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The high-power laser diode (HPLD) has witnessed increasing application in space, as the aerospace industry is developing rapidly. To cope with the space environment, optimizing the heat-dissipation structure and improving the heat-dissipation ability via heat conduction have become key to researching the thermal reliability of the HPLD in space environments. Based on a theoretical analysis of the HPLD, a simulation model of the HPLD was constructed for numerical simulation, and it was found that the maximum temperature and thermal resistance of lasers were efficaciously decreased by changing the packaging position of laser bars. The packaging position of the bars and the cutting angle of the microchannel heat sink (MCHS) were determined based on the light-emitting angle of the light-emitting unit and the internal structure of the MCHS. The internal structure of the MCHS was optimized through a single-factor experiment, an orthogonal experiment, and the combination of neural networks and genetic algorithms (GAs), using three key structural parameters, namely the MCHS ridge width, W1, the channel width, W2, and the channel length, L1. After optimization, the performance of the MCHS was obviously improved. Finally, an analysis was carried out on the applicability of the optimized MCHS to bars with a higher power. [ABSTRACT FROM AUTHOR]

The high-power laser diode (HPLD) has witnessed increasing application in space, as the aerospace industry is developing rapidly. To cope with the space environment, optimizing the heat-dissipation structure and improving the heat-dissipation ability via heat conduction have become key to researching the thermal reliability of the HPLD in space environments. Based on a theoretical analysis of the HPLD, a simulation model of the HPLD was constructed for numerical simulation, and it was found that the maximum temperature and thermal resistance of lasers were efficaciously decreased by changing the packaging position of laser bars. The packaging position of the bars and the cutting angle of the microchannel heat sink (MCHS) were determined based on the light-emitting angle of the light-emitting unit and the internal structure of the MCHS. The internal structure of the MCHS was optimized through a single-factor experiment, an orthogonal experiment, and the combination of neural networks and genetic algorithms (GAs), using three key structural parameters, namely the MCHS ridge width, W1, the channel width, W2, and the channel length, L1. After optimization, the performance of the MCHS was obviously improved. Finally, an analysis was carried out on the applicability of the optimized MCHS to bars with a higher power.

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. [ABSTRACT FROM AUTHOR]

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.

As piezoelectric pumps are used in more fields, they are gradually failing to meet the application requirements due to their low output performance. Therefore, improving the output performance of piezoelectric pumps helps to expand their applications. This paper argued that the dynamic load of liquid in the inlet and outlet pipelines was an important factor that weakened the performance of piezoelectric pumps. Therefore, in order to reduce the dynamic load, it was proposed to replace the conventional piezoelectric pump inlet and outlet by an elastic inlet and outlet. After introducing the structure and working principle of elastic inlet and outlet, the mechanism of reducing the dynamic load by elastic inlet and outlet was analyzed. Then, the influence of the elastic cavity height on the performance of the piezoelectric pump was studied from both fluid simulation and theoretical analysis. Finally, several prototypes were made. The effectiveness of the elastic inlet and outlet on improving the performance of the prototype and the effect of the elastic cavity height on the performance of the prototype were tested, respectively. The test results showed that the elastic inlet and outlet effectively improved the flow rate and output backpressure without increasing the maximum output backpressure. The maximum flow rate of the pump system without load was increased by 36%. In addition, the elastic cavity height adversely affected the flow rate and output backpressure of the prototypes, but had no effect on the maximum output backpressure. In summary, the elastic inlet and outlet can effectively increase the output performance of the piezoelectric pump, but the design height should be appropriately reduced.

In order to make the gastrointestinal microrobot (GMR) expand and anchor in the gastrointestinal tract reliably, a novel expanding mechanism of the GMR is proposed in this paper. The overlapping expanding arm is designed to be used to increase the variable diameter ratio (ratio of fully expanded diameter to fully folded diameter) to 3.3, which makes the robot more adaptable to the intestinal tract of different sections of the human body. The double-layer structure of the expanding arm increases the contact area with the intestine, reducing the risk of intestinal damage. The kinematics and mechanical model of the expanding arm are established, and the rigid velocity, rigid acceleration, and expanding force of the expanding arm are analyzed. The elastodynamics model of the expanding arm is established. Through the finite element analysis (FEA), the velocity, acceleration, and the value and distribution of the stress of the expanding arm under elastic deformation are obtained. Based on the elastodynamics analysis, the structure of the expanding arm is optimized. By the structure optimization, the thickness of the expanding mechanism is reduced by 0.4mm, the weight is reduced by 31%, and the stress distribution is more uniform. Through the mechanical test, the minimum expanding force of the expanding mechanism is 1.3 N and the maximum expanding force is 6.5 N. Finally, the robot is tested in the rigid pipeline and the isolated intestine to verify the reliability and safety of the expanding mechanism.

As piezoelectric pumps are used in more fields, they are gradually failing to meet the application requirements due to their low output performance. Therefore, improving the output performance of piezoelectric pumps helps to expand their applications. This paper argued that the dynamic load of liquid in the inlet and outlet pipelines was an important factor that weakened the performance of piezoelectric pumps. Therefore, in order to reduce the dynamic load, it was proposed to replace the conventional piezoelectric pump inlet and outlet by an elastic inlet and outlet. After introducing the structure and working principle of elastic inlet and outlet, the mechanism of reducing the dynamic load by elastic inlet and outlet was analyzed. Then, the influence of the elastic cavity height on the performance of the piezoelectric pump was studied from both fluid simulation and theoretical analysis. Finally, several prototypes were made. The effectiveness of the elastic inlet and outlet on improving the performance of the prototype and the effect of the elastic cavity height on the performance of the prototype were tested, respectively. The test results showed that the elastic inlet and outlet effectively improved the flow rate and output backpressure without increasing the maximum output backpressure. The maximum flow rate of the pump system without load was increased by 36%. In addition, the elastic cavity height adversely affected the flow rate and output backpressure of the prototypes, but had no effect on the maximum output backpressure. In summary, the elastic inlet and outlet can effectively increase the output performance of the piezoelectric pump, but the design height should be appropriately reduced. [ABSTRACT FROM AUTHOR]

In order to make the gastrointestinal microrobot (GMR) expand and anchor in the gastrointestinal tract reliably, a novel expanding mechanism of the GMR is proposed in this paper. The overlapping expanding arm is designed to be used to increase the variable diameter ratio (ratio of fully expanded diameter to fully folded diameter) to 3.3, which makes the robot more adaptable to the intestinal tract of different sections of the human body. The double-layer structure of the expanding arm increases the contact area with the intestine, reducing the risk of intestinal damage. The kinematics and mechanical model of the expanding arm are established, and the rigid velocity, rigid acceleration, and expanding force of the expanding arm are analyzed. The elastodynamics model of the expanding arm is established. Through the finite element analysis (FEA), the velocity, acceleration, and the value and distribution of the stress of the expanding arm under elastic deformation are obtained. Based on the elastodynamics analysis, the structure of the expanding arm is optimized. By the structure optimization, the thickness of the expanding mechanism is reduced by 0.4mm, the weight is reduced by 31%, and the stress distribution is more uniform. Through the mechanical test, the minimum expanding force of the expanding mechanism is 1.3 N and the maximum expanding force is 6.5 N. Finally, the robot is tested in the rigid pipeline and the isolated intestine to verify the reliability and safety of the expanding mechanism. [ABSTRACT FROM AUTHOR]