In the past decade, biopharmaceutical manufacturers have demonstrated major improvements in monoclonal antibody (MAb) production, exhibiting product titers frequently in the range of 5–10 g/L using standard fed-batch mammalian cell cultures (1, 2). Increased product yields allow for smaller-scale production vessels. With 2,000-L single-use bioreactors already commercially available, single-use manufacturing of biomolecules becomes more and more an option. Other recent developments in the biopharmaceutical industry — e.g., drugs for smaller indications and more potent drugs allowing for lower dosages — will further stimulate the demand for smaller and more f lexible single-use manufacturing facilities. Although single-use technology in general has matured considerably over the past few years, some unit operations (e.g., cell removal) still need more attention to become more economical and robust. High product titers often result from increased cell densities rather than increased specific productivities per cell, and the resulting solids content poses considerable challenges on commonly applied harvesting technologies. Currently the most prevalent single-use harvesting technology, depth filters block at lower loading capacities with higher biomass concentrations. Higher contaminant concentrations also make depth filters more sensitive to batch variation, which can lead to 50% oversizing of filter area to compensate for f luctuating filtration capacities. That drives up costs and increases waste. Other new commercially available single-use cell-removal technologies such as centrifuges still lack capacity. For harvesting higher–cell-density cultures, a major technical breakthrough would be welcomed.