13 June 2023
By Søren Bjørn-Hansen
Getting a complex piece of hardware to work with all the variables of the real world is difficult. But through a DIREC-project collaboration, Luca Pezzarossa got much closer to having a working prototype.
Photo: Bax Lindhardt
For most people the term digital microfluidics doesn’t mean a whole lot. But it’s a technology which could revolutionise lab work completely.
“The idea is that whatever a biochemist normally spends a lot of time doing with pipettes, can be done by a chip instead,” Luca Pezzarossa explains and plays a short video of the technology at work.
The lab on a chip is basically a biochemical lab scaled down to the size of a small portable device. The idea is to make tiny droplets of fluid move around on a chip by activating a sequence of electrodes. Luca Pezzarossa’s job is to make the hardware and software work together to move the microfluidic droplets the right way.
“But one thing that is very common in this field is that the people who do this research are not biochemists, ” he says.
The problem with this is that there are real-world constraints, which makes moving the droplets much harder.
“Two droplets cannot go as close as they do in a simulation, because they would touch and merge. Or from a biological point of view, some droplets might leave behind a contaminating residue. Blood that leaves a trail for example, and so other droplets cannot move where this has moved earlier,” Luca Pezzarossa explains.
This represents a difficult problem. To translate from a high-level protocol that is user-friendly – something which is useful for a biochemist – down to a controlling sequence is very difficult. Especially when the constraints are complex real-world issues, like a droplet leaving a contaminating trail of blood on the chip.
“When I presented these challenges at a DIREC seminar, two algorithm-oriented scientists said: ‘This is very cool from a theoretical point of view. We should apply for a DIREC Explore project.’ And we did,” Luca Pezzarossa says.
Digital Research Centre Denmark (DIREC) supports multidisciplinary research – often with external partners – with the so called Explore projects, which are small agile research projects with the purpose of screening new ideas.
So for most of 2022 he worked with two fellow assistant professors, Eva Rotenberg from DTU Compute and Lene Monrad Favrholdt from University of Southern Denmark, on developing algorithms that could do this scheduling and routing on applied cyber-physical systems – while DTU research assistant Kasper Skov Johansen, who is now a PhD student at DTU, did most of the practical work.
Photo: Bax Lindhardt
“We ended up building a mathematical framework to describe the constraints. What are the different boundaries and rules these droplets need to respect?”, he explains.
They have laid out the ideas and know where they want to take the project next. Now they are looking for funding. Long term their goal is to make the lab on a chip better so it works well in the real world instead of in a simulation.
Luca Pezzarossa believes a prototype is a couple of years away. But it all depends on how the users of the lab on a chip react.
“When people start using something they will tell you ‘this shouldn’t behave like that’. But that is the point. To try to do something useful and not just move coloured droplets around. Some issues you only discover when you bring things into the real world,” he says.
Through their collaboration, the team discovered that developing the right algorithms was much more complex than they thought. They only partially succeeded in creating the right algorithms. And that is okay, he thinks:
“It’s a difficult problem to solve. And that is also the purpose of DIREC Explore. You explore an idea, and you see if there is more that you can do. And in this case, there was more. Which is why we are looking for more funding.”
According to Luca Pezzarossa the DIREC Explore project was essential because it got them thinking differently.
“We tried to bring two worlds together that are very different. I’m from the embedded systems world, which is very noisy and real. We build things inside rockets and cars. But the world of algorithms is very formal and abstract at the same time. And this, I think, was one of the aims of the explore project, to bring people together from different fields,” he says and continues:
“I learned a lot about communication and the need to explain things in a common language. It is sometimes difficult, but so worth it. Otherwise, you are in your perfect box with all the things you know. Which is also good research, in principle. But the real world isn’t really made out of clean boxes.”
Luca Pezzarossa is an assistant professor at DTU Compute. He first arrived at DTU from his native Italy on an Erasmus Exchange Program in 2012. He did his master thesis at DTU two years later and has been at DTU ever since.