The problem
A myoelectric hand reads muscle signals through electrodes in the socket. The signal works in a fitting room. It is harder to keep in a life.
01 · Switching
"Too slow, unreliable, unintuitive and mentally exhausting."
That is how users of multi-function hands described grip switching by muscle contraction in a 2019 study. Most of them used only two or three functions, because more was confusing and hard to remember.
02 · The signal
Temperature, humidity, sweat, socket displacement, and the weight of the arm all change the signal. The result is a signal artefact, and an unintended movement of the hand.
03 · The training
A user must learn to produce a contraction the electrodes can read, then keep it repeatable. A user who cannot produce a stable signal has no path into a multi-grip hand at all.
The literature does not show that people abandon electric devices more often than body-powered ones. For adults the rates are close: about 23 % for electric devices against about 26 % for body-powered ones. Comfort, socket fit, and weight lead the list of reasons, and price sits near the bottom.
So the claim here is narrow and it is the one the evidence supports: EMG control is a documented problem of cognitive load and usability. This control method removes that load. It does not, on its own, solve comfort, weight, or socket fit.
The control
The residual limb already moves. The method uses that movement directly, as a position, and not as a signal that must be classified.
The calibration is two button holds on the hand. It needs no clinic visit, no laptop, and no software that only a specialist can run. A user who changes their mind holds the button again.
The shell, the finger pads, and the buttons are each specified on their own. The hand can be matched to a skin tone, or made to stand out on purpose.
The hand runs on its own battery. An ordinary USB power bank tops that battery up, and the user keeps the hand on while it charges.
It needs a preserved rotation of the residual limb. That is the eligibility criterion, and it is the first question to put to a prosthetist.
The user holds one button for 2 seconds at the position that means "fully open".
The user holds the other button for 2 seconds at the position that means "fully closed".
The two saved points become the whole range. The kit clamps anything outside them.
A short press steps forward or back through five grips. Nothing waits for a gate.
Video
A control method is easy to describe and hard to believe. So here is the hand, doing the thing this page says it does.
