A team of international researchers led by Francesca Santoro from Jülich has developed a biochip that mimics the human retina. This innovation is part of a broader bioelectronics effort to repair bodily and brain dysfunction. The creation of this chip is a joint achievement with the participation of experts from Forschungszentrum Jülich, RWTH Aachen University, Istituto Italiano di Tecnologia and the University of Naples. Their studies and findings were published in a journal Nature Communication.

The combination of man and machine is the epitome of science fiction. In real life, the first steps towards such cyborgs were taken a long time ago: humans have pacemakers to treat arrhythmias or cochlear implants to improve hearing, and retinal implants help the nearly blind to see at least a little. A new chip could help retina implants fit better with the human body in the future. It is based on conductive polymers and light-sensitive molecules that can be used to mimic the retina along with its visual pathways. It was developed by Francesca Santoro’s research group at the Jülich Institute of Bioelectronics (IBI-3) in collaboration with RWTH Aachen University, the Italian Institute of Technology in Genoa and the University of Naples.

“Our organic semiconductor detects how much light falls on it. Something similar happens in our eyes. The amount of light hitting individual photoreceptors ultimately creates an image in the brain,” explains Professor of Neuroelectronic Interfaces at RWTH Aachen University and Visiting Researcher at the Istituto Italiano di Tecnologia Santoro.

universal chip

The new semiconductor is unique in that it consists entirely of non-toxic organic components, is flexible, and works with ions, that is, charged atoms or molecules. Thus, it can be integrated into biological systems much better than traditional semiconductor components made of silicon, which are hard and work only with electrons. “Our body’s cells specifically use ions to control certain processes and exchange information,” the researcher explains. But he emphasizes that the development is only a “proof of concept” so far. The material was synthesized and then characterized: “We were able to show that the typical properties of the retina could be mimicked with it,” he says.

The researchers are currently considering another possible application: The chip could also function as an artificial synapse, as exposure to light changes the conductivity of the polymer used in the short and long term. Real synapses work similarly: They change their size and efficiency as they transmit electrical signals; this underlies, for example, learning and our brain’s ability to remember. Santoro is looking ahead: “In future experiments we want to combine components with biological cells and interconnect many individual cells.”

understanding neurons

In addition to the artificial retina, Santoro’s team is developing other approaches to bioelectronic chips that could similarly interact with the human body, particularly nervous system cells. “While we are trying to reproduce the three-dimensional structure of nerve cells, we are also trying to reproduce their functions such as processing and storing information.”

It turned out that the biopolymers they used in the artificial retina were a suitable starting material for this. “We can use them to reproduce the branched structure of human nerve cells, which contain many dendrites. You can imagine it looking a bit like a tree,” explains the scientist. This is important because real cells prefer such branched three-dimensional structures to smooth surfaces and thus come into close contact with artificial ones.

First, various biochips can be used to study actual neurons (e.g., the exchange of information between cells). Second, Santoro and his team hope to one day be able to use their compounds to actively interfere with cells’ communication pathways to produce specific effects. For example, Santoro is looking to correct errors in the processing and transmission of information that occur in neurodegenerative diseases such as Parkinson’s or Alzheimer’s, or in supporting organs that no longer function properly. Additionally, such components can serve as an interface between artificial limbs or joints.

Computer technology can also be used. Due to their characteristics, chips are destined to serve as hardware for artificial neural networks. So far, artificial intelligence applications are still working with classical processors that cannot adapt to their structure. They simply imitate the working principle of self-learning neural networks and modify them with the help of advanced software. This is very inefficient. Artificial neurons could address this previous shortcoming: “They will enable computer technology that mimics the brain at every level,” says Santoro.