This is an intructable in which we are gonna build a flex/bend sensor that is compatible with an arduino board and does not require static bags or anything unusual, you can make this right now from things you have around the house. :D
Good luck !
Step 1: What You Will Need
This is all you need for your sensor plus a multimeter and some wires, Heat-shrink tubing is optional for masking the mask tape, instead of masking tape you can use normal duct tape but this is what i've had laying around.
The Heat-shrink tubing should be 2mm wider and 1 cm longer than your finished product, masking tape should be 2 cm wide.
Step 2: Making the "static Bag Material"
If you don't have or don't want to use static bags you are gonna have to make some conductive material.
Now you need to make some lines on a paper untill you have the color of the black paper in the right, make scribblings on a surface of at least 1.2/12 cm you can make it bigger, the bigger the better.
After you think you have made it, take your trusty multimeter and measure the resistance on 12 cm of the coloured paper (it is black but still, you know what i mean) and it should be 8 kohms, if it isn't you need to make more scribblings on the paper untill you have around 8 kohms, it does not matter if it is smaller resistance.
Tips: 1. Don't press too much on the lead pencil to scratch the paper, if you've done this you need to make another one.
2. Measure resistance on 12 cm of paper, where it is the bigges density of carbon, if you did not know, this is the stuff in the pencil leads :)
Step 3: Making the Contact Pads
For this you are gonna need two pieces of aluminum 3cm/1cm, two pieces of paper 1.6/8 cm and two wires of 7 cm.
Make one hole in each of the papers just a little bit smaller than the aluminum strips, (the location of the holes is in the picture with the masking tape) so that the aluminum strips can stick to the masking tape.
After that stick the paper to the tape like shown and then the aluminum strip on the hole in the paper, make two of these, you will see later why.
You will need to put a piece of striped wire (striped at the end about 2.5cm) underneath the aluminum.
Step 4: Making the Final Product
To make it you need to fold in half the "static bag material" made in step 2 and place it with the two free ends on the top of the aluminum, make sure you don't stick the material, just place it on the paper (paper piece it is bigger than the "static bag material piece"),sandwich the other contact pad on the material-contact pad element you've just built and you are done.
You can now put it inside a heat shrink tube if you want.
If you want more resistance you can just add a resistor on one wire.
Don't forget to vote this instructable if it is in a contest !
Thank you for reading !