3-Way Syringe Mixer Capstone

Hello, and welcome the our team's capstone page.

Currently this website in under construction and will be added to as the project moves foreward. In the meantime here is some information that we have available to you right now.

Project Description

In society today, most if not all medical procedures have some sort of automation to them, however most syringe mixing procedures are still done by hand.  Due to the recent focus of treating aneurysms using a liquid embolic method for filling and removing the aneurysm within a vessel, there has been a higher demand for an automated mixing system. As of this report there is no recorded existence of an automated three way mixer.  While the process of understanding how the syringes are mixed is not complicated, the amount of factors that need to be monitored or regulated during the process is what makes the design cumbersome. Due to the recent development of the PPODA-QT liquid embolic treatment, there is no known precise flow rate or energy requirement for the liquids to mix properly.

Our team has been tasked with the creation of an automated mixing system which will interface with syringe models already in existence. The user will set the t-jointed syringe configuration, holding 3 syringes, into our design. After the syringes are placed within the device the user will be able to input the duration of time that the device should take when mixing the liquids which will effect what flow rates the mixing occurs at. By including user input, this device will be able to accurately test what the effective flow rates for this system will be, considering there is currently not a precise threshold in which proper mixing occurs. Following the input from the user, the device will mix the three liquids while giving the user an accurate readout of the flow rates occurring within the device in real time. After the mixing is done, the user will be able to safely extract the finished mixture which will be used in the liquid embolic treatment.

 

Original Design

Our design was broken down intro three different components that are controlled by our microcontroller.

Starting from the bottom we have our user input. From here the user will be able to put in information into our microcontroller that will in turn control the mixing of our syringes. Things like being able to affect the speed or duration of the mixing would be our goal.

To the right of our microcontroller we have our GUI. The perpose of this section is display information about the mixing to the user so they have an understanding of what is happening within the device. As this embolic liquid is created from the energy put into the system it is important to us to display this energy as this would be important information to be displaying. Another thing that will be displayed is the amount of time currently passing while mixing. Within two minutes the liquid becomes too thick to put through a catheter so this information is also important to show to our client.

Finally we have the control circuit that connects to our motors. The perpose of this control circuit is to take information that is inputted from the microcontroller to choose what syringes to be talking to and to control the mixing.

 

Final Design

The Base:

In the final design's base there are some 3D printed parts attached to the steel T-Bar. The steel bar is layed out In the T-Shape as the joint connection puts the syringes into a T. The syringes need to be steady when the mixing is occuring, as bending a plunger of the syringe can cause the actuator to keep pushing and eventually snapping the plastic. To hold these syringes there are three 3D printed holders ( yellow ) that have divits for the syringe to fit into. Then a top is put through screws and clamped down with the use of wing nuts. These were chosen as they are fast to remove and put on.

Once this is done the end of the plunger will be placed inside of the lips in the blue 3D printed parts. These are there to allow the actuators to not only push but pull the actuators to help relieve the load for other actuators while mixing as well as having the ability to pull liquid into one syringe.

The actuators themselves are clamped to the steel bar with the use of hose clamps, one right before the piston and one around the largest point. With the use of hose clamps, the actuators can be adjusted in location based on how filled the syringes are as well as varying syringes. While this process is slightly time consuming it allows for variable syringes and well as different cc’s of fluid. If similar conditions are set, the actuators should not have to be adjusted.

 

PCB and Microcontroller:

Voltage to the circuit starts from the power socket, and then immediately runs to the the MUX component which selects which motor is to be on at which times. This was duty was shifted to a proto board off of the schematic, due to the positioning of the MUX on the board being unable to handle the current load of the power supply. After reaching the motor select the circuit would lead into the control of the output via BJTs. These can be thought of as switches which require an external voltage to turn them on. The BJTs were taken off of the board entirely, due to the fact that they were limited by the voltage that was supplied to turn them on. To remedy this issue, relays were used to replace these on the same proto board used for the MUX. A relay is also similar to a switch but requires more inputs and is more bulky and allows for better current to flow through the circuit. This portion of the circuit only has the switch on when the signal controlling the switch is high, which means that with a pulse width modulation controlling the input, the duty cycle being sent to the output can be adjusted.

Following the output control is the output’s direction control. This is controlled by an H-bridge connected to the SmartFusion, giving it the ability to determine which motor output is considered ground or power. Many believe that they can simply make an H-bridge themselves with the correct components, but it is a complex system which requires specific devices. The H-bridges currently being used on the design can only handle 1 amp of current, before they begin to fry. Finally after running through these important components the output can be hooked up to the motors.

The microprocessor used in this design is called the SmartFusion. SmartFusion is an System on Chip (SoC) microcontroller.  This means it comes with all the tools necessary to develop the system. It does an excellent job at sending and reading signals,  generating PWM signals ( Pulse Width Modulation, which allows digital outputs to act like analog ), and has a full FPGA right on the board. It is coded in C# the goto to language for professional developers in embedded systems.  C has a bit of a learning curve however, as engineers we are already experienced in the language. Libero is used to program the controller giving it an easy graphical user interface. Thus the SmartFusion is an easy controller to use as well.

End Results:

The overall design of this project an be summed up as seen in the picture above. The display was not implemented into the final design, due to the prioritization of the other subsystems. The button pad was implemented successfully with fewer inputs than orignally intended, but with the ability to still function. The base and actuators were implemented without a problem. Through alterations of the PCB's design the actuators themselves were able to push and pull appropriately. The PCB itself began exhibiting problems due to the internal lines not being able to sustain the amount of current runnuing through them, and as such external connections were needed. Before the end of this project, an altered PCB schematic along with recommended part replacements were given to the client for future endeavors.

 

 

Team Members

  Vincent Jencks  vkj3@nau.edu

  Andrew VanDenburgh  amv336@nau.edu

  Colton Smith  css266@nau.edu

  Yunchen Zhu  yz246@nau.edu

  Handi Xi  hx25@nau.edu