Scientist Explains How to Levitate Objects With Sound | WIRED

WIRED
28 Jan 202010:01
EducationalLearning
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TLDRAcoustic levitation, a gravity-defying technology that uses sound waves to suspend objects, offers unique advantages for scientific applications. Despite its current limitations to small objects, such as a three-millimeter bead, it enables the study of chemical reactions and the development of better drugs and robotic arms. Developed by NASA, this method uses standing waves to create nodes for levitation, with potential for scaling up through arrays of transducers and integration with other levitation methods.

Takeaways
  • 🌐 Acoustic levitation is a real technology that uses sound waves to counteract gravity, distinct from science fiction.
  • 🔊 It can suspend both liquids and solids, unlike magnetic levitation which typically only works with conductive materials.
  • 📈 The largest object levitated so far is a three-millimeter bead, showcasing the technology's precision and delicacy.
  • 🧪 Acoustic levitation has practical applications, such as analyzing chemical reactions and improving drug development.
  • 🤖 It enhances robotic arms' ability to handle tiny and delicate objects without touch, reducing damage or contamination risks.
  • 🚀 The technology was initially developed by NASA in the '60s and '70s to study the effects of anti-gravity.
  • 🌀 Transducers create sound waves that interact to form standing waves, with nodes and antinodes determining levitation points.
  • 📏 The size of levitated objects is limited by the spacing between nodes, which is determined by the frequency of the sound waves.
  • 💥 Scaling up levitation to larger objects would require immense sound levels that could be deafening and destructive.
  • 🔄 Arrays of levitators can be used to levitate and move larger objects by adjusting the power and amplitude of individual units.
  • 🔮 Future applications may include combining acoustic levitation with other methods, such as aerodynamic levitation, for enhanced capabilities.
Q & A

  • What is acoustic levitation?

    -Acoustic levitation is a technology that uses sound waves to generate a force that counteracts gravity, effectively suspending objects in mid-air.

  • How is acoustic levitation different from magnetic levitation?

    -Acoustic levitation is unique because it can suspend both liquids and solids, unlike magnetic levitation which typically only works with materials that are conductive to magnetic fields.

  • What is the largest object that has been levitated using acoustic levitation?

    -The largest object levitated using acoustic levitation has been a three-millimeter bead.

  • What are some applications of acoustic levitation?

    -Applications of acoustic levitation include analyzing chemical reactions in suspension, creating better drugs, and improving robotic arms that can manipulate tiny, delicate objects.

  • How does the device used for acoustic levitation work?

    -The device uses transducers that drive horns, causing them to vibrate and generate sound waves. These waves interact to produce a standing wave with nodes and anti-nodes, where objects can be levitated.

  • What is the frequency of the sound waves used in acoustic levitation?

    -The sound waves used in acoustic levitation operate at 22 kilohertz, which is just on the edge of human hearing.

  • Why is there a limitation on the size of the objects that can be levitated?

    -The limitation is due to the spacing between the nodes of the standing wave, which is six millimeters. This spacing allows only objects smaller than half the node distance, such as a three-millimeter bead, to be levitated.

  • How do you precisely place an object in the levitation point?

    -You can calculate the precise distance between the nodes or use a mist of water to see the vortex formed, which indicates the most stable places within the levitation region where the droplets will be drawn.

  • What are the potential downsides of scaling up acoustic levitation for larger objects?

    -Scaling up would require larger transducers that generate a lot of sound, which could be deafening and destructive. For example, the sound level would be equivalent to that of a rock concert.

  • How can acoustic levitation be combined with other forms of levitation?

    -Acoustic levitation can be combined with aerodynamic levitation to get the benefits of both methods, allowing for the levitation of a wider range of objects and potentially more stability.

  • Is it possible for external sound waves to disrupt an acoustic levitation experiment?

    -Yes, external sound waves can disrupt the experiment because the device is unstable in the horizontal direction, especially if it's a single-axis levitator.

  • What are the future possibilities for scaling up acoustic levitation to levitate heavier objects?

    -Future possibilities include creating arrays of levitators to levitate larger objects by levitating in certain places rather than increasing the size of a single transducer. This also allows for the movement of objects in multiple directions.

Outlines
00:00
🌐 Introduction to Acoustic Levitation

This paragraph introduces the concept of acoustic levitation, a technology that uses sound waves to counteract gravity and suspend objects. It highlights the difference between acoustic and magnetic levitation, emphasizing the unique ability of acoustic levitation to handle both liquids and solids. The narrator mentions the current limitations in terms of the size of the objects that can be levitated, with the largest being a three-millimeter bead. The applications of this technology are also discussed, including its use in analyzing chemical reactions, drug creation, and enhancing robotic arms for manipulating delicate objects. The segment concludes with an introduction to Chris Benmore, a physicist at Argonne National Laboratory, who provides insights into how acoustic levitation works and its potential uses.

05:03
🔊 How Acoustic Levitation Functions

This paragraph delves into the mechanics of acoustic levitation, explaining how it uses sound waves to generate a force that counteracts gravity. It describes the development of the technology by NASA in the '60s and '70s for ground-based experiments. The narrator and Chris Benmore discuss the components of the levitation device, including transducers and horns, and how they create a standing wave that produces nodes and anti-nodes, which are essential for levitation. A demonstration is provided, showing how objects can be levitated within the cavities formed by the standing waves. The interaction of sound waves and their frequency is also discussed, noting that the high frequency of 22 kilohertz is at the edge of human hearing. The limitations of the technology in terms of the size of the objects that can be levitated are explored, along with the potential for scaling up the process.

Mindmap
Keywords
💡Acoustic Levitation
Acoustic levitation is a method that uses sound waves to counteract gravity and suspend objects in mid-air. It is unique because it can handle both liquids and solids, unlike magnetic levitation which is limited to conductive materials. In the video, it's mentioned that this technology was developed by NASA in the '60s and '70s for ground-based experiments. The process involves creating a standing wave that generates nodes and anti-nodes, where objects can be placed and levitated. An example from the script is levitating a three-millimeter bead using this technique.
💡Standing Wave
A standing wave is a wave pattern that occurs when two waves of the same frequency and amplitude interact, resulting in a wave that appears to stand still. In the context of acoustic levitation, standing waves are created by the interaction of sound waves from transducers and horns, which generate nodes and anti-nodes. These nodes are points of destructive interference where the wave amplitude is zero, and anti-nodes are points of constructive interference where the amplitude is at its maximum. Objects are levitated at the anti-nodes where the upward force of the sound wave balances the force of gravity. The video demonstrates this by levitating a brass rod in the cavity created by the standing wave.
💡Transducers
Transducers are devices that convert one form of energy into another. In the video, transducers are used to convert electrical energy into sound energy, which then drives the horns to vibrate and generate sound waves. These sound waves are crucial for creating the standing wave necessary for acoustic levitation. The script mentions that the transducers drive the horns, causing them to vibrate at 22,000 times per second, which is the frequency needed to create the standing wave for levitation.
💡Nodes and Antinodes
Nodes and antinodes are points within a standing wave where the wave's amplitude is at its minimum (nodes) or maximum (antinodes). In acoustic levitation, nodes are locations of destructive interference where the sound waves cancel each other out, and antinodes are locations of constructive interference where the sound waves amplify each other. Objects can be levitated at antinodes because the upward force of the sound wave at these points counteracts the force of gravity. The video explains that the levitation occurs in the spaces where the sound waves cancel, which are the antinodes of the standing wave.
💡Argonne National Laboratory
Argonne National Laboratory is a research facility dedicated to the support of the United States Naval Nuclear Propulsion Program. In the video, physicist Chris Benmore from Argonne National Laboratory explains how acoustic levitation works and its applications. The laboratory is noted for its intense X-ray source, which is used in conjunction with acoustic levitation to analyze the atomic structure of pharmaceutical drugs, aiding in the development of more effective medications.
💡Pharmaceutical Analysis
Pharmaceutical analysis refers to the process of studying the physical, chemical, and biological properties of drugs to ensure their safety, efficacy, and quality. In the video, it's mentioned that acoustic levitation is used at Argonne National Laboratory to hold droplets in space with no other interactions, allowing for precise analysis of pharmaceutical drugs. The combination of acoustic levitation and an extremely powerful X-ray source enables researchers to examine the atomic structure of drugs, identify molecular shapes, and understand how molecules interact, which is crucial for optimizing the manufacturing process and creating more effective pharmaceuticals.
💡X-ray Source
An X-ray source is a device that generates X-rays, which are a form of electromagnetic radiation with high energy and short wavelength. In the context of the video, Argonne National Laboratory possesses the most intense X-ray source in the western hemisphere. This X-ray source is used in conjunction with acoustic levitation to analyze the atomic structure of pharmaceutical drugs at the molecular level. By examining where all the atoms are arranged, researchers can identify the molecular shape and interactions, providing insights into the conditions needed to manufacture more effective drugs.
💡Robotic Arms
Robotic arms are mechanical devices that mimic the function of a human arm, with similar joints and movements. In the video, it's mentioned that acoustic levitation can be used to move objects without ever touching them, which reduces the risk of damage or contamination. This technology could potentially give robotic arms a more delicate touch, allowing them to handle fragile or small objects with precision. The video provides an example of a robotic arm that uses acoustic levitation to manipulate objects, showcasing the potential for future advancements in robotics and manufacturing.
💡Aerodynamic Levitation
Aerodynamic levitation is a method of suspending objects using air or gas flow. It's a simple and effective form of levitation where an object is held in place by the pressure differences created by the flow of air around it. In the video, the narrator mentions aerodynamic levitation as an example of another type of levitation, comparing it to the effect seen when a ping pong ball is placed on a hair dryer and lifted by the airflow. While this method is effective for certain objects, acoustic levitation is highlighted as being particularly useful for handling tiny, fragile objects and non-conductive substances like liquids.
💡Magnetic Levitation (Maglev)
Magnetic levitation, or maglev, is a method of suspending objects by using the principles of magnetism, specifically opposing magnetic forces. This technology is capable of supporting large loads, such as trains, by creating a magnetic field that counteracts gravity. In the video, maglev is mentioned as one of the many types of levitation methods available. However, it's noted that maglev is limited to conductive materials and is not suitable for non-conductive substances like liquids, which acoustic levitation can handle effectively.
💡Scale-up
Scale-up refers to the process of increasing the size or capacity of a system or process while maintaining its functionality. In the context of the video, scale-up relates to the challenge of levitating larger objects using acoustic levitation. The script discusses how researchers are attempting to scale up by creating arrays of levitators, which allows for levitating larger objects by using multiple devices in a coordinated manner. This approach avoids the need for a single, larger transducer, which would produce an extremely loud and potentially destructive sound.
Highlights

Acoustic levitation uses sound waves to counteract gravity, making it a unique technology different from magnetic levitation.

It can effectively suspend both liquids and solids, unlike other levitation methods.

The largest object levitated so far is a three-millimeter bead, showing the current scale of this technology.

Acoustic levitation has practical applications such as analyzing chemical reactions in suspension and the creation of better drugs.

The technology was developed by NASA in the '60s and '70s for ground-based experiments.

The device uses transducers to drive horns that vibrate and generate sound waves at 22,000 times per second.

The interaction of two sound waves creates a standing wave, which can suspend objects at the points where they cancel each other out.

The high frequency of the sound waves is almost imperceptible to humans, despite the device being loud.

The six-millimeter spacing between nodes in the standing wave limits the size of the objects that can be levitated.

Objects levitate in the precise positions determined by the geometry of the standing wave.

The technology has limitations for size due to the intensity of sound required, which can be deafening and destructive.

An outside actor could potentially disrupt the levitation process by introducing their own sound waves.

Acoustic levitation is ideal for holding droplets in space with no other interactions, making it useful for studying them.

The Argonne National Laboratory is using acoustic levitation to analyze pharmaceutical drugs with an extremely powerful X-ray.

Scaling up levitation involves using arrays of levitators to levitate larger objects in certain places.

Robotic arms using acoustic levitation can move objects without touching them, reducing damage or contamination risks.

Acoustic levitation is particularly effective for handling tiny, fragile objects and non-conductive substances like liquids.

Combining acoustic levitator with an aerodynamic levitator is an ongoing application that leverages the benefits of both technologies.

While levitating a hoverboard or a person is not feasible with current technology, it is possible to levitate heavier objects than before.

Transcripts

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Acoustic LevitationGravity DefyingScience FictionNASA TechnologyArgonne National LabChris BenmoreStanding WavesPharmaceutical AnalysisRobotic PrecisionInnovative Research