3D-printed syringe holder with synchronized push-pull action

Controlled liquid exchange is a fundamental requirement for numerous biological and chemical experimental protocols. However, achieving constant-volume exchange often requires electronic syringe pumps that are cost-prohibitive and time-consuming to set up in a push-pull configuration. To address these limitations, we developed the Push2Pull syringe holder, a simple 3D-printed device that mechanically synchronizes two syringes to simultaneously add and extract equal fluid volumes. This device is compatible with standard disposable syringes from 1 to 60 mL in size and operates without electricity or additional hardware, making it ideal for both laboratory and field settings. Validation experiments demonstrate an exchange accuracy within $\pm 2\text{\%}v/v$ across the whole travel range, while fluid exchange efficiency was calculated for various use cases using CFD simulations. The Push2Pull syringe holder offers an accessible, open-source solution for precise fluid handling, for a material cost of less than $10.