Self‐Powered Microscale Pumps Based on Analyte‐Initiated Depolymerization Reactions

Abstract

Pump it up: Insoluble polymer films that depolymerize to release soluble monomeric products when exposed to a specific analyte act as a microscale pump. Products formed as a result of depolymerization amplify the signal and create a concentration gradient that pumps fluids and insoluble particles away from the bulk polymer by a diffusiophoretic mechanism. These pumps can respond to a variety of analytes, from small molecules to enzymes.

Synthetic Nano- and Micromachines in Analytical Chemistry: Sensing, Migration, Capture, Delivery, and Separation

“…For exothermic reactions, i.e., pumps that generate heat, fluids are pumped inward near the substrate, and for endothermic ones, outward fluid flows are generated. Density gradients can also result from density differences between reactants and products (106). Unlike the phoretic pumps discussed above, fluid velocities in density-driven pumps are influenced by the cell dimensions: for example, a sevenfold increase of velocity was observed upon doubling the cell height (105).…”

“…Synthetic micropumps are also triggered by, and hence sensitive to, certain chemical stimuli, e.g., hydrogen peroxide (72,101,102), hydrazine and its derivatives (100), fluoride, and magnesium ions (93,106,118), as well as enzyme substrates, such as urea and glucose (105). Similar to motors, the detection limit for pumps is currently on the order of millimolar concentration.…”

“…Micropumps based on density gradients (Figure 2g) that are largely unaffected by high electrolyte concentrations have also been designed (105,106). Chemical reactions at pump surfaces (64) are almost always coupled with heat generation or consumption (105).…”

“…This heat flux leads to temperature gradients and thus density differences across the solution. Due to the buoyancy effect, lighter fluids move up, and denser ones settle down, which leads to convective fluid flows (106). For exothermic reactions, i.e., pumps that generate heat, fluids are pumped inward near the substrate, and for endothermic ones, outward fluid flows are generated.…”

“…Similar to motors, the detection limit for pumps is currently on the order of millimolar concentration. Recently, pumps based on depolymerization (104,106,118,119) and enzyme catalysis (93,105) have attracted significant attention because of their ability to sense and pump in response to specific analytes. The depolymerization pumps consist of insoluble polymer films that depolymerize to release soluble monomeric products when exposed to a specific analyte, whereas the surface-anchored enzyme pumps are turned on in the presence of either the substrate, a promoter (cofactor), or a related biomarker.…”