A new type of tiny electronic biosensors has the potential to make DNA sequencing and other bio-chemical analysis quicker and cheaper. Zhen Zhang is exploring the advanced nanofabrication technology used in microelectronics to develop a lab-on-a-chip – a miniature laboratory capable of detecting low concentrations of ions in chemical and biological samples.
Associate Professor of Physical Engineering
Wallenberg Academy Fellow 2015
Microelectronic biosensors for nanoscale biochemical analysis
On the bottom floor of the Ångström Laboratory in Uppsala there is a clean room, where Zhen Zhang and his research team fabricate their tiny electronic chips and sensors, visible only in a powerful microscope. The components are made of silicon, and are measured in nanometers. They are tailor-made to detect specific chemical ions or biological molecules. Zhang elaborates:
“The technology we’re using is really cool. We are targeting to make a large number of parallel analysis of different samples on the same chip – creating a miniaturized lab on a very small surface.”
Zhang is an associate professor of physical engineering, specializing in electronics. He began his academic journey in China – his home country – with a master’s degree in electronic ceramics at Shanghai Institute of Ceramics, Chinese Academy of Sciences. It was merely by chance that he ended up in Sweden.
“Semiconductors were very much the coming thing, and I wanted to learn more. I happened to meet a professor who recommended KTH Royal Institute of Technology, and in 2003 I came to Sweden to study semiconductors and microelectronics. It turned out to be the right decision.”
A few years later Zhang gained his PhD at KTH in Kista, Stockholm with a thesis on tiny transistors based on silicon nanowires. He then worked for five years at the IBM Research Center in New York.
“It’s a center of excellence in research on semiconductors, and I was working on the most advanced chip technology. I really enjoyed my time there, and built up a valuable network. My former colleagues are key collaborators in the work I’m now doing.”
In 2013 Zhen Zhang got the Ingvar Carlsson Award, and moved back to Sweden to pursue the next step in his research career at Uppsala University.
“With this beautiful semiconductor technology you can build billions of identical electronic components on a tiny chip. We can use it for many things, but I chose to study how we can create electronic biochips for different purposes, like monitoring water pollution in real time, for example.”
Unlike current biochip systems, which are usually optical-based, and require the support of costly laboratory equipment, Zhang’s biosensors are integrated with the electronics.
He explains that there are two major application domains for electronic sensors. One domain is the Internet of Things, which is a gigantic network of sensors. Here, there is enormous demand for low-price sensors that do not need to have top-class performance.
“The other application domain is precision medicine. Here, electronic sensors can be used to map a person’s DNA or detect biomarkers. Sensors can also be used in new “smart” diagnostic tools. But then they need to be high-performing, highly sensitive, and reliable.”
Zhang has received much help to develop his research in Sweden.
“Without the support of Shi-li Zhang, the chair professor on Solid State Electronics at Uppsala University, this project would have been impossible. We have built up an excellent lab. I have also been greatly supported by Professor Mikael Östling at KTH; we work closely together on another electronics project.”
Biosensor detects charges
In recent years Zhen Zhang has concentrated on developing the technology needed to build the biochips.
“The electronics are all in place and work really well now. We have made nanowire transistors and very small sensors in the new lab. Now we are testing to see how they can detect DNA molecules. We’re also trying to find ways to detect heavy metals and antibiotic residues in aquatic environments.”
With the support of a grant from the Knut and Alice Wallenberg Foundation, the research team will make an in-depth study of the interface interactions between the electronics and the liquid sample to be analyzed. In the world of electronics, they are dealing with charges, Zhang explains:
“We have an electronic component that can detect charge, which may be from different ions in the chemical or biological sample. We want to be able to distinguish between signals from different charged particles.”
Another problem to solve is the noise generated in the sensing experiments, which makes it harder to decode the signals.
“Signal divided by noise equals performance. We want to understand which processes produce the noise, and how we can reduce it. This will enable us to design high-performance biochips capable of analyzing low concentrations of ions.”
The project is interdisciplinary. As well as with KTH, Karolinska Institutet and IBM, Zhen Zhang is collaborating in various fields with universities in China, the U.S., Finland and other countries.
“The technology I am working on here at the Ångström Laboratory is like art. I want to see what kind of exciting applications this beautiful art will lead to. It’s challenging, but at the same time a lot of fun.”
“It is fantastic, and most of all, a wonderful acknowledgement of my research. The funding will enable me to establish our laboratory and build a research team to develop new advanced nanoscale biosensors.”
Text Susanne Rosén
Translation Maxwell Arding
Photo Magnus Bergström