| In this paper,piezoelectric control method of noninvasive ultrasonic transdermal drug delivery system is studied in order to improve the accuracy and efficiency of drug delivery,aiming at the demand of precise drug delivery method for patients with drug-dependent chronic diseases.A multi-field coupling model of sound-liquid-solid-heat in the process of ultrasonic transdermal drug delivery in in vitro is established by finite element method.Analyzing a promotion of permeation mechanism of noninvasive transdermal drug delivery of low frequency ultrasound and presenting a pressure control strategy combining a lead screw linear ultrasonic motor and an ultrasonic transducer.A prototype of low frequency ultrasonic transdermal drug delivery device is developed.Also,a feasibility of the pressure parameter control method is verified and the accuracy control of low-frequency sonophoresis is realized.In addition,an ultrasonic transdermal drug delivery positioning device is constructed with a legged robot based on piezoelectric bending actuators and the ultrasonic transducer,which is suitable for fixed-point ultrasonic drug delivery operation in in vitro.The main contents of this paper are as follows:1.A simulating calculation of coupling model of sound-liquid-solid-heat in the process of noninvasive ultrasonic transdermal drug delivery is established.This model can effectively predict the temperature change in the system by calculating the vector cloud diagram of sound field and flow field in the system combining with thermodynamic equilibrium equation,so as to ensure that the temperature rise in the ultrasonic transdermal drug delivery can meet the clinical safety requirements(? 43 ?).Theoretical and experimental results show that the ultrasonic transducer driven by the voltage of 40 V0p(21 k Hz)can decrease the maximum temperature in the system from 54.0 ? to 43.0 ? by duty ratio control method.At the same time,the permeability remains stable at 0.018 ?Mol/min within 90 min,achieving the objective of drug permeability optimization at clinical safety temperature.2.The influence law of different factors on the drug permeability is analyzed and the sensitivity of pressure to the drug permeability is theoretically and experimentally obtained.Based on this,a novel ultrasonic transdermal drug delivery system combining an ultrasonic transducer and an ultrasonic motor is proposed.The fluid pressure is continuously controlled by adjusting the driving voltage amplitude and duty ratio of the ultrasonic motor to meet the permeability control requirements of low-frequency sonophoresis in in vitro and control resolution achieves 0.07 ?Mol/min.3.A legged robot based on piezoelectric bending actuators is designed.Its length,width and height are 35 mm × 30 mm × 9 mm,and its mass is 9 grams.It can realize straight line and turning movement,the maximum speed can reach 330 mm/s,and the minimum turning radius is 102 mm.The load can reach 55 grams at a speed of 20 mm/s,while the ultrasonic transducer used in the experiment is only 1.8 grams.In the motion precision control experiment,which is similar to "Reverse Parking",the positioning error of it is less than 0.5 cm through the program design of Labview.Therefore,the function of precise positioning of ultrasonic transdermal drug delivery is preliminarily realized. |
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