A low-cost, eco-friendly, and responsive flex sensor made using graphite-coated filter paper enhanced with sodium chloride (NaCl) โ designed for wearable and assistive applications. This project demonstrates the design, fabrication, and characterization of a sustainable alternative to conventional silicon-based flex sensors.
- ๐ Power-efficient and responsive sensor for real-time bending detection
- ๐ฟ Eco-friendly materials: graphite, filter paper, NaCl
- ๐ธ Ultra-low cost fabrication (~INR 10)
- ๐ง Easily integrable with Arduino (ATmega328P)
- ๐ฎ Ideal for gesture-based control, assistive devices, and wearable electronics
- Grade A Filter Paper
- 10B Graphite Pencil
- NaCl solution (1g/5ml in distilled water)
- Copper tape, X-ray plate (as flexible backing)
- Transparent protective sheet
- Arduino UNO (ATmega328P) for data acquisition
- Optimal sensor size:
6 cm ร 1 cm - Varying lengths and widths were tested for sensitivity and stability
- Outline the sensor on filter paper (6ร1 cm)
- Fill with graphite for conductivity
- Apply NaCl solution to enhance ionic conductivity
- Dry overnight and attach copper tape + backing
- Solder wires and add protective layer
- Interface with Arduino using a voltage divider (R1 = 1ฮฉ)
- Uses Arduinoโs 10-bit ADC
- Real-time monitoring via Serial Monitor & Plotter
- Voltage output calculated by:
Voltage = (ADC_Value ร 5) / 1023- Output varies with bending due to resistance changes in sensor
| Parameter | Paper Sensor | Commercial Sensor |
|---|---|---|
| Sensitivity (Up) | 0.0022 | 0.0007 |
| Sensitivity (Down) | 0.0012 | 0.0009 |
| Peak Voltage | ~5.0V | ~4.97V |
| Repeatability | High | Medium |
| Durability | Excellent | Moderate |
- Shows higher sensitivity at small angles
- Excellent repeatability and durability over 20+ cycles
- Sustainable alternative for budget-constrained environments
- ๐ค Assistive Glove: For individuals with motor impairments
- ๐ฎ Gesture-Based Gaming: Affordable, sensitive input control
- ๐ฆพ Robotics: Real-time bending angle detection
- ๐งฅ Smart Textiles: Integration into wearables and health monitors
| Fabrication Steps | Final Setup |
|---|---|
 |
 |
- Use of CNC plotters for consistent graphite application
- Integration with wireless modules for IoT-based wearables
- Advanced machine learning models for gesture interpretation