Open Blink: Low-cost TIRF microscopy for super-resolutionimaging via μManager

The paper introduces Open Blink, a low-cost, open-source TIRF microscope built with off-the-shelf components and integrated with μManager, which enables accessible, high-performance, and quantitative multi-color super-resolution imaging for biological research.

The Gist

Imagine you want to take a photograph of a bustling city street, but you want to see every single person's face clearly, even though they are tiny and moving fast. In the world of biology, scientists want to do this with the tiny machinery inside our cells. For years, the only way to get these incredibly sharp, "super-resolution" pictures was to buy a microscope that costs as much as a luxury sports car (around $280,000) and requires a PhD just to turn it on.

Enter Open Blink. Think of Open Blink not as a luxury car, but as a high-performance, DIY electric bike. It's built by a team of scientists to be cheap, easy to use, and open for anyone to build, yet it still goes just as fast as the expensive models.

Here is how they did it, broken down into simple concepts:

1. The "Light Bulb" Problem (The Laser Combiner)

To see tiny things, you need a very bright, perfectly even light. Usually, these lights are expensive single-mode lasers.

• The Analogy: Imagine trying to light a room with a single, expensive spotlight. If you want more light, you have to buy another expensive spotlight.
• The Open Blink Solution: Instead of one expensive spotlight, they took four cheaper, powerful "flashlights" (laser diodes) and glued them together into a single unit. They put these into a special fiber-optic cable that acts like a "stirrer." Just like stirring a pot of soup makes the heat spread evenly, a tiny vibrating motor shakes the cable to mix the light, ensuring the entire sample is lit up perfectly evenly.
• The Result: They got the same brightness as the expensive systems but for a fraction of the price.

2. The "Camera Lens" Problem (The Microscope Body)

Standard microscopes are built for a small view. To see a whole neighborhood of cells at once, you need a wide view, but keeping the focus sharp over a large area is hard.

• The Analogy: Imagine trying to take a panoramic photo of a landscape. If you use a standard camera lens, the edges get blurry.
• The Open Blink Solution: They modified an existing open-source microscope frame (called "MiCube") by shrinking its width slightly. This allowed them to use a different lens that spreads the light out much wider. Now, instead of seeing just one house, they can see an entire block of houses at once without losing clarity.
• The Result: A "Large Field of View" that lets scientists watch many cells interacting at the same time.

3. The "Shaky Hand" Problem (Focus Lock)

Taking these super-sharp pictures takes a long time—sometimes hours. If the microscope moves even a tiny bit (like a shaky hand), the picture blurs. Commercial microscopes have expensive motors to fix this.

• The Analogy: Imagine trying to draw a perfect circle on a piece of paper while someone is gently pushing the paper up and down. You'd need a robot hand to hold the paper steady.
• The Open Blink Solution: They built a "smart robot hand" called fgFocus. It shoots a harmless infrared laser beam (invisible to the eye) at the sample. A sensor watches where that beam bounces back. If the sample moves even a hair's width, the sensor tells a computer to instantly move the stage back to the perfect spot.
• The Result: The microscope stays rock-steady for hours, allowing for long, detailed experiments.

4. The "Remote Control" Problem (Software)

Building a custom microscope is useless if you have to write complex code to control it.

• The Analogy: Imagine building a custom car but having to write your own engine code every time you want to start it.
• The Open Blink Solution: They integrated everything into µManager, a free, popular software that scientists already know and love. It's like plugging your custom car into a universal dashboard. You can control the lasers, the camera, and the focus lock with simple sliders and buttons, and the software automatically saves all the details of the experiment so you can repeat it later.

The Big Picture

The team managed to build a machine that costs about $70,000 (roughly 75% cheaper than the competition) while delivering the same high-quality results.

• They proved it works by taking super-clear pictures of the "skeleton" inside cells (microtubules) using three different advanced imaging techniques.
• They made it open: Every blueprint, every piece of code, and every part list is free online.

In short: Open Blink is like giving every biology lab a Ferrari engine, but putting it in a reliable, affordable, and easy-to-fix chassis. It removes the financial and technical barriers, allowing more scientists to explore the nanoscale world and make new discoveries.

Technical Summary

1. Problem Statement

Super-resolution localization microscopy (SMLM) is a critical tool for nanoscale biological research, offering high spatial resolution and compatibility with wide-field microscopy. However, achieving quantitative SMLM requires three specific, often expensive, technical features:

1. Homogeneous high-power illumination over a large field of view (FOV) to ensure consistent localization precision.
2. Nanometric axial stability to prevent focus drift during long acquisition times (tens of thousands of frames).
3. Precise multi-channel detection for quantitative analysis.

Currently, these features are restricted to high-end commercial instruments or complex custom solutions in specialized labs. While open-source alternatives exist, they often suffer from:

• Limited laser power or FOV.
• Lack of fully integrated, user-friendly control software.
• High technical barriers requiring expertise in optics, electronics, and programming.
• Designs that are difficult to replicate or transfer between laboratories due to reliance on specific, non-standard components.

2. Methodology

The authors designed Open Blink, a compact, open-source Total Internal Reflection Fluorescence (TIRF) microscope. The system was engineered to balance high performance with accessibility, using predominantly off-the-shelf components and full integration with the open-source software µManager.

A. Hardware Architecture

• Laser Combiner & Illumination:
  • Utilizes a quad-line laser combiner with semi-turnkey diode lasers (405 nm, 488 nm, 561 nm, and dual 638 nm).
  • Cost Reduction: Replaces expensive single-mode lasers with high-power multimode diode lasers, reducing laser costs to ~29% of the total system cost.
  • Homogeneity: Uses a multimode fiber (MMF) with a 70 µm × 70 µm square core. To eliminate speckle patterns inherent to MMFs, a vibrational motor (VM) agitates the fiber, acting as a mode scrambler to ensure uniform illumination.
  • Power: Achieves up to 1.3 W at 638 nm (6.94 kW/cm²), sufficient for dSTORM.
• Microscope Body (Modified miCube):
  • Based on the open-source miCube frame but modified to accommodate a 150 mm focusing lens (instead of the standard 200 mm).
  • This modification allows for a large Field of View (FOV) of 257 µm × 257 µm while maintaining TIRF conditions.
  • Includes a beam size reducer (telescope configuration) to switch between large FOV (high throughput) and small FOV (high intensity) modes.
  • Features a dual-channel detection path split by a 595 nm dichroic mirror, imaging onto a single sCMOS camera with a final magnification of 59.9×.
• Focus-Lock Module (fgFocus):
  • An active stabilization system adapted from previous designs (pgFocus/qgFocus).
  • Uses an 830 nm infrared laser coupled into the TIRF path. The reflected beam is detected by a 1D sensor array.
  • A PID controller adjusts the sample Z-stage (SmarAct) in real-time to compensate for drift, ensuring nanometric stability over hours.

B. Software Integration

• Platform: Full integration into µManager, a standard open-source control software for the bioimaging community.
• Control Electronics: Custom micro-controllers (Raspberry Pi Pico and XIAO SAMD21) handle:
  • Laser intensity modulation (0–5 V analog).
  • Vibrational motor speed (PWM).
  • Infrared sensor readout for focus locking.
• Plugins: Custom µManager plugins (via the Easier Micro-manager User interface - EMU) were developed to control the laser combiner and fgFocus. These plugins enable metadata registration (recording laser power, stage position, exposure time) directly into image files, ensuring reproducibility.

3. Key Contributions

1. Low-Cost High-Performance Hardware: Demonstrated that high-power, homogeneous illumination can be achieved using multimode diode lasers and fiber agitation, cutting the cost of a full SMLM system to approximately €70,000 (vs. >€250,000 for commercial systems).
2. Large FOV TIRF: Successfully adapted the TIRF condition to a multimode fiber setup, enabling a 257 × 257 µm² FOV without sacrificing localization precision.
3. Active Focus Stabilization: Developed fgFocus, the first µManager-compatible focus-lock module for SmarAct stages, achieving axial stability of -1.58 nm ± 2.00 nm over 250 minutes.
4. Seamless Software Integration: Provided a "semi-turnkey" solution where complex hardware control is abstracted into user-friendly µManager plugins, removing the need for users to write custom code.
5. Open Science: All design files (CAD), PCB layouts, firmware, and compiled plugins are publicly available on GitHub and 4TU.ResearchData.

4. Results

The system was validated using three distinct SMLM modalities on fixed COS-7 cells (microtubules):

• dSTORM:
  • Used with Alexa Fluor 647 under high-power (1.2 kW/cm²) excitation.
  • Achieved a localization precision of 8.21 nm.
  • Demonstrated successful single-molecule blinking and reconstruction.
• DNA-PAINT:
  • Used Cy3B imagers under TIRF illumination with a large FOV.
  • Achieved a localization precision of 13.0 nm, proving that large FOV does not compromise resolution.
• SOFI (Super-resolution Optical Fluctuation Imaging):
  • Used 5×R1 DNA-PAINT docking strands with high imager concentration for dense blinking.
  • Performed second-order SOFI reconstruction on a stitched 4×4 grid (0.23 mm × 0.23 mm total FOV).
  • Demonstrated high-throughput capability, acquiring the full dataset within a total camera exposure time of 80 ms per tile.

Stability Test:

• Over a 250-minute acquisition, the system with fgFocus enabled showed negligible axial drift (-1.58 nm), whereas the system without focus-lock drifted by 94.2 nm.

5. Significance

Open Blink represents a paradigm shift in the accessibility of super-resolution microscopy. By decoupling high performance from high cost and technical complexity, it enables a broader range of laboratories to perform quantitative, multi-color, single-molecule imaging.

• Scalability: The modular design allows for easy upgrades or adaptation to specific needs (e.g., live-cell imaging with environmental control).
• Reproducibility: The use of standard components and rigorous metadata recording ensures that experiments can be replicated across different labs.
• Community Impact: By providing a complete, documented, and software-integrated solution, Open Blink lowers the barrier to entry for SMLM, fostering innovation in the open-hardware community and accelerating biological discovery.