ABSTRACT
A novel composite control method for actuated chamber air pressure of pneumatic microfluidic chip via a three-way electromagnetic microvalve is presented in this paper. The purpose of the control methods is to improve air pressure controlling precision for pneumatic control. By using the Bang-Bang (on-off) controller for pneumatic control, the step-response time, air pressure steady-state accuracy, and air pressure fluctuations are performed with different maximum thresholds and minimum thresholds. Moreover, by using the k (proportional ) plus PWM (Pulse-Width Modulation) control method for pneumatic control, the step-response time, air pressure steady-state accuracy, and air pressure fluctuations are performed with different carrier frequencies and carrier amplitudes. Both advantages and disadvantages of the two control methods are compared and analyzed based on the experimental data. According to the variable volume of the actuated chamber and the response characteristics of the three-way electromagnetic microvalve, the composite control method of the Bang-Bang plus k plus PWM is developed to control the actuated chamber air pressure. The experimental results show that when the absolute air pressure of the actuated chamber is set to 150kPa, the rising time is 69.3ms, which is about 8.0ms shorter than that of the k+PWM control method alone. The steady-state error is reduced from 0.90kPa to 0.65kPa, and the air pressure steady-state fluctuation is reduced from 1.60kPa to 0.90kPa, compared with the Bang-Bang control method alone.
Subject(s)
Electromagnetic Phenomena , MicrofluidicsABSTRACT
OBJECTIVE: Rheumatoid wrist arthritis is a chronic autoimmune disease, resulting in joint deformity and functional impairment. We aimed to compare the wrist synovial ultrasound indices and serum vascular endothelial growth factor (VEGF) level in patients with RA before and after treatment, and to explore the correlation between the two. METHODS: Forty patients with RA in wrist underwent ultrasound examination to determine wrist synovial thickness, synovial blood flow grade, and synovial artery resistive index (RI) before and after treatment. The serum level of VEGF was detected by enzyme-linked immunosorbent assay. Correlation between synovial ultrasound indices and serum VEGF level was assessed. RESULTS: Pre-treatment synovial thickness, synovial artery RI, and serum VEGF level were 8.60 ± 2.82 mm, 0.62 ± 0.07, and 419.49 ± 19.27 pg/mL, respectively. The corresponding post-treatment levels were 4.05 ± 1.89 mm, 0.83 ± 0.10, and 199.30 ± 16.18 pg/mL. Pre-treatment distribution of synovial blood flow grades was as follows: grade 0, nil; grade I, 1 case; grade II, 17 cases; grade III, 22 cases. The post-treatment distribution was as follows: grade 0, 6 cases; grade I, 23 cases; grade II, 11 cases; and grade III, nil. There were significant differences between pre- and post-treatment wrist synovial thickness, artery RI, and blood flow grading. Wrist synovial thickness and synovial blood flow grade showed a strong positive correlation with serum VEGF level (P < 0.01). There was strong negative correlation between wrist synovial artery RI and serum VEGF level (P < 0.01). CONCLUSION: The strong correlation between wrist synovial ultrasound indicators and serum VEGF may be clinically useful for diagnosis and therapy.
