Laser-based cell printing techniques for additive biomanufacturing

The potential of microfluidics-enhanced extrusion bioprinting

Microfluidics-enhanced bioprinting holds great promise in the field of biofabrication as it enables the fabrication of complex constructs with high shape fidelity and utilization of a broad range of bioinks with varying viscosities. Microfluidic systems contain channels on the micrometer-scale, causing a change in fluid behaviors, enabling unconventional bioprinting applications such as facilitating the precise spatial positioning and switching between bioinks with higher accuracy compared to traditional approaches. These systems can roughly be divided into three groups: microfluidic chips, co- and triaxial printheads, and printheads combining both. Although several aspects and parameters remain to be improved, this technology is promising as it is a step toward recapitulating the complex native histoarchitecture of human tissues more precisely. In this Perspective, key research on these different systems will be discussed before moving onto the limitations and outlook of microfluidics-enhanced bioprinting as a whole.

Precision ejection of microfluidic droplets into air with a superhydrophobic outlet

Dispensing micron-scale droplets from a suspended nozzle is important for applications in bioprinting, analytical chemistry, and pharmaceutical formulation. Here, we describe a general approach to eject droplets from microfluidic devices using superhydrophobic patterning; this facilitates release of wetted fluids, allowing droplets to break contact with channel surfaces and travel along regular paths to achieve a printing accuracy of ∼3 μm. We demonstrate the utility of the approach by using it to print droplets of varied composition from a microfluidic mixing device. Our approach is compatible with common fabrication techniques making it applicable to devices configured for diverse applications.

Direct-write and sacrifice-based techniques for vasculatures

Fabricating biomimetic vasculatures is considered one of the greatest challenges in tissue regeneration due to their complex structures across various length scales. Many strategies have been investigated on how to fabricate tissue-engineering vasculatures (TEVs), including vascular-like and vascularized structures that can replace their native counterparts. The advancement of additive manufacturing (AM) technologies has enabled a wide range of fabrication techniques that can directly-write TEVs with complex and delicate structures. Meanwhile, sacrifice-based techniques, which rely on the removal of encapsulated sacrificial templates to form desired cavity-like structures, have also been widely studied. This review will specifically focus on the two most promising methods in these recently developed technologies, which are the direct-write method and the sacrifice-based method. The performance, advantages, and shortcomings of each technique are analyzed and compared. In the discussion, we list current challenges in this field and present our vision of next-generation TEVs technologies. Perspectives on future research in this field are given at the end.