Research On Micro Piezoelectric Driving System Applied To Drug Delivery

In the traditional endoscopic surgery for tumor and polypus,the method of surgical excision is extremely risky on condition that the focus of infection is located near some vital arteries,and the radiotherapy and chemotherapy also have many terrible side effects.With the development of ultrasound technique,a treatment method of targeted drugs delivery to the focus can be realized by the technology of sonophoresis.Due to the tiny size of biopsy channel in the endoscope,the driving equipment of micro ultrasonic transducer is required.Therefore,an injection system for the dose controlling and a biped actuator for the transducer driving are proposed,fabricated,and tested in this paper.The main contents are as follows:1.A lead linear ultrasonic motor is designed as the driving element of the injection system with the size of 4 mm × 4 mm × 15 mm.In flow velocity experiments,the voltage and duty factor of driving signal can be used to accurately control the flow speed.Without any speed reducer,the flow velocity can be adjusted from 0.01μL/s to 61.87μL/s,which demonstrates that its precision is better than traditional injection pumps whose minimum flow velocity is 0.028μL/s.2.To drive a micro ultrasonic transducer for the drug delivery in the biopsy channel of an endoscope,a biped piezoelectric actuator is designed,fabricated and tested.It has a weight of only 0.135 g with package size of 6 mm × 2 mm × 2 mm.Operating at the second order out-of-plane flexural vibration mode,this actuator is able to realize a linear movement on demand,and its principle can be calculated and proved by a finite element method.In addition,a preload control method of the actuator is proposed based on magnetic field,which can effectively enhance the performance including its velocity and drag force.Experimental results show that the maximum velocity and drag force of the actuator can reach up to 200 mm/s and 10 mN,respectively.The velocity can be smoothly adjusted over a range of 0.15 mm/s to 200 mm/s,and its startup time is as quick as 6 ms.3.The size of biped piezoelectric actuator is further reduced in order to be installed with a permanent magnet in the biopsy channel of an endoscope.The shrunken actuator has a weight of only 0.063 g with size of 4.5 mm × 1.5 mm × 1.5 mm.A magnetic track is designed and installed in the biopsy channel of an endoscope with the actuator.Experimental results demonstrate that the maximum velocity of the shrunken actuator is 168 mm/s on the magnetic track,which proves that the actuator can work in endoscopy on demand.