The present invention is a filter apparatus with methods to capture a desired amount of material suspended in a liquid or gas for monolayer deposition, analysis or other uses. Novel filter devices are employed to capture material which may be used for the purification or enrichment of various sample constituents or captured material may be observed or analyzed. Alternatively, particulate material may be used as a transport mechanism for proteins or chemicals which in turn may be assessed or used. The filter device employs sensors to sense pressure and adjust, halt or otherwise control sample flow. The pressure sensor essentially monitors the flow rate of sample suspension through a filter, typically responding at a predetermined pressure associated with capture of a desired amount of material on the filter. A separate valve or valve integrated with pressure sensing provides a means to adjust sample flow. Typically, pressure is used to provide a means to cause the sample suspension to flow through the filter, which is preferably a membrane filter for monolayer deposition. In some embodiments a novel syringe provides this pressure, functioning as a vacuum source. The filter apparatus may be further automated to process a plurality of samples, simultaneously.