Overview
On behalf of a client in the ergonomics department in Duke hospital, a coworker and I developed the mechanical and electrical systems for a device that can automate the use of a syringe. My duties focused on the electrical systems, which included two custom PCBs and the control code for the device.
This device has been delivered to the client and is now undergoing clinical testing and critique from users.
Background
A subset of employees in the hospital experienced repetitive strain injuries and fatigue from using a liquid measuring syringe to transfer fluid from one receptacle to another. Under a fume hood, these employees desired to be able to use larger 60mL syringes with one hand and aiding one-handed operation for smaller syringes.
1 | Ease of Use
Intuitive device that can be operated numerous times during a day without much thought
2 | Sterilizable
Able to be wiped down with sterile wipes and not be prone to collecting contaminants
3 | Reliable
Failure modes are predictable and safe for user in case of misuse or malfunction
Solution
Our device is built around a linear rail fitted with a leadscrew movement system to allow for travel in and out. This system gave us superior rigidity and enough torque to allow movement while operating with viscous fluids.
All buttons are color-coded and resistant to fluid ingress to meet the sanitation needs of the client. Work will be done in the future to remove all exposed screws and screwheads as well as shrink wrapping the entire device for an added layer of protection.
Power is provided through a standard 12V wall adapter into a barrel jack with a removable water-resistant flap. Additionally, two rubber flaps on the top of the device allow for linear motion while protecting the electronics below.
Motion
The pushing and pulling of the syringe is achieved by a lead screw drive mechanism powered by a 12V DC motor.
Aluminum mounting plates for the syringe flange and plunger allow the syringe to easily be changed out.
Control
Buttons on the side of the device control the direction of motion, and a potentiometer controls speed.
A "zero" button allows for a variable maximum extension length to be set so that the syringe does not overextend.
An LED power button is located on the side of the device to ensure that there is no accidental use.
Electronics
Powered by an Arduino Nano, the two custom PCBs provide a neat soldering point for the UI and motor driver.
Limit switches are also soldered onto the main board and serve as hard stops for the motion of the device.
Gallery
