We develop ultra-stable precision positioning solutions for applications in cryogenic and vacuum environments with a special focus on extreme cryogenic conditions of millikelvin temperatures, as realised in wet and dry dilution refrigerators. Our technology is backed up by 15 years of experience in developing, building, and using nanopositioning technology for microscopy applications in cryogenic environments, often at 10 mK and below. Our nanopositioning stages are purpose-developed to deliver peak performance at milli-Kelvin temperatures through the innovative design of the stage geometry and the stick-slip-drive, optimised motion interfaces, the exclusive use of high-performance alloys and ceramics, and premium-line piezo-electric actuators. Some people use this technology to build space ships, we use it to build market-leading nanopositioning technology for you. Continue reading if you are curious about our technological edge and how we address the challenges of nanopositioning at sub-Kelvin temperatures!

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The Challenge: Nanopositioning below one kelvin

Impact on Stick-Slip Mechanism

The operation of stick-slip driven positioning stages at cryogenic temperatures comes with a set of formidable challenges. The stroke of the piezoelectric actuator is reduced and the lubricating effect of air and humidity on the motion interfaces is absent and the friction coefficient the stick-slip interface becomes exposed to the combination of surface physics and chemistry. In combination with thermal contraction of the stage components, these effects can impede the reliable operation of the positioning stage.

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Thermalisation of positioning stages

Moreover, at sub-Kelvin temperatures, the efficient thermalisation of the positioning stage and their attachments, such as a sample stage, becomes very challenging. Here, thermalisation refers to the cooling of the positioning stage components to the base temperature of the cryogenic system. The thermal conductivity of materials is dramatically reduced at low temperatures. Many materials commonly used for building nanopositioning stages, such as titanium and alumina, practically don't conduct heat at all, because they enter a superconductor state (titanium) or are electric insulators (alumina). In combination with poor heat conduction across material interfaces, such as metal-metal interfaces in the presence of thermal oxides or glue joints, the removal of heat from and across the positioning stage is effectively suppressed.

 

Energy dissipation of the stick-slip drive

Driving nanopositioning stages can cause substantial energy dissipation that can lead to an increase of the temperature of the cryogenic system, especially in systems with small cooling power such as dilution refrigerators. This energy dissipation arises through the combined effect of resistive heating in the electric leads owing to the drive signal of the piezoelectric actuator, dissipation in the charging/discharging of the piezoelectric element, and friction of the motion interface. In combination with the bandwidth requirement for the electric leads, nanopositioning stages with large piezoelectric elements made from very soft piezoelectric materials are not suitable for operation at sub-Kelvin temperatures.

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Mechanical stability and robustness

Many applications of nanopositioning stages, such as scanning probe microscopy techniques and optical instruments, cannot tolerate mechanical vibrations. In some cases, even vibration amplitudes of one nanometer cannot be tolerated. The effect of mechanical vibrations can become particularly severe in cryogen-free cryostats, such as dry dilution refrigerators, in which the cooling mechanism causes effective broad band mechanical noise up to a few hundreds of hertz. Most conventional positioning stages have mechanical resonance frequencies at or below 1 kHz and are susceptible to this type of environmental noise, making the operation of scanning probe microscopy applications challenging

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Our Solution

Fifteen years of experience in developing, building, and using nanopositioning technology for microscopy applications in cryogenic environments enable us to successfully answer to these challenges and provide using with ultra-stable nanopositioning stages tailor-made for the application in extreme cryogenic conditions. We achieve this goal by looking at the comprehensive set of bespoken challenges and then implement a holistic technical solution.

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Innovative Stage Design and Advanced Manufacturing

We have developed a proprietary design of the stick-slip drive that utilises smallest form factors and solid-body joints to facilitate nanopositioning stages with unmatched mechanical stability. The absence of structural glue joints further imbues our stages with an unmatched mechanical robustness and optimised heat conduction. These advances in nanopositioning technology are also made possible through our state-of-the-art manufacturing capabilities in Hong Kong and the Greater Bay Area.

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High Performance Materials 

Our stages are manufactures solely from high-performance materials, such as sapphire and beryllium copper (CuBe) alloys, to facilitate stages with unmatched thermal conductivity at low temperatures. Unlike titanium and alumina used by many nanopositioning stage suppliers, sapphire and CuBe offer superior thermal conductance at low temperatures, while also exhibiting outstanding mechanical properties. Access to the commodity market of China enables our company to only using the best possible materials while maintaining a competitive pricing scheme. 

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Optimised Motion Interfaces

The performance of the stick-slip drive is extremely sensitive to the properties of the motion interface between the drive axis and the movable carrier. The friction properties of this interface are determined by the physical properties of the interface at macroscopic length scales, such as the surface roughness, as well as the chemical properties at microscopic length scales, such as chemical bonds forming between the drive axis and movable carrier. Combining advanced physical and chemical surface treatments of the stage components with judicious material choices, our nanopositioning stages are outfit with highly optimised motion interfaces to enable reliable and low-dissipation motion under extreme cryogenic conditions and even ultra-high vacuums.