Figure 4.

Nanoimprint lithography (NIL) techniques were used to generate micro/nanoparticles with controllable features for therapeutic delivery to cells. (A) NIL relies on printing a mold onto a layer of photo or thermal materials. UV light was used to transform the materials into a solid shape. The residual materials during printing will connect the nanoparticles together and thus require reactive ion etching techniques to remove the residual layer, generating isolated nanoparticles [131]; (B) NIL based techniques were able to generate nanoparticles with different shapes. Four shapes were illustrated in this work [130]; (C) The NIL-based nanoparticle production techniques allow the cumulative release of therapeutic cargos. These techniques also allow the loading of smart materials (i.e., enzyme triggered materials), thus the cargos can be released in a certain enzyme environment [130], with copyright permission from © Elsevier.