A brisk ride with the rehearsal taxi

Dhe analysis of our blood or urine samples is increasingly being carried out by highly specialized laboratories that perform many thousands of analyses per day. Today, they too can benefit from state-of-the-art automation technology. As in many other automation tasks, powerful microdrives play a key role here as well. They impress above all with their good efficiency, high torque in a small design, reliability and low power consumption.

Still a lot of manual work

Many laboratories that perform medical sample analyses still work with manual distribution systems. This means that the incoming samples are first recorded in terms of data, then placed in racks in batches, carried by employees to the various analysis stations and, if necessary, also re-sorted in between for further analyses. With thousands or even tens of thousands of material samples per day, this is not only a strenuous and monotonous activity, but also error-prone. Troubleshooting then requires additional effort. It costs further time if individual samples have to undergo special treatment, e.g. because they have to pass through several stations for step-by-step diagnostics. The same applies to the dilution of samples for certain analyses or to the division of samples for different analyses, the so-called aliquoting. Disruptions to the orderly workflow are inevitable here. The situation is further aggravated by the fact that the trend today is for patients to provide only one material sample for all necessary analyses. There is no relief of the situation in sight; on the contrary, the problem will become even more acute in the future, especially due to the centralization of laboratory services.

What does an automatic sample distribution system have to do?

Therefore, there is no way around the use of practical automation technology that frees employees from monotonous tasks and eliminates sources of error in modern laboratory operations. Ideally, an automated sample transport system transports the samples directly to the corresponding analysis system and performs other tasks as well: Based on the identification of the sample after delivery, the route through the laboratory can be planned and optimized, whereby many parameters can be taken into account, e.g. the type of vessel, 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 being processed should remain accessible, i.e. several hundred samples are ideally in transit in the distribution system at the same time. Analyses can then be repeated quickly or carried out additionally and any assessments that may subsequently be required can be carried out. Once the analysis is complete, the samples should then be automatically discharged, disposed of after being stored for a few days or, if necessary, transferred to suitable containers for long-term archiving.

High flexibilityThe demands on an automatic sample distribution system are therefore high, not only in terms of capacity and reliability, but also in terms of flexibility, and this in two respects: The distribution system must be able to cope with changing work tasks and process changes, but at the same time it must also be easy to expand, so that, for example, new or different analytical instruments can be integrated subsequently and without great effort. With the development of the fully automatic sample distribution system lab.sms® , GLP Systems (see Box 1) has proven that these requirements can be met today. It transports each sample (specimen) separately, as this is the only way to ensure flexible, individual and optimisable organisation of individual samples. It therefore differs fundamentally from systems that convey racks of five or ten specimens.

High flexibility in transport and distribution

In the sample distribution system of the Hamburg specialists, the identification of the specimen is linked to the identification of the mobile sample carrier after delivery in the assignment point. The distribution system therefore knows the sample and "knows" which trolley it is currently on and which analyses are required. Subsequent changes to the sequence are also unproblematic because random access is possible. For this purpose, the position of the specimens and their assignment to the trolley are checked repeatedly at identification points during transport. The trolleys with the blood samples then travel fully automatically along plastic tracks to the respective analysis stations (Fig. 1). The switches they pass on the way are set accordingly by the higher-level control system (Fig. 2).

Each diverter manages an average of 4,500 sorting processes per hour: 4,500 specimens per hour can therefore be detected and individually routed in one of two directions. Since all diverters are able to work simultaneously, this results, for example, in a system with 50 divergent diverters, in a sorting capacity of 225,000 sorting processes per hour or more than 60 per second; a performance that is definitely needed, since many specimens are in the waiting loop before and after analytics and thus diverters are frequently passed through. The high sorting performance of the switches thus provides an important prerequisite for organizational flexibility in laboratory operations. Equally important for smooth operation are the "trolleys" with which the samples travel through the laboratory. Speed and reliability have top priority here.

Compact drives for fast, reliable transport

The compact carts, i.e. the "sample taxis", are actually quite simple in design. The drive, battery, electronics and proximity switch are integrated so that the taxis can accelerate, brake or stop with pinpoint accuracy, e.g. in front of the analysis stations. For the drives, the choice fell on brushless DC motors, so-called flat-rotor motors. The motors from the extensive Faulhaber range (cf. box text 2) are designed for high reliability and long service life, so they can easily cover many, many kilometres in the automatic distribution systems without any fear of wear. In addition, they are also convincing in this application ,due to their quiet, cogging-free running characteristics, which is particularly important because open blood samples usually have to be transported. In addition, the drives operate quietly. The rare-earth magnet of the rotor and the Faulhaber helical winding also ensure high performance and dynamics with a small construction volume (Fig. 3).

The drives, which deliver about 0.3 W and a torque of up to 6 mNm at a diameter of approx. 15 mm and a length of 15 mm, drive the wheel of the "sample taxi" at the ideal operating point via a diameter-conforming spur gear (reduction ratio 1:10). Thanks to their compact dimensions, they were easy to integrate and their low power requirements also suited the application; the recharging intervals of the battery are correspondingly long. To ensure that the wagons are always ready for use, the electronics integrated in them constantly monitor the charge status so that recharging is carried out in good time before the vehicle comes to a standstill. But the electronics also have other tasks. For example, the identification number of the "taxi" is stored here and it evaluates the signals from the proximity switch. The motor electronics can then adjust the speed of the brushless DC motors accordingly, e.g. reduce or stop the speed.

Interesting also for other applications

The solution has already proven itself in practical use in a large medical laboratory in Hamburg. Here, 3000 hematological specimens are processed daily with 19 online analyzers. Further applications will follow. Modern miniature drives have thus once again proven their versatility. However, the "sample taxi" principle could certainly be transferred to other areas of application. Similar automated distribution systems are conceivable, for example, wherever small parts pass separately through different production or testing stations.