# Design and Validation of a Pressure-Driven Liquid Metering System with Heated PTFE Tubing for Laboratory Automation

## TL;DR

The paper introduces a heated PTFE-based liquid metering system that improves accuracy in laboratory automation by managing temperature and compensating for fluid slip.

## Contribution

A novel pressure-driven system with thermal management and slip compensation for precise liquid metering in automated labs.

## Key findings

- Heated operation with slip compensation achieved dispensing accuracy within ±4%.
- Unheated operation had larger errors due to temperature gradients.
- Slip length depends on temperature and flow rate.

## Abstract

This paper presents a pressure-driven liquid transfer system for laboratory automation, along with a physics-based model and calibration method. The device maintains near-isothermal transport by storing reagents at a prescribed temperature and routing the flow through a single PTFE tube enclosed within a heated jacket. The pressure-drop model accounts for temperature-dependent viscosity and the thermal expansion of PTFE. Residual deviations from the no-slip prediction in submillimeter tubing are represented by an effective slip length, which is identified through linear regression. This parameter is subsequently used to calculate the pressure required to achieve a target flow rate. Experimental results compare unheated and heated operating conditions and characterize the dependence of slip length on temperature and flow rate. Under heated operation with slip-compensated pressure commands, the system achieved dispensing accuracy within ±4% over the tested range, whereas unheated operation exhibited larger errors due to axial temperature gradients. These results demonstrate that effective thermal management and slip compensation are critical for accurate pressure-based metering under temperature-sensitive conditions, as validated using water-based tests.