Fabrication and tracking of Artificial Bacterial Flagella using stereo holographic diffraction

Abstract: The emerging eld of mobile microrobotics has been suggestive of a plethora ofapplications, from intelligent micromanipulation to diversifying the prospects ofminimally invasive surgeries. Several designs of microrobots have been proposedand are being notoriously studied to enhance the knowledge of their behaviorin dierent environments to cater such applications. At present, control andsurveillance of these microrobots have been aided by the convergence of varioustechnologies like magnetic actuation, microscopy and computer vision. Thequintessential knowledge of their maneuverability could provide interesting implicationsof these microrobots in their targeted applications.In context of widening this understanding of their behavior, several dexterousmethods have been proposed to study and control these microrobots, employingmicroscopy in stereo vision for visual surveillance. The intuitive drawbackof microscopy, jeopardizing its focusing accuracy against eld of imaging, haslimited these studies to smaller observable volumes. Addressing limitations ofconventional microscopy, holography has been explored as a potential candidatefor imaging and spatial tracking of these microrobots by means of reconstructing2-D information in the images. However, the resolution of depth estimation andprocessing cost incurred in reconstruction posed drawbacks on its applicability.The novel method proposed in this report, employed the holographic imaging instereo vision, overcoming the limitations of both conventional microscopy andholographic reconstruction. The cost of processing this image information at amuch lower processing speeds further benchmarked its candidature for spatialtracking of microrobots. The inventive setup design proposed in the report wasinspired by conventional stereo vision. It also entails the tracking procedure ofa class of agellated microrobots called Articial Bacterial Flagella (ABF) basedon retrieval of its two diraction based holograms, and estimating its 3-D positionbased on lateral positions in the two stereo projections. It further suggestsfeasible design metrics for fabrication of these ABFs based on Fresnel diraction.The central idea behind this 3-D estimation proposed here is based on processingdiraction pattern produced by the ABFs using an image segmentation algorithmand further projecting the lateral coordinates so obtained to real space, achievingmuch more nesse over the depth resolution in either direction.