Biomass-based nanomaterials such as bacterial cellulose (BC) are one of the most promising building blocks for the development of sustainable materials with the potential to outperform their conventional, synthetic, counterparts. The formation of BC occurs at the air–water interface, which has been exploited to engineer materials with finely controlled microtopographical features or simple three-dimensional morphologies for a wide range of applications. However, a high degree of control over the 3D morphology of BC films across several length scales (micro to macro) has not yet been achieved. Herein, we describe a simple yet customizable process to finely engineer the morphology of BC in all (x, y, z) directions, enabling new advanced functionalities, by using hydrophobic particles and superhydrophobized surfaces. This results in hollow, seamless, cellulose-based objects of given shapes and with sizes from ca. 200 μm to several centimeters. We demonstrate some of the unique properties of the process and the resulting objects via post-fabrication merging (biowelding), by in situ encapsulation of active cargo and by multi-compartmentalization for near limitless combinations, thus extending current and new applications for example in advanced carbon materials or regenerative medicine.

Nanocellulose has a wide range of applications in the field of functional materials, and it has piqued the interest of researchers for some time. This is because nanocellulose inherits the advantages of environmental friendliness and easy availability of plant cell walls in nature, as well as the unique morphology of nanostructures. This review presents four types of nanocellulose including cellulose nanocrystals (CNCs), cellulose nanofibrils (CNFs), regenerated nanocellulose (RNC) and bacterial cellulose (BC), introduces the different preparation routes and their mechanisms, analyzes the advantages and drawbacks between these approaches, and summarizes the potential applications in the field of functional materials such as reinforced composite materials, biomedical materials, soft templates, and optical materials. Finally, future development directions are proposed including further enrichment of nanocellulose raw materials, improvement of preparation methods to adapt to more diversified raw materials, and classification of products according to their morphology and properties to improve the use efficiency. Graphical Abstract