Modelling, Validation and Application of Triboelectrification

Collisional and sliding contacts of two different materials are commonly associated with electric charge transfer, leading to charge accumulation. This causes an overwhelming number of handling and processing problems and explosion hazards, thereby degrading manufacturing efficiency and causing out of specification products and wastage. Examples are strong adhesion to containing walls and deposition in pipes, impairing flowability and aggravating segregation of components in a mixture, thereby upsetting formulations. It is common to experience highly active drugs filling up a spiral jet mill (thereby upsetting its functioning), components of a formulation preferentially depositing on grounded surfaces, getting concentration spikes of minor components of a formulation, poor powder spreading due to charging in additive manufacturing. In contrast, the phenomenon has been used to good effect in xerography and more recently for Tribo-Electric Nano Generators (TENG). Despite being known for millennia, the triboelectrification phenomenon is not well understood and actually not predictable for non-metallic surfaces. The role of environmental humidity and temperature adds to the complexity. Considering its importance in advanced manufacturing of new materials, for which little material is initially available, a timely project with internationally leading-edge participation is proposed to tackle triboelectrification from a molecular level solid-state formation, right up to large scale manufacturing of active pharmaceutical ingredients and polymers. The project has seven industrial partners and six international collaborators from Japan, Brazil, Italy and Canada, contributing to seven work packages, each addressing a topic of scientific as well as industrial interest. The activities range from molecular solid-state level work function calculations by Density Functional Theory, to particle charge transfer characterisation by developing specialised instruments for charge distribution measurement and TENG, to unit operation level, including fast fluidisation and risers, pneumatic conveying and cyclone separation. The work is of strategic interest in manufacturing, ranging from pharmaceuticals, foods and plastics to additive manufacturing. It will have a huge impact on manufacturing sustainability, as the mitigation of  triboelectrification issues will have a notable reduction in wastage and environmental footprint, and on the performance and  material optimisation for the fast-growing new technology of TENG.

Impact

The proposal is closely aligned with the EPSRC’s Manufacturing the Future Programme. It is also of great relevance to Health Care Technologies, e.g. for the secondary manufacturing of APIs such as feeding, dosing and tabletting. The Additive Manufacturing industry will also benefit, as polymer powders and metal powders having an oxide layer charge readily, adversely affecting the ability to spread powder uniformly. The proposal will also benefit industries that suffer from the widespread problem of soft agglomerate formation in their powders, by enabling the role of triboelectric charging to be rapidly assessed. In fact, two pharmaceutical companies have already set up their own aerodynamic dispersion for triboelectric charging based on the UoL design.  Thus, a fundamental understanding of the phenomenon is of paramount importance in manufacturing. 

Publications and outputs

Publications:
1.    Goh, W. P., Guo, J., Jia, X., & Ghadiri, M. (2024). Influence of type of aluminium stearate on triboelectrification of dry-coated surfaces of functionalised glass beads. Frontiers in Chemical Engineering, 6, 1347342. https://doi.org/10.3389/FCENG.2024.1347342/BIBTEX
2.    Middleton, J. R., Ghadiri, M., & Scott, A. J. (2024). Triboelectric Charging Properties of the Functional Groups of Common Pharmaceutical Materials Using Density Functional Theory Calculations. Pharmaceutics, 16(3), 433. https://doi.org/10.3390/PHARMACEUTICS16030433/S1
Invited Talks:
1.    Invited Keynote at IoP Electrostatics (5th September 2023, Brunel, UK) • Triboelectrification of Powder and Grains: Effect of Surface Functional Groups by Prof. Mojtaba Ghadiri
2.    Conference oral presentation at IoP Electrostatics (5th September 2023, Brunel, UK) on triboelectric charging properties of the functional groups of common pharmaceutical materials using density functional theory calculations by Dr James Middleton
3.    Invited talk at STEP Meeting (7th September 2023, Brunel, UK) • Charge Mitigating Properties of ATMER 163 on Functionalised Glass Surfaces by Dr Wei Pin Goh
4.    Conference oral presentation at Electrostatics Society of America Annual Meeting (10th June 2024, Ottawa, Canada)  on Triboelectric charging properties of the functional groups of common pharmaceutical materials using density functional theory calculations by Dr James Middleton 
5.    Conference oral presentation at Electrostatics Society of America Annual Meeting (12th June 2024, Ottawa, Canada)  on Charge Mitigating Effect of ATMER 163 on Functionalised Glass Surfaces by Dr James Middleton on behalf of Dr Wei Pin Goh
6.    Conference oral presentation at 18th European Symposium of Comminution  and Classification (24th June 2024, Miskolc, Hungary) on Characterisation of breakage of crystals by aerodynamic dispersion by Dr Wei Pin Goh
7.    Conference oral presentation at 18th European Symposium of Comminution  and Classification (24th June 2024, Miskolc, Hungary) on Optimisation of a new vertical roller mill by DEM modelling by Dr Muzammil Ali on behalf of Prof Mojtaba Ghadiri
 

Project website

https://triboelectrification.org/