On-Chip Micro Mixer Driven by Elastic Wall with Virtual Actuator

Influence of Structural Parameters on the Performance of an Asymmetric Rhombus Micromixer with Baffles

As an important part of lab-on-a-chip and micro-total analysis systems, micromixers have a wide range of applications in biochemical analysis, pharmaceutical preparation and material synthesis. In the work, a novel rhombic separation and recombination micromixer with baffles was presented to further improve the performance of the micromixer and study the effect of multiple structural parameters on mixing. The effects of the rhombic angle, the width ratio of sub-channel and the size and relative positions of baffles on the mixing index were studied numerically at different Reynolds numbers (Re), and the sensitivity of the mixing index to various structures was also investigated. The results showed that the mixing index increased with the subchannel's width ratio and slowly decreased after reaching the peak value in the range of Re from 0.1 to 60. The maximum mixing index appeared when the width ratio was 6.5. The pressure drops in the microchannel were proportional to the width ratio. The mixing effect can be further improved by adding baffle structure to asymmetric rhombus micromixer, and more baffle quantity and larger baffle height were beneficial to the improvement of the mixing index. The research results can provide reference and new ideas for the structure design of passive micromixers.

Modeling and Analysis of a High-Speed Adjustable Grasping Robot Controlled by a Pneumatic Actuator

This paper discusses the modeling and analysis of a high-speed adjustable grasping robot controlled by a pneumatic actuator. The robot is composed of two grippers, two wires for connecting a pneumatic cylinder and an arm with gripper joints with a spring as well as two stoppers for controlling the gripper stopping point with a brake. By supplying pressurized air into the pneumatic cylinder, the two grippers move forward together with the arm and capture the object by adjusting the air pressure in the cylinder. After capturing the target object, the system can release the object by changing the pressure air in the air cylinder using another port. By considering the state equation of the air, we obtain a dynamic model of the robot, including the actuator. Through numerical simulation, we show that the simulation results can explain the experimental results from the developed robot system. Through our experiments, we confirm that the developed high-speed grasping robot can grasp continuously moving objects with a gap of ±15 mm at 300 mm/s.

Generation of Concentration Gradients by a Outer-Circumference-Driven On-Chip Mixer

The concentration control of reagents is an important factor in microfluidic devices for cell cultivation and chemical mixing, but it is difficult to realize owing to the characteristics of microfluidic devices. We developed a microfluidic device that can generate concentration gradients among multiple main chambers. Multiple main chambers are connected in parallel to the body channel via the neck channel. The main chamber is subjected to a volume change through a driving chamber that surrounds the main chamber, and agitation is performed on the basis of the inequality of flow caused by expansion or contraction. The neck channel is connected tangentially to the main chamber. When the main chamber expands or contracts, the flow in the main chamber is unequal, and a net vortex is generated. The liquid moving back and forth in the neck channel gradually absorbs the liquid in the body channel into the main chamber. As the concentration in the main chamber changes depending on the pressure applied to the driving chamber, we generated a concentration gradient by arranging chambers along the pressure gradient. This allowed for us to create an environment with different concentrations on a single microchip, which is expected to improve observation efficiency and save space.