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Torsional fracture of viscoelastic liquid bridges.

ABSTRACT: Short liquid bridges are stable under the action of surface tension. In applications like electronic packaging, food engineering, and additive manufacturing, this poses challenges to the clean and fast dispensing of viscoelastic fluids. Here, we investigate how viscoelastic liquid bridges can be destabilized by torsion. By combining high-speed imaging and numerical simulation, we show that concave surfaces of liquid bridges can localize shear, in turn localizing normal stresses and making the surface more concave. Such positive feedback creates an indent, which propagates toward the center and leads to breakup of the liquid bridge. The indent formation mechanism closely resembles edge fracture, an often undesired viscoelastic flow instability characterized by the sudden indentation of the fluid's free surface when the fluid is subjected to shear. By applying torsion, even short, capillary stable liquid bridges can be broken in the order of 1 s. This may lead to the development of dispensing protocols that reduce substrate contamination by the satellite droplets and long capillary tails formed by capillary retraction, which is the current mainstream industrial method for destabilizing viscoelastic liquid bridges.

SUBMITTER: Chan ST

PROVIDER: S-EPMC8214669 | biostudies-literature | 2021 Jun

REPOSITORIES: biostudies-literature

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Torsional fracture of viscoelastic liquid bridges.

Chan San To ST van Berlo Frank P A FPA Faizi Hammad A HA Matsumoto Atsushi A Haward Simon J SJ Anderson Patrick D PD Shen Amy Q AQ

Proceedings of the National Academy of Sciences of the United States of America 20210601 24

Short liquid bridges are stable under the action of surface tension. In applications like electronic packaging, food engineering, and additive manufacturing, this poses challenges to the clean and fast dispensing of viscoelastic fluids. Here, we investigate how viscoelastic liquid bridges can be destabilized by torsion. By combining high-speed imaging and numerical simulation, we show that concave surfaces of liquid bridges can localize shear, in turn localizing normal stresses and making the su ...[more]

PMID: 34117125

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Project description:ObjectiveLong bone fractures are a common injury in the pediatric population. Differentiation between abusive, or non-accidental trauma, and accidental trauma in children remains challenging for forensic practitioners. A recent clinical-based study was able to separate pediatric abusive from accidental trauma based on femoral fracture pattern using the ratio of fracture length over bone diameter (fracture ratio), as determined from radiographic analysis of this fractured bone. The forensic literature indicates more cases of abuse in younger pediatric victims than accidental cases. While this was the case in the clinical study, the effect was not shown to be statistically significant. Furthermore, while speed of trauma was not considered in the clinical study, a laboratory study with an immature bovine model indicates rotational speed influences fracture pattern, but specimen age was not varied in that study. Therefore, the objective of the current study was to use immature porcine femora to investigate the effects of age and rate of twist on a modified version of this fracture ratio parameter.MethodsFifteen pairs of porcine femora with various ages were twisted until observable failure using a custom-built torsional fixture. The left femur of each pair was twisted to failure at a rate of 3 deg/s, while the right femur was twisted at a rate of 90 deg/s. The torque and angle of rotation were recorded at a sampling rate of 10,000 Hz. Fracture ratio was defined as total fracture length divided by bone diameter.ResultsFracture ratio increased with specimen age, with specimens under the low rate of twist yielding a consistently lower fracture ratio than those from specimens under the high rate of twist. The results showed that both specimen age and rate of twist were significant factors influencing fracture ratio.ConclusionThe determination of abusive from accidental trauma in criminal cases, based on the pattern of long bone fracture alone, may need to include additional data on the specific age of the pediatric victim and the potential speed of the traumatic event.

Dataset Information

Torsional fracture of viscoelastic liquid bridges.

Publications

Torsional fracture of viscoelastic liquid bridges.

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