Self-assembling of large ordered DNA arrays using superhydrophobic patterned surfaces

Abstract

In this paper we present a simple and robust method to realize highly ordered arrays of stretched and suspended DNA molecules over the millimeter length scale. To this end we used an ad hoc designed superhydrophobic surface made of high aspect-ratio silicon pillars, where we deposited a droplet containing genomic DNA. A precise positioning of DNA strands was achieved by shaping the silicon pillars so that sharpened features resembling tips were included. Such features allowed us to accurately control the droplet de-wetting dynamics, pinning DNA strands in a well-defined position above pillars. The proposed technique has the potential to positively impact on the development of novel DNA chips for genetic analysis.

Buoyancy-induced on-the-spot mixing in droplets evaporating on nonwetting surfaces

“…A cross section of the toroidal vortex, appearing as a counter-rotating vortex pair in the 2D plane, is observed with flow directed inward towards the center of the droplet along the substrate and upward along the vertical axis. This flow behavior is opposite to that on a hydrophilic surface where the flow along the substrate is directed outwards towards the contact line [2,10]. The axisymmetric nature of the toroidal vortex pattern is further confirmed by PIV visualization in the horizontal plane of the droplet at its maximum diameter (at y/ h ≈ 0.23, where y and h represent the distance from the base of the droplet and the droplet height, respectively), as shown in Fig.…”

“…Prediction and control of evaporation-driven convection patterns during droplet evaporation on nonwetting surfaces, and the resulting spatial distribution of particulate deposits on the surfaces, are crucial for application in crystal arrays [1], DNA microarrays [2], nanofabrication [3,4], and sensors [5][6][7]. These applications call for an improved understanding of the physics of flow inside an evaporating sessile droplet and its dependence on the substrate wetting properties, which can assist in the development of nonintrusive methods for manipulating flow inside microdroplets.…”

Effect of superhydrophobic surface morphology on evaporative deposition patterns

“…A correlation between deposit size and surface morphology, explained in terms of the interface pressure balance at the transition between wetting states, reveals an optimum surface morphology for minimizing the deposit coverage area. 4 DNA microarrays, 5,6 biosensors, 7-9 and protein delivery systems 10 rely on localized, evaporative deposition to detect and analyze biological materials. For processes that require uniform particulate deposits from inkjet-printed droplets, the effects of particle concentration 11 and solvent composition 11,12 have been studied to eliminate undesirable ringlike patterns.…”

“…32 In Figure 2(c), the droplet begins to evaporate with an initial contact angle of 160. 5 . For 0.43 Շ s Շ 0.90, the contact radius recedes as the contact line abruptly pins and de-pins repeatedly to maintain an average contact angle of $148.…”

Biomechanical investigation of colorectal cancer cells

“…Before images acquisition, cells were fixed in glutaraldehyde and sputter coated with gold as previously described. [9][10][11] The mechanical properties of cells were probed by atomic force microscopy (Nanowizard II, JPK, Germany) mounted on an inverted optical microscope (Axio Observer ZEISS, Germany). Cells were kept in the cell culture medium at a constant temperature (37 C) throughout data acquisition.…”