August 8, 2012 — Lab-on-a-chip (LOC) devices are micro-chip-sized systems that prepare and analyze very small volumes of fluids — from a few ml to sub-nl. They hold promise for disease diagnostics and forensic evidence investigation. These devices are fabricated by microfluidics makers, a segment of the micro electro mechanical systems (MEMS) industry.

The National Institute of Standards and Technology (NIST) believes that before LOC technology can be fully commercialized, testing standards need to be developed and implemented. These will define the procedures used to determine if a lab on a chip device, and the materials from which it is made, conform to specifications, said Samuel Stavis, NIST physical scientist.

Standardized testing and measurement methods, Stavis said, will enable MEMS LOC manufacturers to accurately determine important physical characteristics of LOC devices such as dimensions, electrical surface properties, and fluid flow rates and temperatures. These must be calculable at all stages of production, from processing of raw materials to final rollout of products.

Figure. A microfluidic lab on a chip device sitting on a polystyrene dish. Stainless steel needles inserted into the device serve as access points for fluids into small channels within the device, which are about the size of a human hair. Credit: Cooksey/NIST.

Stavis focuses on autofluorescence, the background fluorescent glow of an LOC device that can interfere with sample analysis. Multiple factors must be considered in the development of a testing standard for autofluorescence, including: the materials used in the device, the measurement methods used to test the device, and how the measurements are interpreted. For meaningful sample analysis, all autofluorescence factors must be controlled for or excluded from the measurements.

Quality control during LOC device manufacturing, Stavis says, may require different tests of autofluorescence throughout the process. The raw block of plastic may be measured for autofluorescence, then the substrate the block has been fabricated into, then the final device with functional microfluidics and substrate, Stavis said.

Stavis also emphasizes that it is important not to confuse testing standards with product standards, and to understand how the former facilitates the latter. "A product standard specifies the technical requirements for a lab on a chip device to be rated as top quality," he says. "A testing standard is needed to measure those specifications, as well as to make fair comparisons between competing products."

The argument for testing standards is proposed in a paper in Lab on a Chip: Stavis, S.M. A glowing future for lab on a chip testing standards. Lab on a Chip (2012), DOI: 10.1039/c2lc40511c

Learn more at www.nist.gov.

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