Living specimens under field immobilization and smartphone microscopic observation

In this work a single glycerol-water mixture, determined to be most apt at 30% (wt/vol), was used to immobilize Drosophila samples as well as to create a liquid lens for smartphone magnification viewing. This provides the advantage of being able to observe immobilized insects directly in the field rather than in the laboratory. In order to avoid having bubbles in the liquid lens and immobilizing medium that hinder visibility, an approach was developed where a stable pendant drop is moved in tandem with the dispensing tip by gravity and stopped abruptly so that sufficient momentum is transferred to the drop for its dislodgement. With 30% glycerol-water (wt/vol) mixtures, applying a minimal stroke of 10 mm with longitudinal impact delivered a momentum of 0.1464 N/s that allowed transfer of a preselected liquid volume for the processes.