RIM-D2 is a low-cost 3D-printed hand prosthesis that is capable of responding to nerve impulses picked up by an EMG sensor that processes the signal transmitted by the brain through the nervous system. It is also developed parametrically; this means that using variables and equations in the dimensions of the mechanical design is possible to enter the measurements of any person with the characteristics required to rebuild it in seconds with custom dimensions. Also, it is modular, the hand part can be removed and connected in another socket, this is very helpful when the person needs to change the socket because his or her anatomy changed but they can keep the same hand part instead of replacing the whole prosthesis.

The EMG sensor has been performed in a real situation and the results were amazing because a girl with the characteristics was able to control the movements of the prosthesis. RIM-D2 has a gyroscope and accelerometer sensors that help to change the movements of the fingers when the EMG sensor gets a muscle contraction but with those sensors, I noticed that I could make a regression algorithm (Machine learning) to improve the gestures of the hand based on the movements, acceleration, position, and contraction of the muscle. It works with a battery that can be replaced very easily. Also, it has a vibrator motor to give a nicer user experience when the person changes the movement of the fingers. Now, it has five movements but can be programmed with any customized one.

• Fist: helps the user to take medium things like bottles, glasses, and stuff with a similar size and shape.
• Pinch: this movement is helpful when the user needs to grab small things with precision.
• Tripod: Same as pinch but with three fingers.
• Hook: Useful to carry bags, take and move chairs, use a bike, or grab a steering wheel.
• Finger point: Ideal to use a computer or a cellphone.

The development of this arm prosthetic was guided by experts in mechanical prostheses, mechanisms, doctors, biomedicals, physiotherapists, and persons with the characteristics of the prosthesis.

Currently, I have a lot of feedback on this first functional prototype and I know exactly what to improve for the next version that could be manufactured in mass production. The idea is to develop three sizes of hand (small, medium, and large) and improve the parametric design of the socket to generate it with any custom measurements in seconds. One idea for the next version is to add an APP that can be used to program the movements of the hand and calibrate the sensor to improve the performance. Also, add a sensor on the fingertips to control the force that applies to the object that is touching, this will give a realistic experience.

Prostheses with a similar impact in the market are very expensive and are not accessible to most of the people with those characteristics. Here born my initiative to bring this technology to the people who need it.