Dover Direct Drive Technology Exceeds Piezo Performance for Cell Imaging Application

A Dover XYZ stage solution increased the client’s productivity and helped them acquire FDA approval for their cancer screening instrument.

At a Glance

  • A client was developing a digital cytology instrument for cancer screening
  • Their piezo-based prototypes had been unable to focus at the resolution required and was pushing the client beyond their cost and timeline targets
  • We collaborated with their development team to create a XY and Z stages that increased the instrument’s productivity by 50% and got the client back on track with their timeline and budget
  • The instrument received FDA approval and captured 70% of the specific diagnostics test market within 4 years

Prototype Problems

A company was developing an automated digital cytology instrument for cancer screening, and had used piezo-based technology in the prototype units for the slide positioning and objective focusing. The issue was that the large friction deadband and poor control stability inherent in piezo systems could not deliver the ultra-high precision required to focus at the cellular level. Because of this, these prototypes had been unable to meet the cost or performance requirements to replace the slow, error-prone process of having a pathologist manually analyze each slide.

The company was falling behind schedule when they came to Dover Motion for a solution.

What They Needed

Dover Motion worked with the client’s development team to identify their design goals, and together we decided that a direct drive linear motor XY and Z stage was the best solution.

The client required:

  • An XY linear stage that was stiff with high precision to position the slides
  • A separate Z axis mechanism to focus the objective lens
  • An objective lens that was small, low-cost, and had extremely high precision
  • Rigid and stable alignment in the XY linear stage and Z axis assembly
  • An XY translation stage and Z axis that were fast enough to make 20 measurements per second
  • To have the positioning system be developed in parallel with the diagnostics instrument to keep the project on time
  • The positioning system to be cost-effective, self-contained, and have a pre-tested modular assembly

How We Got Them Back on Track

In a concurrent and collaborative effort, Dover Motion designed a compact, custom XYZ stage solution in parallel with the instrument design that produced high-precision cell imaging.

We designed a small, high-precision direct drive XY translation stage to position the slide. It had stiff crossed roller guide ways for high stability, and direct drive linear motors with encoder feedback for high speed, accuracy, and repeatability.

For focusing the Z axis, a unique low-cost and high-precision approach was used. The objective lens was potted directly into a flexure rod-based motion assembly which eliminated the need for the client to perform any optical alignment.

The flexure rod assembly did not require the precision machining of a conventional mechanical stage, and it had greater precision. Each of these features greatly reduced the cost and complexity of the Z axis.

The XY stage and the Z axis motion assembly were mounted within a rigid, co-developed, cast metal frame that integrated into the instrument structure. Dover Motion fully tested and servo tuned the imager axes, so there was no additional customer functional testing needed.

Dover Motion’s Cell Imaging yields High Precision Rates for Cancer Screening Instrument

Objective Z Focus Axis

Dover Motion’s XYZ Stages Cuts Third of the Cost of Competing Piezo Technology

XY for Sample Positioning

The Result

We worked closely with the client in order to:

  • Engineer their motion system in parallel with their instrument development
  • Keep the project on its cost and schedule targets
  • Quickly deliver a positioning system that had better cell imaging positioning performance at a third the cost of the competing piezo technology
  • Confirm the instrument’s necessary high throughput and precision rates, processing 20 stable images a second while accurately moving 384 microns between sites

No longer needing a pathologist to manually analyze each slide, the new cancer screening instrument automatically examines hundreds of slides and selects the appropriate ones for human review. This resulted in a 50% increase in lab productivity and more accurate clinical diagnoses. The new instrument quickly received FDA approval and captured 70% of the specific diagnostics test market within 4 years. As of 2017, it was in its thirteenth year of production.

This Dover direct drive XY translation stage positioning technology is also being used in other diagnostics imaging instruments due to its compact size and accurate positioning.

More Case Studies

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3D Metrology XY Stage

To minimize the overall size, Dover Motion used compact stepper motors with integrated lead screws. Placing the motors within the stage structure enabled all wiring to be concealed and to exit at the bottom of the stage.

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