To prepare the coating process, the PVDF membrane was
first placed on a glass plate (6 cm × 8 cm) along the coating
direction (Figure 1a) to air-dry excess liquid for 10 min. The
primary antibody solution was then fed into the TDC coater
using a syringe pump (100 μL/min). The TDC coater was
mounted on the vertical axis of a traversing stage to control the
coating gap between the coater and the membrane by a selfwritten LABVIEW program (National Instruments). The stage
speed was programmable, and the setting in the study was 1
mm/s. The coating process can be further divided into three
steps as shown in Figure 1b. The coater first descended to the
surface of the cover glass and fluid pumping began. The coater
then moved from the cover glass to a PVDF membrane without
direct contact (to PVDF) along the coating direction. When
the coating process finished, fluid pumping stopped and the
thin-film coater ascended to the resetting position. In the
present study, each stroke used less than 0.1 mL (for 20 mm
coating width and 60 mm coating length) of the primary
antibody solution, and the operation duration was less than a
minute (depending on the coating length and speed). After the
antibody coating was complete, the PVDF membrane was
ready for the subsequent detection and analysis procedures