A thermal cycling method, whereby capillary tubes holding polymerase chain reactions are subjected to programmed tilt displacements so that they are moved using gravity over three spatial regions (I, II, and III) kept at different constant temperatures to facilitate deoxyribonucleic acid (DNA) denaturation, annealing, and extension, is described. At tilt speeds in excess of 0.2 rad/s, the standard deviation of static coefficient of friction values was below 0.03, indicating in sync movement of multiple capillary tubes over the holding platform. The travel time during the acceleration phase and under constant velocity between adjacent regions (I to II and II to III) and distant regions (III to I) was 0.03 s and 0.31 s, respectively. The deviations in temperature did not exceed 0.05 °C from the average at the prescribed denaturing, annealing, and extension temperatures applied. DNA amplification was determined by optical readings, the fluorescence signal was found to increase twofold after 30 thermal cycles, and 1.16 × 106 DNA copies/μl could be detected. The approach also overcomes problems associated with thermal inertia, sample adhesion, sample blockage, and handling of the reaction vessels encountered in the other thermal cycling schemes used.

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Highly wetting and nonwetting substrates have been widely used in fogwater collection systems for enhanced water harvesting. In this work, fog harvesting substrates comprising PVC strips of different wetting properties and widths ranging from 1–5 mm were vertically aligned and spaced apart at regular intervals to give the same solid area fraction of 0.8. Evaluation of the water collection efficiencies of the tested configurations revealed that 1 mm wide superhydrophilic strips was the most efficient, achieving double the amount of water harvested compared with 2.8 mm wide strips. This finding was attributed to the low Stokes numbers of the aerosol particle distribution of the fog which tended to result in them being brought by the flow streamlines toward the air gaps between the strips. Stagnant flow regions at the edges of each strip, revealed through potential flow calculations, then caused higher liquid imbibition and impaction there for water harvesting. It was also found that the Cassie nonwetting substrates that originally exhibited contact angles of 161° transformed to Wenzel wetting with zero contact angle within 60 min of fog interception. Optical profilometry revealed no obvious difference in surface roughness between the central region and edges of the strips, indicating that surface morphology was unlikely to be a contributing factor for enhanced water collection at the edges. The findings here indicated that highly wetting vertical strip architectures with narrow widths (1 mm) were favorable over wider strips for water harvesting provided that clogging and re-entrainment were not significant factors.

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