Micropatterning and Its Applications in Biomedical Research

Based on the micro-fabrication techniques combining with biochemistry and biophysics, we can get function structures with feature sizes close to the biomacromolecule scale, which promotes the applications of micropatterning in many research fields such as drug screening and discovery, tissue engineering and disease diagnosis. This review summarizes the development of micropatterning techniques in biomedical field and analyzes the advantages, limitations and application scopes of each micropatterning approach including photolithography, soft lithography, stencil-assisted patterning, scanning-probe lithography, jet patterning and laser guided patterning. Photolithography usually includes several steps such as exposure, development, lift-off and so on. Although it has the advantages of high accuracy, high efficiency and accurate alignment system, it depends on super-clean labs and lift-off processes, which means high cost and unsatisfied bio-compatibility. Soft lithography and stencil-assisted patterning methods avoid exposure and lift-off steps by using elastomeric stamps, which can enhance the bio-compatibility and reduce the cost. However, these two methods have deficiencies in alignment accuracy. Different from above methods, scanning-probe lithography is a kind of direct-writing technique, which sacrifices the advantage of high efficiency to improve its accuracy. Jet patterning is developed from industry with the advantages of low complexity and cost. However, its low accuracy of 10 pm scale is the limitation. Two novel laser based micropatterning techniques are also discussed. Although laser-induced transfer method solves the problem of jet patterning technique in the patterning thickness control, the low accuracy is still a problem. Optical tweezers technique offers a substitution for the scanning-probe lithography, although it has a long way to go in terms of liquor environment limitation and efficiency. It is indicated that current micropatterning methods already have the ability to make micro devices featured from nanometer scale to millimeter scale on a variety of surface materials different in geometry, stiffness and so on. The resolution and accuracy, the patterning scale and the processing condition are the bases for choosing micropatterning methods. The development of micropatterning techniques provides a rapid, real time, and accurate study tool in biological mechanism, drug action and biochemical reaction research. Micropatterning methods can enhance the sensitivity, the automation degree and the integration scale biosensors, which will further improve the efficiency of drug screening and diseases diagnosis. Also by micropatterning techniques, we can control the cells action easily, accurately and concurrently, which is helpful to shorten the development cycle. The main trends of micropatterning research are the further physicochemical analyses of the particles on nano-scale based on biochemistry and biophysics, the further enhancement of its bio-compatibility and material adaptability, as well as the development of in vivo microenvironment simulations suitable for micropatterning chips.