Flexible e-QR Codes 🔲 The Future of Printed Electronics

TL;DR

Researchers microfabricated a flexible electronic QR code display using printed electronics on Kapton, enabling low-cost, real-time sensor data sharing via smartphone scans.

Breaking it Down

📱 From Paper to Pixels: Why Electronic QR Codes?

When you scan a QR code on a poster, a menu, or even a bus stop ad, you’re looking at a static block of black-and-white squares. But what if those little squares weren’t just printed ink… what if they were electronic and capable of changing in real time? ⚡

That’s exactly what researchers from the University of Pretoria have achieved: the microfabrication of an electronic QR (e-QR) code on a flexible substrate. Their work shows how printed electronics can power real-time sensor data displays, offering a low-cost and energy-efficient alternative to traditional sensor networks.

Instead of cloud-heavy, hardware-intensive IoT setups, this approach allows you to simply scan a dynamic e-QR code with your phone to instantly see updated sensor readings—whether it’s air quality, temperature, or other environmental data. 🌍

🧩 The Big Idea: Microfabrication Meets QR Tech

Traditional sensors often rely on costly wireless communication systems that push data to the cloud. That’s powerful but comes with downsides: 🖥️ high energy use, complex hardware, and ongoing costs.

The team’s alternative? Use microfabrication and printed electronics to build a dynamic QR code directly on a flexible film.

• Each LED = one pixel of the QR code.
• A 21 × 21 matrix = 441 pixels total, the standard size for a Version 1 QR code.
• These LEDs light up in patterns that encode data, creating a scannable code that updates as sensors feed new values.

In short: the QR code itself becomes the screen. No bulky LCDs or OLED panels needed! 📸✨

🧪 How They Built It: Step-by-Step in Microfabrication

The magic comes from a careful mix of additive and subtractive microfabrication techniques. Here’s a simplified breakdown of how the team made it happen:

1. 🎨 Designing the Circuit

• The LED driver circuit was created using EasyEDA (a Printed Circuit Board design tool).
• The design was converted into a format suitable for inkjet printing.

2. 🖨️ Printing on Kapton

• They used DuPont Kapton® 500B, a black polyimide film known for its strength, flexibility, and heat resistance.
• Silver nanoparticle ink was inkjet-printed onto the film to form conductive tracks.
• The substrate was heated (first at 50 °C, then at 200 °C) to “sinter” the ink, ensuring electrical conductivity.

3. 🔍 Aligning the Layers

Since the circuit was double-sided, alignment was crucial:

• Fiducial markers (small square reference points) were printed and laser-cut into the Kapton.
• These markers allowed precise alignment when printing the bottom layer and drilling vias (tiny holes connecting the two layers).

4. 🕳️ Creating Vias

• Using a laser system, they cut 441 tiny holes (0.31 mm diameter each).
• These were then filled with conductive paste to electrically connect both layers.
• The board was reheated to cure the connections.

5. ⚡ Adding Components

• Surface-mount components (like resistors and drivers) were added using semi-automatic pick-and-place tools.
• A microcontroller was connected to manage the LED patterns and update the QR code in real time.
• The result? A flexible, fully functional e-QR display that can be scanned with an ordinary smartphone 📲.

💡 What Did They Achieve?

The team successfully demonstrated:

✔️ A working 21 × 21 LED matrix on flexible Kapton.
✔️ Reliable vias — all 441 laser-drilled holes connected the top and bottom layers without issue.
✔️ Dynamic QR display — capable of encoding real-time sensor data into a scannable electronic QR code.

This proves that microfabrication + printed electronics can yield functional, low-cost display systems without the need for traditional, resource-hungry display technologies.

🌟 Why It Matters: Beyond Lab Prototypes

Let’s break down why this is such a game-changer:

✅ Cost Efficiency

• No need for large-scale wireless IoT setups.
• Uses cheap, scalable printed electronics instead of silicon-heavy circuits.

✅ Flexibility & Durability

Kapton substrates bend without breaking, opening doors for wearables, smart labels, and portable sensors.

✅ Accessibility

Any smartphone with a camera can read the data—no special equipment needed. 📸

✅ Citizen Science Potential

Imagine communities deploying low-cost air-quality monitors, where volunteers simply scan e-QR codes around their neighborhood to contribute data. 🏙️🌱

🔭 Future Prospects for Printed e-QR Codes

The researchers see plenty of room for improvement:

1. Digital Additive Manufacturing: Instead of using stencils for solder paste, future systems could rely entirely on digital printing—boosting scalability.
2. Dielectric Printing: Printing insulating layers with built-in via holes could streamline the process.
3. Scaling Up: More pixels = higher QR code versions = more data capacity. Imagine dynamic QR codes that can carry larger datasets.
4. Wearables & Smart Packaging: Flexible e-QRs could be embedded in clothing, medical patches, or even food packaging, updating freshness or usage data in real time. 🥗👕💊
5. IoT Without the “I”: By bypassing constant internet connections, these displays could create localized data-sharing ecosystems, especially useful in resource-constrained regions. 🌍

🚀 The Road Ahead

This work represents a bridge between traditional IoT sensors and next-gen printed electronics. By embedding intelligence into something as simple and universal as a QR code, the team has opened possibilities for:

• Smart cities that monitor infrastructure with scannable tags.
• Healthcare devices that update status with a quick scan.
• Supply chains that offer live product condition updates.

It’s a prime example of how microfabrication doesn’t just shrink technology—it makes it more accessible, sustainable, and human-friendly.

✨ Wrapping Up

The University of Pretoria’s demonstration of a microfabricated e-QR code on Kapton shows us a future where printed electronics meet everyday life. By turning QR codes into dynamic, flexible displays, they’ve transformed a familiar technology into a powerful, low-cost tool for sharing real-time information.

Next time you scan a QR code, imagine it’s not just a static link, but a living, glowing window into real-world data. 📲✨

Terms to Know

🔬 Microfabrication - The science of making really tiny structures—like circuits and sensors—on a microscopic scale, often using special printing, etching, or laser techniques. Think of it as miniaturized manufacturing.

🖨️ Printed Electronics - Electronics made by “printing” conductive materials (like silver inks) onto surfaces, instead of traditional silicon chipmaking. It’s like 3D printing, but for circuits! - More about this concept in the article "Revolutionizing Diabetes Care: The 3D-Printed Sensor Changing Glucose Monitoring 🍭 🩸".

📱 Electronic QR Code (e-QR) - A QR code made of electronic pixels (like LEDs) instead of just ink on paper. These can change in real time, displaying new information that your phone can still scan.

📄 Flexible Substrate - A bendable material (like plastic films or polyimide sheets) that circuits can be built on. Unlike rigid circuit boards, these can twist and flex without breaking.

🌟 Kapton - A tough, heat-resistant plastic film often used in electronics. Imagine a super-thin, bendable sheet that can survive high temperatures—perfect for flexible circuits.

⚡ Via - Tiny holes drilled into a circuit board that connect different layers together, letting electricity flow between them—like mini “elevators” for electrons.

✨ Fiducial Markers - Small printed reference points used to align different layers of a circuit during manufacturing. Basically, “guide dots” that help keep everything lined up.

🔲 LED Matrix - A grid of tiny LEDs arranged in rows and columns, where each LED can turn on or off to create patterns, images, or in this case, a QR code.

🌐 IoT (Internet of Things) - A network of everyday objects (sensors, appliances, wearables) that collect and share data online. Your smart watch or smart thermostat? That’s IoT in action. - More about this concept in the article "Digital Twin Boosts Vertical Farming 🌱".

Source: Raju, A.E.; Laue, H.E.A.; Joubert, T.-H. Microfabrication of an e-QR Code Sensor Display on a Flexible Substrate. Eng. Proc. 2025, 109, 16. https://doi.org/10.3390/engproc2025109016

From: University of Pretoria.