Figure 1. Microfluidics and innate immunity, two fields of exponential growth.

(A) Graph shows PubMed citations/yr in response to the search terms “Cellular innate immunity” (magenta columns) and “Microfluidic” (green columns). Invention of the Boyden chamber corresponds to a surge in research in the field, peaking in the mid-1980s. Since its resurgence in the early 2000s, the field of leukocyte biology continues to expand exponentially. Following the first microfluidic prototypes for biomedical applications in the early 2000s, this area of study also exhibits exponential growth. (B) Graph shows PubMed citations/yr in response to the search term “Leukocyte” in combination with “Microfluidic” (magenta columns). Use of microfluidic assays to measure leukocyte behavior is becoming increasingly common, with ∼60% of publications emerging in the last 5 yr.