Linear guides are spot on for bio research

A THK product story

Edited by the Engineeringtalk editorial team Apr 21, 2004

To ensure that its ground-breaking pick-and-place system is consistently accurate, Arrayjet opted for THK's linear motion components, which offer long-term, maintenance-free operation.

To ensure that its ground-breaking pick-and-place system is consistently accurate, Arrayjet opted for THK's linear motion components, which offer long-term, maintenance-free operation.

Creating a truly innovative machine that has the potential to redefine biological research is a mammoth undertaking.

For Edinburgh-based Arrayjet, it took nearly three years.

The company's innovative prototype pick-and-place liquid-handling system is currently undergoing field trials and production has already started on the first production models.

A major feature of Arrayjet's machine is the astonishing number of samples the system is able to place on the 3 x 1in microscope slides - otherwise known as microarrays - used in biological research.

The ground-breaking system picks up liquid samples from well plates and deposits them using standard ink jet printheads.

The resulting 100pl sample spots are much smaller than some sample sizes and therefore use less biological fluid.

Cameron Kennedy, Senior Mechanical Engineer at Arrayjet, says the system's accuracy is critical in terms of both sample placement and subsequent information recovery.

"We were looking for an accuracy of +/-5um, or better", he explains.

"This would enable us to place around 30,000 dots on each slide and, more importantly, it would help us determine accurately where each sample was located".

Central to the development of the ingenious system was the highly accurate linear motion components supplied by THK, the world's leading manufacturer of motion and guidance systems for machine tools, robots, semiconductor applications and computer-controlled systems.

For Arrayjet and its biotech robot, THK's linear motion systems were pivotal.

"They're utterly critical", says Kennedy, "everything is based around them".

In total, six SHS and two SRS LM guides are incorporated into each machine along with a number of ballscrews and linear bearing units.

They manoeuvre the printhead over the well plates for sample loading and then move it over the slides to deposit the liquids onto them.

As you'd expect, accuracy and consistency played an important part in the component selection process.

"We wanted linear motion components that wouldn't need servicing during the life time of the machine", Kennedy notes.

"We considered a roller system, but we couldn't tolerate the inaccuracies a system like that would throw up.

We needed consistency of accuracy, and that's why we opted for THK".

The reliability sought by Arrayjet was achievable thanks to THK's advanced linear motion technology, which included its caged ball system.

Here, equal spacing of the balls in the block and the retention of the lubricating grease between the balls offer a number of distinct advantages over conventional linear motion guides, including reduced noise output, minimal variations in rolling resistance and high-speed positioning.

More importantly, THK's caged ball system offers precise, smooth linear movements and long-term, maintenance-free operation.

"We got exactly what we were looking for", Kennedy says, "and that was accuracy.

There's a lot of innovation in our machine, and I simply don't have the time to worry about the linear motion side of things.

So I opted for the best available, and that was THK's guides and rails".