Tiny pump senses chemical changes and acts
09 February 2012
A team of researchers at Pennsylvania State University has developed a microscale pump that turns on in the presence of a particular chemical, with a flow rate that depends on that chemical's concentration. Because of its specificity for a specific analyte, the pump doubles as a chemical sensor - a useful combination for diagnostic devices.
The rapid release of polymer monomers creates an osmotic gradient that pumps the polystyrene nanoparticles away from the device
© Angew. Chem., Int. Ed.
The team made two versions of their pump: one with tert-butyldimethylsilyl (TBS) end-capped poly(phthalaldehyde) (TBS-PPHA), which reacts to fluoride, and the other with poly(ethyl cyanoacrylate) (PECA), which responds to high pH. TBS-PPHA chains, which can be as long as 1000 monomers, break down completely when the fluoride cleaves the TBS end-cap. While PECA's depolymerisation is more complex, it better lends itself to medical applications because it is non-toxic and non-immunogenic in humans. The explosive release of monomers is one of the pump's main attributes, says author Scott Phillips: 'Depolymerisation offers a highly amplified sensor response'.
The team measured pump speeds by observing polystyrene tracer particles. With a NaF concentration of 0.1M, the TBS-PPHA pump pushed the fluid at a top speed of about 1.15Ám/s while the PECA pump managed 11Ám/s with 1M OH-. Both pumps cleared the polystyrene beads from their vicinities.
According to Ramin Golestanian of Oxford University, UK, the most novel and exciting aspect is the combination of sensing and pumping, which allows mechanical action 'to be switched on with a chemical signal'.
In order to demonstrate the pump's potential in microfluidic devices, the team used the TBS-PPHA film to pump particles on a millimetre scale and around corners. They also used a reagent that releases fluoride ions upon reacting with beta-D-glucuronidase, a marker of Escherichia coli, to turn the pump into an E coli detector.
With this sensing ability, Phillips says that the pump could check water quality or diagnose medical conditions such as bacterial infections. The team is also interested in exploring the pump as a self-cleaning surface, pushing bacteria away as it did with the polystyrene beads. Co-author Ayusman Sen suggests that drug delivery could be its most important application, with the drug embedded in the polymer film and released on exposure to a disease biomarker.
Interesting? Spread the word using the 'tools' menu on the left.
H Zhang et al, Angew. Chem., Int. Ed., 2012. DOI:10.1002/anie.201107787
Also of interest
21 September 2010
Synthetic, self-pumping membranes could be use to generate energy in compartment-less fuel cells
29 March 2009
Novel DNA-based hydrogels completely free of living cells function as mini protein factories
20 March 2009
New drug delivery system has three different ways to drop off medicine where it is needed
Comment on this story at the Chemistry World blog
Read other posts and join in the discussion
External links will open in a new browser window