Fabrication of 3-D curved microstructures by constrained gas expansion and photopolymerization

Rapid fabrication of a large-area close-packed quasi-periodic microlens array on BK7 glass

Large-area close-packed microlens arrays (MLAs) are highly desirable for structured light and integrated optical applications. However, efficient realization of ultralarge area MLAs with a high fill factor is still technically challenging, especially on glass material. In this Letter we propose a high-efficiency MLA fabrication method using single-pulsed femtosecond laser wet etch and close-packed quasi-periodic concave MLAs consisting of three million units fabricated on silica glass within an hour. The fabricated MLAs are demonstrated to have extreme optical smoothness (∼8.5 nm) by an atomic force microscope. It has also been demonstrated that the profile of the quasi-periodic concave structures could be easily tuned by changing the laser scanning speed or the pulse energy. Additionally, the optical performances of the MLA diffusers were investigated by using sharp focusing, high-resolution imaging, and flat-top illumination.

Rapid fabrication of a microdevice with concave microwells and its application in embryoid body formation

Here, we report a novel method for the fabrication of polydimethylsiloxane microdevices with complicated 3-D structures, such as concave and crater shapes, using an easily machined polymethyl methacrylate mold combined with a one-step molding process. The procedure presented here enables rapid preparation of complex 3-D microstructures varying in shape and dimensions. To regulate embryoid body (EB) formation, we fabricated a microfluidic device with an array of concave microwells and found that EBs growing in microwells maintained their shape, viability, and a high degree of homogeneity. We believe that this novel method provides an alternative for rapid prototyping, especially in fabricating devices with curved 3-D microstructures.

Micro/nano-fabrication technologies for cell biology

Micro/nano-fabrication techniques, such as soft lithography and electrospinning, have been well-developed and widely applied in many research fields in the past decade. Due to the low costs and simple procedures, these techniques have become important and popular for biological studies. In this review, we focus on the studies integrating micro/nano-fabrication work to elucidate the molecular mechanism of signaling transduction in cell biology. We first describe different micro/nano-fabrication technologies, including techniques generating three-dimensional scaffolds for tissue engineering. We then introduce the application of these technologies in manipulating the physical or chemical micro/nano-environment to regulate the cellular behavior and response, such as cell life and death, differentiation, proliferation, and cell migration. Recent advancement in integrating the micro/nano-technologies and live cell imaging are also discussed. Finally, potential schemes in cell biology involving micro/nano-fabrication technologies are proposed to provide perspectives on the future research activities.

Study of cellular behaviors on concave and convex microstructures fabricated from elastic PDMS membranes

Cells respond to geometrical cues, as well as to biochemical and mechanical stimuli. Recent progress in micro- and nano-technology has allowed researchers to create microbeads, micro-circular islands, and microposts, that can be used to examine the effect of geometrical cues on cellular behavior. Knowledge of changes in cell mechanics and morphology in response to geometric cues is important for understanding the basic behavior of cells during development and pathological processes. Most previous research in this area has focused on cell responses to two-dimensional planar or rectilinear structures. Very few studies have examined cell responses to three-dimensional curved structures because of the difficulty of fabricating such microstructures. Here we describe a novel method for the fabrication of convex and concave microstructures by use of a thin poly(dimethylsiloxane) (PDMS) membrane, SU-8 shadow mask, and negative air pressure without using any complicated silicon processes. We successfully fabricated concave and convex microstructures, with base diameters of 200-300 microm and depth (or height) of 50-150 microm (aspect ratios up to 1 : 0.5), and used these microstructures to study the responses of cultured L929 mouse fibroblast cells and human mesenchymal stem cells. These cells clearly sensed the three-dimensional microscale curvature and actively "escaped" from concave patterns, but not from those which were convex. Thus, it appears that microscale concave structures suppress cell adhesion and proliferation. We hypothesized that this might relate to deformation of the plasma membrane and subsequent opening of membrane channels. We anticipate that our system will be useful for various bio-MEMS (micro electro mechanical system) applications, including formation of uniformly-sized embryoid bodies, embryonic stem cell differentiation, and the fabrication of cell docking devices, microbioreactors, and microlenses as well as cell mechanics study.