Introduction: The Sixth Finger

The project is based on circuit playground express and cricket. The concept is to reimagine what will happen if people have one more finger? Will our life become easier or will it cause troubles? The deliverable is a 3d printed finger which is controlled by a servo and the servo will be activated by flex sensor. The idea is inspired by different technologies for disabilities and the devices soldiers can put on in sci-fi movies. In those movies, such as Edge of Tomorrow and Elysium, People like soldiers wear these devices, which can work perfectly with human body motion. In reality, people make artificial limb using different technologies, such as using natural muscle signals (When muscles contract they generate electricity) to enhance the control of hand and arm prosthetics.

Step 1: Flex Sensor Connection

For this tutorial you will need a flex sensor, Circuit Playground Express, Adafruit CRICKIT for Circuit Playground Express, a 10k resistor (brown, black, orange) and wires.

10k resistor (red) to 3.3V

Flex sensor (black) to GND

Bule node to A3

Step 2: 3D Printing

You need to print: the finger, a servo holder, a mount for cricket and a bracelet.

The finger has two different stl files (one with different components and needs assembling, the other one with only one component). You can use PLA or SLA to print the one with different components or use thermoplastic elastomers (TPEs) to print the other one.

Step 3: Control the Servo

Connect the servo to your cricket and use this code. The servo will be rotating if you are bending the flex sensor.

Step 4: Assembling

The mechanism of the finger is using servo to pull the string inside the finger and using rubber band to pull the finger back to the original position. So you will start with gluing rubber band on the back of the finger and putting the string through the holes.Then, you need to attach the flex sensor to your real finger. You can use tap or make a finger cap with a pocket for the sensor. After finishing the finger cap, you need to attach the servo and finger to you hand, you can use head band for this step. The last step would be screwing the cricket onto the mount and wearing it.