Microfibrillated cellulose(MFC)is a new kind of functional nano-materials. Due to its advantages of biocompatibility, biodegradable, excellent mechanical, special optical and high barrier properties, it has extensive application prospects such as nanopaper, aerogel, nanocomposite materials, papermaking, medicine, etc. However, there remains many problems of MFC preparation and application. The main challenge is the high energy consumption regarding the mechanical fibrillation, which makes it impossible to industrial production. Meanwhile, the strong polar of MFC restricts its good dispersion in non-polar matrices and limits its applications in nanocomposites production. Accordingly, pretreatments before mechanical isolation are needed to reduce the high energy consumption and the composite mechanism of MFC and polymers should be studied systematically to satisfy more possible applications. This review focuses on MFC preparation and its applications in nanopaper, aerogel, nanocomposites. At last the future development of MFC is prospected.

Contents
1 Introduction
1.1 Nanocrystalline cellulose
1.2 Bacterial nanocellulose
1.3 Microfibrillated cellulose
2 Preparation of MFC
2.1 Mechanical methods
2.2 Pretreatment
3 Applications of MFC
3.1 Nanopaper
3.2 Aerogel
3.3 MFC nanocomposites
3.4 Other applications
4 Conclusion and outlook