Membrane madness

by Tyler Shendruk

Published: Apr 7

The problem
ONE IMPORTANT STEP in water treatment is filtration. Nobody wants little gritty pieces of dreg or oily bits of gunk in their drinking water. River water is passed through membranes in water treatment plants which block oversized contaminants from going any farther. Making membranes with large surface areas, but with small enough pores (micro- or nanofiltration), is possible by casting polymers into a film. These films are either hydrophilic (water-loving) or hydrophobic (water-hating).
It turns out that most contaminants are oily, hydrophobic gook, and since “the enemy of my enemy is my friend” the contaminants are very likely to bury themselves in the hydrophobic membrane to hide from the water. They can’t get through at first, but eventually contamination degradates the membrane’s performance.
On the other hand, hydrophilic membranes have their own set of problems. The contaminants don’t like the membrane, don’t bury themselves in it, and so degradation is slower. But hydrophilic membranes tend to be significantly weaker than hydrophobic ones, and so will often break during water treatment.

The researcher
Takeshi Matsuura is a chemical engineer at the University of Ottawa who develops modified membranes that can improve the distillation and filtration processes. In particular, he is interested in modifying surfaces using large macromolecules that can be attached to membranes.

The project
Filtration science would really benefit from filters that are strong, and that do not rapidly degrade. Hydrophobic and hydrophilic membranes each have their drawbacks, but by combining them, Matsuura hopes that he can get the best of both worlds.

The key
While other scientists cast a strong hydrophobic membrane, and later modify it by grafting hydrophilic polymers on top to make a protective coating, Matsuura thinks this is too slow (and costly). He mixes the hydrophilic and hydrophobic polymers together in solution and then casts them. As the water evaporates, the polymers naturally separate. Matsuura is left with a single membrane with a strong bottom layer and protective coating on top. In just one step, he gets a surface modified film that has the strength of a hydrophobic filter, but degrades slowly like a hydrophilic filter. That really is the best of both worlds.

Busy bees

by Allan Johnson

Published: Mar 31

The problem
THERE’S AN OLD urban myth that scientists don’t know how bees fly, that their wings can’t beat fast enough to keep the bees in the air. In reality, bees beat their wings 200–300 times a second, courtesy of the most efficient metabolic rate in nature. This ultra-efficient energy use makes them the ideal creature for studying the workhorse of biological systems: the metabolism.
This system breaks down large energy storing molecules via a series of chemical reactions, each assisted by enzymes. This creates ATP, the energy-carrying molecule that provides power to all the other functions in the body. The general pathways of this process are common to all higher organisms, so what’s true for bees is true for the animal kingdom.

The researcher
University of Ottawa professor Charles Darveau studies metabolism from a physiological and evolutionary perspective, using bees as a model organism. By comparing metabolic differences across different species of bees and weighing them with physiological differences, he can identify which changes in the series of reactions that make up bees’ metabolisms are important.

The project
Most people are familiar with the honeybee and bumblebee, but there are over 300 species of bees in Ontario alone. Darveau has a wide array of species to make comparisons. In addition to this cross-species approach, he can also look at variations within a species to examine these changes. The goal is to develop a complete characterization of the metabolic process: which enzymes make key changes, what steps bottleneck the metabolic rate, and what kind of system is most favoured evolutionarily.

The key
Darveau’s research is on the fundamentals of physiological change, but it has a number of immediate consequences. Because bees burn energy so quickly and efficiently, their wing muscles can heat up to 40°C. This allows them to flourish in environments where many other pollinators would be unable to survive, making bees an important part of northern ecosystems. Darveau’s fundamental characterization also allows other researchers to determine which species have metabolisms suited to adapting to different conditions, vital in determining the impact of climate change on fauna.