Flow Cytometry Gets Disposable Printed Electronics
December 6, 2012, Printed Electronics USA, Santa Clara, CA—Gordon Smith from GSI Technologies described the steps towards commercializing a printed electronic subsystem. This effort moved a sensor and fluidics on to a plastic substrate for a disposable, hand-held flow cytometer.
Flow cytometry is the process of counting and classifying cells for analysis and disease detection. Most tests are performed in laboratories and take hours or days to complete. The tests are used in life science, clinical and diagnostic research, veterinary work, and now moving to the food and beverage industry. Some of the technologies for the work include photodetectors, image capture, electrical, and the mainstay, static vision; looking at samples on a glass slide. Most of these technologies require a desk-size machine that costs many thousands of dollars.
Based on the Coulter principle, which refers to the use of an electric field for counting and sizing dilute suspensions of particles in conducting liquids, and a counter, they created a disposable sensor for a hand-held flow cytometer. The sensor detects the passage of cells through a change in resistance.
The disposable sensor uses basic screen printing technologies and processes. The full integration of all steps including stencils is applicable to sheet or roll-to-roll processing. The product is automatically inspected and 100 percent electrically tested before shipment. After the basic printing steps, finishing with die cutting and lamination steps gets the sensors ready for shipment. The sensor is part of a pipette system and the tip and sensor are disposable. The sensor is a part of a stack structure that includes a fluidic channel and electrodes. The electrodes require laser processing in addition to the printing.
On the first pass, they tried to use standard flex circuit materials. These materials don’t scale for large changes in product volume. They looked at printing as a way to reduce costs and increase performance. The product required developments in ink for some of the structures, and engineering for the whole system function. The big break through was laser drilling of the vias and printed silver-silver chloride conductors.
