Figure 2

Effect of optical trapping on viability. (A) Survival percentage of E. coli after being trapped with stationary and oscillating optical traps with various IR doses. For oscillating traps, trap length and frequency were 3 μm and 330 Hz, respectively. The IR dose is the product of laser power and holding time. In the experiments, the laser power was varied from 56 to 72 mW, and the holding time from less than one minute to ten minutes. Each symbol was determined from at least 7 cells (average: 13 cells). Data are from 12 experiments. Lines are for illustration purposes. (B) Increasing the ratio of trap to cell length in the oscillating trap method leads to a higher survival percentage. Cells were exposed to 30 J of IR dose in an oscillating trap with 280 Hz of scanning frequency and 2.5 to 4.5 μm trap length. For every trapped cell, its length was determined according to a bright field picture taken immediately after the positioning step. Each bin contains at least 27 cells. If the laser intensity was increased for larger trap lengths, to keep a constant flux density, a decrease in survival was observed (Supplementary Figure S2A).