Contact assembly of cell-laden hollow microtubes through automated micromanipulator tip locating

Abstract

This paper presents an automated contact assembly method to fabricate a cell-laden microtube based on accurate locating of the micromanipulator tip. Essential for delivering nutrients in thick engineered tissues, a vessel-mimetic microtube can be precisely assembled through microrobotic contact biomanipulation. The biomanipulation is a technique to spatially order and immobilize cellular targets with high precision. However, due to image occlusion during contact, it is challenging to locate the micromanipulator tip for fully automated assembly. To achieve pixel-wise tracking and locating of the tip in contact, a particle filter algorithm integrated with a determined level set model is employed here. The model ensures precise convergence of the micromanipulator’s contour during occlusion. With the converged active contour, the algorithm is able to pixel-wisely separate the micromanipulator from the low-contrast background and precisely locate the tip with error around 1 pixel (2 µm at 4 × magnification). As a result, the cell-laden microtube is automatically assembled at six layers/min, which is effective enough to fabricate vessel-mimetic constructs for vascularization in tissue engineering.

Advanced medical micro-robotics for early diagnosis and therapeutic interventions

“…Tethered micro-robotic systems are effective tools for micro-assembly tasks, since they can ensure high precision and flexibility compared to manual operation methods. For example, a system with two tethered micro-tools has been developed to automatically grasp micro-modules to achieve bottom-up assembly of cell-laden hollow micro-tubes, which can also be used to construct other biomimetic structures with micro-structural features ( Wang et al., 2016 ). A seven DoFs haptic interface was used to control the motions of the tethered micro-tools remotely, which can ensure safety during the micro-manipulation and enhance efficiency by providing intuitive haptic feedback to the operator ( Feng et al., 2022 ).…”

A Review of Computer Microvision-Based Precision Motion Measurement: Principles, Characteristics, and Applications

“…Consequently, the silhouette of the nonrigid topology-varying target can be precisely computed from one image to another in the image sequence. Multiple improvements based on active contour models have also been developed, which can greatly enhance the accuracy, efficiency, and robustness [143], [145], [146]. After the target silhouette is matched in the image sequence, the optical flow estimation can be applied, and the silhouette motion is confirmed by the dominant flow according to the calculation.…”

“…Contour tracking results in red with the occlusion situation for the moving target (tip of the micromanipulator). Reproduced from[143] with the permission from IOP Publishing.…”

New Perspectives in Liver Transplantation: From Regeneration to Bioengineering

“…Scaffolds containing biodegradable polymers, such as polylactic acid, polyglycolic acid, polyanhydrides, polyfumarates, polyorthoesters, polycaprolactones, poly-L-lactic acid, and polycarbonates facilitate cell regeneration, transplantation, and degradation on time [130]. The biocompatibility of bioengineered matrices and scaffold adhesion properties could also be improved by chemically modifying these polymers (e.g., by incorporating proteins and special bioactive domains), stimulating cell attachment and migration, and thereby facilitating liver tissue repair [131].…”