Abstract
AutoSpin™ technology is a novel centrifuge which will enable the separation process to be easier and less labor intensive when compared to using a conventional centrifuge. The technology enables construction of a small, low cost, simple, bench top clinical centrifuge that disassociates the operator from the normal physical interaction with the centrifuge rotor. The operator places blood tubes not in the rotor, but into a bulk loadable input carousel. Samples are added to the carousel at any time and thereafter automatically transferred to the rotor as positions become available. After centrifugation, the samples are automatically placed in test tube racks. With these features, the operator is free to conduct the separation phase at his or her convenience rather than be bound to the rotor spin cycle. AutoSpin also reduces labor by eliminating the tasks associated with placing a balanced load into the centrifuge and emptying the rotors at the end of the run. Virtually any mix of standard tube sizes can be loaded into the 100+ tube capacity carousel without regard for setup changes. Draw tubes are simply presented to the carousel as they enter the lab. A pre-selected location on the carousel provides STAT queuing into the rotor. Rotor balancing is automatic, thus obviating the need for balance tubes.
The AutoSpin rotor and gyro module.
AutoSpin™ technology permits control panel selection of a swinging bucket rotor or fixed angle 45 degree or a combination of the two rotor angles in a single separation sequence. The operator can select these according to processing needs in addition to non-linear acceleration/deceleration rates.
Unlike other approaches to automating blood tube centrifugation, AutoSpin™ does not employ conventional robotics; that is, the use of reprogrammable gantry or articulating arm robotics. Classic robotics was deemed to be spatially and cost prohibitive for this application. Our approach to centrifuge automation was to create a special rotor that would permit gravity loading and unloading. This intrinsically minimizes the overall box size and simplifies the system due to a diminished need for parts and mechanisms. The 12 bucket rotor is constructed with a switchable cam-like mechanism that allows the swinging buckets to be locked to a 45° angle on demand. This feature is provided to capitalize on a blood properties phenomenon known generally as rouleaux. When exposed to the same gravitational field, blood cells separate more quickly with the tube oriented at an angle than longitudinal with respect to the applied centrifugal force.
With this feature the operator can select from the three processing modes. Conventional swinging bucket, fixed angle 45 degree or a combination of the two. In combination mode, the speed advantages of fixed angle are combined with the desire to position the thixotropic gel at a right angle with respect to the tubes' long axes as is achieved with the conventional swinging bucket in a horizontal position.
The author finds time to relax after completing his invention.
A complicated “front end” could have been developed featuring perhaps video logic to interrogate incoming tube demographics. It would match tube size, tube fill level and tube number to effect balancing the rotor. Alternatively, we decided to develop a gyro (the hub on which the rotor is suspended and rotates) that would allow the rotor to load any standard tube with regard only for the presence of a single tube. In other words, if a gyro could be developed that would allow the rotor to run with a single, full, large (10ml) glass tube, then the front end could be simplified to merely recognize the presence of a tube in the carousel. This is in fact a major feature of AutoSpin™ technology.
It is customary to inhibit the natural tendency of an asymmetric rotating mass from assuming its mass center. This is best achieved by supporting the rotor on bearings and a rigidly affixed axle. The result is vibration as the asymmetric mass attempts to reposition itself against a nearly immovable support. Our AutoSpin gyro simply allows the rotor to shift as needed from a rotation about a center of geometry to a rotation about the center of mass. For example, in an abnormal test sequence, two 24 gram tubes were set adjacent to each other. This caused the 4.5 pound rotor to spin approximately .140 inches off the geometric center; the normal single 24 gram tube causes an offset of half that distance.
Of course, design of a mass centering gyro is not so simple or straight forward in consideration of the overall complicated dynamics, cost, space and reliability. Our design employs a unique disk structure to support ball bearings which in turn supports the rotor shaft. The disk carrying the rotor is free to move radially but restricted angularly by slidable mounted bearings. No elastomeric material is used.
Taken together, the AutoSpin gravity load/unload rotor with its bi-angle spin capability coupled with a true mass centering gyro allows the consumer features as stated above and the potential of a archetypical shift in laboratory blood tube centrifuge automation.