Provided are apparatuses for the processing of one or more components of a fluid into the surface of a linear substrate. The apparatuses include a processing barrel having a chamber defined therein as well as a linear substrate inlet and a linear substrate outlet. The processing barrel also includes a fluid inlet and a fluid outlet in fluid communication with the chamber. An exposure gap is defined between the linear substrate inlet and the linear substrate outlet. The chamber is dimensionally reconfigurable so that the exposure gap can have a length from zero to greater than zero.