Many laboratories that perform medical sample analyses still use manual distribution systems even today. This means that first the data for the incoming samples is captured. The samples are then placed in racks in batches, carried by employees to the various analysis stations and, if necessary, resorted from time to time for further analyses. With thousands or even tens of thousands of material samples per day, this is not only a laborious and monotonous task, but is also prone to errors. Troubleshooting then necessitates additional time and effort. More time is required if individual samples need special handling, e.g., because they must pass through several stations for step-wise diagnostics. The same applies for the dilution of samples for certain analyses or for splitting samples for different analyses; the production of so-called aliquots. Disruptions to an orderly workflow are therefore inevitable. This process is made more difficult by the current trend towards collecting only one sample from patients for all of the necessary analyses where possible. There is no relief for the situation in sight. Rather, the problem will become more acute in the future, particularly through the centralization of laboratory services.
What must an automatic sample distribution system be able to do?
The use of practically oriented automation technology that frees employees from monotonous activities and eliminates sources of error will therefore become unavoidable in modern laboratories. An automatic sample transport system ideally transports the samples directly to the appropriate analysis system and, while doing so, performs other tasks along the way: following delivery, the sample identification can be used to plan and optimise the route through the laboratory, whereby many parameters can be taken into account, e.g., the type of container, the preparation, the filling level and, of course, the sequence of the individual analysis steps. For the duration of the analysis and the evaluation, all samples currently to be processed should then remain accessible, i.e., several hundred samples are ideally underway in the distribution system simultaneously. Analyses can then be quickly repeated or additional analyses performed and any subsequently necessary assessments undertaken. Upon completion of the analysis, the samples should be automatically ejected, disposed of following a storage period of a couple of days or, if necessary, transferred to a suitable container for long-term archiving.Thus, the requirements placed on an automatic sample distribution system are high – not only with respect to capacity and reliability – but particularly in terms of flexibility, and that in two ways: the distribution system must be able to handle alternating tasks and changes to the workflow. It must also be easily expandable so that, e.g., new or modified analysis devices can be integrated even at a later point in time without considerable effort. With the development of the lab.sms® fully automatic sample distribution system, GLP Systems has demonstrated that these requirements can be met today. It transports each sample (specimen) separately, as this is the only way to achieve flexible, custom, and optimum organization of individual samples. Thus, it differs fundamentally from systems that transport racks with five or ten specimens.
High flexibility during transport and Distribution
In the sample distribution system designed by the Hamburg-based specialists, the identity of the specimen is linked to the identity of the moveable sample carrier upon delivery to the allocation point. The distribution system therefore knows the sample and knows on which trolley it is currently being transported and which analysis are necessary. Changes to the sequence can even be made retroactively without problem since random access is possible. For this purpose, the position of the specimen and the assignment to the trolley are checked periodically during transport at identification points. The trolleys with the specimens then move fully automatically over plastic rails to the respective analysis stations. The track switches which they pass over while underway are appropriately set by the primary control system.Each track switch handles an average of 4,500 sorting processes per hour: 4,500 specimens per hour can be recognized and individually guided in one of two directions. Since all track switches are able to operate simultaneously, in an example system with 50 different track switches this yields a sorting capacity of 225,000 sorting operations per hour or more than 60 per second. This capacity is necessary, since many specimens are in a waiting queue before and after the analysis and thus move over track switches frequently. The high sorting capacity of the track switches thereby satisfies an important prerequisite for the organizational flexibility in laboratory operation. Also important for smooth operation are the "small trolleys" on which the samples travel through the laboratory. Speed and reliability have top priority here.
Compact drives for fast, reliable Transport
The compact trolleys, i.e., "specimen taxis", actually have a very simple design. Drive, battery, electronics and proximity switch are all integrated, allowing the taxis to very precisely accelerate, decelerate or stop, e.g., at the analysis stations. Chosen for the drives were brushless small gear motors. The gear motors from the comprehensive FAULHABER product range are designed for high reliability and a long service life; they can thus travel many, many kilometres in the automatic distribution systems without wear being a concern. Moreover, they also convince in this application with their smooth, cogging-free running properties. This is particularly important, as the blood samples are usually transported without a cover. In addition, the drives operate very quietly. The rare earth magnet of the rotor and the coreless winding also ensure high performance and dynamics in a compact size.
The drives, which deliver approx. 0.3 W and a torque of up to 6 mNm with a diameter of about 15 mm and length of 15 mm, drive the wheel of the "specimen taxi" via a diameter-compliant spur gearhead (reduction 1:10) at the ideal operating point. Thanks to their compact dimensions, they could be easily integrated, and their low power requirements were ideally suited to the application; the charging intervals of the batteries are sufficiently long. To ensure that the trolleys are always ready for use, the charge state is constantly monitored by integrated electronics so that they can be recharged before they come to a standstill. The electronics perform still other tasks, however. The identification number of the "taxi" is stored here and they evaluate the signals of the proximity switch. The motor electronics can appropriately adjust the speed of the brushless small gear motors, i.e., reduce the speed or stop the motor.
The solution has already proven effective in practical use in a large medical laboratory in Hamburg. Some 3,000 haematology specimens are processed here daily with 19 online analysers. Additional applications are planned. Modern small gear motors have thereby proven their versatility once again. It may also be possible to apply the "specimen taxi" principle to other application areas. Similar automatic distribution systems are conceivable, for example, wherever small parts pass through different production or inspection stations separately.