We supply three classes of sandwich covers:

• classic sandwich covers
• robot-friendly covers
• disposable covers

They all serve the same purpose (prevention of (cross)-contamination, supply of a defined degree of headspace refreshment, to turn the wells into individual bioreactors), but have their own advantages and disadvantages.

Classic sandwich covers (from the CR1200 and CR1300 series) are made of a robust stainless-steel housing, a silicone rubber seal (high quality, with the best compression set values in the market), with ePTFE and microfiber filters in between. The seals and filters can easily be replaced if necessary (after e.g. 50 uses). Some of our first customers already use the same covers for more than 20 years. They can be autoclaved and re-used an almost  infinite number of times without quality loss, and are therefore the most economical and environmentally friendly covers (in terms of waste production). However, the weight is relatively high (~ 170 gram) and therefore contributes relatively strongly to the total load on a shaker platform. Further, the cleaning, autoclaving, and drying process requires a significant labour and energy input. The relatively high weight (and "slippery" stainless steel walls) may be problematic with robotic handling, as well as the relatively tight fit (allowing less than 0.5 mm "mispositioning" by the robot arm).

Robot-friendly covers (from the CR2200 series) are also re-usable and autoclavable, but are two-fold lighter (~ 80 g), and have thin stainless steel walls that "flare-out", allowing "mis-positioning" of the cover by a robot arm of approximately 1 mm, in both horizontal directions. Further, the seal part rests on the walls of the MTP under an angle of approximately 50 degrees, and therefore "rattling" does not occur when - temporarily - shaken without a clamping force. Also, the rough structure at the sides reduces the risk of sliding out of a gripper. The seals are made of medically-grade SEBS, which has the advantage (in comparison to silicone) of a lower water permeability, and so even lower evaporation rates, while still being autoclavable. The top surface is made of carbon-epoxy plate, which is stiff, extremely flat, and light.

Disposable covers (market introduction: May 2025) are single use (supplied gamma-irradiated), and made of non-autoclavable materials (polystyrene, PEVA seal), that can be well recycled, For now, our disposable covers are only available for 6- and 24 well MTPs. They are very light (~ 23 g), and so contribute relatively little to the total amount of waste material generated. An advantage of their light weight is that more MTPs + covers can be incubated on a shaker, without the risk of exceeding its maximal load. They are efficient in terms of labour input because they are supplied gamma-irradiated, on top of a polystyrene MTP, and so are ready to use. The seal is made of PEVA foam (instead of silicone), that  is inferior in the sense of poor compression set characteristic (they do not come back to the original shape after they have been compressed), but superior in the sense of a lower permeability for water (so a slightly lower evaporation in comparison to seals made of silicone rubber). Our disposable covers are much less stiff than our re-usable covers, and so can only be used in combination with our clamps from the CR1800 series, that make sure that the vertical pressure is evenly distributed over the whole cover, so that all wells are equally hermetically closed.