Question: I use Gillette's new vibrating razor. I can feel a difference after the shave, but I don't understand how they get the razor to vibrate, and how that vibration gets smoother results.
Answer: My friend, this is a question that has plagued man for months. Where does the vibrating razor get its magic? The question involves physics, biology, and some alchemy.
During my tenure at Mad Physics I’ve risked life and limb in countless ways, and today I go under the knife for the sake of science. I certainly didn’t look very happy (left) in my precarious state—five razor sharp blades vibrating against my unshaven skin. I could have been cut to shreds!
As it turned out though, I walked away not only unscathed, but marvelously shaved. It appears that the vibrating razor really did provide a closer, smoother shave. The science was a mystery though. Gillette explains, “With the M3Power, micro-pulses are sent to the blades making it dramatically easier to shave more thoroughly with one easy power stroke.” Other than sounding ridiculous (power stroke!), the explanation really doesn't tell us much. Therefore, we are left to ask the question, “How are these ‘micro-pulses’ sent, and how do they make it dramatically easier?” Let’s break it down one piece at a time. First off we'll cover the physics, or the mechanics of what actually makes the razor vibrate. Then we'll get to why any of that does any good, or the physiological explanation. There you have it, physics and biology living in perfect harmony, who would have ever predicted this happening?
The vibrator embedded in the M3Power and the Fusion is just like the vibrators in pagers, cell phones, and well, vibrators! The idea behind this oscillator is that of unbalanced weights. There is a 1.5V electric motor in the razor. When engaged, it spins; however, mounted on top of the motor is an unbalanced weight. As the weight swings to one side, some directional forces increase and the whole system shifts towards the weight. In this asymmetrical system, there is symmetry though. Since the motor spins rapidly, these shifts are only temporary because they are countered by other directional forces. This causes the whole system to be in a state of constant oscillation—i.e. back and forth movement.
After tearing apart the razor, I found that when pressing the button, one closes the direct circuit between the AAA battery and the motor, and razor could vibrate. Below you can see the wreckage, and the incredibly small motor:
The biological explanation revolves around the physiology of our hair follicles. Mammals have the ability to raise hairs; this razor depends on that ability. While humans cannot control their hair raising, it can be triggered. Attached to each and every follicle is a bundle of muscle fiber called the arrector pili, which as its name suggests, is responsible for raising hairs. This muscle is smooth muscle and not a skeletal muscle, so its functionality is controlled by the sympathetic nervous system. This means that we can only involuntarily flex this muscle—an example of this is goose bumps! In the case of the Gillette razor, the follicles on your face are reacting to the stimulus of vibration. The muscles contract, the hair stands perpendicular to your face, and the razor is able to shave better.
Below is a diagram with the arrector pili pointed out with an arrow:
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