Wettability gradient surfaces are specific gradients on which surface wettability continuously changes with surface position variation.In the past 20 years

due to the wide applications in smart coatings

microfluidic devices and liquid self-transportations

people investigated and prepared a lot of kinds wettability gradient surfaces

which overall could be divided into three categories:(1) chemical-composition gradients

(2) surface-morphology gradients and (3) topography/chemical composition gradients.This paper focuses on the classification and distinction of these three categorized gradients

and also summarizes novel and mainly techniques appeared recently in the preparation of wettability gradients

such as diffusion method

immersion method

etching/printing

mechanical stretching method

meniscus template and the temperature gradient method

etc .The advantages and disadvantages of these methods are also summarized.At present

although the research of wettabilty gradients is still in infancy

however

the applications of these gradients in the research of biological protein or cell adsorption

liquid transportation have developed into a mature discipline.At the end of this paper

the recent research progresses of wettabilty gradient surfaces in the areas of biological protein

cell adsorption

liquid self-transportation and the future development of this subject are reviewed.