Materials matter in microfluidics. Since the introduction of soft lithography as a prototyping technique and polydimethylsiloxane (PDMS) as material of choice the microfluidics community has settled with using this material almost exclusively. However, for many applications PDMS is not an ideal material given its limited solvent resistance and hydrophobicity which makes it especially disadvantageous for certain cell-based assays. For these applications polystyrene (PS) would be a better choice. PS has been used in biology research and analytics for decades and numerous protocols have been developed and optimized for it. However, PS has not found widespread use in microfluidics mainly because, being a thermoplastic material, it is typically structured using industrial polymer replication techniques. This makes PS unsuitable for prototyping. In this paper, we introduce a new structuring method for PS which is compatible with soft lithography prototyping. We develop a liquid PS prepolymer which we term as "Liquid Polystyrene" (liqPS). liqPS is a viscous free-flowing liquid which can be cured by visible light exposure using soft replication templates, e.g., made from PDMS. Using liqPS prototyping microfluidic systems in PS is as easy as prototyping microfluidic systems in PDMS. We demonstrate that cured liqPS is (chemically and physically) identical to commercial PS. Comparative studies on mouse fibroblasts L929 showed that liqPS cannot be distinguished from commercial PS in such experiments. Researchers can develop and optimize microfluidic structures using liqPS and soft lithography. Once the device is to be commercialized it can be manufactured using scalable industrial polymer replication techniques in PS--the material is the same in both cases. Therefore, liqPS effectively closes the gap between "microfluidic prototyping" and "industrial microfluidics" by providing a common material.

A facile photolithographic platform for the design of cell-guiding polymeric substrates is introduced. Specific areas of the substrate are photo-deactivated for the subsequent growth of bioresistant polymer brushes, creating zones for cell proliferation, and protein adhesion.

The modification of the backbone properties of DNA origami nanostructures through noncovalent interactions with designed intercalators, based on acridine derivatized with side chains containing esterified fatty acids or oligo(ethylene glycol) residues is reported. Spectroscopic analyses indicate that these intercalators bind to DNA origami structures. Atomic force microscopy studies reveal that intercalator binding does not affect the structural intactness but leads to altered surface properties of the highly negatively charged nanostructures, as demonstrated by their interaction with solid mica or graphite supports. Moreover, the noncovalent interaction between the intercalators and the origami structures leads to alteration in cellular uptake, as shown by confocal microscopy studies using two different eukaryotic cell lines. Hence, the intercalator approach offers a potential means for tailoring the surface properties of DNA nanostructures.

future applications. To obtain biofunctional surfaces, amongst others the mode of immobilization, the distribution of the tethered molecules on a micrometer scale and the microtopography of the substrate need to be tailored. [ 2 ] So far, in vitro studies were mainly carried out on planar surfaces. To permit highly miniaturized and thus parallelized assays with low compound consumption, for instance to test the response of cells to effector molecules, microarrays of protein or ligandcoated spots ranging from 100-500 μ m in diameter can be produced by microcontact printing, spotting or patterning with microfl uidic networks. [ 3 ] To investigate the role of surface bound chemical cues on cell behavior, often patterns of biomolecules, particularly proteins, such as growth factors or cell adhesion proteins, have to be created. Biologically active molecules can be immobilized on chemically modifi ed patterns on the substrate. As in the production of microarrays, spatially-defi ned patterns of functional groups have been generated by microcontact printing [ 4 ] and microfl uidic networks, [ 5 ] but they can also be drawn by dip pen nanolithography (DPN) using the tip of a probe controlled by an atomic force microscope, [ 6 ] or created by mask-based lithography with biocompatible resists. [ 7 ] Another option to obtain patterns of functional groups is chemical vapor deposition (CVD) polymerization of [2.2]paracyclophane derivatives. [ 8 ] This

A novel SMART module, dubbed "DNA-SMART" (DNA substrate modification and replication by thermoforming) is reported, where polymer films are premodified with single-stranded DNA capture strands, microthermoformed into 3D structures, and postmodified with complementary DNA-protein conjugates to realize complex biologically active surfaces within microfluidic devices. As a proof of feasibility, it is demonstrated that microchannels presenting three different proteins on their inner curvilinear surface can be used for selective capture of cells under flow conditions.