12. Skin Electronics

Research

Electronic skin (e-skin) is a flexible electronic device that mimics human skin and has inherent natural stimuli. It is used in engineering prosthetics and wearable electronics to collect biophysical data from patients. E-skin is stretchable and flexible, allowing it to adhere to a patient and collect data.

From: Polymers in Energy Conversion and Storage [2022], Advances in the measurement of prosthetic socket interface mechanics: a review of technology, techniques, and a 20-year update [2023], Nanosensors for Futuristic Smart and Intelligent Healthcare Systems [2022]

The main difference between skin electronics and wearables is that skin electronics, as the name suggests, goes directly against or in contact with the skin using an insulator as a barrier, while wearables technology are integrated into accessories or clothing.

References & Inspiration

Developed by a team of students at the University of California, Berkeley, Skintillates is a wearable technology that mimics tattoos.

(Photos: Eric Paulos)

These "epidermal wearable interactive devices" can serve as everything from passive and active displays on the skin to capacitive and resistive sensors for controlling devices, or strain gauges for posture detection.

I was also very inspired by the projects of Beauty Technology's, such as the twinkle nails presented by Katia Vega. For this project, they used RFID nails.

RFID (Radio Frequency Identification) refers to technology that uses radio waves to wirelessly identify and track objects, people, or animals.

Other projects of inspiration from Beauty Technology:

Tools

• Arduino UNO
• Arduino IDE

The microcontroller that i used fot his assigment is the Xiao RP2040

-Xiao RP2040 layout, by Daniela Maldonado

Glowing hands

Moodboard of inspiration

Photos from Pinterest

For a first exercise I wanted to do something with light, I started thinking about what I could develop and ended up with the idea of ​​doing something in the hands "passing the energy" so that the other could work, from one to the other when they are put together.

Electronics

I started by doing the electronics, using some foam for the fingertips avoiding putting directly the copper tape on the skin, for the LEDS I connected a resistor of 3.30 to the negative, to make all the connections i used conductive thread.

Testing

First I did everything without applying it to the skin, to verify that everything worked as I expected.

On skin

Once I had the whole circuit working, I started placing it on the hands, not just putting it anywhere, but I wanted the LEDs to form an attractive design.

I put masking tape as a barrier so that none of the components, such as the resistor and the microcontroller, would directly touch the skin.

Schematics

Code

I ask ChatGTP for this code with the prompt : I am using a XiaoRP2040, I want to connect two LEDs, one in D7 and the other in D6, I want them to have an effect, like fading

// Pines de los LEDs
const int led1 = D6;
const int led2 = D7;

void setup() {
  pinMode(led1, OUTPUT);
  pinMode(led2, OUTPUT);
}

void loop() {
  // Subir intensidad (0 → 255)
  for (int brillo = 0; brillo <= 255; brillo++) {
    analogWrite(led1, brillo);
    analogWrite(led2, brillo);
    delay(5);  // Controla la velocidad del fade
  }

  // Bajar intensidad (255 → 0)
  for (int brillo = 255; brillo >= 0; brillo--) {
    analogWrite(led1, brillo);
    analogWrite(led2, brillo);
    delay(5);
  }
}

Outcome

Demonstrations

Piano Nails

Now, different to the project Twinkle nails, I didn't have that kind of technology, so I did it the rough way. I started by making kind of an extension of the pins and GND of the microcontroller in a piece of foam, so that it would be easier to connect everything later.

Once I had everything sewn, I asked ChatGPT to modify the code I used for my wearable week with my invisible piano project, so that it only used the 5 main notes. Then I assembled the entire circuit from the circle with the sewn-on pin extensions to the tips of my nails using copper tape, but...

First attempt- FAIL :(

They have been many reason why this easy of doing it didn’t work out, one could be that I was using copper tape directly on the skin, and it could have made interference, the second is that when I sew the microcontroller to the circle of foam, I over-sewed and that was also creating a dead short. Anyways, I wasn’t giving up, so I took everything up and started to make little changes, the first thing I did was to re-make all the sewing from the Xiao, doing it just in one direction, but it still wasn’t working, the buzzer was doing strange noises, so I changed them to conductive thread, and nothing, so after some thinking, it occurred to me that it might be the buzzer, so I tested it connecting it directly to 5V and GND, and it did the strange noise, so I changed it. I connected the second buzzer to the same pin but it made the same noise even though when I connected it to 5V and GND it sounded good, so I changed the buzzer to another pin and it finally WORKED!

Second atempt- SUCCESS :)

Electronics:

So, now knowing that it was working, I did the cupper tape on the tip of the fingernails, kind of like a French style.

Mimicking the little game some of us play with our fingers I decided to place GND on the fingerprint of the thumb, and for the thumb I place cupper tape on the pinky so that it could also work in an ergonomical way.

Then placed the circle with the connections on my arm, sewing and securing in each conductive thread. Then I started to guide each of them to their corresponding nail, securing it with copper tape.

Schematic

Code

int botonDo = D1;
int botonRe = D3;
int botonMi = D5;
int botonFa = D6;
int botonSol = D7;
int botonLa = D8;
int botonSi = D10;

int buzzer = D8;   // <--- AHORA EL BUZZER ESTÁ AQUÍ

void setup() {
  pinMode(botonDo,  INPUT_PULLUP);
  pinMode(botonRe,  INPUT_PULLUP);
  pinMode(botonMi,  INPUT_PULLUP);
  pinMode(botonFa,  INPUT_PULLUP);
  pinMode(botonSol, INPUT_PULLUP);
  pinMode(botonLa,  INPUT_PULLUP);
  pinMode(botonSi,  INPUT_PULLUP);

  pinMode(buzzer, OUTPUT);
}

void loop() {
  if (digitalRead(botonDo) == LOW) {
    tone(buzzer, 262); // DO
    delay(200);
    noTone(buzzer);
    delay(200);
  }

  if (digitalRead(botonRe) == LOW) {
    tone(buzzer, 294); // RE
    delay(200);
    noTone(buzzer);
    delay(200);
  }

  if (digitalRead(botonMi) == LOW) {
    tone(buzzer, 330); // MI
    delay(200);
    noTone(buzzer);
    delay(200);
  }

  if (digitalRead(botonFa) == LOW) {
    tone(buzzer, 349); // FA
    delay(200);
    noTone(buzzer);
    delay(200);
  }

  if (digitalRead(botonSol) == LOW) {
    tone(buzzer, 392); // SOL
    delay(200);
    noTone(buzzer);
    delay(200);
  }

  if (digitalRead(botonLa) == LOW) {
    tone(buzzer, 440); // LA
    delay(200);
    noTone(buzzer);
    delay(200);
  }

  if (digitalRead(botonSi) == LOW) {
    tone(buzzer, 494); // SI
    delay(200);
    noTone(buzzer);
    delay(200);
  }
}

Outcome

Demonstration