📄 Paper-Based Flexible Sensor for Wearable Applications

A low-cost, eco-friendly, and responsive flex sensor made using graphite-coated filter paper enhanced with sodium chloride (NaCl) — designed for wearable and assistive applications. This project demonstrates the design, fabrication, and characterization of a sustainable alternative to conventional silicon-based flex sensors.

📌 Key Features

• 🔋 Power-efficient and responsive sensor for real-time bending detection
• 🌿 Eco-friendly materials: graphite, filter paper, NaCl
• 💸 Ultra-low cost fabrication (~INR 10)
• 🔧 Easily integrable with Arduino (ATmega328P)
• 🎮 Ideal for gesture-based control, assistive devices, and wearable electronics

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🧪 Sensor Construction

Materials Used:

• 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

Dimensions:

• Optimal sensor size: 6 cm × 1 cm
• Varying lengths and widths were tested for sensitivity and stability

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🛠️ Fabrication Steps

1. Outline the sensor on filter paper (6×1 cm)
2. Fill with graphite for conductivity
3. Apply NaCl solution to enhance ionic conductivity
4. Dry overnight and attach copper tape + backing
5. Solder wires and add protective layer
6. Interface with Arduino using a voltage divider (R1 = 1Ω)

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📈 Data Acquisition

• Uses Arduino’s 10-bit ADC
• Real-time monitoring via Serial Monitor & Plotter
• Voltage output calculated by:

  Voltage = (ADC_Value × 5) / 1023

• Output varies with bending due to resistance changes in sensor

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📊 Performance Summary

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

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🚀 Applications

• 🤖 Assistive Glove: For individuals with motor impairments
• 🎮 Gesture-Based Gaming: Affordable, sensitive input control
• 🦾 Robotics: Real-time bending angle detection
• 🧥 Smart Textiles: Integration into wearables and health monitors

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📷 Visual Overview

Fabrication Steps	Final Setup

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🧠 Future Improvements

• Use of CNC plotters for consistent graphite application
• Integration with wireless modules for IoT-based wearables
• Advanced machine learning models for gesture interpretation

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