Lan Hongbo

Research on active mixing printhead for multi-material and multi-scale 3D printing

The emerging multi-material and multi-scale 3D printing technique possesses great potential to implement the simultaneous and full control for fabricated objects including external geometry, internal architecture, functional surface, material composition and ratio as well as gradient distribution, feature size ranging from nano, micro, to marco-scale, embedded components and electro-circuit, etc. It is able to construct the heterogeneous and hierarchical structured object with tailored properties and multiple functionalities which cannot be achieved through the existing technologies. Such technology has been considered as a revolutionary technology and next-generation manufacturing tool which can really fulfill the “creating material” and “creating life”, especially subvert traditional product design and manufacturing scheme. This paper presents a multi-scale and multi-material 3D printing process based on single printhead. A novel active mixing printhead which is regarded as one of the core functional elements is proposed and investigated systematically by combining the theoretical analysis, numerical simulation and experimental verification. The influence and laws of the impeller diameter, the impeller velocity, and fluid viscosity for the mixing efficiency and performance were revealed by numerical simulation using COMOSOL software. Three typical cases regarding the variable color model, variable stiffness model and micro-scale model printed were provided to verify the result of the theoretical analysis and numerical simulation for the active mixing printhead. These findings are valuable in providing a theoretical basis for multi-scale and multi-material 3D printing, and further enhancing the performance of active mixing printhead, developing multi-scale and multi-material 3D printers.

Polymer flow and filling behavior for electroosmosis-drivennanoimprint lithography

Electroosmosis-driven nanoimprint lithography (NIL) is an emerging nanopatterning approach which has shown great potential and unique strength in large-area nanoimprinting, fabricating high-aspect-ratio micro/nanostructures, patterning fragile substrates and non-flat surface. However, compared to the conventional pressure-driven NIL and the electrocapillary force-driven UV-imprinting, there is a big difference for such novel electroosmotic flow driven imprinting process. This paper investigated the mechanism, influencing factors and laws of polymer flow and filling behavior for the electroosmosis-driven nanoimprinting. Based on the principle of electroosmosis-driven micro flows, a theoretical model estimated body force was established. And the model of filling velocity and the model of filling time were derived. Furthermore, the dynamic filling process of electroosmosis-driven NIL, influence and laws of polymer flow and filling behavior regarding the imprint process parameters, the feature patterns and the properties of polymer were revealed by numerical simulation using COMSOL Multiphysics simulation software. These findings are valuable in providing a theoretical basis for electroosmosis-driven nanoimprinting, optimizing imprinting process and further enhancing the performance of the new patterning method.