For a long time, the electron microscope has been regarded as the crown jewel of precision instruments. However, its bulky size, high cost, and complex maintenance requirements have made it an intimidating “black box” that deters most ordinary laboratories from adopting it. Yet, with the rise of the open-source hardware movement and advances in micro- and nanofabrication technologies, a “desktop revolution” in electron microscopy is quietly underway. This article takes the open-source electron-microscopy project NanoMi as its technical blueprint, offering an in-depth analysis of the modular design philosophy underlying electron optics and exploring the role of electrostatic lenses and... Magnetic lens The debate over the technological roadmap.

Introduction: The Electron Beam Stepping Out of the “Ivory Tower”

In most people’s minds, transmission electron microscopes or scanning electron microscopes often require a dedicated laboratory that is exclusively equipped with constant temperature, constant humidity, and vibration-proof features. The hissing sound of liquid-nitrogen tanks, intricate vacuum pipelines, and the densely packed knobs on the control panel—all these elements together form the stereotypical image of “high-end microscopy.”

However, for the vast majority of engineering students and materials research engineers, what they often need is not atomic-level resolution but rather a tool that can quickly provide feedback on microscopic data. Is it possible to disassemble and reassemble an electron microscope so that it becomes as flexible as building with LEGO bricks—and can even be placed on an ordinary office desk?

In 2022, a paper titled “NanoMi: An open source electron microscope hardware and software platform,” published in the journal Micron, lifted the veil on this possibility. The NanoMi project, led by Canada’s National Research Council (NRC), aims to develop an electron microscope with a cost of less than US$100,000, based on... CERN Open Hardware License The universal electron microscopy platform from (OHL). It’s not just a piece of equipment—it’s a statement: the era of the “black box” in electron microscopy is coming to an end, and the age of modularity and miniaturization has arrived.

NanoMi’s core architecture: Building electron microscopes like building blocks.

NanoMi was originally designed for educational purposes and proof-of-principle demonstrations. Its design philosophy holds great reference value for understanding the architecture of modern desktop electron microscopes. It breaks away from the traditional integrated design of electron microscopes, in which the column itself serves as the vacuum chamber, and instead adopts a highly innovative approach— Vacuum breadboard (In-vacuum Breadboard) structure.

1. Physical Architecture: Halfpipe and Building Blocks

At the heart of NanoMi is a half-pipe with a diameter of 127 mm, which is suspended within a standard DN160 CF vacuum flange. All the electro-optical components—including the electron gun, lenses, deflectors, and astigmatism correctors—are mounted onto this half-pipe like building blocks.

The ingenuity of this design lies in achieving the decoupling of vacuum envelope and electron optics.

Traditional electron microscopy: The wall of the lens barrel must not only maintain a vacuum but also serve as the magnetic circuit loop (iron yoke) for the magnetic lens, placing extremely high demands on both machining precision and the magnetic permeability of the material. 
Modular design: The vacuum chamber is merely a container; the optical alignment inside relies entirely on precisely machined mounting plates. This means that engineers can replace a particular lens stage or insert a new detector at any time without having to redesign the entire vacuum system.

2. Optical Selection: The Revival of Electrostatic Lenses

In the design of NanoMi, one of the most striking technical details is its use of an electrostatic lens instead of a conventional high-performance magnetic lens.

For electronic-optical engineers, this is a choice fraught with trade-offs:

Magnetic lens: It uses the Lorentz force for focusing, has low aberration coefficients, and performs exceptionally well especially under high pressure. However, it is bulky and heavy, requires a sophisticated water-cooling system to dissipate coil heat, and exhibits hysteresis effects. 
Electrostatic lens: Using an electric field to accelerate or decelerate and focus electrons (typically for Single lens Structure). The advantage is that the structure is extremely simple (requiring only three concentric electrodes), with no hysteresis, no thermal dissipation, and no need for a water-cooling system—thus removing the biggest obstacle to “desktopization.” However, the challenges lie in significant aberrations and extreme sensitivity to ripple in the high-voltage power supply.

NanoMi chose electrostatic lenses primarily for their exceptional light weight and low cost. The Einzel lenses it uses are machined from aluminum or stainless steel, insulated with PEEK material, and can withstand voltages up to 50 kV. Although their resolution is limited to around 10 nm, this is sufficient proof that, with proper design, a fully functional electron-optical system can indeed be accommodated within the compact space of a desktop-level device.

The Path to Advancement: An Engineering Leap from “Functional” to “User-Friendly”

NanoMi demonstrated the “lower limit” of desktop electron microscopes—building a fully functional system using only the most basic components. However, in real-world industrial inspection, semiconductor failure analysis, or cutting-edge materials research, users simply cannot accept having to manually calibrate the optical axis every day or enduring image jitter caused by drift in the high-voltage power supply.

This is precisely the significance of commercial desktop electron microscopes. Take ZEPTOOLS Technology as an example: its ZEM series desktop scanning electron microscopes have, building upon the “miniaturization and modularity” philosophy embodied by NanoMi, successfully made a leap toward industrial-grade performance characterized by “high stability, high resolution, and multi-functionality.”

1. The Evolution of Electron Sources: From Tungsten Filaments to Field Emission—a Quantum Leap

NanoMi primarily uses tungsten hairpin filaments or lanthanum hexaboride filaments. Tungsten filaments are low in cost, but they have low brightness, a short lifespan (tens of hours), and significant energy dispersion, leading to severe chromatic aberration and limiting resolution at low voltages.

ZEM Ultra from ZEPTOOLS Technology is directly introduced. Schottky field-emission electron gun By utilizing a strong electric field to lower the potential barrier, electrons undergo quantum tunneling. The brightness is more than 1,000 times that of tungsten filaments, and the energy spread is extremely narrow, enabling the ZEM Ultra to achieve a resolution better than 2.5 nm at 15 kV.

Field emission requires extremely high vacuum levels. By employing a unique three-stage independent vacuum design and ion pump technology, ZEPTOOLS Technology has achieved an ultra-high vacuum environment within the compact footprint of a desktop device—a significant upgrade to NanoMi’s foundational vacuum architecture.

2. Reconstruction of the optical system’s stability

In its paper, NanoMi acknowledged that its resolution is limited by the ripple of the high-voltage power supply and mechanical vibrations.

In  ZEM scanning electron microscope series, we see the rigor of industrial-grade solutions:

Lens tube design: It adopts a modular barrel design, but rather than simply stacking building blocks, it integrates high-precision electromagnetic shielding and anti-vibration features. 
Optical path control: Unlike the NanoMi, which requires manual adjustment of a potentiometer, the ZEM series features fully automated electron-beam control. Thanks to advanced algorithms that automatically perform astigmatism correction and focusing, steps that previously demanded specialized femtosecond-level operations have been simplified to a single mouse click. 
Detector integration: Standard equipment includes a high-sensitivity secondary electron (SE) detector and a four-segment backscattered electron (BSE) detector. In particular, the four-segment BSE detector not only provides compositional contrast but also offers morphological information through signal addition and subtraction operations—this is a direct benefit of the modular detector layout.

The ultimate form of modularity: in-situ characterization

A key vision of the NanoMi project is “customizing electron microscopes according to experimental needs.” This principle is now more fully realized in ZEPTOOLS Technology’s product lineup. For materials scientists, the static microstructure is merely the tip of the iceberg—they’re far more interested in understanding what happens to a material when it’s subjected to stress, heat, or electric current.

Traditional large-scale electron microscopes equipped with in-situ stages are extremely complex, whereas desktop electron microscopes, thanks to their compact chambers and short optical paths, actually possess unique advantages. Leveraging its deep expertise in MEMS micro- and nano-manipulation, ZEPTOOLS Technology has transformed the ZEM series into a “microscopic laboratory.”

Mechanics Module: The ZEM series can be optionally equipped with an in-situ tensile stage, enabling real-time observation of crack initiation and propagation in metals and fibers under tensile and compressive forces within the electron microscope. 
Thermodynamics Module: An integrated TEC cooling or heating stage allows observation of phase transition processes in materials under temperatures ranging from -25°C to high temperatures. This is crucial for studying battery separators, biological samples, and polymer materials.

This design approach—where the sample stage is expanded as a standalone module—is fully aligned with NanoMi’s open-source ethos. However, ZEPTOOLS Technology has standardized and productized this approach, enabling users to perform sophisticated in-situ experiments without having to write their own driver code.

From NanoMi’s open-source exploration to the mature applications of ZEML’s ZEM series, we can clearly trace the evolution of electron microscopy technology: from mystery to openness, from bulkiness to compactness, and from single-mode observation to multidimensional analysis.

NanoMi has demonstrated to the engineering community that the physical principles underlying electron microscopy do not require a bulky, massive structure to support them; meanwhile, ZEPTOOLS Technology has shown the industrial sector that, through sophisticated engineering design and manufacturing processes, desktop electron microscopes can achieve resolution and stability comparable to those of traditional large-scale electron microscopes.

For today’s researchers and engineers, the electron microscope is no longer that “black box” requiring appointments, queuing, and painstakingly careful operation. The ZEM series scanning electron microscopes from ZEPTOOLS Technology are precisely the embodiment of this technological revolution. They’re not just observation instruments—they’re modular microscopic analysis platforms right at your fingertips. Whether it’s basic morphological characterization or sophisticated energy spectrum analysis and in-situ testing, they can open the door to the microscopic world for you with exceptional efficiency and an incredibly low barrier to entry.

In this era of breaking the black box, the microscopic world has become within reach.

Reference materials 
1. Marek Malac. “NanoMi: An open-source electron microscope hardware and software platform.” Micron 163 (2022): Article 103362. 
2. Williams, David B. and C. B. Carter. “Transmission Electron Microscopy: A Textbook for Materials Science.” 
3. Egerton, R. “Physical Principles of Electron Microscopy: An Introduction to TEM, SEM, and AEM.” 
4. T. Everhart, R. Thornley. “Wide-band detector for micro-microampere low-energy electron currents.” Journal of Scientific Instruments 31 5 (1960): 246–248.