Papers by Author: Xiong Biao Chen

Abstract: Tissue scaffolds play a vital role in tissue engineering by providing a native tissue-mimicking environment for cell proliferation and differentiation as well as tissue regeneration. Fabrication of tissue scaffolds has been drawing increasing research attention and a number of fabrication techniques have been developed. To better mimic the microenvironment of native tissues, novel techniques have emerged in recent years to encapsulate cells into the engineered scaffolds during the scaffold fabrication process. Among them, bio-Rapid-Prototyping (bioRP) techniques, by which scaffolds with encapsulated cells can be fabricated with controlled internal microstructure and external shape, shows significant promise. It is noted in the bioRP processes, cells may be continuously subjected to environmental stresses such as mechanical, electrical forces and laser exposure. If the stress is greater than a certain level, the cell membrane may be ruptured, leading to the so-called process-induced cell damage. This paper reviews various cell encapsulation techniques for tissue scaffold fabrication, with emphasis on the bioRP technologies and their technical features. To understand the process-induced cell damage in the bioRP processes, this paper also surveys the cell damage mechanisms under different stresses. The process-induced cell damage models are also examined to provide a cue to the cell viability preservation in the fabrication process. Discussions on further improvements of bioRP technologies are given and ongoing research into mechanical cell damage mechanism are also suggested in this review.

Abstract: Motor plays an important role in the dynamic property of the rotary-screw-driven dispensing system. Dynamic model of the motor was developed and validated in this paper. The output angle displacement and input voltage were measured from photoelectric digital encoder which is used to measure the angle displacement of the motor. In order to realize data smooth processing, Alpha-Beta filter was used. Discrete model of the motor was developed based on the Least Square Method and Model Selection criterion. Computational studies show that the system is equivalent to second order system. Moreover, the model was validated based on the experiment results under the different applied pressure and angular speed of motor. It is revealed that there is a good fit between experiment data and model simulation.

Abstract: In nerve tissue engineering, scaffolds act as carriers for cells and biochemical factors and as constructs providing appropriate mechanical conditions. During nerve regeneration, new tissue grows into the scaffolds, which degrade gradually. To optimize this process, researchers must study and analyze various morphological and structural features of the scaffolds, the ingrowth of nerve tissue, and scaffold degradation. Therefore, visualization of the scaffolds as well as the generated nerve tissue is essential, yet challenging Visualization techniques currently used in nerve tissue engineering include electron microscopy, confocal laser scanning microscopy (CLSM), and micro-computed tomography (micro-CT or μCT). Synchrotron-based micro-CT (SRμCT) is an emerging and promising technique, drawing considerable recent attention. Here, we review typical applications of these visualization techniques in nerve tissue engineering. The promise, feasibility, and challenges of SRμCT as a visualization technique applied to nerve tissue engineering are also discussed.

Abstract: The functionality of tissue scaffolds in vivo plays a critical role in the treatment process. Due to the time dependent nature of the mechanical properties of the constituent phases of the scaffold, a wide range of mechanical property histories may be observed during the treatment process, possibly influencing outcomes. The critical nature of the mechanical properties in load bearing applications indicates a need for the simultaneous modelling of both scaffold degradation and tissue regeneration with time, and the resulting effective properties of the tissue engineering construct. To this end, a review of the literature is conducted to identify the various existing approaches to modelling scaffold degradation, tissue behavior, and the dependency of the two processes on one another.

Abstract: Piezoelectric-driven stick-slip actuators have been drawing extensive attention for applications in the fields of scanning microscopy, micro robotics, and microsystems due to their well-defined step size and theoretically-unlimited displacement. In such an actuator, the dynamics of the end-effector displacement is of importance for its control and optimal design, yet challenging to be modeled due to the complexity involved. By taking into account the dynamics of piezoelectric element and the presliding friction acting on the end-effector, a model representative of the end-effector displacement is presented in this paper. The effectiveness of the developed model is illustrated by the experiments on the piezoelectric-driven stick-slip actuator prototyped in the authors’ lab.