High-Speed Laser and Motion Control with Intelligent DAQ

Author(s):
Piero Zucchelli - SpinX Technologies S.A.

Industry:
Industrial Controls/ Devices/ Systems, Research, Biotechnology

Products:
Data Acquisition, FPGA Module, Digital I/O

The Challenge:
Developing a cost-effective method for controlling a large number of valves on a miniaturized card for performing microfluidics operations.

The Solution:
Using National Instruments LabVIEW FPGA and R Series intelligent data acquisition (DAQ) hardware to develop a system capable of performing very fast calculations for highly accurate and precise perforation of thousands of microfluidic structures.

Like the revolution of microelectronics before it, microfluidics has been the catalyst for biochemical application advancements in fields such as drug discovery, diagnostics, and the food industry. The “lab-on-a-chip” concept entails performing, on a miniaturized card, what is done today in full-sized biochemistry laboratories using robots, expensive equipment, and large quantities of reagents. Most of today’s electronics applications were made possible only after the advent of multiple low-cost transistors on one small chip. Similarly, the “lab-on-a-chip” concept can open new roads to biochemistry.

Until now, the microfluidics revolution, targeted by many companies and research groups, has been waiting for “zero-cost,” miniaturized (around 10 micrometers) valves that can be incorporated onto a single plastic card; thousands of valves must be independently and easily controlled from the outside to achieve “lab-on-a-chip” functionality. Unfortunately, microfluidic cards must be disposed of after a single use for contamination reasons, challenging the potential parallel to the microelectronics revolution.

At SpinX Technologies, we have invented a proprietary technology called Virtual Laser Valve (VLV) that uses an external pulsed beam of light to actuate and locally perforate the film contained in a plastic card. The film sits between two transparent substrates containing microchannels and microchambers. A laser-generated hole allows fluids to pass through, and the design of the microstructures around this simple valve lets engineers perform the basic operations of an “FPGA for the biochemist,” including metering and arbitrary multiplexing of nanovolumes of fluids.

We developed a prototype card based on this VLV technology and used it to test how staurosporine molecules interact with a kinase protein (as found in many cancers) at various concentrations. We performed nine different and complete experiments in parallel on a small section of the card   – about the size of a postage stamp – with 100X lower consumption of precious reagents. Each valve is opened in just a few microseconds while the card is turning on a rotating spindle, achieving localization precision within a few micrometers.

In our final deployed system, a pulsed-laser diode is focused, through a DVD pickup, onto cards mounted on a rotary spindle. Shooting a 10-micrometer laser beam onto six flying plastic cards – each twice the size of a credit card and containing thousands of microfluidic structures – can perforate a polymer film in a precise position within a tolerance of only a few micrometers. The precise measurement of a rotating card’s instantaneous speed lets us calculate its exact position at a precise time. The National Instruments PXI-7833R measures all the required parameters without the use of custom hardware and computes deterministically the correct shooting time in just a few microseconds, so we can achieve an angular accuracy exceeding 20 microradians (about 0.001 degrees) – far surpassing the precision of commercially available encoders.

An FPGA-Based Solution

It would be impossible to localize the laser beam with an optical encoder or a magnetic resolver because the resolution would be too coarse by two orders of magnitude. Our solution relies completely on the existence of programmable, flexible, and high-speed electronics capable of performing customized kinematical calculations continuously and at high speed to convert space into time.

With this system, we can measure, with a high level of precision, the time required for a given movement of the rotating spindle. The movement is sensed through the internal Hall sensors of the brushless motor rotating the spindle, which generates 24 digital signals per turn.

To pulse the laser at a desired angle, we simply compute a suitable delay time after the occurrence of a synchronization signal that has an angular position. This calculation requires measuring the instantaneous angular speed, which is determined by the previous turn period or, in practice, by the lag time between two consecutive signals from the Hall sensors of the motor. Of course, the Hall signals are not precisely spaced, and their angular position varies largely from motor to motor. However, a full turn always corresponds to a 360-degree rotation. The measurement over a few calibration turns of the lag time between consecutive signals lets us determine, experimentally and with high precision, the exact angular distance between each Hall signal.

The Intelligent DAQ Implementation

The technology – including laser positioning, firing, spinning speed control, readout lasers, single photon detection and imaging on the rotating cards, and laser pickup focusing onto the film – is controlled by a single NI PXI-7833R reconfigurable I/O intelligent DAQ module. More than 13 control loops, some independent and some sharing resources, run concurrently with the determinism of a single clock cycle period of 25ns.

Despite these fundamentally simple concepts, their implementation onto rapid electronics is far from trivial without prior FPGA programming experience. Graphical programming with the National Instruments LabVIEW FPGA Module let us achieve overall instrument functionality in about four months of development time by one person. The tight integration of intelligent DAQ hardware and valving functionality achieved with this technology reduces the manual laboratory activity by two days, to just three hours of unattended operations.

The potential of graphically programmable FPGAs accessible to non-specialized programmers is still far from being fully explored. The possibility of applying this technology to testing, rapid prototyping, and product development opens up new roads to innovation, decreasing timescale, costs, and risks. Investment in multipurpose, off-the-shelf solutions – in contrast to highly specialized custom development projects – is another key advantage for flexible R&D. Using intelligent DAQ technology from National Instruments, our company has been able to achieve our targets and improve on all aspects of this development cycle, most importantly time to market.

For more information, contact:

Piero Zucchelli, CSO and Founder

SpinX Technologies S.A.

29 Rue Lect

CH-1217 Meyrin (Switzerland)

Tel. +41-22-719-0947

E-mail: Piero.Zucchelli@SpinX-technologies.com

 

 

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