By Terry Persun, Contributing Editor
Tomtec has over forty years of experience in the designing and manufacturing of automated liquid handling equipment. Their Quadra4 is the latest to receive upgraded design components for a liquid handling workstation for life science workflows. The workstation is designed using a fixed-head, air displacement syringe design, which services a six station shuttle. Each of the six stations can support a range of accessories for automating complex workloads such as solid phase extraction (SPE) and an optional plate-stacker can be used to queue up to 50 assays.
The latest upgrade of the Quadra4 uses stepper drivers and linear actuators for precision or high-speed movements depending on the specifications for the particular stage. Where the Quadra4 used to have an embedded PC board with older-technology drivers, the company has upgraded considerably through the use of AllMotion motor controls + drivers. By switching to stepper motors, Tomtec was able to increase the overall precision of the workstation. The AllMotion controls allowed the company to use NEMA 11 to NEMA 34 motors without having to switch to a different control system.
The Quadra4 is a liquid handling workstation with a built in XY shuttle, an XYZ stage that brings the microplate into position for the dispensing, and a pipetting head with linear actuator that vertically moves 96 pistons on the 96-tip head. The standard unit incorporates 96 dispensing tips used with the standard 96 well microplate, but can also operate with up to 384 standard well microplates through a unique design strategy where the 96 footprint is indexed through four quadrants. The workstation can also operate with an optional 384 pistons created for a small volume tip head. The indexing portion of the workstation uses three axes, while the shuttle system uses two, and the pipette pistons use only one. This means there are six AllMotion controller drivers used in each Quadra4.
Two models of stepper motor controls are used in each workstation. There are four EZHR23 controllers used, three in the XYZ staging system and one in the pipette pistons. Then there are two EZHR23ENHC controllers used in the
robotic shuttle operation. Both controllers were specifically designed for simple, user-friendly implementation of stepper motor solutions, especially for automation, and have found their way into medical, aerospace, electronics production, consumer products, and other applications.
The EZHR23 controller measures 2-in in diameter and is a fully intelligent controller that can be bolted onto the back of the stepper motor it controls. The EZHR23 uses a single 4-wire bus, which contains two power wires and two communications wires, and can link up to 16 controllers in a daisy chain. Commands are issued from any serial terminal program.
The EZHR23ENHC controllers used for the shuttles are 2.25 x 2.25-in and offer the same fully intelligent design that the EZHR23 provides. Commands for the controllers are intuitive and simple. For example, a command of A10000 will move the stepper motor to Absolute position 10000. The controllers can also be set to execute a preset string of commands upon power up. Commands include nested loops and execution halt pending a switch closure, which is useful in stand-alone applications.
Each EZHR23 and EZHR23ENHC controller is capable of stand-alone operation with no connection to a PC. The devices can easily be set to execute a preset string of commands upon power up. The commands include nested loops and execution halt pending a switch closure, which is useful in stand-alone applications.
A key operation for the Quadra4 is the system’s ability to run air through the piston of each dispensing tip. The company calls this operation time dispense/air dispense. Since liquid is hydrophilic when using plastic materials, it leaves a residual amount of up to 3 micro-liters of liquid behind in the syringe. The time dispense/air dispense system uses air to push that residue into the wells, which improves the overall accuracy of the station.
Through simple straightforward programming, following the customer’s manual methods, the system can be programmed to add plates to the shuttle or put them back into the stackers. The customer may automatically move reservoirs of reagents from the stacker to the shuttle and back. With some creative ingenuity customers can easily program complete walk away automation for some very complex protocols.
Filed Under: Controls (not motion controls), Drives (stepper) + amplifiers, Motors • stepper