to facilitate the combination of electronics, such as magnets, sensors and LEDs and the cultivation of biological microorganisms we developed a number of prototypes by casting of a transparent silicone rubber. Polydimethylsiloxan PDMS, which can be ordered from dow corning, product name is sylgard 184.
- mix the two components at a ratio of 10:1. a plastic cup is useful for a container.
- stir and mix thouroughly
- leave it sit for 2-3 hours to get rid of the bubbles. if you have access to a vacuum you could do it in a few minutes.
the PDMS will be processable for about 24 hours if you leave it at roomtemperature. for curing its est to put it in an oven at around 60 to 80° C for about 1 h at least. full curing should be achieved after 4 h.
assembling and casting of the bioelectronic device
we prepared all the electronic parts by soldering insulated copper wire to them and attaching a standard connector on the other end.
first we glued the electronics to a plastic petridish, so they can be fixed and positioned. then a first layer of PDMS is cast on it and left at roomtemperature for 1-2 hours to get rid of bubbles coming out of the magnets. then its cured in the oven for 1 hour. if needed you can cast and cure a second layer on top of it to cover all the electronics.
then a well has to be cut or punched out in the middle to hold the microorganisms and the liquids. and finally a small drop of PDMS is poured into the well to seal it. you can allways fill the well again with pdms and cut out a new well.