Papers by Keyword: Micropillars

Abstract: Studies have shown that surface texture can improve lubrication state and reduce friction and wear. The cold pressing process of micro-units can prepare surface textures at low cost, in large quantities, and with high efficiency, but the micro-pillar array mold required for the cold pressing process is difficult to prepare. In this study, the influence of mask electrochemical processing parameters on the height and height uniformity of the micropillar array was studied by orthogonal experiment on the 42CrMo alloy steel. Four main factors are designed in the orthogonal experiment, namely voltage, duty cycle, frequency, and mask spacing, and each factor is set to three levels. The results of the range analysis show that: voltage and duty cycle are positively correlated with the height of the microcolumn, but negatively correlated with uniformity, and when the duty cycle is 50%, the uniformity of the microcolumn decreases sharply; The height and uniformity of the microcolumns increase with the increase of mask spacing. The height of the microcolumn is positively correlated with the frequency, and the uniformity of the microcolumn first increases and then decreases with the increase of frequency. Therefore, in order to meet the height and uniformity requirements at the same time, the grey correlation analysis method was used to obtain the optimal processing parameters: 35 V (voltage), 30% (duty cycle), 300 um (spacing), and 5 kHz (frequency). The average height of the microcolumns prepared by this parameter is 57.632 um and the microcolumn has excellent high uniformity.

Abstract: This paper presents a study on monitoring the native oxide growth on silicon micro-pillars. It also presents a comparison between the rates of oxide growth on pillars fabricated using the reactive ion etching (RIE) approach and the metal assisted chemical etching (MACE) approach. The native oxide growth is monitored using photoluminescence (PL) measurements. PL measurements showed that native silicon oxide grows at a higher rate on MACE pillars compared to RIE pillars. SEM images showed that the MACE pillars exhibit a porous outer layer while the RIE pillars show a dense outer layer. It is concluded that the porosity of the pillars enhances the native oxide growth.

Abstract: It is well-known that cellular behavior can be guided by chemical signals and physical interactions at the cell-substrate interface. The patterns that cells encounter in their natural environment include nanometer-to-micrometer-sized topographies comprising extracellular matrix, proteins, and adjacent cells. Whether cells transduce substrate rigidity at the microscopic scale (for example, sensing the rigidity between adhesion sites) or the nanoscopic scale remains an open question. Here we report that micromolded elastomeric micropost arrays can decouple substrate rigidity from adhesive and surface properties. Arrays of poly (dimethylsiloxane) (PDMS) microposts from microfabricated silicon masters have been fabricated. To control substrate rigidity they present the same post heights but different surface area and spacing between posts. The main advantage of micropost arrays over other surface modification solutions (i.e. hydrogels) is that measured subcellular traction forces could be attributed directly to focal adhesions. This would allow to map traction forces to individual focal adhesions and spatially quantify subcellular distributions of focal-adhesion area, traction force and focal-adhesion stress. Moreover, different adhesion intracellular pathways could be used by the cells to differentiate toward a proliferative or a contractile cellular phenotype, for instance. This particular application is advantageous for vascular tissue engineering applications, where mimicking as close as possible the vessels dynamics should be a step forward in this research field.