In the never-ending quest for miniaturization, optically controlled particle trapping has opened up new possibilities for handling microscopic matter non-invasively. This thesis presents the application of photorefractive crystals as active substrate materials for optoelectronic tweezers. In these tweezers, flexible optical patterns are transformed into electrical forces by a photoconductive material, making it possible to handle matter with very high forces and high throughput. Potential substrate materials’ properties are investigated and ways to tune their figures-of-merit are demonstrated. A large part of the thesis is devoted to potential applications in the field of optofluidics, where photorefractive optoelectronic tweezers are used to trap, sort and guide droplets or particles in microfluidic channels, or to shape liquid polymers into optical elements prior to their solidification. Furthermore, a new surface discharge model is employed to discuss the experimental conditions needed for photorefractive optoelectronic tweezers.
In the never-ending quest for miniaturization, optically controlled particle trapping has opened up new possibilities for handling microscopic matter non-invasively. This thesis presents the application of photorefractive crystals as active substrate materials for optoelectronic tweezers. In these tweezers, flexible optical patterns are transformed into electrical forces by a photoconductive material, making it possible to handle matter with very high forces and high throughput. Potential substrate materials’ properties are investigated and ways to tune their figures-of-merit are demonstrated. A large part of the thesis is devoted to potential applications in the field of optofluidics, where photorefractive optoelectronic tweezers are used to trap, sort and guide droplets or particles in microfluidic channels, or to shape liquid polymers into optical elements prior to their solidification. Furthermore, a new surface discharge model is employed to discuss the experimental conditions needed for photorefractive optoelectronic tweezers.
This book offers the reader sound advice on how to perform optimal conventional pediatric radiographs and how to obtain quick and easy organ dose estimates in order to improve the optimization process in pediatric imaging. Clear guidelines are provided for minimization of the radiation exposure of children through optimization of the radiation exposure conditions, and conversion coefficients are presented for calculation of the organ doses achieved in organs and tissues during conventional pediatric radiography, taking into consideration both optimal and suboptimal radiation field settings. Previously published conversion coefficients have failed to represent the variation in radiation field settings in daily clinical routine, which has made it difficult for the pediatric radiologist to estimate the impact of the field settings on absorbed doses in organs and tissues. The aim of this book, co-written by a pediatric radiologist, a physician and physicist, and a medical radiation technologist, is to address this issue by providing, for the first time, a thorough overview of clinical radiation field settings and their implications for radiation protection. An accompanying volume is devoted to fluoroscopy.
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