João T Cabral

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Frontal photopolymerization (FPP) offers numerous advantages for the rapid prototyping of microfluidic devices. Quantitative utilization of this method, however, requires a control of the vertical dimensions of the patterned resist material. To address this fundamental problem, we study the ultraviolet (UV) photopolymerization of a series of multifunctional(More)
Rapid prototyping photolithography of a thiolene-based resin was used to fabricate microfluidic devices stable to aliphatic and aromatic organic solvents. The swelling of the cross-linked polymer matrix in various organic solvents was quantified, and the solvent resistance properties of these microfluidic devices are described. Discrete droplets of hexanes(More)
We report a microfluidic instrument to rapidly measure the interfacial tension of multi-component immiscible liquids. The measurement principle rests upon the deformation and retraction dynamics of drops under extensional flow and was implemented for the first time in microfluidics (S. D. Hudson et al., Appl. Phys. Lett., 2005, 87, 081905 (ref. )). Here we(More)
While many parallel synthesis methods developed by the pharmaceutical and life science communities are being applied to polymer synthesis, there remains a need to construct "libraries" of polymeric materials that explore a wider range of polymer structures with accuracy, flexibility, and rapid, often small, changes. We report the use of microfluidics to(More)
We investigate the surface plasma oxidation of polydimethylsiloxane (PDMS) elastomers and its implication for the morphologies attainable by wrinkling of glassy-elastomer 'bilayers'. The kinetics of glassy skin formation is found to follow a logarithmic dependence with plasma exposure time t and, for various plasma intensities I, the relevant control(More)
We have demonstrated that polycondensation reactions can be carried out in a combinatorial fashion and that the polymer library can be screened at high throughput using a rapid prototyping technique to fabricate multiwell substrates. A linearly varying compositional library of 100 different biodegradable polyanhydride random copolymers that are promising(More)
A key challenge to the commercialization of organic bulk heterojunction solar cells is the achievement of morphological stability, particularly under thermal stress conditions. Here we show that a low-level light exposure processing step during fabrication of blend polymer:PC60BM solar cells can result in a 10-fold increase in device thermal stability and,(More)
We study the surface oxidation of polydimethylsiloxane (PDMS) by air plasma exposure and its implications for the mechanically-induced surface wrinkling of the resulting glass-elastomer bilayers. The effect of plasma frequency (kHz and MHz), oxygen content (from O2 to air), pressure (0.5 ≤ P ≤ 1.5 mbar), as well as exposure time and power, is quantified in(More)
We report a general light processing strategy for organic solar cells (OSC) that exploits the propensity of the fullerene derivative PC60BM to photo-oligomerize, which is capable of both stabilizing the polymer:PC60BM active layer morphology and enhancing the device stability under thermal annealing. The observations hold for blends of PC60BM with an array(More)