Deteriorating dams in Great Lakes tributaries have increased the need to develop strategies that allow native and desirable fish to pass but block or remove invasive or undesirable fish. A primary challenge to developing such selective fish passage structures in the Great Lakes is preventing sea lamprey from getting through. As a result, detection becomes key.
Researchers at Michigan State University and the US Geological Survey Hammond Bay Biological Station are working on a smart electronic skin or e-skin that can autonomously detect the presence of a sea lamprey when the parasite attaches to the e-skin via suction.
Adult lampreys commonly attach to smooth surfaces when they want to take a rest while traveling upstream. The e-skin, mimicking human skin, is meant to sense the suction as it occurs. The work is funded by the Great Lakes Fishery Commission Sea Lamprey Research Program.
The e-skin is comprised of soft pressure sensors embedded in a flexible substrate, which allows it to be mounted to non-flat surfaces (such as dams or boulders) within or near a fishway.
The basic idea is that a lamprey mouth sucking onto the soft e-skin will produce a distinct pressure profile. By monitoring the pressure distribution on the e-skin, researchers hope to detect the attachment of the animal and then trigger a localized electrical stimulus to repel or deter it.
The smart e-skin technology, once developed, also could be deployed in streams to determine the timing of entry and upstream migration of sea lampreys to help understand their refuge-seeking behavior.
The e-skin team has focused on a pressure-sensing principle based on the resulting capacitance change of a capacitor. A capacitor, just like a resistor, is a basic element in electrical circuit with the function of storing electrical charges.
By embedding air cavities in the soft substrate, the team has been able to create an e-skin that is sensitive to positive and negative pressures. The device has shown the capability of capturing the pressure distribution induced by a suction cup underwater, which emulates the sea lamprey suction.
The research has been published in the scientific journal Advanced Functional Materials.
The researchers also have conducted preliminary tests on sea lampreys in a still water tank. These tests have not resulted in measurement of anticipated pressure profiles like that of a suction cup, but the team has identified several factors for this.
Using another customized pressure-sensing apparatus, they’ve determined that the suction pressure of a sea lamprey is weaker in still water than in fast-moving water. And unlike a suction cup, the lamprey suction pressure varies quickly over time. Unless the capacitance changes of all capacitors can be read fast enough, the e-skin will not be able to capture the lamprey’s characteristic suction pressure profile and detect the attachment.
The team is addressing these technical challenges and aims to conduct another round of animal tests in the summer of 2020.