ggplot2, getting a % symbol in subscript within axis labels

Question

I'm trying to get a % symbol in the axis as subscript. Typically, using expression and square brakets [] you can get subscripts. But symbols don't seem to be parsing correctly as I get an error. Does anyone know how to fix or a work around? For instance, what would I do if I want % in subscript below:

library(tidyverse)
  
iris %>% ggplot(aes(x = Sepal.Length, y = Sepal.Width)) + 
  geom_point(aes(colour = Species)) + 
  geom_smooth(method = loess) + 
  labs(y = expression(Blah[1*d]*"%"))

When the % sign is moved in the brackets

iris %>% ggplot(aes(x = Sepal.Length, y = Sepal.Width)) + 
  geom_point(aes(colour = Species)) + 
  geom_smooth(method = loess) + 
  labs(y = expression(Blah[1d%]))

the following error message appears:

Error: unexpected symbol in: " geom_smooth(method = loess) +
labs(y = expression(Blah[1d"