Liquid-immune trigger circuit for surgical instrument

An apparatus includes a body, a shaft assembly, an end effector, an activation circuit, and a user input feature. The activation circuit includes an end effector driver and a driver activation switch. The end effector driver is operable to drive the end effector to perform an operation on tissue. The driver activation switch is configured to transition between an open state and a closed state. The end effector driver is configured to activate in response to the driver activation switch transitioning to the open state. The user input feature is operable to transition between a non-actuated state and an actuated state. The driver activation switch remains in the closed state when the user input feature is in the non-actuated state. The driver activation switch is configured to transition to the open state in response to the user input feature transitioning from the non-actuated state to the actuated state.