The full extent of plant species which practice this form of seed dispersal is still being investigated. The list of known plant and fungus species within this classification is not finalized. In 2006 Pia Parolin, an Italian biologist and ecologist, provided a brief review of the known species in her paper published in Flora. In it she reports that only 2 species of fungi have been observed to use this dispersal (bird's nest fungi and gemma cups of Merchantia), while several families and genera of flowering plants have been confirmed as splash-cup plants. These include the 9 families, 10 genera, and 19 species that Nakanishi reported from Southern Japan. However, these plant species have been found to be common in areas where rain and water are either very common or uncommon (like rain forests, rocky shores of streams and waterfalls, and deserts).

This phenomenon was observed in some of our experiments when we forgot to dry the cups. We noticed that when the cups were partially filled the splash resembled the splash of a liquid drop onto a shallow pool. After impact, a corona forms in the cup. The production of this corona dissipates a portion of the kinetic energy of the incoming drop and prevents formation of the amplified jet that was observed for dry splash cups.

The drop impact location, denoted as the splash parameter in the paper, dictates what kind of impact occurs, either on or off center. The off center splashes, which occur when the rain drop and the splash cup centers are not aligned, result in much farther dispersal distances. In our experiments, we observed dispersal distances that were 2-5 times larger for off center versus on center splashes.

We conducted two sets of experiments using a small wind tunnel and a flat, circular eye mimic. The first set of experiments were used to measure how eyelash length affects evaporation of the tear film. The eye mimic used was a small dish filled with water. The dish was surrounded by eyelashes and synthetic meshes with the same porosity as eyelashes (porosity is the ratio of void area to total area, and is directly related to eyelash density). The mimic was placed on top of an analytical scale and exposed to airflows typically experienced when walking in still air. The scale took a mass reading every 10 seconds for 10 minutes. We then used the readings to calculate the evaporation rate, or how much water evaporates per second. We tested 8 different eyelash lengths as well as one without lashes. The second set of experiments were used to measure how much eyelash length affects deposition of particles onto the tear film. The eye mimic used was an absorbent paper disk. The wind tunnel was combined with the outflow of a commercial humidifier. The humidifier generates water droplets with a diameter of 10 microns, which is similar to the size of typical airborne particles, like dust. A fluorescent dye that emits a green glow when illuminated with UV light was mixed with the water of the humidifier. Pictures of the paper disk were taken before and after exposure to the particle-laden flow and the intensity of the green glow measured. The intensity of the green glow increases when more of the drops impact the mimic.l.

Through numerical simulation and aerodynamic theory, we found that short eyelashes and long eyelashes affect the surrounding airflow differently. Short eyelashes generate a zone of stagnant air immediately above the eye surface. This causes the incoming airflow to divert, preventing it from reaching the eye surface. On the other hand, long eyelashes penetrate further into the incoming flow and guide airflow towards the eye surface. The airflow channeled by the long eyelashes reaches the eye surface, and so we observe higher evaporation and contamination rates.

This research has implications in both medicine and technology. The aerodynamic mechanism identified can help explain why certain individuals are prone to dry eye syndrome. Individuals using mascara/extensions to make their eyelashes longer can experience higher rates of evaporation and contamination of their tear film. Additionally, individuals with madarosis lack eyelashes and experience increased rates of viral infections. These higher infection rates could potentially be explained by the fact that they don't have eyelashes to help keep harmful particles out of their eyes. False eyelashes could be used as a way to help reduce the occurrence of infection in these individuals. Eyelash-inspired filaments can also be implemented around sensors and solar panels to help reduce soiling. These would serve as new filters that, rather than intercepting particles, prevent particles from reaching the surface simply by interacting with airflows.

Following our results, if false eyelashes longer than one-third the eye width are used, there will be more, faster airflow at the eye surface. This increased airflow may cause greater evaporation and contamination of the tear film. However, our work also finds that denser eyelashes will help to decrease the evaporation and contamination of the tear film. If long but dense false eyelashes are used, the high density may overcome the negative effects arising from the long length. In addition to increasing airflow at the eye surface, the glues used to adhere false eyelashes may have negative effects on the eyes. An article by Linda Carroll from Today Health provides details on the harmful chemicals found in the glues of false eyelashes. A PDF of the article may be found here.

Our study looked exclusively at mammals. As far as mammals are concerned, only aquatic species and some rodents were observed to lack eyelashes. However, some rodents appear to have fur surrounding their eyes, which may serve a similar role as eyelashes in protecting the eye. Outside of mammals, most reptiles and birds were observed to not possess eyelashes. Birds and reptiles have a nictitating membrane (or third eyelid) that may be used to protect the eye in the absence of eyelashes. Additionally, most reptiles do not have wet eyes, so they do not have to worry about their eyes drying out. Some species of geckos have been observed to lick their eyes, which may help to remove accumulated particles.