Smart Food Monitoring System on Biodegradable Packaging

Project Overview

The EEE 4861 assignment investigates how smart sensing can be embedded within biodegradable packaging to improve food safety in Bangladesh. Our team designed and analyzed a MOSFET-based temperature monitoring circuit that can be fabricated through a VLSI workflow and embedded into Sonali Bag® packaging to detect unsafe temperature excursions for perishable goods.

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Motivation

• Widespread reliance on conventional plastic packaging continues despite Bangladesh’s 2002 polythene ban
• Retailers cite low cost, convenience, and limited biodegradable alternatives as barriers
• Smart packaging can curb post-harvest losses, improve food safety, enhance traceability, and reduce waste through proactive alerts

Critical Challenges

• Conventional barcodes offer billing convenience but no quality assurance
• Biodegradable substrates are costlier and harder to integrate with electronics in low-income contexts
• Limited public awareness of food safety practices complicates adoption

Literature Review Highlights

• Bangladesh Context: Enforcement gaps, lack of affordable alternatives, and low consumer awareness hinder the 2002 polythene ban
• Biodegradable Options: Surveyed mushroom, bamboo, algae-based, sugarcane fiber, coconut husk, wheat straw, PLA, starch, chitosan, and cellulose materials
• Key Trade-offs: Cost, mechanical strength, biodegradation timeframe, scalability, and moisture resistance

Selecting Sonali Bag®

• Indigenous jute-based biopolymer pioneered by Bangladeshi scientists; production cost around Tk. 1200/kg
• Demonstrated biodegradation within 100 days without toxic residue
• Thermal stability up to 250 °C and controlled degradation characteristics
• Aligns with local supply chains, policy goals, and consumer familiarity better than alternatives (e.g., Polka Bags, corn starch)

Sensor Circuit Design

• Electronic temperature monitoring chosen for precision, low power, and digital compatibility
• All-MOSFET architecture minimizes area (≈0.013 mm² in 180nm CMOS including reference) and power (≈40 nW @ 1.2 V)
• Achieves ±0.6 °C inaccuracy without calibration; suitable for smart packaging, room monitoring, refrigeration, and automotive use cases

Complementary Temperature Sensor Workflow

1. Reference Current Generator: Resistor-less beta multiplier provides PTAT current to both sensing cores
2. CTAT Core: NMOS transistors in subthreshold produce voltage decreasing with temperature (≈−2.1 mV/°C)
3. PTAT Core: PMOS configuration generates proportional output increasing with temperature
4. Differential Readout: Temperature calculated from VPTAT − VCTAT, cancelling process variations and enabling calibration-free operation
5. Signal Processing: External ADC digitizes readings; microcontroller maps voltage difference to temperature thresholds

Integration with Biodegradable Packaging

• Embed the temperature sensor within Sonali Bag® layers for direct exposure to food environment
• Use MOSFET-based threshold detection to drive LED or buzzer alerts when temperatures exceed safe ranges
• Multi-level cues: normal (no alert), warning (blinking LED), alert (solid LED), critical (buzzer)
• Maintain moisture protection for electronics while keeping indicators accessible

Decision-Making Framework

• Step 1 – Monitoring: Continuous temperature sampling tailored to food type
• Step 2 – Alerting: Trigger visual/audible cues when thresholds are crossed
• Step 3 – Action Guide:
  • <2 h exposure: consume immediately or refrigerate

  • 2 h exposure: dispose responsibly

  • Disposal: Compost both food waste and Sonali Bag® when feasible
• Priorities: Human health → Environmental stewardship → Cost feasibility
• Regulatory Alignment: Supports Bangladesh Environmental Conservation Rules 2023 via better waste management, reduced pollution, and consumer education