Highly parallel microscale force measurement device for mechanically directed cell growth

In this dissertation a novel method to measure micro-nano Newton forces in parallel was presented. An array of PDMS microbeams with diameters of 10--40 mum and lengths of 118--250 mum was fabricated for parallel force measurement. The highly compliant, transparent, biocompatible PDMS microbeam array offers a method for rapid throughput in cell mechanics force measurement experiments with sensitivities necessary for highly compliant structures such as axons. Force is measured using a combination of beam theory, optical microscopy, and image analysis. The primary instrument is a calibrated polymeric microbeam array mounted on a micromanipulator with the eventual purpose of measuring traction forces on cell arrays. The elastic modulus of a 20%-curing ratio PDMS array was measured with the designed device. An Otsu-based image analysis code was developed and calculates displacement and force on cellular or other soft structures by using edge detection and image subtraction on digitally captured optical microscopy images. Forces as small as 250 nN +/- 50 nN and as great as 25 muN +/- 2.5 muN may be applied and measured upon as few as one or as many as hundreds of structures in parallel. As an enabling technology, two different methods of protein printing, dip-pen and microcontact printing, for arraying neurons were also employed. The eventual goal of the device being force measurements on cells, the initial results on forebrain neurons are also presented. This work has two endpoints. One is to use a neural array as an experimental test bed for investigating neuronal cell growth hypotheses. The other endpoint is to enable the next generation of cell based sensors.