Machine Vision Based Measurement of Dynamic Contact Angles in Microchannel Flows

When characterizing flows in miniaturized channels, the determination of the dynamic contact angle is important. By measuring the dynamic contact angle, the flow properties of the flowing liquid and the effect of material properties on the flow can be characterized. A machine vision based system to measure the contact angle of front or rear menisci of a moving liquid plug is described in this article. In this research, transparent flow channels fabricated on thermoplastic polymer and sealed with an adhesive tape are used. The transparency of the channels enables image based monitoring and measurement of flow variables, including the dynamic contact angle. It is shown that the dynamic angle can be measured from a liquid flow in a channel using the image based measurement system. An image processing algorithm has been developed in a MATLAB environment. Images are taken using a CCD camera and the channels are illuminated using a custom made ring light. Two fitting methods, a circle and two parabolas, are experimented and the results are compared in the measurement of the dynamic contact angles.

Enhancing synchronizability by rewiring networks

According to different forms of synchronized region, complex networks are divided into type Ⅰ （unbounded synchronization region） and type Ⅱ （bounded synchronization region） networks. This paper presents a rewiring algorithm to enhance the synchronizability of type Ⅰ and type Ⅱ networks. By utilizing the algorithm for an unweighted and undirected network, a better synchronizability of network with the same number of nodes and edges can be obtained. Numerical simulations on several different network models are used to support the proposed procedure. The relationship between different topological properties of the networks and the number of rewirings are shown. It finds that the final optimized network is independent of the initial network, and becomes homogeneous. In addition the optimized networks have similar structural properties in the sense of degree, and node and edge betweenness centralities. However, they do not have similar cluster coefficients for type Ⅱ networks. The research may be useful for designing more synchronizable networks and understanding the synchronization behaviour of networks.

Event-Triggered Sampled-Data Consensus of Nonlinear Multi-Agent Systems with Control Input Losses

This paper investigates the leader-following consensus problem for multi-agent systems with event-triggered mechanism and control packet losses.Based on the local synchronization error, event-triggered mechanisms are proposed in order to reduce the number of controller update.The control packet may lose due to unreliability of communication channel.With the assumption that once the packet loss happens the controller will be set to zero,sufficient consensus criteria for multi-agent system with event-triggered mechanism and control packet losses is obtained.It is also shown that the interplay among the allowable packet loss rate,event-triggered mechanism and sampling period.An illustrative example is given to demonstrate the effectiveness of the theoretical results.

Structured PDMS Chambers for Enhanced Human Neuronal Cell Activity on MEA Platforms

Structured poly（dimethylsiloxane） （PDMS） chambers were designed and fabricated to enhance the signaling of human Embryonic Stem Cell （hESC） - derived neuronal networks on Microelectrode Array （MEA） platforms. The structured PDMS chambers enable cell seeding on restricted areas and thus, reduce the amount of needed coating materials and cells. In addition, the neuronal cells formed spontaneously active networks faster in the structured PDMS chambers than that in control chambers. In the PDMS chambers, the neuronal networks were more active and able to develop their signaling into organized signal trains faster than control cultures. The PDMS chamber design enables much more repeatable analysis and rapid growth of functional neuronal network in vitro. Moreover, due to its easy and cheap fabrication process, new configurations can be easily fabricated based on investigator requirements.