Demonstration

The goal of our project is to provide a working product that can collect a substantial amount of water. To this end, we performed some experiments to measure the exact quantity of water collected by our 3D-printed shape, coated with polylactic acid (PLA) and biotin, and treated with the Ice Nucleating Protein (INP)-streptavidin complex. A mixture of PLA and biotin, dissolved in dichloromethane, was used to coat the water collectors. The coated objects were left to dry overnight in a laminar flow cabinet, allowing the solvent to evaporate.

We considered four biological treatments:

1. INP + INP_NC-mSA2: whole cells expressing both full length INP and membrane-bound monomeric streptavidin (mSA2)
2. RFP + INP_NC-mSA2: Control, cells expressing membrane-bound mSA2 and a red fluorescent protein
3. INP_RC-mSA2: protein extract: INP nucleating domain - mSA2 fusion protein
4. mGFPuv2-mSA2: Control, mGFPuv2-mSA2 fusion protein

In each experiment, the measurements were performed in a controlled humidified chamber. Both the temperature and the humidity were constantly measured and the latter was actively controlled using bang-bang control.

Effect biological treatments on the water collectors

Setup

In this demonstrative experiment, we assesed the effect of the four biological treatments described above.

The dome of four water collectors were coated using the PLA-biotin solution. Subsequently each collector was sawn in half in order to have a treatment and associated control for each experimental unit.

Half of a water collector.

One half of each collector was treated with a different biological function (i.e. INP + INP_NC-mSA2, RFP + INP_NC-mSA2, INP_RC-mSA2 and mGFPuv2-mSA2). After waiting five minutes, to allow biotin-streptavidin bonds to form, all half-collectors were rinsed thoroughly with a physiological solution. Each halve was placed on a petri dish.

All halves were dried and weighted on an analytical scale. Finally, all petri dishes were randomly placed in the humidified chamber. They were left under a flow of humid air for one night. Afterwards, all halves were weighed again, to measure the accumulation of water.

The collectors in the humidified chamber.

Results

The following bar chart shows the differences in water accumulation of each treatment-half compared to the control-half.

Differences in water collection between treatment and control, for all four treatments.

The average water amount of water collected by all the experimental units is 3.07 ± 0.38 gram. The difference in weight of the treatment-halves compared to the control-halves of the different treatments were between -0.92 and 0.6 gram. Unfortunately, it appears that the INP treatments result in a decrease in water collection. As the effect is quite small and we could not perform any replications, it is perhaps safest to conclude that these results do not support any conclusions either way.