I love Microsoft’s Arc Touch Mouse. It seems like one of those fancy design concepts that never make it beyond a rendering, but it is actually a real product we can buy. A Bluetooth computer mouse that is also a transformer that flattens for easy portability? I thought it was so cool, I bought one of the early versions: Surface Edition model 1592. Looking at the latest edition, I see they now have fully capacitive touch surfaces. Mine had two physical buttons for left and right click, and a touch surface in the middle to emulate a mouse scroll wheel and center button.
I would not have been surprised if the collapsible mechanism failed after years of use, but it has actually proven very durable. My problem is the forward section plastic which has degraded and oozing a sticky liquid I could not clean. It captures dust and dirt, and leaves my finger sticky after I touch it. It feels unpleasant so I don’t use it as a mouse anymore, making it an ideal teardown project.
Note: There will be some inconsistencies in these pictures. Partway through this teardown, I finally saw enough of the internals to realize I did not take it apart in the optimal order. I’m presenting these pictures in the order I should have used to take it apart.
Arc Touch Mouse has a smooth and unornamented exterior. All the legal requirements and identifiers are on a label inside the battery compartment.
Peel off that label to unveil a set of debug/test points and two T5 screws.
Removing them releases the top button surface, though it is still attached by two cables.
Disconnecting a ribbon cable and a two-pin haptic feedback connector will allow the top to be removed. I set this aside for a closer look later.
Once the top is removed, we can safely remove four screws holding a bracket for the rubber skin in place. Once freed, the flexible portion should be something we can peel off like a sock. Of course, I had already cut it apart with a knife by the time I realized this, so I’m not sure. Only the bracket itself is left visible in this picture as I had already cut the rest of the rubber sock away.
With the rubber sock removed, we can see the transformer mechanism. Holy parts count, batman! There are ten plastic segments to this mechanism, held by flexible spring steel top and bottom fastened by screws and plastic rivets. I did not expect this much complexity.
All of those parts were necessary so the mechanism can take one of two positions.
Top sheet of steel is fastened by melted bits of plastic forming rivets. The bottom is a four-sheet assembly so they could slide past each other as the mechanism curves. Under those four sheets is a long strip of copper-colored metal which is the key to how this mouse can hold one of two distinct positions. A strong magnet lives in a cavity at the end of the curvature, with two bits of steel at either end. The magnet wants to be up against one of those two pieces of steel, which corresponds to the flat and curved positions of the mouse. This is very clever! It also reminds me of another magnetic mechanism a convertible tablet used to stick to its keyboard dock.
The curved/flat transforming mechanism is also the power switch for the mouse, implemented as a tiny little thing adjacent to the magnet cavity actuated by a right-angle fold in the copper strip. I am amused that they had to make a circuit board just for the sake of hosting this surface-mounted switch.
Returning to the top plate, most of the complexity here is centered on the capacitive touch strip in the middle. At the lower right, we have a side-lit LED activity indicator. Behind the circuit board is a long rectangular haptic feedback device. Printed on this flexible circuit is the following:
Foxlink CO., LTD. CONFIDENTIAL Dali_Capsense V2R1+
I infer “Dali” was the development codename for this device.
I tried to extract the capacitive touch flex circuit intact, but I unintentionally ripped it in half.
Before this teardown I had assumed the haptic feedback came from a motor with an eccentric weight on its shaft, common for cell phone vibrations and such. This device was too long to be a spinning motor, so I wanted to see inside. It was wrapped in no less than four layers of sheet metal. So thin, they were barely more rigid than paper and practically razor blades. I had to be very careful peeling them apart to find a small coil-wrapped armature between two magnets.
The mainboard of the mouse is almost boring in comparison to the rest of this device, but it does confirm the Dali name with:
I was surprised to see that the mouse position optical sensor is separate from its illuminating LED instead of together in an integrated enclosure. I briefly thought about removing the sensor for novelty’s sake, but these things are tiny. I decided not to spend time getting something I’ll lose the next time I sneezed.
This was an epic teardown. The Microsoft Arc Mouse is a premium product, significantly more expensive than lowest-bidder Bluetooth mice on Amazon. But I love its novel design. After seeing all its components, I’m actually surprised it isn’t more expensive. In fact, I’m surprised it got approved for manufacture at all! I wonder if mechanical engineers have managed to simplify construction of current generation Arc Mouse, but they are too expensive for me to buy one just to take apart. Perhaps someday I’ll have a chance to pick up a broken unit and take it apart for comparison.