Daily Note: 3D Printing and Embedded Interactivity

These notes are a summary of concepts presented in “PrintPut: Resistive and Capacitive Input Widgets for Interactive 3D Prints.”

Burstyn, Jesse & Fellion, Nicholas & Strohmeier, Paul & Vertegaal, Roel. (2015). PrintPut: Resistive and Capacitive Input Widgets for Interactive 3D Prints. 9296. 332-339. 10.1007/978-3-319-22701-6_25.

  1. Introduction
    • Method for embedding interactivity in printed objects
    • Includes buttons, pressure sensors, sliders, touchpads, flex sensors
    • Enables a new category of objects with intrinsic touch sensing capabilities
  2. Key Components
    • Conductive ABS filament
      • High resistance, typically in the MΩ range
      • Can be read with Arduino or microcontroller
    • Connected via alligator clips
  3. Types of Sensors
    • Capacitive sensing
      • Single terminal sensors detecting touch by capacitance change
    • Digital resistive sensing:
      • Two terminals with gap; bridging the gap completes the circuit
    • Analog resistive sensing
      • Similar to digital resistive but modulates current based on bridge resistance
  4. Button Types
    • Capacitive buttons
      • Simple conductive filament pads connected to input pins
    • Resistive buttons
      • Split conductive filament pads that create a bridge when touched
      • Requires a 1mm gap for proper touch detection
  5. Sliders
    • Resistive slider
      • Detects linear position using spaced resistive buttons
      • Can use basic interpolation and multi-touch
    • Resistive X-Y touch pad
      • Combines multiple touch sliders in 2D, reducing pin requirements via multiplexing
  6. Pressure Sensors
    • GSR pressure sensor
      • Analog resistive sensor using galvanic skin response
      • Detects relative pressure changes based on finger conductivity
    • Spring pressure sensor
      • Analog resistive sensor with reduced terminal gap under pressure
      • Provides consistent values, independent of finger touch
  7. Flex Sensors
    • Printed conductive filament in a thin or hollow structure
    • Resistance changes as the structure flexes due to separation of carbon particles
    • Alternatively, flex sensors can be made using spring pressure sensors
  8. Design Considerations
    • Spacing for touch points
      • Keep touch points at least 3mm apart for accuracy when dealing with multiple touch points
  9. Example Applications
    • Dome touch pad
      • X-Y touch pad integrated into a dome-shaped structure
    • Sound wave slider
      • Slider printed along a decaying sine wave
    • Multiple sensor toy
      • Combination of sensors placed around the form of a toy