KLA Instruments’ comprehensive portfolio of Optical Profiler products, software, analysis, services and expertise is designed to help scientists, researchers and engineers address their toughest measurement challenges in the characterisation of Microfluidics Devices. 

Nano Technology Solutions is the exclusive distributor of KLA Instruments and supplies, installs, supports surface metrology products and accessories across Australia and New Zealand.

Contact us to discuss your specific requirements or objectives regarding metrology for microfluidics applications.

Multi-surface imaging and measurement of the depth of a channel on a closed ‘lab-on-a-chip’ device.
Multi-surface imaging and measurement of the depth of a channel (above) on a closed ‘lab-on-a-chip’ device. Source: Zeta Instruments (www.zeta-inst.com).

In the production of Microfluidic devices, measurements of the fabricated topologies are the foundation upon which modelling is done to design, analyse, and improve their performance. The measured depth, as well as the uniformity of depth throughout the channel, are key contributors to the overall effectiveness of the device in providing uniform, laminar flow within the channel, which is highly affected by surface roughness and interlayer mating methodology, as well as the channel cross-sectional area. Once the channel has been defined in the manufacturing process, it is enclosed by affixing a transparent layer across the upper surface. Due to the installation of the transparent layer(s), tensile, shear, and/or compressive stresses may be induced at the interfaces that slightly alter the original channel dimensions.

In order to ensure optimal device performance, the channel interior dimensions must be well-characterised, regardless of the number of transparent layers and any applied surface treatments.

Quality control procedures for microfluidic devices must meet the following criteria for choice of metrology technique and instrument:

  • Be non-contact and non-destructive: Because of the requirements of the medical industry, once manufactured, contact with other surfaces needs to be minimised. Contact profilometers would not be able to analyse the inside of a closed channel.
  • Cost-effective: Unlike the semiconductor industry, the cost per device does not justify a huge investment in metrology equipment. Any tool being used for these measurements needs to meet the economic constraints of the industry.
  • Optical: Of the three microfluidics materials typically used, two materials (polymers and glass) are transparent to white light, making an optical technique a cost-effective measurement technology. Silicon, the far distant third choice for a microfluidic device material, could also benefit from an optical technique.
  • Fast: For any production, quality assessments should be quick. A few minutes to confirm that a device meets or exceeds specifications is all that can be tolerated.

 

Zeta 3D height profile of a fully open microfluidics channel. (ZI mode) Zeta image of the channel with a transparent cover plate, showing top, middle, and bottom surfaces.
(Left) Zeta 3D height profile of a fully open microfluidics channel. (ZI mode)(Right) Zeta image of the channel with a transparent cover plate, showing top, middle, and bottom surfaces. Source: KLA Instruments

KLA’s Zeta Optical Profilers offer the optimal solution for both open- and closed-channel microfluidics device metrology. These measurements may be performed quickly and non-destructively at any point in the fabrication process, for up to eight separate transparent surfaces simultaneously, even when the devices are manufactured on a highly reflective surface such as silicon. The ZFT mode is highly advantageous for any application where thin film thickness of interfaces in multi-stack samples must be measured without cutting. 

Zeta measurements of cover plate thickness and channel depth, showing the XY location of the measured Z profile across the channel.
Zeta measurements of cover plate thickness and channel depth, showing the XY location of the measured Z profile across the channel. Source: KLA Instruments

Specifically, the Zeta-20 Multi-mode Optical Profiler is ideal for microfluidics applications because of the following capabilities:

  • Multi-surface 3D imaging and metrology, large Z range, large field of view (FOV), and material independence. 
  • Proprietary Z-dot technology that includes unique transmissive and dark field illumination methods. It maximises signal strength at each focal depth, which includes the top surface of the device, the surface height at all interfaces, and the bottom surface of the channel.
  • High sensitivity of Z-Dot technology which allows measurements of transparent surfaces exhibiting very little optical contrast.
  • Interference contrast imaging (ZIC) for characterising nm-level surface roughness, shearing interferometry (ZSI) for sub-nm vertical resolution, and reflectometry (ZFT) for thin film thickness measurement.
  • The capacity for multiple automated measurements which enables the manufacturing process to be more tightly controlled, resulting in improved device fabrication and consistency in production.

Contact us to discuss your specific requirements or objectives regarding metrology for microfluidics applications.