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When performing endoluminal surgery inside the colon using a flexible endoscopic robot, there is a problem of losing visualization and task space due to the collapsing of the surrounding wall. This happens mainly because of the intra-abdominal pressure and peristalsis of the colon. Although insufflation is commonly used for expanding the colon, it does not function when a full-thickness incision is created on the colon wall. To support the collapsing colon and ensure sufficient visualization and task space even with a hole, we developed a deployable colon support structure (CSS) that can be seamlessly adapted to the existing procedures. While the CSS is designed to be small and flexible enough to pass through an endoscopic channel that can be tortuous, it becomes steady enough to hold the collapsing/squeezing colon after being deployed. Also, the CSS is collapsible after task completion, for retraction through an endoscopic channel. Through the ex-vivo and in-vivo studies with a swine, we have successfully demonstrated the feasibility of supporting the colon wall during endoluminal interventions with the CSS. We confirmed that the CSS was easily deliverable and deployable and the created space was large enough to perform surgical tasks using robotic arms. National Research Foundation (NRF) Published version This work was supported by the National Research Foundation (NRF) Singapore under Grant NRFI2016-07

Liquid crystals (LCs) composed of mesogens play important roles in various scientific and engineering problems. How a system with many mesogens can enter a LC state is an interesting and important problem. Using stiff and free-joint Lennard-Jones chain molecules as mesogens, we study the conditions under which the mesogens can enter various LC phases. The guideline is to eliminate the unwanted translational orders under a controlled fine-tuning procedure across a sequence of systems. Instead of monitoring the growth of order out of the disorder, we prepare a configuration of high orientation ordering and find out where it relaxes to. Such a procedure begins with a reference system, consisting of short chains of homogeneous soft spheres, in a liquid-vapor coexistence situation, at which the thermodynamic instability triggers a fast spontaneous growing process. By applying a short pulse of auxiliary field to align the dispersedly oriented clusters, followed by reducing the volume and, finally, changing the homogeneous molecules into heterogeneous chains, we are able to obtain a range of systems, including nematic and smectic LCs, at their stable ordered states. The model can be extended to study the influence of nanoparticles or external field on the LC structure., Comment: 20 pages, 9 figures

As a meta-heuristic approach, Ant colony optimization (ACO) has many applications. In the algorithm selection of pheromone models is the top priority. Selecting pheromone models that don't suffer negative biases is a natural choice. Specifically for the travelling salesman problem, the first order pheromone is widely recognized. When come across travelling salesman problem, we study the reasons for the success of ant colony optimization from the perspective of pheromone models, and unify different order pheromone models. In tests, we have introduced the concept of sample locations and the similarity coefficient to pheromone models. The first order pheromone model and the second order pheromone model are compared and are further analysed. We illustrate that the second order pheromone model has better global search ability and diversity of population than the former. With appropriate-scale travelling salesman problems, the second order model performs better than the first order pheromone model.