A MULTI-PIN END-EFFECTOR FOR A ROBOTIC COLONY PICKER

In the fast paced world of molecular discovery, laboratory automation techniques play a vital role in expediting basic and applied research. As new automation techniques allow more samples to be processed and analyzed faster, researchers need better tools for routine and repetitive tasks like bacteria colony picking. As manual colony picking is insufficient in terms of speed and accuracy, this process has been automated by various manufacturers. In this paper, a novel and inexpensive design of the multipin End-Effector for a Cartesian robotic colony picker is introduced. The End-Effector reuses the picking tools by cleaning and sterilizing them in the same cycle of inoculation, achieving an estimated throughput rate of 1200 colonies/hr. The sterilization is done in 2 sec inside a ceramic heater made up of nichrome wire producing a temperature of ≥400°C. The End-Effector was successfully tested on Escherichia coli colonies using statistically designed experiments. Further analyses using statistical software packages revealed the optimal levels of the significant factors for the efficient working of the End-Effector. INTRODUCTION Colony picking is a process of picking unique bacteria colonies from the randomly grown colonies on a petri dish and then inoculating wells of a microtiter plate or some suitable substrate in a required pattern. A typical bacteria colonies plate and microtiter plate might look Fig. 1. It is very important to pick only unique and valid colonies as overlapping or satellite colonies could contaminate downstream data and waste resources as well as time. The picking process, when completed manually, is slow and highly prone to contamination due to the limited precision of human vision and hand accuracy. The history of colony picking started with the discovery of the double helical structure of DNA by Watson and Crick [1] in 1953. Genetic engineering techniques like growing genes having a desired characteristic were some of the first to create the need for automated colony pickers. Jaklevic et al. [2] emphasized the importance of automated colony pickers in the final sequencing step in which template DNA is cloned. Another application requiring automated colony picking is yeast fermentation in the food industry. In addition, Kodzius et al. [3] showed the importance of colony pickers in a rapid allergen identification system. All these applications created a need for the technology that can assist in carrying out biological, genetic, and molecular experiments at high speed, low cost, and minimum contamination. Although the basic task of a colony picking is simple, designing such an instrument is in many aspects more difficult than designing most other laboratory automation robots because the bacteria colonies are randomly spaced throughout the plate and each colony has a different size, shape, and morphology. Hence the robot cannot just follow a preprogrammed set of movements. Instead, it needs to image the agar plate, identify the colonies, and then determine the picking routine. The colony pickers of the mid-90s integrated machine vision and robotic sample handling. Currently, industrial strength colony pickers have been developed by several manufacturers that, for a price, can provide speed and precision necessary for various research applications [4-6]. Colony picking systems is deemed a ‘mature’ market with little development in the last several years [7]. A market exists for the manufacturers of all kinds of colony pickers if they can meet the budget requirements of researchers and scientists. As low priced, high performance technology is introduced every day, the colony picking industry is undergoing recurring changes. Table 1 shows various automated colony pickers spanning from the earliest systems to current systems. This paper presents a new low-cost End-Effector for Cartesian robot resulting in fast and accurate colony picking. Donald R. Briner Briner Technology LLC, Tempe, AZ, USA. Ashish D. Sardhara M.S. Student, Department of Mechanical Engineering, Arizona State University, Tempe, AZ, USA. Thomas G. Sugar Associate Professor, Department of Engineering, Arizona State University, Mesa, AZ, USA.