A three-dimensional illustration and photography of the plate/plate flow chamber model is shown in Fig. 1. A detailed list of used parts can be found in Appendix 1.

The circulation within the flow chamber was generated by an externally attached electric motor, which rotates up to 500 rounds per minute (rpm). A commercial grade 4 pure medical titanium gear shaft (length = 40 mm, diameter = 4 mm) was connected to the motor by a set screw-fixed gearwheel. For the attachment of the custom-made biocompatible glass panel (diameter = 60 mm, thickness = 2 mm; 4-mm central circular opening), the gear shafts’ lower end was disc shaped (diameter = 10 mm). The glass panel was fixed by an adjusting ring with an additional set screw from above. The cover of the lower petri dish contained guiding grooves to stabilise an inverted larger petri dish placed on, which in turn served as a holding device to the electric motor (Fig. 1).

Under sterile conditions, the cell-bearing glass plate was attached to the lower end of the gear shaft with the cells facing the bottom plate. A space of 2 mm between the two plates was determined via computational simulations. After filling the lower petri dish to 70% of its capacity with culture medium, a closing plate with a centred recess for the gear shaft (4 mm) was placed on top to seal the lower compartment. Lastly, a larger petri dish, having a central recess (4 mm), with an externally attached electric motor, was reversely installed above to form the upper compartment. As shown in Fig. 1, the transmission between motor and gear shaft was realised by using two same-sized gearwheels, one fixed on each of the two components within the non-sterile upper compartment.

Frequently used flow chambers are characterised by an internal fluid flow along a stationary cell-bearing surface, whereas the osteoblast test cells of this newly developed model are circulating within a resting culture medium.