The figure schematically illustrates a developmental automated hybrid acoustic/electrostatic apparatus for levitating both electrically charged and electrically neutral liquid drops with sizes up to about 1 mm. The apparatus is particularly suitable for experiments on the growth of protein crystals from solution and on the growth of cells and tissues, all under controlled conditions. In addition to the obvious advantage of levitation for preventing the chemical and thermal contamination that accompanies contact between drops and external objects, this apparatus provides controllable rotation about a horizontal axis (for example, to reduce sedimentation). Moreover, the direction of rotation can be varied to randomize the effective direction of gravitation. Thus, on Earth, the apparatus is expected to provide some of the advantages of low gravitation for suppressing the buoyancy-induced flows that interfere with the growth of high-quality protein crystals and for reducing the adverse effects that gravitation exerts on some cell and tissue cultures.
An electrically neutral drop can be levitated acoustically. An electrically charged drop can be levitated electrostatically and/or acoustically. An important advantage of using both kinds of levitation is that if the acoustic field is used to produce rotation, the intensity of this field can be minimized, thereby minimizing disturbances in the drop. It has been conjectured that aerodynamic drag from acoustic streaming in the surrounding air is the physical mechanism through which the acoustic field exerts torque on the drop. The direction and amount of torque can be controlled by horizontal displacement of the acoustic transducer from its nominal central position under the acoustic reflector.
The apparatus allows optical access for observation, diagnosis, and process control. For example, optical diagnoses could be performed by imaging, light-scattering, and spectroscopic techniques. Temperature and humidity can be controlled and purity can be maintained by placing the apparatus in a closed chamber. A focused beam of light from a laser or other radiant source can be used for directional heating of a levitated drop.
This Hybrid Acoustic/Electrostatic Levitation Apparatus provides relatively quiescent levitation under controlled conditions, plus optical access for observation, diagnosis, and process control.
This work was done by Eugene H. Trinh and Sang K. Chung of Caltech for NASA's Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free on-line at www.nasatech.com under the Physical Sciences category.
In accordance with Public Law 96-517, the contractor has elected to retain title to this invention. Inquiries concerning rights for its commercial use should be addressed to
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Refer to NPO-20165, volume and number of this NASA Tech Briefs issue, and the page number.
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Hybrid acoustic/electrostatic levitation apparatus
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Overview
The document presents a technical report on a novel Hybrid Acoustic/Electrostatic Levitation Apparatus developed by Sang K. Chung and Eugene H. Trinh at NASA's Jet Propulsion Laboratory (JPL). This innovative device addresses the challenges of crystal growth and biological experiments in the presence of gravity, which can adversely affect the quality and yield of protein crystals and cell cultures.
The primary issue with traditional crystal growth methods is that gravity induces buoyancy-driven flows and sedimentation, leading to the formation of lower quality crystals. The report highlights that low-gravity environments, such as those experienced in space, significantly enhance the growth of high-quality crystals. To replicate these beneficial conditions on Earth, the apparatus employs a hybrid levitation system that combines electrostatic and ultrasonic levitation techniques.
The device can levitate charged and uncharged droplets ranging from 0.5 to 10 mm in diameter, allowing for precise control over their rotational state. By rotating the droplets along a horizontal axis, the apparatus simulates low-gravity conditions, which helps mitigate sedimentation and enhances crystal growth. The rotation can be adjusted in various directions, providing flexibility in experimental setups.
Key features of the apparatus include:
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Hybrid Levitation: The combination of electrostatic and ultrasonic levitation minimizes disturbances to the droplet, allowing for a stable environment conducive to crystal growth.
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Rotation Control: The system can induce slow or rapid rotation, enabling researchers to explore the effects of varying gravitational conditions on crystal formation and biological processes.
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Controlled Environment: The apparatus operates in a closed chamber where temperature, humidity, and purity can be tightly regulated. This isolation from external contaminants is crucial for achieving high-quality results.
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Automation and Diagnostics: The device is semi-automated and can be further developed for full automation. Its compact size allows for the integration of optical and spectroscopic diagnostic tools, facilitating real-time monitoring and process control.
Overall, this hybrid levitation apparatus represents a significant advancement in the field of materials science and biological research, providing a versatile platform for studying the effects of gravity on crystal growth and cellular behavior. The work is funded by NASA and aims to enhance the understanding of fundamental processes in crystal growth and tissue culture under controlled conditions.
