Better ergonomic mouse based on fingerstyle guitar

March 28, 2017

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Status: Acknowledged

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Three years ago I began to suffer from RSI caused by prolonged and intense mouse use as part of my work as an environmental modeller. My office (an engineering firm) generously offered to pay for whatever equipment I needed, so was able to test several ergonomic mice in the market. None of them well enough to completely relieve my symptoms. I then decided to build my own mouse.

I started my design from the fact that I can play fingerstyle guitar (plucking) for hours without issues, yet 15 minutes of working with a conventional mouse will bring on my symptoms. This suggested that instead of pushing down to click on mouse buttons, pulling in my fingers to click (the way I do when I pluck a guitar string) was the ergonomic way to do this.

The other differences between clicking a mouse button and plucking a guitar string involve the range of motion (ROM) and the force applied. A mouse button has an ROM of a couple of millimeters, but plucking a guitar string involves at least 20 mm. In theory the small ROM in a mouse should be a good thing, but it is not because it takes more force to click the button than to pluck a string. Most ergonomic mice use the same buttons as conventional ones. Some ergonomic mice had buttons are lighter than others (including touch mice), but they pose a problem of accidental clicks that required me to lift my fingers while using them. I realized that the solution was to use the principle of a lever: increase the ROM to click the button, thus requiring less force to do so while avoiding accidental clicks. To achieve this leverage, the point where the finger clicks the mouse should be farther forward of the mouse button. This revises a feature found in all mice, conventional or ergonomic, where the finger is right over the buttons.

I have attached a picture of my mouse. It is actually built of two travel mice, one piggybacked on the other. The one on top has no electronics but has the buttons, the other on the bottom has the electronics. The levers used to click the buttons are caps from a medicine bottle. The body is a piece of foam.

One the left side is a padded button for the thumb, which is the middle click. Due to the placement of the wheel, I could not build a lever for this button. Using the thumb made sense, since it is the strongest digit on the hand, but does nothing on a conventional mouse.

My travel mouse had a large wheel, which I retained because I found it to be easier to use. But the big change I adopted was to move the wheel farther to the front of the mouse, which I achieved by cutting off as much of the PCB as possible. The advantage of this placement is that it prevents my fingers from curling or bending back to turn the wheel. I also wanted to place the wheel even lower but I could not do so without radically modifying the mouse. Again, this goes against the convention of placing the wheel on top of the mouse.

The other innovation I wanted to put in was to place the mouse wheel over the pointing finger rather than the middle. This is after all the finger I use to turn the wheel, and often the one I use to click it. An informal survey of my co-workers showed that they do the same thing. But like the QWERTYY keyboard, there is really no strong reason for the mouse wheel to be between the two buttons other than symmetry and tradition. Others might prefer to use their middle fingers to operate the wheel, but still use their stronger index finger to click it. 

The remarkable thing was that after I came up with my mouse with the idea to click a button by pulling in my fingers, Microsoft came up with the Sculpt mouse that had this feature. I tried it, but I went back to my homebuilt mouse. The Sculpt was too big for my hand, and it did not have the leverage (as well as the other features of my mouse).

My mouse completely stopped my RSI. I enjoyed it for about a year until the buttons started to fail, and I did not have the energy to rebuild it. Fortunately I found your Dell WM 311 which I believe helped my symptoms though its lightness and low profile. It did not completely eliminate my RSI but if I took enough breaks I was able to avoid the pain. A week ago the middle button on this mouse stopped working, and I learned that it is no longer in production. This morning I received what is supposed to be closest model to it available, the WM514, but it is larger and heavier. I am concerned that I will soon need to resume my search for the perfect mouse. I therefore hope that you consider my suggested design elements so that I won’t have to.

Homemade mouse

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