COMSOL Blog » Mark Fowler Fri, 20 Jan 2017 20:18:02 +0000 en-US hourly 1 Magnetic Damping of a Vibrating Cantilever Beam Mon, 12 Jan 2015 09:02:12 +0000 What happens when you place a vibrating conductive object in a static magnetic field? The magnetic field will induce a current in the moving solid and the charges moving through a magnetic field will experience a force. The resultant force acts to oppose the motion of the structure, which will lead to damping.

Modeling Example: Damping a Vibrating Cantilever Beam

Let’s consider a cantilever beam in a magnetic field, as shown below. It is assumed that there is some structural excitation at the free end of the beam that vibrates the beam at a constant frequency. The magnitude of this excitation is quite low and, as a consequence, the displacements will be small. We will also assume linear elastic material behavior and thus model the structural problem in the frequency domain. However, even though the displacements are small, the velocity (which is the time-derivative of displacement) can be quite large.

From the point of view of the electromagnetic problem, we also assume that the displacements of the beam are small — that is, the magnetic field lines will not change as the beam vibrates. As a consequence, we can compute the magnetic fields with the beam in its unperturbed position. We consider a modeling domain consisting of the beam and a current-carrying wire. An air box around the two encloses the modeling space, and the air box is assumed to be truncated by a good electric conductor — that is, the system sits inside a metallic box.

Now, although the beam itself is assumed to have zero displacement, its velocity is non-zero. A good conductor moving through a static magnetic field, , will experience induced currents, , given by:

{\mathbf{J}{_i}} = \sigma\mathbf{v} \times {\mathbf{B}}

where is the material conductivity and is the velocity of the conductor. It is further assumed that the magnetic fields induced by these currents are relatively small compared to the magnetic field due to the current flowing in the wire. These induced currents in the beam will interact with the static magnetic field due to the current-carrying wire and exert a local force on the conductive beam (a Lorentz force):

{\mathbf{F = J \times B}}

This force acts to oppose the velocity of the material, leading to a damping of the vibrations. The lost vibrational energy is dissipated as an ohmic heat loss:

\mathbf{Q} = |\mathbf{J}|^2/ \sigma

A model shows a cantilever beam in a magnetic field.
The system under consideration: A vibrating conductive beam next to a wire carrying a large DC current.

Coupling the Magnetic and Electric Fields and Solid Mechanics Interfaces

So, does the magnetic field provide significant damping of the beam? Let’s turn to COMSOL Multiphysics, the AC/DC Module, and the Structural Mechanics Module to find out. (Note that we could use the Acoustics Module or MEMS Module instead of the Structural Mechanics Module.)

In our modeling example, we will assume the following to be true:

  • The driving current in the wire and the resultant background magnetic field remain constant over time
  • The relative magnitude of the structural displacements of the beam is small
  • The magnetic fields arising from the induced currents are small relative to the background field
  • The material has isotropic and linear properties

Under these assumptions, we can pose the following question: How much damping will the vibrating metallic beam experience due to different background magnetic field intensities?

In order to answer this question, we will need to couple the Magnetic and Electric Fields and Solid Mechanics interfaces.

The model is set up in two steps. First, we compute the magnetic field due to the current-carrying wire next to the cantilever beam using a Stationary study. In the second step, we solve for the (small) displacements of the cantilever beam for a range of harmonically excited loads using the Solid Mechanics interface and a Frequency Domain study. We can set up additional variables with the graphical user interface to define the induced currents and the Lorentz force. This force vector can be applied as a body load for the structural problem. In addition, the strength of the magnetic fields is varied using the Parametric Sweep study. This lets us observe the effect of magnetic damping on the oscillating beam for different magnetic field strengths.

First, we can simulate the magnetic flux due to the current flowing through the wire. As the current through the wire increases, the magnitude of the magnetic flux increases.

An image highlighting the magnetic flux density.
The magnetic field due to a constant current flowing through the wire.

Next, we plot the cantilever beam’s tip displacement versus structural excitation frequency for different magnetic field intensities. As shown in the graph, the beam is significantly damped by the stronger magnetic field.

A displacement point graph.
Tip displacement versus excitation frequency for different magnetic field strengths.

Model Download

]]> 0
Happy 223rd Birthday, Michael Faraday Mon, 22 Sep 2014 08:10:44 +0000 Today marks the 223rd birthday of Michael Faraday, the famous British physicist and chemist. His remarkable contributions, particularly within electrochemistry and electromagnetism, helped pave the way for breakthroughs in modern science.

From Rags to Respect

Born on September 22, 1791 in Newington Butts (a former village now known as the London Borough of Southwark), Michael Faraday was raised in a less-than-affluent household. Because he received limited formal education due to his social status, Faraday educated himself by reading many books during an apprenticeship with George Riebu, a local bookbinder and bookseller.

An oil painting of Michael Faraday.
Oil painting of Michael Faraday.

While reading countless books at his apprenticeship, Faraday took an interest in science and wound up attending lectures given by Sir Humphry Davy, an English chemist and professor at the Royal Institution in London, in 1812. (William Dance, a customer of Riebu’s, lent Faraday tickets to attend Davy’s lectures.)

There, Faraday took many notes and proceeded to send the professor a 300-page book, based on his compiled records. Soon after receiving his book, Davy employed Faraday as a secretary and, years later, promoted him to Chemical Assistant at the institution. In 1825, he was appointed as a life-time Fullerian Professor of Chemistry.

Faraday’s Chemistry Work

It has been noted that Faraday’s earliest work in chemistry dates back to his days as an assistant to Humphry Davy. While often eclipsed by his research on electricity and magnetism, his work in chemistry should not go unrecognized.

Diffusion Experiments and Liquefying Gases

Faraday studied gases extensively. At the institution’s lab, Faraday performed some of the first experiments on the diffusion of gases, a phenomenon first identified by John Dalton. Although Faraday is credited with performing the first diffusion experiments, it wasn’t until years later that Thomas Graham and Joseph Loschmidt revealed the true physical importance of the phenomenon.

Furthermore, Faraday spent ample time studying chlorine and was successful in liquefying it, among other gases. This work helped with the acceptance of the fact that gases are merely liquid vapors with extremely low boiling points.

A painting showing Faraday in his lab.
Watercolor of Michael Faraday in his lab.

Discovering Chemical Substances

Moreover, Faraday discovered multiple chemical substances, such as benzene — an organic chemical compound. Early on, prior to the 1920s, benzene was used as an industrial solvent, until its carcinogenic properties became apparent. Interestingly enough, it had a short-lived use as an after-shave lotion because of its fragrance. Today, benzene is commonly found in motor oil, as it is a natural component of crude oil.

Laws of Electrolysis

Michael Faraday’s most notable contribution to chemistry is his discovery of the laws of electrolysis. These laws help describe the strengths of electrolytic effects.

Electrolysis is a method of using direct currents (DC) through an electrolyte to create a non-spontaneous chemical reaction. Today, electrolysis is commercially used to create various substances (e.g., caustic soda and aluminum), in electroplating, and in the process of anodization.

Faraday’s Work in Electricity and Magnetism

While it is evident Faraday’s work in chemistry is noteworthy, his research on electricity and magnetism is what makes him one of the most influential people in the history of science.

Electromagnetic Rotation

In response to other researchers’ many failed attempts at designing an electric motor, Faraday constructed two devices that produced electromagnetic rotation in 1821. One of his devices, which is recognized today as the homopolar motor, generated a continuous circular motion that was caused by a circular magnetic force around a wire, which was extended into a pool of mercury.

Image depicting the electromagnetic rotation experiment.
Drawing of Faraday’s electromagnetic rotation experiment.

Coupled with past research, Faraday’s invention was a building block for the electric motors that are still commonly relied upon and used today.

Discovering Electromagnetic Induction

Michael Faraday is also credited with discovering electromagnetic induction in 1831. His discovery came to light during an experiment where he took two insulated coils of wire and wrapped them around an iron ring. He noticed that when one electric current passed through one of the insulated coils, a brief current was generated in the other one.

Additionally, Faraday found that by moving a magnet through a loop of wire, an electric current will flow through the wire. This discovery led to what is known today as Faraday’s law, which describes how electric fields are produced by varying magnetic fields. Faraday’s law is still used as the underlying operating principle for inductors, transformers, electric motors, and generators.

Further Reading Related to Michael Faraday’s Work

]]> 0
Shape-Memory Polymer May Help in Facial Reconstructions Fri, 19 Sep 2014 08:06:34 +0000 Facial reconstruction methods are often needed to treat bone gaps that result from birth defects and injuries. At Texas A&M, researchers have developed a shape-memory polymer that has the potential to fill in critical-sized bone defects in the face, as well as allow for the growth of new bone cells.

Biodegradable Shape-Memory Polymer

The research team’s “self-fitting” material is a biodegradable shape-memory polymer (SMP), a type of material that becomes malleable when heated to a specific temperature. When heated, the polymer can transmute from a rigid state to become extremely pliable, allowing for it to be easily molded. With its physical properties, the SMP could be used to fill in bone defects in the head, face, or jaw.

The research team, spearheaded by Melissa Grunlan, Ph.D., presented their work at the 248th National Meeting & Exposition of the American Chemical Society (ACS) last month.

Image of a sample shape-memory polymer.
Sample of a shape-memory polymer foam used for research on shape-memory airplanes. Image By Science Museum London / Science and Society Picture Library CC-BY-SA-2.0, via Wikimedia Commons.

How Does It Work?

The Texas A&M team engineered their SMP by combining molecules of a biodegradable and elastic substance called poly(ε-caprolactone). This combination resulted in a material that appears to look and feel like a hard sponge, as it contains many pores.

During a procedure, a surgeon can heat up the material until it becomes malleable, mold it, and proceed to fill in the area where the bone defect exists. The SMP will recover its initial hardness and lock into place when cooled at body temperature.

Diagram highlighting the shape-memory effect.
Schematic of the shape-memory effect.

What makes the research team’s material so special is that it possesses porous properties that makes it act similar to a scaffold, allowing for new bone cells to migrate and grow within its pores. Because the material is biodegradable, the scaffold will eventually disappear over time, leaving only new bone behind.

Advantages Over Current Methods

Grunlan’s research team was tasked with developing a material that both remained stiff after cooling and promoted new bone cell growth — two traits that do not seem to exist with current reconstruction procedures.

A more common procedure used today is autografting, which involves extracting bone from one area of the body and molding it in such a way to fit the bone defect. Using a patient’s own bone tissue (the autograft), however, creates yet another surgery the patient needs to recover from, which means additional discomfort and a more extensive stay in the hospital.

An alternate procedure involves the use of bone putty or cement to fill in bone gaps. However, these materials tend to become fragile when hardened. Additionally, these same materials do not promote the growth of new bone cells because they lack holes or pores. Meanwhile, the Texas A&M researchers claim their SMP does not become brittle when hardened and allows for new bone cell growth, thanks to its porous properties.

Further Reading

]]> 0
Modeling a Complementary Split Ring Resonator with Ease Wed, 06 Aug 2014 20:54:10 +0000 Last month, my colleague Alexandra Foley introduced an RF modeling example that uses periodic boundary conditions. Another RF model that can be created with ease by taking advantage of periodic boundary conditions is the Frequency Selective Surface, Periodic Complementary Split Ring Resonator model.

About Frequency Selective Surfaces (FSS)

Frequency selective surfaces (FSS) are periodic structures that function as filters for plane waves, such as microwave frequency waves. These structures can transmit, absorb, or reflect different amounts of radiation at varied frequencies. Typically, they have a bandstop or bandpass frequency response.

Frequency selective surfaces are used in a variety of applications. For example, the article “Picking the Pattern for a Stealth Antenna” from COMSOL News 2013 describes how engineers at Altran used FSS as RF filters to reduce the radar cross sections (RCS) of stealth antennas. In the article, designers employed FSS to reduce antenna gain in order to lower the RCS. There, the FSS were designed to absorb incident radiation, rather than scatter it. FSS surfaces are typically constructed with metallic patterns that are arranged periodically. Complementary split ring resonators can be used to build such structures.

Complementary Split Ring Resonators

As a type of planar resonator, complementary split ring resonators are primarily used to simulate metamaterial elements. When designing a bandpass structure, for example, they can be arranged periodically. Modeling these resonators in a periodic configuration can become quite complex and time-consuming. However, you can overcome these design challenges by implementing periodic boundary conditions into your model.

Modeling a Periodic Complementary Split Ring Resonator

COMSOL Multiphysics, together with the RF Module, enables you to model a periodic complementary split ring resonator with ease by utilizing perfectly matched layers and periodic boundary conditions. As an example, we can refer to the Frequency Selective Surface, Periodic Complementary Split Ring Resonator model, which is available in our Model Gallery.

In this model, a split ring slot is patterned on a thin copper layer (which is modeled as a perfect electric conductor) that rests on a PTFE substrate that is 2 mm in thickness.

2d infinite array of complementary split ring resonators

A single unit cell of the complementary split ring resonator. The model is created with periodic boundary conditions.

To simulate a 2D infinite array, as shown above, you can model just one unit cell of the complementary split ring resonator. This is done using Floquet-periodic boundary conditions on each of the four sides of the unit cell.

To learn how to do this, check out the model documentation, where step-by-step instructions are provided.

While this post mostly focuses on how you can save time modeling using periodic boundary conditions, this particular model’s documentation goes into further detail regarding the periodic structure’s bandpass frequency response in terms of S-parameters, as shown below.

S-parameter plot generated with COMSOL Multiphysics showing that the periodic structure has a bandpass filter
S-parameter plot showing the periodic structure functions as a bandpass filter near 4.6 GHz.

Model Download

]]> 1
Tesla Microvalve Model as a Topological Optimization Example Wed, 23 Jul 2014 08:02:38 +0000 Topological optimization is routinely used in the design and refinement of microfluidics devices. The process also comes in handy for modeling a Tesla microvalve.

What Is a Tesla Microvalve?

The Tesla microvalve is a valve that allows fluid to flow freely in one direction but not in the reverse. This valve is one of the many inventions designed by the famous late Nikola Tesla. In recognition of Tesla’s 158th birthday anniversary, my colleague Fanny Littmarck wrote about his life and many contributions to science and engineering. She did not mention the microvalve, however. Perhaps because it is often overshadowed by his electrical inventions.

What makes this valve so fascinating is the fact that it has no moving mechanical parts. This design greatly reduces the risk of wearing out or breaking down. You may be asking yourself, “Well, how does the valve stop fluid without any moving parts?” Interestingly enough, the valve’s fixed geometry inhibits reverse flow through the utilization of friction forces. Thanks to the design, the fluid itself becomes the inhibiting force.

The geometry of a Tesla microvalve.
Tesla microvalve schematic from Tesla’s “Valvular conduit” patent. Inlet on the right end, outlet on the left end.

To achieve this effect, the microvalve design can be optimized by dispersing a distinct amount of material within the modeling domain.

Optimizing the Tesla Microvalve Design

When modeling microfluidic devices, topological optimization is often used to refine the model. The Topological Optimization of a Tesla Microvalve model serves as an exceptional example of how you can do just that, using COMSOL Multiphysics together with the Microfluidics Module. In the case of a Tesla microvalve, you can gauge the effectiveness of your design by obtaining the ratio of the pressure drop between the inlet and outlet for both forward and reverse flows.

By checking out the model, you will learn how to work with two laminar flow interfaces, one for the forward flow and another for the reverse. Additionally, you will see how two instances of the Navier-Stokes equations are computed for the same flow types.

In this example, the optimized design has a triangular-shaped material placed close to the outlet, allowing the forward flow to bend around it. This results in a low pressure drop between the inlet and outlet.

Design shows the forward flow interface within the topological optimization model.
Forward flow in the optimized design after 150 iterations.

In the reverse direction, the flow meets the triangular material’s flat edge, causing the backward flow’s velocity to reroute upwards and downwards toward the device’s walls. The redirected flow’s path is further impeded as it is forced toward additional obstacles.

Optimized design depicting the reverse flow interface of the model.
Reverse flow in the optimized design.

Using a global evaluation, the ratio of the pressure drop between the forward and reverse flow is computed. The value is approximately 1.85.

Model Download

]]> 0
AltaSim Simulates Mie Scattering of Electromagnetic Waves Tue, 22 Jul 2014 08:02:58 +0000 Researchers from AltaSim Technologies presented a paper at last year’s COMSOL Conference in Boston sharing their analyses on Mie scattering of electromagnetic waves and how they compare to the Mie solution.



Mie Scattering


COMSOL Multiphysics model showing Mie scattering by a spherical particle.

Modeling Mie Scattering of Electromagnetic Waves



Here are their results for the magnetic particle:



Download the Paper and Presentation

]]> 6
Computing Voltages Produced by Electromagnetic Induction Tue, 17 Jun 2014 16:14:51 +0000

When you lose power at home, you may use a shaker flashlight to navigate about your house. This type of flashlight relies on voltage produced by electromagnetic induction in order to be powered. How much voltage can one of these flashlights produce, do you think? Here, we find out through computation, using the AC/DC Module.

Electromagnetic Induction

One way electromagnetic induction arises is when a stationary conductor is exposed to a time-varying magnetic field. The other way is by moving a conductor in a stationary magnetic field. In both cases, an induced voltage will develop across a conductor. Examples of the phenomenon are endless and many occur in everyday life; electrical generators, magnetic pickups on electrical guitars, and induction stoves are just a few applications where you can witness induction.

Each type of application involves numerous additional factors that contribute to the amount of voltage that can be produced in a specific device. The Voltage Induced in a Coil by a Moving Magnet model serves as a prime example of how you can determine the amount of voltage produced across a conductor through means of electromagnetic induction.

Shaker Flashlight

In the example model, electromagnetic induction produces voltage to charge a battery of a shaker flashlight (also referred to as a Faraday or linear induction flashlight).

Image of the Faraday or linear induction flashlight
Linear induction flashlight.

In order to produce voltage in this type of flashlight, you shake it back and forth length-wise. The shaking leads to the oscillation of a powerful permanent magnet within (typically a rare-earth magnet). The magnet oscillates up and down through a multi-turn coil, causing the magnetic flux to change. This action is similar to a linear electrical generator and produces voltages on the coil’s walls. In turn, these create an electric current that powers the flashlight’s battery.

In our example, a magnet of strength 1.2 T is displaced sinusoidally at 4 Hz with a 30-millimeter peak displacement inside an 800-turn coil.

Diagram of an oscillating magnet that is moving up and down in a multi-turn coil
Oscillating magnet in a multi-turn coil.

Computing the Voltage

In order to solve for the voltage, you must take the integral of the magnetic fields over domains of the flashlight. The AC/DC Module contains a series of interfaces and functionality that allow you to do so based on the domain boundaries involved, among other factors.

This is a two-step process. First, we must perform a stationary analysis of the magnetic fields. Doing so allows us to provide the appropriate initial conditions for performing the second step: a transient analysis of the magnetic fields. If we solve our model, we will get the following plot, depicting the induced voltage in the coil:

Plot showing the amount of voltage induced in a shaker flashlight by electromagnetic induction
Induced voltage for the coil’s open circuit configuration.

Modeling the Motion

Along with computing the voltage, this example also models the motion of the magnet. Here, the displacement of the magnet is significant. This model uses a moving and sliding mesh functionality to define the displacement of the magnet and the surrounding air domains.


Motion of the magnet.

It is best to define the Moving Mesh physics in the magnet and the air domains because neither the coil nor air domains surrounding it need to deform.

Concluding Thoughts

A number of external factors can influence the amount of voltage induced in this particular scenario, including the components of the flashlight as well as how fast the flashlight is shaken. Considering that the amount of electricity produced depends on how fast the flashlight is shaken (changing the magnetic flux), how do you suppose the amount of voltage would change if we shook a flashlight containing a 1,000-turn coil twice as fast?

Model Download

]]> 1
Investigating Eddy Current Braking Wed, 21 May 2014 13:10:51 +0000 Have you ever wondered how a roller coaster or a train is brought to a stop? A braking effect produced by eddy currents is most likely the cause. Today, we’re going to discuss eddy current braking as well as investigate this phenomenon through an example model.

Eddy Current Braking

Eddy current braking is an effect that occurs when an object’s motion slows down due to forces produced by eddy currents. Eddy currents are induced in a conductor due to time-varying magnetic fields or moving magnetic sources, such as magnets. The induced eddy currents, in turn, create a magnetic field that opposes the magnetic field of the source. The opposing magnetic field, produced by eddy currents, will eventually generate a braking force. When this happens in the eddy current brakes of a roller coaster or train, the vehicle is slowed down and eventually stops.

Here, we’ll explore this phenomenon through an alternative example of a magnet falling through a copper tube.

Solving for the Magnet’s Terminal Velocity and Acceleration

In this model, a cylindrical magnet is dropped down a copper tube. During its fall, the magnet produces eddy currents on the tube walls. The magnetic field — generated by the eddy currents — opposes the magnetic field of the magnet, creating a braking force. This force gets stronger as the velocity of the magnet increases. At some point, the force of gravity equals the braking force produced, i.e., the magnet reaches terminal velocity.

Illustration of a magnet falling through the copper tube

The AC/DC Module contains a set of interfaces and features to help us solve for the magnet’s magnetic field, the magnetic field produced by the eddy currents, and the Lorentz force acting upon the magnet. With the software, we can solve for the dynamic equations of a falling magnet and calculate the magnet’s velocity and acceleration as it reaches terminal velocity.

This problem can be solved in a two-step process. First, we would need to solve for the vector potential field in and around the stationary magnet. Using the resulting solution as an initial condition, we can then perform a time-dependent study to solve for the falling magnet’s terminal velocity and acceleration.


Let’s have a look at the graphs after all of the necessary steps have been implemented.

Terminal velocity of the falling magnet versus time:

Line graph generated by COMSOL Multiphysics that shows the terminal velocity of a magnet when falling through a copper tube

The falling magnet’s acceleration versus time:

Line graph showing the acceleration of the magnet agrees with its terminal velocity

We can see that the acceleration of the magnet decreases and becomes zero after 20 milliseconds, which agrees with the magnet’s constant velocity of 0.26 m/s after t = 20 ms.

Other factors can influence our results, like the thickness of the copper tube. What do you think happens if we use a copper tube that is twice as thick?

Further Reading

]]> 2
Simulating the Focusing Effect of Magnetic Quadrupoles Mon, 19 May 2014 12:05:56 +0000 If you walked into a particle or nuclear physics center, like the world-renowned CERN, you may come across a magnetic quadrupole lens (after security clearance, I would imagine). Here, we’re going to discuss what magnetic quadrupole lenses are and study the focusing effect three consecutive quadrupole assemblies have on B5+ ions traveling through such a lens.

Magnetic Lenses

Magnetic lenses are utilized for focusing or defocusing beams of charged particles, such as ions and electrons. The applications they can be found in are diverse — from particle accelerators to cathode ray tubes.

The lenses consist of multiple magnets or electromagnets that can be arranged in various formats, including quadrupole or sextupole. Today, we’re going to study the focusing effect magnetic quadrupoles have on ions traveling through a magnetic lens.

Magnetic Quadrupoles

A magnetic quadrupole consists of four permanent magnets that are arranged perpendicular to one another, such that the north pole of one magnet is next to the south pole of another, similar to the image below.

Permanent bar magnets in a quadrupole arrangment
A quadrupole arrangement of permanent bar magnets.

The Focusing Ions with a Quadrupole Lens model serves as a good example of how you can study the focusing effect magnetic quadrupoles have on B5+ ion particles traveling through a magnetic lens.

Studying the Focusing Effect

The geometry of our example model consists of three consecutive magnetic quadrupoles. The middle quadrupole is twice as long as the other ones and is rotated 90 degrees, reversing its polarities. Surrounding the magnets is an iron cylinder that is used to strengthen and contain the produced magnetic fields. Following the quadrupoles is 1 meter of empty space, where the ions, which are fed through the lens by an accelerator, are left to drift.

2D view of the geometry of a magnetic quadrupole
A 3D geometry of the magnetic quadrupole lens

2D cross-sectional view of a magnetic quadrupole surrounded by the iron cylinder (left). 3D cutout of the quadrupole lens (right).

The AC/DC Module features a set of interfaces that help us study the focusing effects magnetic quadrupoles can have on ions. It allows us to calculate the forces on the ions by using all components of their velocities. Additionally, the module features an equation for magnetostatics without currents, which substantially and conveniently reduces computational memory compared to formulations including currents.


In the image below, the necessary formulas have been applied and the model has been solved.

Particle tracing plot showing the strength of the magnetic forces on the ions
Particle tracing plots of the ions (requires the Particle Tracing Module). The magnetic forces on the ions are shown by the line colors.

We can gather that the effect the three magnetic quadrupoles have on the ions results in focusing in all directions. The force on each ion is approximately proportional to its distance from the z-axis. The red color tells us that the magnetic force grows stronger farther away from the center of the beam. The blue color conveys that the force is weaker at the point where the two oppositely polarized quadrupoles are joined.

Model Download

]]> 0
Shaping Crystals for Camouflage Surfaces Mon, 28 Apr 2014 12:55:07 +0000 A recent discovery indicates that certain particles can be drawn into crystalline structures through the controlled use of ultraviolet light and chemistry. This discovery can eventually lead to the possibility of creating color-changing surfaces and materials for reasons of dynamic camouflaging.

Shaping Crystals Using Just Light

According to an article posted on, researchers at the University of Michigan College of Engineering have discovered a way to shape crystals with a photochemical reaction, enabling crystal structures to appear in various patterns and colors. Such a technique could lead to materials and surfaces with color-changing, camouflage-like properties (much like a chameleon!).

A chameleon on a twig

In their experiments, the research team shone ultraviolet light in the shape of the University of Michigan’s “M” logo onto a solution of latex paint microparticles in a kerosene-like fluid. As a result, the microparticles were successfully arranged in the desired “M” shape. When the light was pulled away, the crystal formation dissolved.

The Science Behind it

The Michigan Engineering researchers concluded that a photochemical reaction occurs between a layer of indium tin oxide at the bottom of the solution and is responsible for the crystal formation when illuminated. A current of ions is generated in the fluid due to the reaction. Microparticles are attracted to the area of indium tin oxide if they are negatively charged, while they create a void in the shape of the light if they are positively charged.

You may be wondering how the color changes, too. The color of a crystal can be altered by adjusting the spacing between the particles that compose the crystal structure. If you can manipulate the shape of the structure, you can change its color.

Other Potential Applications

The team has already imagined potential uses for their discovery other than color-changing coatings. One potential case includes alternative ways to dynamically update graphics on billboards and e-readers. Another is a more complex application: they envision sensors whose color will change in order to detect molecules crucial for environmental and medical surveillance.

Further Reading

Read the original article and watch the videos: “Chameleon crystals could enable active camouflage (w/ video)

]]> 0
Happy 140th Birthday, Guglielmo Marconi Fri, 25 Apr 2014 12:08:02 +0000 Born 140 years ago today, Guglielmo Marconi was a Nobel Prize-winning electrical engineer and an Italian inventor who is best known for pioneering long-distance radio transmission and the commercial success of radio.

About Guglielmo Marconi

On April 25, 1874, Guglielmo Marconi was born into nobility in Bologna, Italy. While being privately educated in Florence, Bologna, and Leghorn, a young Marconi became intrigued by the electrical and physical sciences, studying the works of Maxwell, Hertz, Righi, Lodge, and more.

Portrait of Guglielmo Marconi
Guglielmo Marconi.

In 1895, Marconi started to conduct experiments with the goal of using radio waves to transmit telegraph messages without the connection of wires (i.e. wireless telegraphy). While this was not a “break-through” idea at the time as others had explored this concept before him, no one had proven the concept to be both technically and commercially practical.

During the experiments he performed at his father’s estate in Pentecchico, Marconi was successful in sending wireless signals over a distance of 1.5 miles with his apparatus. Soon thereafter, in 1896, Marconi took his device to England where he was granted the world’s first patent for a system of wireless telegraphy. After receiving his patent, Marconi founded The Wireless Telegraph & Signal Company (later known as the Marconi Company) in 1897.

Wireless Transatlantic Transmissions

Marconi is also credited with transmitting the first wireless signals across the Atlantic ocean. At the beginning of the 20th century, Marconi began investigating this technology in order to compete with transatlantic telegraph cables. The 1901 investigation involved passing signals between his company’s high-powered base station in Poldu, Cornwall and St. John’s, Newfoundland, covering a distance of roughly 2,100 miles.

Also in 1901, Marconi built a base station near South Wellfleet, Massachusetts. On January 18th, 1903, this base station sent a greeting to the United Kingdom’s King Edward VII from Theodore Roosevelt, the President of the United States at the time. This event marked the first time a transatlantic radio transmission originated in the United States. Another interesting fact about Marconi’s base station: it was one of the first to receive distress signals from the infamous RMS Titanic’s maiden voyage.

Photograph the remnants of the Marconi Station in South Wellfleet, Massachusetts
Remnants of the Marconi base station in Wellfleet, Massachusetts.

Honors and Awards

Thanks to his work, Guglielmo Marconi received numerous international honors and awards. Among them was a Nobel Prize for Physics, which he received in 1909 for his contributions to radio communications. He shared the award with Karl Braun.

It’s rather amazing how long wireless technology has been around.

]]> 0