New low-frequency ultrasound penetration instrument design (1)

Transdermal drug delivery system in the medical field has become a new and important tool.

Transdermal drugs through the skin and the capillary absorption into the systemic circulation produces effects in such a way that it can avoid the first pass effect on the liver, extended half-life shorter drug therapy, can be a long time to maintain a constant speed of delivery, and therefore are subject to extensive attention. In fact as early as 1954 Fellinger. And Schmidt, through ultrasound import hydrocortisone cream successfully treating a finger of multiple arthritis. Initially on ultrasound antireflection effect begins at the intermediate frequency therapy with ultrasound (0.7 ~ 3.0 MHz), but later found that low-frequency ultrasound of antireflection effect is better. Research shows that different frequency and intensity ultrasound on the body's role is different, and secondly, the temperature for transdermal delivery also has certain effects, such as certain temperature can increase penetration rate, but too high a temperature can cause skin burns, because there are thermal effect of ultrasound; therefore, how the various factors taken into account in order to achieve both guarantee a higher penetration rate and avoid human body burns and physiological function of injury is one of the difficulties of the study.

SCM as a smart control chip, electronic information, automatic control of all areas play an extremely important role.

Medical device design and development of more and more application-chip technology to advance towards the miniaturization of intelligent,. Comprehensive consideration of various factors, this introduces a high-performance single-chip C8051F340 as core control chip transmission frequency, intensity, adjustable, controllable temperature of low-frequency ultrasound and transdermal system.

1 hardware design

The system includes: temperature measurement and control modules, high power ultrasonic generator, constant temperature control module, overcurrent protection module, display modules and power-off enclosure.

The overall structure as shown in Figure 1.

System part of the work is made of high-performance MCU controlled coordinate C8051F340.

It is the core of the entire system. SCM is integrated in C8051F340 a chip-chip mixed system level. With 8051 instruction set fully compatible CIP-51 kernel, using the line command structure, its operating speed of up to 48 MIPS, compared with standard 8051, in the same clock cycle of instruction is run under a single rate of the original 12 times. And, it's a chip integrates a single-chip data acquisition and control system required features; analog multiplexer, programmable gain amplifier, ADC, voltage comparator, voltage reference, temperature sensors, SMBus/I2C, SPI, UART, USB programmable counter/timer array (PCA), timer, I/O ports, internal oscillator, watchdog timer and power monitors, and so on almost all analog and digital peripherals and other features. Programming by C8051F340, you can implement more than one function.

The system uses keyboard input circuit to obtain the operational staff on the part of the conditions of work, on the basis of these requirements on the heating wires and ultrasound emission set, at the same time in every time and control during all parts of the temperature values sent to display LCD, and the audio and judgment, when the temperature with the audio beep alarm circuit starts.

Temperature control with power control electric wire heating makes experimental process to maintain constant temperature, including temperature reading, the temperature value of processing and output signal driver load.

1.1 temperature measurement and control modules