This repository contains the hardware designs, electronics schematics, MATLAB analysis codes, and example datasets associated with the manuscript:
Development of a Low-Cost In-Situ Viscosity Measurement System for Extrusion-Based Bioprinting
Submitted to Bioprinting (Elsevier)
The In-Situ Viscosity Measurement System (IVMS) enables real-time estimation of bioink viscosity during extrusion-based bioprinting by integrating a compact load cell into a syringe-based extrusion head. The system functions as an on-board capillary rheometer and applies established rheological corrections to extract true, shear-rate-dependent viscosity under realistic printing conditions.
Extrusion-based bioprinting critically depends on bioink viscosity, which governs print fidelity, filament stability, and cell viability. Conventional rheometry is typically performed offline and may not capture the dynamic conditions experienced during printing, including nozzle geometry, shear history, and temperature effects.
IVMS addresses this gap by enabling:
- Real-time measurement of extrusion force during printing
- Conversion of force to pressure and viscosity under printing-relevant conditions
- Quantitative rheological characterization of shear-thinning bioinks
- Direct benchmarking against conventional parallel-plate rheometry
The system is designed to be low-cost, modular, and open-source, facilitating broad adoption across academic and research bioprinting platforms.
- Integrated load-cell-based extrusion system for in-situ force and pressure measurement
- Sequential rheological correction pipeline, including:
- Friction correction
- Bagley (entrance loss) correction
- Mooney wall-slip correction
- Rabinowitsch correction for shear-thinning fluids
- Viscosity estimation using Power Law and Carreau–Yasuda models
- Experimental validation using gelatin methacryloyl (GelMA) bioinks:
- Concentrations: 5%, 7%, 10% (w/v)
- Temperatures: 25 °C, 30 °C, 37 °C
- Quantitative comparison with parallel-plate rheometry, demonstrating strong agreement and expected rheological trends
- Custom 3D-printed extrusion head compatible with open-source bioprinters
- Integrated S-beam load cell mounted coaxially above the syringe
- Modular design supporting multiple syringe sizes and nozzle geometries
- Typical system cost: < USD $150 (excluding printer)
- Load cell amplifier and custom signal conditioning circuit
- Voltage shifting and filtering to interface with microcontrollers
- Data acquisition via Arduino or higher-resolution DAQ systems (e.g., LabJack)
- MATLAB-based analysis framework
- Object-oriented implementation of the rheological correction pipeline
- Automated viscosity computation and non-Newtonian model fitting
- Exportable datasets for comparison with rheometer measurements
The IVMS was validated using gelatin methacryloyl (GelMA) as a model shear-thinning hydrogel. Results demonstrate that:
- Increasing GelMA concentration increases viscosity
- Increasing temperature decreases viscosity
- Viscosity decreases with increasing shear rate (shear-thinning behavior)
- IVMS measurements align closely with parallel-plate rheometry
These trends are consistent with established rheological behavior reported in the literature.
IVMS is intended for:
- Bioink formulation screening
- Extrusion parameter optimization
- Comparative rheological studies
- In-air and support-bath bioprinting workflows
- Research environments where frequent offline rheometry is impractical
- Viscosity calculations are performed offline
- Mechanical friction from 3D-printed components introduces minor variability
- Low-cost electronics introduce measurable noise and drift
- Real-time, on-board viscosity computation
- Closed-loop extrusion control
- Integration with machine-learning-based adaptive printing
- Improved mechanical precision and higher-resolution data acquisition
If you use this repository or the IVMS system in your research, please cite:
Zgeib, R., Zhao, X., Zaeri, A., Zhang, F., Cao, K., Chang, R.
Development and characterization of a low-cost in-situ viscosity measurement system for extrusion-based bioprinting.
Bioprinting, 2026, e00475. https://doi.org/10.1016/j.bprint.2026.e00475.
This project is released under the GNU General Public License v3.0.
See the LICENSE file for details.
For questions, issues, or contributions:
- Robert Chang (Corresponding Author): rchang6@stevens.edu
- Ralf Zgeib (First Author): rzgeib@stevens.edu
Issues and pull requests are welcome.
This repository supports transparency and reproducibility for the IVMS platform described in the associated Bioprinting journal manuscript.