  We present a portable, simple-to-operate, point-of-use analyte surface
localization device. We take advantage of a set of hydrodynamic design features
and components that achieve passive analyte localization by means of a single
vacuum input. The vacuum source can be supplied by mechanical or
battery-operated vacuum sources that are portable and allow point-of-use
operation in the absence of electricity. We discuss the governing hydrodynamic
principle and design parameters in detail. In a case study, we demonstrate the
applicability of our technology to successfully localize a solution of
rhodamine on a polydimethylsiloxane (PDMS) substrate and produce
sub-millimetre-sized spots via application of a mild vacuum pressure of less
than 10 kPa. In addition, we demonstrate local staining of breast cancer cell
blocks and on human breast cancer tissue sections.
