Highly aligned metal nanowire arrays with feature sizes approaching 10 nm are fabricated. This is made possible by the self-assembly of block copolymers (BCPs) on graphene-wrinkle arrays. Thickness-modulated BCP films confined on the wrinkled reduced graphene oxide (rGO) surface promote the strict alignment of the self-assembled BCP lamellae in the direction of the film thickness gradient.

Understanding the effects of topographic characteristics on tumor cell migration is important for the development of new anti-migratory therapies. However, simplified in vitro culture systems often lead to inaccurate results regarding the efficacy of drugs. Histopathologically, glioblastoma multiform (GBM) cells migrate along the orientation of thin, elongated anatomical structures, such as white-matter tracts. Here, a tapered microtract array platform which mimics the anatomical features of brain tissue is introduced. This platform enables optimization of design for platform fabrication depending on topographic effects. By monitoring the migration of GBM cells on a simple tapered microtract, a saltatory migration resembling the migratory phenotype of human GBM cells in vivo is observed. The platform effectively induces the native characteristics and behavior of cells by topographic cues, allowing to observe the critical point for crawling to saltatory transition. Furthermore, this platform can be applied to efficiently screen anti-cancer drug by inhibiting associated signaling pathways on GBM cells. In conclusion, the microtract array platform reported here may provide a better understanding of the effects of topographic characteristics on cell migration, and may also be useful to determine the efficacy of antimigratory drugs for glioblastoma cells with cellular and molecular research and high-throughput screening.

systems consisted of thin fi lm bounded onto a moduli-patterned soft substrate under compressive stress. The spatial occurrence of wrinkles or folds is controlled by the induction of heterogeneous pre-strain distributions onto the moduli-patterned elastic substrate. Figure 1 A illustrates the experimental process in generating a spatially controlled wrinkle or fold pattern. Pre-patterned PDMS was prepared by using photolithography and soft lithography. To fabricate moduli-patterned elastic substrate, the trench of the pre-patterned PDMS elastomer was fi lled entirely with a 10:1 mixture of the PDMS prepolymer and cross-linker through a scraping-assisted micromolding process ( Figure S1, Supporting Information). After a certain curing time, the liquid PDMS in the trench was partially cross-linked. This provides a lower modulus region ( E s1 , Young's Modulus ≈ 30 kPa) than that of a groove-patterned PDMS ( E s2 , Young's Modulus ≈ 2 MPa) ( Figure S2, Supporting Information). By applying mechanical pre-stretching, the local strain was varied over the surface due to the modulus difference (Figure 1 B). Simplistically, the top surface of the moduli-patterned substrate can be assumed to be a serial arrangement of elastic materials with different spring constants ( k 1 < k 2 ) in the direction of pre-stretching. Next, the surface was exposed to UV light/ozone; under exposure, the top surface of the PDMS was converted into a silica-like stiff fi lm, with a fi lm thickness of around 4 µm ( Figure S3, Supporting Information). The fi lm thickness was obtained from model-based calculations. [ 27 ] The elastic modulus of the thin fi lm was ≈ 40 MPa, [ 28 ] corresponding to the moduli ratio that 1333 and 20 for the soft and hard regions, respectively. After the pre-stretching release, a certain level of compressive stress was conversely induced on the fi lm surface, resulting in selective wrinkle or fold pattern formation on the soft regions, while pattern formation did not occur on the hard regions. Figure 1 C shows the scanning electron micro scopy (SEM) images of each step in the procedure. For a 100 µm pitch groove-patterned PDMS substrate, the bilayered system buckled into wrinkles with a sinusoidal deformation of 50 µm in wavelength with a strain of 0.32. By increasing the strain acting on the fi lm, folds were formed in the soft regions. The curvature measurements of the folds were up to 0.3 µm −1 and that of the wrinkles were up to 0.2 µm −1 . The ratios of depth to width for these structures were coupled with curvature.

Histopathologically, brain tumor cells, especially glioblastoma multiform (GBM) cells, migrate along the orientation of thin, elongated anatomical structures, such as white‐matter tracts. On page 405, P. Kim and team show how the thinnest width of tapered microtract array platform can induce the in vivo saltatory migration of brain tumor cells, as in white matter tract.