Theo Jansen's mechanism

Go to the simulation

Theo Jansen is a Dutch artist and kinetic sculptor who builds large works that resemble skeletons of animals that are able to walk using the wind on the beach. His works are a fusion of art and engineering.

Theo Jansen's famous mechanism can be simulated by using the Molecular Workbench software. Shown in this blog post is a screenshot of the simulation. You can click the link below the screenshot to watch the simulation.

Water permeation across paper and colors under the sun

Yesterday I reported evidence of tiny water permeation across a piece of paper on top of a cup of water. In order to double-check my theory, I placed a piece of transparency film on top of another cup of water and left the two cups overnight. When I came back this morning, I removed the paper and the film from the two cups and viewed the IR image of the two cups of water. To the right is the image I saw.

The cup of water that had paper atop was cooler (the dark circle on the right) than the cup of water that had transparency film atop (the light gray circle on the left). This means evaporation was stopped by the film but not the paper. The only explanation of this effect is that water can permeate through the paper but not the film.

Last October, I blogged about visualizing different colors' ability to absorb light. In that experiment, I used a table lamp as the light source. Later, I realized a flaw in that experiment because a table lamp is, after all, a point source. For the color bars to have equal illumination, we need a light source that is far far way. The sun is such a light source. So I brought the color plate outside and put it under the sun. You can now have a better idea of which color is more capable of absorbing heat. No doubt black won. To my surprise, purple and yellow have approximately the same light absorptivity. So do blue and green. Red, on the other hand, absorbed about the same amount of light as light gray. The background is white. It absorbed the least amount of light energy and appeared to be bluest in the IR image. Amazingly, paper doesn't conduct heat well, otherwise the color bars in the IR image would not have been so well separated.

Seeing permeation of water molecules

I have blogged about some intriguing IR images when a piece of paper is placed on top of a cup of water. The part of paper above the water warms up (Figure 1) because of the release of latent heat of condensation of water vapor to its underside. If you want to reproduce this effect, note that the shallow the cup, the more pronounced the effect (I used a lid and turned it over to use as a shallow cup). In these IR images, I chose the gray coloring mode. So white represents the hottest and black the coldest.

The warming stops after a minute because the condensate layer reaches the maximal thickness due to the dynamic equilibrium of condensation and evaporation. So we see there is no difference of temperature across the paper any more (see Figure 2). (Well, except for the ring area that touches the edge of the cup, in which it gets the temperature of the cup.)

If we leave the paper for a couple more minutes, the part of paper actually becomes cooler (Figure 3). So what is going on?

My theory is that water molecules have percolated through the paper, which is porous (having a lot of small holes), to the other side and evaporate from there. So we are seeing the evaporative cooling effect from the above side of the paper. Figure 4 presents evidence that supports this theory. If we shift the paper a little bit, we will see three zones with three different temperatures. The coolest zone shows the effect of evaporative cooling from both sides. The overlap zone shows the effect of evaporative cooling from only the above side. And the warmest zone shows the effect of condensation heating from the underside. (Is this pattern beautiful?!)

Figure 5 shows the comparison between direct evaporation (the dark area on the left) and permeation-then-evaporation (the less dark area on the right). The result indicates that the paper did impede evaporation, even though its micro pores allow water to percolate through.

This follow-up study shows that even a humble experiment like placing a piece of paper atop water has many surprises that reveal the richness of science, which all become transparent under an IR camera. I will blog more surprises derived from this experiment later.

A theory of multisensory learning for IR visualization of hands-on experiments

I have been "shopping" for a learning theory that can frame the value added by infrared (IR) visualization to hands-on experiments. Here is a candidate theory.

There are four learning pathways to the brain: visual, auditory, kinesthetic, and tactile. Theory has it that memory and learning could be enhanced if multiple learning pathways are utilized simultaneously.

Let's look at a notorious misconception in heat and temperature. Many people believe that metals are colder than wood or paper. This misconception cannot be easily dispelled because that is how they feel through the sense of touch. As heat transfer is invisible, the tactile experience is all they have.

Now, what if the heat transfer process can be visualized? In other words, what if students have multisensory learning experience: they feel and see it at the same time? IR imaging has enabled us to design such an experiment. The image above shows an IR view that compares heat flow through paper and metal from hands.

Recent studies from Swedish scholars including Konrad J. Schönborn, whom I ran into at a conference and who was enticed by my IR magic, showed that adding haptics to visualization could improve student learning of biomolecular interactions such as docking. Visual and tactile sensorimotor interactions could enhance the cognitive process. Or, in this case, the visualization could "correct" the erroneous idea tangibly gained. The IR visualization shows that the metal is actually warmer than the paper, creating a contradiction with the tactile input that students must reconcile. Such a contradiction can induce cognitive conflict, a mechanism for learning.

Konrad said he would investigate this through a cognitive experiment with students from his University in Sweden. I was psyched. This is complementary to what he has done. In this case, visualization augments touch--exactly opposite to his prior research on molecular binding in which case haptics augments visualization.