NIL (Nanoimprint lithography) and hot embossing seem to mean the same thing in many instances. Is hot embossing a subset technique of NIL? Or are they completely different methods?
I had the same question recently and was doing some research a wile ago. Sorry that I don't have all the literature prepared.
NIL is for very small structures, the mold is created with a lithography process. Depth are usually not very large. Can be very fast implemented in R2R. There are two basic types:
- Thermal NIL: Mold is places on substrated, mold is heated at first, then cooled down and separated from substrate with finished imprint.
- UV NIL: Same as above but instead of a heating source you have a UV source. [Source: N. Kooy et al. A review of roll-to-roll NIL Nanoscale Research Letters 2014, 9:320]
Hot embossing is also used for small structures but also for bigger ones, small structures with great depth can be achieved. In the process the substrate is preheated and in liquid phase. The mold is pressed on the substrate. Temperature and pressure are controlled. During cooling the mold is removed. Speeds are slower, depending on how big the structure is can be very slow. The mold can also be created by lithography but not necessarily as they often exceed the size possibilities of lithography. The molds are bigger than the imprinted structure depending on the flow characteristics of the material imprinted. Delamination happens during cooling. [Source: M. Heckle et al. Hot embossing - The molding technique for plastic microstructures - Microsystem Technologies 4 (1998) 122-124]
Differences: Hot embossing is: slower, for bigger structures, or small but great depth (holes, lenses, deep channels...), mold is bigger than structure, substrate is preheated, temp. and pressure are always controlled, mold isn´t necessary made with lithography.
For sure there are things I missed but I hope it helps someone.