Ultra-high-throughput microarray generation and liquid dispensing using multiple disposable piezoelectric ejectors
We have constructed an array of twelve piezoelectric ejectors for printing biological materials. A single ejector footprint is only 8-mm in diameter. It stands 4 mm high and has two reservoirs totaling 76 ul. These ejectors are made from stainless steel layers bonded together at high temperature. Each layer is chemically etched to generate two-dimensional patterns and subsequently stacked together to create a three-dimensional fluid path. The top-most layer has a laser-drilled drop exit aperture that is 75 ƒÝm in diameter. Actuation is achieved by pulsing a piezo ceramic element attached to a diaphragm at one of the bottom layers. Micro droplets of fluid as small as 100 pl are ejected at several kHz. Ninety-five percent of all fluid in the system is ejected. By adjusting the shape of the voltage waveform that actuates the elements, drop volume can be precisely controlled. We have demonstrated reliable drop ejection in both humidity-controlled and ambient environments over extended periods of time. Twelve ejectors are arranged in a rack together with an X-Y stage to allow printing any pattern desired. Printed arrays of spots are created with biological materials including oligonucleotides, proteins, and human genomic DNA. These arrays successfully passed their hybridization or PCR assays. Single ejectors could be racked in multiples of 96 that match the standard SBS 96 wellplate pitch to facilitate liquid transfer needs. This ejector system is designed for ultra high throughput generation of arrays on any surface. Up to 100,000 arrays per 8-hr shift is possible. We envision using these single or racked ejectors as long-term storage vessels for biomaterials such as DNA, antibody or cell libraries, which will allow for efficient pre-programmed selection of individual clones and greatly reduce the chance of cross-contamination and loss due to transfer. A new generation of design ideas includes plastic injection-molded ejectors that are inexpensive and disposable and handheld personal pipettes for liquid transfer in the regime of nanoliter.
Hsieh, H. B. ; Fitch, J. ; White, D. ; Torres, F. ; Roy, J. ; Matusiak, R. ; Krivacic, B. ; Kowalski, R. ; Bruce, R. H. ; Elrod, S. A. Ultra-high-throughput microarray generation and liquid dispensing using multiple disposable piezoelectric ejectors. Journal of Biomolecular Screening. 2004 March; 9 (2): 85-94.