Enhancing cell infiltration of electrospun fibrous scaffolds in tissue regeneration

AbstractElectrospinning is one of the most effective approaches to fabricate tissue-engineered scaffolds composed of nano-to sub-microscale fibers that simulate a native extracellular matrix. However, one major concern about electrospun scaffolds for tissue repair and regeneration is that their small pores defined by densely compacted fibers markedly hinder cell infiltration and tissue ingrowth. To address this problem, researchers have developed and investigated various methods of manipulating scaffold structures to increase pore size or loosen the scaffold. These methods involve the use of physical treatments, such as salt leaching, gas foaming and custom-made collectors, and combined techniques to obtain electrospun scaffolds with loose fibrous structures and large pores. This article provides a summary of these motivating electrospinning techniques to enhance cell infiltration of electrospun scaffolds, which may inspire new electrospinning techniques and their new biomedical applications

Cogging torque and torque ripple reduction of a novel exterior-rotor geared motor

The reduction of cogging torque and torque ripple in permanent-magnet motors to suppress the vibration and acoustic noise is a major concern for motor designers. This study presents a novel exterior-rotor geared motor which integrates a brushless permanent-magnet (BLPM) motor with an epicyclic-type gear reducer to form a compact structural assembly without extra transmitting elements. One of the special features of the geared motor lies in the gear-teeth of the epicyclic-type gear reducer merged with the stator of the BLPM motor. The gear-teeth serve as the interfacial medium to connect the BLPM motor with the epicyclic-type gear reducer, which provides functions not only for transmission to achieve a desired speed ratio, but also effectively reduce the cogging torque and torque ripple of the geared motor. Five shape models of pole shoes with different values of the shoe depth and the shoe ramp are presented to effectively reduce the cogging torque and the torque ripple. With the aid of the finite-element analysis, shape model III of the geared motor performs better than the existing BLPM motor on the cogging torque with 87 % decreasing and the torque ripple with 23 % decreasing. Such a unique characteristic of the geared motor is of benefit to the widely applications on accurate motion and position control systems