| RESEARCH HIGHLIGHTS |
chip and testing valve function prior to chip integration, we can achieve much lower defect rates, which boosts yields and results in a much lower cost per device,” says Toh. “This technology will reduce waste and help con- tribute to sustainable manufacturing practices for microfluidic chips.” Getting the valve design right, however,
was complicated. The team used state-of- the-art software to predict the microscopic
interactions between the flexible elastomeric silicone membrane and the fluid in the micro- channel. Using materials that are compatible with the latest microfluidics technologies was also a big constraint. “The industry is rapidly moving toward
more cost effective thermoplastic materials,” says Toh. “By using compatible materials, we can achieve reliable integration without additional surface modification or adhesives.”
Toh and her team are now exploring the
production of microvalve modules using a variety of novel materials. “Greater adoption of microfluidic technology will mean that we could see our modular microvalves being used in a wide spectrum of applications,” she says.
1. Toh, A. G. G., Wang, Z. & Wang, Z. Modular membrane valves for universal integration within thermoplastic devices. Microfluidics and Nanofluidics 20, 85 (2016).
Biofouling
STICKING TO THE STORY AT THE MOLECULAR LEVEL
MOLECULAR INSIGHT INTO PROTEIN NET CHARGE MAY EXPLAIN AND HELP SOLVE THE HARMFUL BUILD-UP OF ORGANISMS IN THE MARINE ENVIRONMENT
10µm 100µm AFM image of cyprid barnacle larva footprint protein (left) and microscope image of the cyprid barnacle larva (right).
www.astar-research.com
A deeper understanding of protein adhesion to solid surfaces may shed new light on biological phenomena such as marine biofouling. In their quest for non-toxic, microorganism-repelling surfaces, A*STAR researchers evaluated the relationship between charge and pH for an adhesive protein that exists in minute quantities in the footprint of barnacle larvae and showed it influences their ability to attach to surfaces1. The measurements led to a specific pH
value known as the isoelectric point (pI), at which the protein net charge equals zero. The pI provides pH ranges for protein solubility and also gives valuable information on a protein’s affinity to charged surfaces, which is essential for protein separation, sensing, and nonspecific adsorption. Proteins lose or gain protons depending on the acidity of their surroundings, which alters their net charge. They typically present a positive net charge under highly acidic conditions and a negative charge in highly basic environments. This enables attractive interactions with oppositely charged substances. At pI, the zero net charge promotes protein aggregation. Several approaches to determine pI values
already exist but tend to be time consuming and require high water solubility and concentration. Under the Innovative Marine Antifouling Solutions program, a team led by Julius Vancso from the A*STAR Institute of Chemical Engineering Sciences and Dominik Jańczewski from the A*STAR Institute of Materials Research and Engineering has developed a strategy that delivers protein pI values using atomic force microscopy (AFM). “AFM has become an enabling platform to
visualize as well as manipulate and study matter at a molecular scale,” explains Vancso, noting
A*STAR RESEARCH 49
© 2017 A*STAR Institute of Materials Research and Engineering
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