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Annika Muehlbradt

Learning about Origami. 11/09

Below are my first origami folds: a seal, a fish, and a turtle.

Analog Circuits and Origami. 11/09

I created an interactive paper frog with two LEDs as eyes. When the frog's body is pressed down and the two sides of the paper touch, the frog's eyes light up. I used conductive ribbon, copper tape, a coin cell battery, and two LEDs.

Click for animation.

Arduino and Origami. 11/10

I created a monster mouth trap. When you stick your hand into the monster's mouth, the mouth closes. I used an Arduino, MOSFET, 9V battery, photoresistor (a.k.a. light sensor), and a nitinol spring.

First, I folded the monster mouth out of 3 pieces of origami paper.

Click for animation.

Second, I placed the photoresistor inside of the mouth and used conductive ribbon to run three traces (power, GND, and signal) outside of the mouth. I glued the nitinol spring to the top and bottom of the mouth and connected a wire to each end of the spring.

Here is the Arduino code:

const int light_sensor = A0; // A0 is the input pin for the light sensor
int power = 9; // output pin for actuator (nitinol wire)
int pwd = 255; // duty cycle (0 - 255)
bool open = true;
void setup() {
  Serial.begin(9600); // set up output for debug monitor
  pinMode(light_sensor, INPUT); // set sensor to input
  pinMode(power, OUTPUT); // set power as output
void loop(){
  int light = analogRead(light_sensor);
  if(light < 25 && open) {
    open = !open;
    Serial.println("Mouth closing");
    analogWrite(power, pwd);
    delay(3000); // wait 3 seconds
    analogWrite(power, LOW);
  } else if(!open) {
    Serial.println("Mouth shut");
    delay(10000); // wait 10 seconds
    // reset mouth
    open = !open;
  } else if(open) {
    Serial.println("Mouth open");

This setup did not work well. When the nitinol became warm, it melted the hot glue and the spring would detach from the top of the mouth. It turned out to be quite difficult to attach the nitinol spring to paper (or anything else).

I tried a different mechanism using string. The string pulls the mouth shut and the string is pulled tight by the nitinol spring.

Click for animation.

annika_muehlbradt.txt · Last modified: 2019/11/24 20:58 by radical