Project Page: Actuated Corneal Hydration

  • This system is meant to take bottled DI water and squirt it onto a pig eye for external corneal hydration during experiments. It is intended to automate a practically cumbersome process that previously was performed by a medical fellow or engineering student who needed to remain beside the eye and squirt water onto the eye every ~30 s to maintain proper hydration. This system interfaces with the robot control software so that the operator, during robot-controlled surgical procedures can hydrate the eye at the click of a button.

  • Like any assembly, we start with a CAD assembly to design the system. To save development time, the tygon tubing is modeled as simple cylinders (yellow).

  • The electronics box takes special consideration since it will be 3D printed and must interface with specific electrical components.

  • The finalized box has two inputs: 12 VDC power and a SIG (signal) line from the controller; and one output: voltage to actuate the solenoid valve.

  • The ON/OFF control is through a simple Darlington transistor pair (Sziklai pair)—no need to draw this up in Eagle. The sketch illustrates the idea and transistor choice: 2N555 for the NPN and MJE2955 for the PNP. Applying a "high" signal (3.3 V) from the controller to the "digital input pin" causes the ground-side of the load (solenoid valve) to connect to ground and complete the circuit, turning it on. Supply voltage is 12 VDC.


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