Biopol, aura and other esoterics find true embodiment in weak electromagnetic fields. Fish of the clover family (mormyrids) can identify food in turbid water and even mud by sensing it with weak disturbances of the electromagnetic field. Hong Kong scientists aim to reproduce the sensor system of these fish in biocompatible layers and equip humans and automation with it.

“Inspired by the ‘electric fish’, we developed a new strategy for 3D motion positioning using electronic skin”, said Xinge Yu, a professor in the Department of Biomedical Engineering at the City University of Hong Kong. The team described their sensor, which uses capacitance to detect an object regardless of its conductivity, in a paper published in the journal November. Nature.

One layer of the sensor acts as a transmitter, producing an electric field that extends far beyond it. Another layer works as a receiver that can determine both the direction and distance of the object. This allows the sensor system to “feel” the object’s position in three-dimensional space.

The sensor’s electrode layers are made of biogel coated on both sides on a dielectric substrate composed of polydimethylsiloxane (PDMS), a silicone-based polymer popular in biomedicine. In the transmitting and receiving part, a pattern is created that generates and recognizes electromagnetic fields (actually antennas). All this is housed in a transparent biogel that is flexible and compatible with human biology. One type of patch can be stretched and bent to fit snugly on a person’s wrist, for example.

When there is a foreign object in the sensor field area, it is fixed by the receiver. Thanks to the sensor array, the direction of the object and its general position in three-dimensional space are determined. The sensor prototype was able to recognize airborne objects up to 10 cm and underwater objects up to 1 m. Light obstacles made of fabric or paper did not prevent the recognition of “disturbers” of peace, but the appearance of another person or large objects within 40 cm of the sensor reduced the accuracy of recognition.

The developers have created a platform that is as energy efficient as possible. As a result, the sensor transfers status-related data to the smartphone via Bluetooth. What is transmitted is not the raw data about the media, but the processed result prepared for post-processing. This saves energy and resource-intensive transmission occurs only when needed. A simple controller and data processing circuit are placed inside the patch and filled with biogel. The built-in lithium battery is charged wirelessly via the electromagnetic coil.

The development promises to improve orientation in the complex environment of humans and robots, but so far it can only recognize objects of a certain size, specifically 8 mm in diameter. The smallest objects are detected with poor accuracy, and large objects are detected very slowly. Currently such a device could be used to recognize gestures indicated by fingertips, for example, but there is still a lot of work involved and research will continue.