Of these, only the DOME is fully open and available for under £1000. The other low cost system \cite{Lam_2017} requires an external optical breadboard which is not included in the cost calculation, and the details of which are not provided in literature. This could make reproduction challenging for users without access to such equipment, and who may have limited experience with such optical systems. The only other fully open system \cite{Stirman_2012} is based on a fluorescence microscope, making the total system cost approximately a factor of 10 higher than that of the DOME.
Conclusion
In summary, the DOME offers a versatile and low-cost platform for the engineering of microscopic collectives using light. The DOME’s open-source modular design makes it easy to adapt for new needs, for example, changing the light source of the projector to enable different forms of fluorescent imaging, different magnification, or adding temperature/gas control to maintain the viability of different types of cell (e.g. mammalian cells), and future extensions could even introduce magnetic, sound, or chemical inputs as additional control modalities. The basic building blocks of local communication, stigmergy, and controllable motion demonstrated here using the DOME platform are fundamental to collective systems, and could, in future work, be combined to allow the engineering of microscale collective behaviours, Entirely new swarm behaviours could even be engineered by combining the closed loop nature of the DOME with automatic discovery processes based on machine learning algorithms \cite{Jones_2019,cichos2020machine,Sol__2018}. Beyond microswarm engineering, the DOME also offers a means to both understand and influence the collective behaviour of natural cellular populations, opening up new avenues for the study of complex systems spanning cancer to the microbiome.