#contact angle

Rubbing a balloon on your hair can build a significant electrical charge. Water droplets have the same issue when they slide across a hydrophobic, electrically-insulated surface.  (Image credit: D. Carlson; research credit: A. Ratschow et al.; via APS Physics) Read the full article

Getting enough water in arid climates can be tough, but Western diamondback rattlesnakes have a secret weapon: their scales. (Video and image credit: ACS; research credit: A. Phadnis et al.; via The Kid Should See This)

Building microfluidic circuits is generally a multi-day process, requiring a clean room and specialized manufacturing equipment. A new study suggests a quicker alternative using fluid walls to define the circuit instead of solid ones. The authors refer to their technique as “Freestyle Fluidics”. As seen above, the shape of the circuit is printed in the operating fluid, then covered by a layer of immiscible, transparent fluid. This outer layer help prevent evaporation. Underneath, the circuit holds its shape due to interfacial forces pinning it in place. Those same forces can be used to passively drive flow in the circuit, as shown in the lower animation, where fluid is pumped from one droplet to the other by pressure differences due to curvature. Changing the width of connecting channels can also direct flow in the circuits. This technique offers better biocompatibility than conventional microfluidic circuits, and the authors hope that this, along with simplified manufacturing, will help the technique spread. (Image and research credit: E. Walsh et al., source)

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THK Linear Motion Guide Model HSR10RM, Single Block: 13mm Height, 20mm Width, 31mm Length, Rail: 7mm Height, 10mm Width, 120mm Length, 25mm Pitch THK Global Standard Full-Ball LM Guide Model HSR. Balls roll in four rows of raceways precision-ground on an LM rail and an LM block, and endplates incorporated in the LM block allow the balls to circulate. Each row of balls is placed at a contact angle of 45° so that the rated loads applied to the LM block are uniform in the four directions (radial, reverse radial and lateral directions), enabling the LM Guide to be used in all orientations and in extensive applications. In addition, the LM block can receive a well-balanced preload, increasing the rigidity in the four directions while maintaining a constant, low friction coefficient. With the low sectional height and the high rigidity design of the LM block, this model achieves highly accurate and stable straight motion. Even under a preload or excessive biased load, differential slip of balls does not occur. As a result, smooth motion, high wear resistance, and long-term maintenance of accuracy are achieved.