Flat Polydimethylsiloxane Surface Research Articles

Effects of nanopillars and surface coating on dynamic traction force

The extracellular matrix serves as structural support for cells and provides biophysical and biochemical cues for cell migration. Topography, material, and surface energy can regulate cell migration behaviors. Here, the responses of MC3T3-E1 cells, including migration speed, morphology, and spreading on various platform surfaces, were investigated. Polydimethylsiloxane (PDMS) micropost sensing platforms with nanopillars, silicon oxide, and titanium oxide on top of the microposts were fabricated, and the dynamic cell traction force during migration was monitored. The relationships between various platform surfaces, migration behaviors, and cell traction forces were studied. Compared with the flat PDMS surface, cells on silicon oxide and titanium oxide surfaces showed reduced mobility and less elongation. On the other hand, cells on the nanopillar surface showed more elongation and a higher migration speed than cells on silicon oxide and titanium oxide surfaces. MC3T3-E1 cells on microposts with nanopillars exerted a larger traction force than those on flat PDMS microposts and had more filopodia and long protrusions. Understanding the relationships between platform surface condition, migration behavior, and cell traction force can potentially lead to better control of cell migration in biomaterials capable of promoting tissue repair and regeneration.

Effects of Biomimetic Micropatterned Surfaces on the Adhesion and Morphology of Cervical Cancer Cells.

It has been demonstrated that micropatterned surfaces have an important influence on modulating cellular behavior. In recent years, with the rapid development of microfabrication techniques and in-depth study of nature, an increasing number of patterned structures imitating natural organisms have been successfully fabricated and widely evaluated. However, there are only a few reports about biomimetic patterned microstructures in biologically related fields. In our work, micropatterned polydimethylsiloxane (PDMS) was fabricated by mimicking the surface microstructures of natural Trifolium and Parthenocissus tricuspidata leaves using the template duplication method. The interactions between the two types of biomimetic micro-PDMS surfaces and two kinds of human cervical cancer cells (HeLa and SiHa) were investigated. HeLa and SiHa cells cultured on the two micropatterned PDMS samples exhibited more stretchable morphology, higher diffusion, and a much lower nuclear/cytoplasmic ratio than those cultured on flat PDMS surfaces, indicating a higher adhesion area of the cells. Both of the micro-PDMS substrates were found to induce significantly different morphological changes between HeLa and SiHa cells. This suggests that the micropatterned structure affects cell adhesion and morphology correlated with their surface geometric structure and roughness. The results reveal that biomimetic micropatterned surfaces from natural leaves significantly regulate the morphology and adhesion behavior of cervical cancer cells and are believed to be the new platforms for investigating the interaction between cells and substrates.

Ultrasonication-induced and diluent-assisted suspension polymerization for size-controllable synthesis of polydimethylsiloxane droplets

Submicroscale polydimethylsiloxane (PDMS) spheres are emerging as a promising solution for a variety of engineering applications due to their unique material properties and size. It is, however, still considered as challenging to produce submicroscale PDMS droplets. This leads to the need for development of a deterministic method for producing size-controllable, monodisperse PDMS droplets and, by extension, comprehensive understanding of the physicochemical players and processes involved in the synthesis method. Here, we develop an ultrasonication-induced and diluent-assisted (UIDA) suspension polymerization process to achieve the scalable synthesis of monodisperse PDMS droplets. The UIDA suspension polymerization process is essentially the same as conventional suspension polymerization processes except ultrasonic agitation and organic diluent addition. The use of ultrasonication is intended to controllably reduce the size of PDMS droplets, while the addition of a diluent to PDMS is designed to enhance the monodispersity of PDMS droplets (major) and decrease their size (minor). First, we explore the dependence of PDMS droplet size and polydispersity on rudimentary factors such as stabilizer (i.e., polyvinyl alcohol (PVA)), magnetic stirring, ultrasonication, diluent (i.e., benzene), and synthesis vessel. Next, a time-variant change in the size and size distribution of PDMS droplets under UIDA suspension polymerization process are investigated by deconvoluting the droplet dispersity in size into two components, each of which is described using an envelope of the log-normal distribution. The main cause of a bimodal distribution is also identified. Finally, we demonstrate the applicability of PDMS droplets in altering the hydrodynamic properties of polymer surfaces by fabricating a set of rose petal-inspired substrates through evaporation coating of PDMS droplets on flat PDMS surfaces. The findings of this study will lead to better understanding of suspension polymerization for synthesizing monodisperse submicroscale droplets made of thermosetting polymers.

Combined Approach of Compression Molding and Magnetic Attraction to Micropatterning of Magnetic Polydimethylsiloxane Composite Surfaces with Excellent Anti-Icing/Deicing Performance.

The accumulation of ice and contaminants on the surface of composite insulators will cause high energy consumption or even major hazards to power systems. In this work, the polydimethylsiloxane (PDMS) silicone rubber was modified by surface micropatterning and material compositing. Highly crosslinked poly(cyclotriphosphazene-co-4,4'-sulfonyldiphenol) (PZS) was used to directly coat ferroferric oxide (Fe3O4) nanoparticles. The obtained core-shell Fe3O4@PZS microspheres were loaded with carbon nanotubes (CNTs) to get CNTs/Fe3O4@PZS as the photothermal magnetic filler. The PDMS/CNTs/Fe3O4@PZS surfaces with micronscale truncated cones were prepared via a combined method of compression molding and magnetic attraction. The 1H,1H,2H,2H-perfluorodecyltrichlorosilane-coated template and magnetic field can increase the height of the microstructure to ∼76 μm and maintain the contact angle of microstructured PDMS/CNTs/Fe3O4@PZS surfaces at a high level (∼152°). Compared with the flat PDMS surface, the micronscale truncated cones extend the freezing time from 4.5 to 11.5 min and also undermine the ice adhesion strength from ∼25 to ∼17 kPa for the microstructured PDMS/CNTs/Fe3O4@PZS surface. The temperature of the PDMS/CNTs/Fe3O4@PZS surface molded with magnetic attraction increases linearly with time and the internal magnetic fillers and achieves 280 °C in 10 s. The efficiency of temperature rise is increased by ∼46%, and hence the entire frozen water droplet can melt within 20 s. The strategy combining active deicing with passive anti-icing undoubtedly promotes the development of high efficiency anti-icing materials and can be applied on insulators to prevent icing flashover.

Post Arrays for the Immobilization of Vapochromic Coordination Polymers for Chemical Sensors

This paper presents a new immobilization method for Vapochromic Coordination Polymers (VCPs) for micromachined fluorescence chemical sensors. The method involves creating a sheet of post arrays in polydimethylsiloxane (PDMS) to trap and adhere the VCPs to the sensing surface. The method is simple, robust, and employs inexpensive micro-molding of PDMS polymer. Results suggest that, compared to un-patterned (flat) PDMS surfaces: 1) the VCPs on the patterned surfaces can detect ammonia gas without rendering the VCP inert (unable to fluoresce) or inaccessible; and 2) the technique has improved immobilization (attachment of VCP). We show that as the shapes of the top of the post arrays are changed from simple to mushroom-shaped caps, the sensitivity of the sensing surface is increased. Ammonia detection in the range of 5 ppm is possible with the most pronounced mushroom-shaped posts.

Microenvironmental topographic cues influence migration dynamics of nasopharyngeal carcinoma cells from tumour spheroids.

Tumour metastasis is a complex process that strongly influences the prognosis and treatment of cancer. Apart from intracellular factors, recent studies have indicated that metastasis also depends on microenvironmental factors such as the biochemical, mechanical and topographical properties of the surrounding extracellular matrix (ECM) of tumours. In this study, as a proof of concept, we conducted tumour spheroid dissemination assay on engineered surfaces with micrograting patterns. Nasopharyngeal spheroids were generated by the 3D culture of nasopharyngeal carcinoma (NPC43) cells, a newly established cell line that maintains a high level of Epstein–Barr virus, a hallmark of NPC. Three types of collagen I-coated polydimethylsiloxane (PDMS) substrates were used, with 15 μm deep “trenches” that grated the surfaces: (a) 40/10 μm ridges (R)/trenches (T), (b) 18/18 μm (R/T) and (c) 50/50 μm (R/T). The dimensions of these patterns were designed to test how various topographical cues, different with respect to the size of tumour spheroids and individual NPC43 cells, might affect dissemination behaviours. Spreading efficiencies on all three patterned surfaces, especially 18/18 μm (R/T), were lower than that on flat PDMS surface. The outspreading cell sheets on flat and 40/10 μm (R/T) surfaces were relatively symmetrical but appeared ellipsoid and aligned with the main axes of the 18/18 μm (R/T) and 50/50 μm (R/T) grating platforms. Focal adhesions (FAs) were found to preferentially formed on the ridges of all patterns. The number of FAs per spheroid was strongly influenced by the grating pattern, with the least FAs on the 40/10 μm (R/T) and the most on the 50/50 μm (R/T) substrate. Taken together, these data indicate a previously unknown effect of surface topography on the efficiency and directionality of cancer cell spreading from tumour spheroids, suggesting that topography, like ECM biochemistry and stiffness, can influence the migration dynamics in 3D cell culture models.

Using Biomimetic Scaffold Platform to Detect Growth Factor Induced Changes in Migration Dynamics of Nasopharyngeal Epithelial Cells

A polydimethylsiloxane two-layer scaffold platform was designed to provide a three-dimensional biomimetic microsystem that allows the detection of epithelial-to-mesenchymal transition without the use of specific biomarkers. As a proof of concept, a novel microsystem that consisted of two layers of $15~\mu \text{m}$ thick grating structures was developed. These layers had gratings with $40~\mu \text{m}$ wide ridges and $10~\mu \text{m}$ wide trenches, and they were stacked together to form a scaffold platform. To investigate the feasibility of using the engineered platforms for detecting changes in epithelial-to-mesenchymal transition, transforming growth factor beta-1 was added to an untransformed nasopharyngeal epithelial cell line. On flat polydimethylsiloxane surfaces, transforming growth factor beta-1 did not significantly affect nasopharyngeal epithelial size, migration speed, or directionality. However, the effect of transforming growth factor beta-1 treatment on migration speed of nasopharyngeal epithelial cells cultured on the two-layer scaffold platform was significantly different. Furthermore, while almost no untreated nasopharyngeal epithelial cells could squeeze into the $10~\mu \text{m}$ wide trenches, 21% of the transforming growth factor beta-1 treated nasopharyngeal epithelial cells exhibited traversing behaviors on the two-layer scaffold platforms. Moreover, fibronectin coating on the trenches and bottom layers of the scaffold platforms further enhanced the transforming growth factor beta-1-induced traversing of nasopharyngeal epithelial cells into the narrow trenches. These results demonstrate that the engineered two-layer scaffold microsystem can be used to monitor epithelial-to-mesenchymal transition induced changes in cell migration and invasiveness, paving the way of using these platforms in high throughput drug screening.

Fabrication of a Novel Nanofluidic Device Featuring ZnO Nanochannels.

We developed a novel fabrication method for nanochannels that are easily scaled up to mass production by selectively growing zinc oxide (ZnO) nanostructures and covering using a flat PDMS surface to make hollow nanochannels. Nanochannels are used in the biotechnological and environmental fields, being employed for DNA analysis and water purification, due to their unique features of capillary-induced negative pressure and an electrical double-layer overlap. However, existing nanochannel fabrication methods are complicated, costly, and not amenable to mass production. Here, we developed a novel nanochannel fabrication method. The pillar-like dense ZnO nanostructures were grown in a solution process, which is easily applicable to mass production. The size of the fabricated ZnO nanostructures has a thickness of 30–300 nm and a diameter on the order of 102 nm, which are easily adjusted by synthesis times. The ZnO nanostructures were covered by the flat polydimethylsiloxane (PDMS) surface, and then the cracks between ZnO nanostructures served as hollow nanochannels. Because the suggested fabrication process has no thermal shrinkage, the process has higher production efficiency than existing nanochannel mass production methods based on the thermal/pressure process. The mechanical strength of the fabricated ZnO nanostructures was tested with repetitive tape peeling tests. Finally, we briefly verified the nanochannel performance by applying the nanochannel to the micro/nanofluidic system, whose performance is easily evaluated and visualized by current–voltage relation.

Silica-coated metallic nanoparticle-based hierarchical super-hydrophobic surfaces fabricated by spin-coating and inverse nanotransfer printing

By combining spin coating and inverse nanotransfer printing, silica-coated gold nanoparticles are patterned onto polydimethylsiloxane (PDMS) superhydrophobic surfaces to form a hierarchical structure. A layer of nanoparticles is spin-coated on a flat silicon substrate serving as the stamp, which is then transferred to the raised regions of PDMS surfaces. Our inverse nanotransfer printing is in contrast to the standard nanotransfer printing, which transfers metal from the raised regions of a stamp to a flat PDMS surface. The fabricated hierarchical surface exhibits a higher contact angle and delays the Cassie-Wenzel transition during evaporation of a sessile droplet, indicating an improvement of superhydrophobicity. Finally, we demonstrate that the fabricated nanoparticle-based superhydrophobic surfaces can enhance the Raman intensity and significantly decrease the surface-enhanced Raman scattering detection limit.

Motile Dendritic Cells Sense and Respond to Substrate Geometry.

Dendritic cell (DC) migration is required for efficient presentation of antigen to T cells and the initiation of an adaptive immune response. In spite of its importance, many aspects of DC migration have not been characterized. DCs encounter a variety of environments with different stiffness and geometry, but the effect of these parameters on DC migration has not yet been determined. We addressed this question by comparing DC motility on standard migration surfaces (polydimethylsiloxane (PDMS)-coated coverslips) and micropost array detectors (mPADs). These two surfaces differ in both stiffness and geometry. We found that DC migration was affected by substrate type, with significant increases in speed and significant decreases in persistence time on mPADs made of PDMS as compared to spin-coated PDMS coverslips. To determine whether the geometry or compliance of the post arrays was responsible for these changes in DC migration, we quantified DC motility on mPADs of identical geometry but different stiffness. Migration was indistinguishable on these mPADs, suggesting that DCs are responsive to geometry of ligand presentation and not stiffness. Further, by micropatterning ligands on flat PDMS surfaces in similar geometries to the mPAD arrays, we determined that DCs respond to the geometry of printed ligand. Finally, we used a variety of small molecule inhibitors to identify pathways involved in geometry sensing. We saw a significant role for myosin contractility and α5β1 integrin engagement. We also noted significant reorganization of the actin cytoskeleton into dynamic actin rings when DCs were motile on posts. From these experiments, we conclude that DCs are insensitive to substrate compliance in the range tested but respond to changes in geometry via a mechanism that involves integrin function, myosin contractility, and remodeling of the actin cytoskeleton. As a possible explanation, we postulate a consistent role for filopodial extension and contraction as the driver of DC motility.

Fabrication of biomimetic superhydrophobic surfaces by a simple flame treatment method

A simple flame treatment method was explored to construct micro/nanostructures on a surface and then fabricate a biomimetic superhydrophobic surface at a relatively low cost. SiO2-containing polydimethylsiloxane (PDMS) was used as a substrate. The PDMS replicas with various micropatterned surfaces were fabricated using grass leaf, sand paper, and PET sheet with parallel groove geometry as templates via PDMS replica molding. The PDMS replica surfaces with micron structures and the surface of a flat PDMS sheet as a control sample were further treated by flame. The fabricated surfaces were characterized by scanning electron microscopy and water contact angle measurements. The effect of surface microstructures on the transparency of PDMS was also investigated. The studies indicate that the fine nanoscale structures can be produced on the surfaces of PDMS replicas and a flat PDMS sheet by a flame treatment method, and that the hierarchical surface roughness can be adjusted and controlled by varying the flame treatment time. The flame-treated surfaces of PDMS replicas and a flat PDMS sheet possess superhydrophobicity and an ultra-low sliding angle reaching a limiting value of 1°, and the anisotropic wettability of the PDMS replica surface with oriented microgroove structures can be greatly suppressed via flame treatment. The visible light transmittance of the flame-treated flat PDMS surface decreases with prolonged flame treatment times. Copyright © 2016 John Wiley & Sons, Ltd.

Wettability of Polymeric Bionic Surface Replicated from Ginkgo Leaves

Ginkgo is one of the oldest extant seed plants through hundreds of millions of years of evolution. Ginkgo biloba has many unique properties and applications such as drug development and drinking tea. In recent years hydrophobic surfaces with bionic structures have attracted increasing interest for fundamental research and practical applications. As we all know, the Ginkgo leaf has remarkable texturing surface. In this manuscript, wettability of the bionic surface replicated from Ginkgo leaves was explored. The Ginkgo leaves were used as the original mold, from which microstructures were replicated into the surface of polydimethylsiloxane (PDMS). Compared with the topography of Ginkgo leaves, the topographical surface of PDMS was investigated by optical microscopy and scanning electron microscopy. By measuring the contact angle of polymeric bionic surfaces, there is the increase of ~20 degree than flat PDMS surfaces. Mechanical compression was applied on the polymeric bionic surfaces in one dimension, with the real-time measurement of the contact angle. The experimental results reveal that the wetting behavior of the surface can be reversibly tuned by applied mechanical stress, which induces the change in micro-scale topography. This research provides a guide for fabricating and tuning hydrophobic surfaces for various surface engineering applications.

Effects of Nanotextured PDMS on Cell Culture and Growth

Cell adhesion, morphology and growth are known to be influenced by microscale topography of the surfaces. Taking this a step further, nanotextured polydimethylsiloxane (PDMS) substrates were fabricated by micro reactive ion etching (Micro-RIE). This simple process gave good control on surface texture to improve the affinity of PDMS to enhance cell growth. The effects of various nanoscale roughnesses on cell growth were also quantified. Three different recipes were used to prepare nanotextured PDMS by micro-RIE using oxygen (O2) and carbon tetrafluoride (CF4). First of all etching was performed for 12 min and flow rate of O2 and CF4 was kept at a ratio of 1:1 to fabricate surface 1. Surface 2 was fabricated just by changing the ratio of O2 and CF4 to 1:2. Then the flow rates of gases were kept same as recipe 1 but the etching time was increased to 25 min to prepare surface 3. Next, surface topography of these PDMS substrates was evaluated quantitatively by measuring root mean square surface roughness using an atomic force microscope (AFM). The measured average roughness of three nanotextured PDMS surfaces were found 242.92±87.709 nm, 515±102.28 nm and 629.17±109.67 nm for surface 1, surface 2 and surface 3 respectively. The roughnesses of three types of nanotextured surfaces showed a correlation on cell growth. The cell growth rate on flat PDMS surfaces is known to be very low but nanotextured PDMS surfaces allowed exciting cell growth for three different types of cells (human glioblastoma (hGBM), astrocytesand fibroblast cells).The cells were seeded on various surfaces coated with laminin and incubated for 3 days at 37oC. The cell densities of experimental surfaces were calculated from their images using ImageJ software. For all types of cells, growth was higher on nantoextured PDMS surfaces compare to flat PDMS surface and surface 3 exhibited highest cell density among three nanotextured surfaces. However density of astrocytes cells was 114 ± 16.15 cells per mm2 in surface 3 where as flat PDMS had only 28 ± 3.58 cells per mm2. But standard well plate had higher cell density compare to surface 3 and it was 140 ± 18.07 cells per mm2. Again density of fibroblasts cells in surface 3 was 272.80 ± 13.68 cells per mm2 which was higher compare to flat PDMS but lower than standard well plate. On the other hand surface 3 exhibited very similar cell density as standard well plate for hGBM cells and cell densities were 346 ± 70.64 cells per mm2 and 334.67 ± 63.23 cells per mm2 respectively. Consequently it can be deduced that cell growth strongly depends on surface nanotexturing. By comparing three nanotextured surfaces it was found that surface 1 exhibited lowest roughness compare to surface 2 and surface 3. Therefore available surface area for laminin attachment was lowest in this surface. But surface 2 and surface 3 had higher roughness and therefore provided larger surface area to attach more laminin. As cell growth is a direct function to available laminin attached in the surface therefore cell density was more in later surfaces. In addition to that circulating tumor cells (CTCs) are known to have very high affinity towards nanotextured surfaces. Therefore density of only hGBM cells in nanotextured surface was very similar to cell density in standard well plate. As a result nanotextured PDMS may be thus useful for cancer cytology devices, especially to culture isolated CTCs for further investigation in microfluidic platforms.

Quantitative analysis of hepatic cell morphology and migration in response to nanoporous and microgrooved surface structures

Material surface topography is an important factor for regulating cellular behaviour. Understanding the mechanism of how surface topography influences mammalian cells is critical for the development of medical implants and tissue engineering. In this study, we investigated the influences of nanoporous and microgrooved substrates on the morphology and migration of hepatic cell line, BEL-7402 cells. Cells were cultured on nanoporous (140nm in diameter) anodized alumina membrane (AAM), nanoporous (140nm in diameter) polydimethylsiloxane (PDMS), and microgrooves (10μm, 30μm, and 50μm in width, and 2μm in depth) patterned PDMS, then imaged by fluorescent microscopy, time-lapse microscopy, and scanning electron microscopy (SEM). Cell morphology and migration were investigated through image analysis. The results suggest that the nanoporous and microgrooved surface structure induced totally different changes on BEL-7402 cells. Compared to the well-spread cells on the flat surface plate, the cells formed spheroids on the nanoporous AAM surface and nanoporous PDMS surface with no elongation and alignment, while the cells grew with elongated and aligned morphology along the microgrooves on the PDMS substrates. The BEL-7402 cell migration speed was significantly higher on the nanoporous substrates than on the flat surfaces. On the microgrooved PDMS substrates, the cells migrated along the groove direction and showed relatively small difference of the overall velocity compared to the cells on the flat PDMS surface. Our findings provide insights into the control of cell morphological features and migratory behaviour by using artificial nanoporous or microgrooved substrates, which can benefit the research on hepatocellular carcinoma metastasis, tissue engineering, and medical implant design.

Interaction of glia with a compliant, microstructured silicone surface

Soft bioengineered surfaces offer a route towards modulating the tissue responses to chronically implanted devices and may enhance their functionality. In this communication we fabricate microtopographically rich and mechanically compliant silicone surfaces for use in soft neural interfaces. We observe the interaction of primary rat microglia and astroglia with arrays of tall and short (4.7 and 0.5μm) vertically oriented polydimethylsiloxane (PDMS) micropillars and a flat PDMS surface in vitro. With the pillar size and spacing that we use (1.3μm diameter and 1.6μm edge to edge), glia are found to engulf and bend tall pillars. The cytoskeleton of cells adhering to the pillar arrays lacks actin stress fibers; instead we observe actin ring formations around individual pillars. Tall, but not short pillar arrays are inhibitory to migration and spreading for both microglia and astrocytes. When compared to a flat PDMS surface and short pillar arrays, tall micropillar arrays cause nearly a 2-fold decrease in proliferation rates for both cell types. The antimitotic properties of tall pillar arrays may be useful for reducing the density of the glial capsule around brain-implanted devices.

Patterning of carbon nanotube films on PDMS using SU-8 microstructures

In this paper, we propose a simple and low-cost fabrication technique for patterning carbon nanotube (CNT) films on polydimethylsiloxane (PDMS), which can be used in flexible sensors and electronics. We demonstrate CNT patterning on both recessed and flat PDMS surfaces using a standard photolithography method. By this proposed technique, we were able to fabricate a CNT film, having a high flexibility and good conductivity, on a PDMS surface. A CNT pattern with a minimum feature resolution of 150 μm was obtained using the proposed fabrication technique. The sheet resistance of the CNT film on the PDMS surface was determined to be in the 100–280 Ω/sq range. The thickness and resultant resistivity of the CNT film can be easily controlled by controlling just the spray duration. Furthermore, the gauge factor of the proposed device is higher than that of metal and it increases as the thickness of the CNT film increases.

Micropatterning and transferring of polymeric semiconductor thin films by hot lift-off and polymer bonding lithography in fabrication of organic field effect transistors (OFETs) on flexible substrate

Micropatterning and transferring of polymeric semiconductor thin films by hot lift-off and polymer bonding lithography in fabrication of OFETs with polymeric dielectric on the flexible substrate was proposed. The desired polymeric semiconductor patterns were fabricated on the flat polydimethylsiloxane (PDMS) surface with a selective lift-off method we proposed previously. The isolated and well defined polymeric semiconductor patterns left on the flat PDMS surface can be further transferred to the gate polymeric dielectric surface by polymer bonding lithography due to the low interfacial energy of PDMS. The transistor fabricated with this ‘dry’ process has a higher field-effect mobility compared with that using spin coated semiconductor layer.

Response of rat osteoblast-like cells to microstructured model surfaces in vitro

The role of surface microtopography in combination with different surface wettability for rat calvaria cell differentiation was examined. Mineralization and alkaline phosphatase (ALP) activity of rat calvaria cells on flat polydimethylsiloxane (PDMS) or PDMS contained pyramids which were either hydrophilic or hydrophobic were compared. ALP expressing cells were more frequent on hydrophilic PDMS contained pyramids. ALP activity, peaked at day 9, was highest for hydrophilic pyramids followed by hydrophobic pyramids and flat hydrophilic PDMS surfaces. A similar pattern was obtained with respect to mineralized nodules. These observations showed that micro-sized surface features promote differentiation of rat calvaria cells. Further, hydrophilic surfaces are more prone to stimulate differentiation in comparison with hydrophobic surfaces. The results suggest that both material surface chemistry and topography affect osteoblast differentiation.