Recently, the team of Professor Ming Xu from the School of Materials Science and Technology of Huazhong University of Science and Technology and his collaborators have developed a new underwater pressure sensor based on the electrochemical sensing mechanism. This type of pressure sensor uses seawater as the electrolyte, and sends out a response electrical signal through the change of electrochemical potential generated by the special structure of the carbon nanotube sensing element with the underwater pressure fluctuation. This type of underwater pressure sensor can detect underwater activities as low as 0.01 Hz, with a detection accuracy of up to 1 mm. Related papers were published online in Advanced Functional Materials (DOI: 10.1002/adfm.202004564; https://onlinelibrary.wiley.com/doi/full/10.1002/adfm.202004564).

In ocean exploration activities, wave monitoring plays a vital role in tidal observation, underwater navigation, marine life migration tracking, and detection of underwater geological activities such as seabed earthquakes. Although the global positioning system has been widely used in various terrestrial environmental geological monitoring, the electromagnetic wave interaction mechanism has limited its application in the field of wave monitoring. At present, wave monitoring must rely on advanced pressure sensors to obtain information on a variety of key parameters including water pressure changes, wave height and wave speed. However, limited by the working mechanism, the current pressure sensor has the problems of low sensitivity, small pressure detection range, poor waterproof performance, high energy consumption, and insensitive detection of low-frequency waves in the process of underwater pressure monitoring. Therefore, it is urgent to develop an underwater pressure sensor based on a new working principle to overcome the above-mentioned bottleneck problems faced by this field.

In response to the above scientific problems, researchers first proposed an underwater pressure detection mechanism based on electrochemical pressure response. They innovatively combined the ion reactive etching method and the water-assisted chemical vapor deposition method to prepare non-array carbon nanotube materials to reduce the aggregation of carbon nanotubes, and maximize the material in the electrolyte (ie, seawater) The electrochemically accessible area; and then mechanical drawing is applied to obtain a highly oriented carbon nanotube film with a nano-groove structure, which is folded in half as the core sensing element to be assembled in the pressure sensor. When the external water pressure changes, the nano-grooves on the inner surface of the material will be embedded and separated from each other due to the action and release of the water pressure, so that the electrochemical contact area changes accordingly to generate a pressure-induced-electrochemical potential Change; while external mechanical energy is converted into electrical energy through electrochemical mechanisms, it sends out electrical signals in response to changes in underwater pressure.

This type of electrochemical pressure sensor does not require an external power supply during the working process, and can monitor wave changes as low as 1 mm and as high as 30 meters. The monitoring range can cover almost all ocean wave motions on the earth; and the temperature is 4-60 ℃ Excellent pressure sensing performance is maintained in the temperature range and salinity range of 0.1-5 mol/L. What's more worth mentioning is that due to the innovation of the sensing mechanism, this type of underwater pressure sensor can detect underwater activities as low as 0.01 Hz; underwater low-frequency detection is a problem that has always plagued this field. Combined with the characteristics of ultra-high sensitivity and fast response, this type of underwater pressure sensor will show great application prospects in the field of ocean wave monitoring.

The researchers believe that this research provides a new strategy for achieving a series of technological breakthroughs in the accuracy and detection range of underwater pressure sensing and low-frequency underwater activity detection. The innovative invention based on this strategy, the "Self-powered Tsunami Warning System", won a special gold award at the 47th Geneva International Invention Exhibition in Switzerland in 2019. The special gold award is selected from the gold awards and requires unanimous approval by all members of the review committee, no one It can only be won by voting against it, so it is also called the gold award in the gold award, which is the highest level gold award in the invention exhibition.