2D and 3D lung phantoms and defines the detectability of the candidate lesions using a non-prewhitening matched filter with an eye filter (NPWE) model observer. Sets of phantom images were simulated for a range of noise levels and two types of noise (Gaussian white noise and CT-like noise). The candidate lesions were classified as true positives and false positives. A proof of concept study showed promising results in the detectability trends the search algorithm described. The trends showed that with increasing noise levels the detectability of true positives decreased. When comparing the detectability indexes of the true positives and false positives, the differences between them became smaller for increasing noise levels. In the future, the algorithm can be applied to the analysis of real CT scans of a lung phantom containing lesions, and used to obtain Free Response Operating Characterisic (FROC) curves.Show less
