Your phone vibrates thanks to a platinum-based material

Cell phone. (Reference image from Pickpik.)

Researchers at Hamburg University of Technology have produced nanoporous platinum (np-Pt), a platinum matrix containing tiny pores to increase energy conduction, in large quantities and in a cost-efficient manner, with the goal of improving actuator materials.

Actuators are common machine components that convert energy into movement, like the muscles in the human body, vibrating elements in mobile phones or electric motors.

Ideal actuator materials need good electrochemical properties to repeatedly conduct electrical currents made of flowing electrons and excellent mechanical properties to withstand the physical stress associated with continual movement.

This is where the new np-Pt material comes in as it is made up of a random, interconnected network of very fine platinum strands, or ligaments, as small as two nanometers (10-9 m) in diameter, which create tiny pores between the strands, improving the movement of electrons or charged atoms through the material.

Importantly, the team used an efficient manufacturing method that decreased the cost associated with synthesizing a np-Pt. By decreasing the diameter of the Pt strands, both the surface-to-volume ratio and the mechanical stability of the np-Pt material go up, improving the material’s actuator performance.

Nanoporous platinum is made up of interconnected small-diameter ligaments, or strands, of platinum as small as two nanometers (10-9 m) in diameter with tiny pores in between.
Nanoporous platinum is made up of interconnected small-diameter ligaments, or strands, of platinum as small as two nanometers (10-9 m) in diameter with tiny pores in between. (Image from Energy Materials and Devices, Tsinghua University Press).

In a paper published in the journal Energy Materials and Devices, the researchers note that compared to other nanoporous metals and materials being investigated for their potential use as actuators, np-Pt is physically more robust and would likely work well as a sensor or detector material versus other nanoporous materials that are too fragile.

“The fine ligament size of np-Pt could provide an enhanced surface area which makes the material a promising… catalyst of chemical reactions as well as an actuator material,” Haonan Sun, first author of the paper, said in a media statement.

According to Sun, as a catalyst, np-Pt would speed the rate of specific chemical reactions. However, in his view, the main breakthrough in this research is that he and his team obtained bulk np-Pt by electrochemical dealloying.

“Past studies on np-Pt were all based on nanoparticles or films that were prepared using more expensive commercial Pt particles. So the easy and cheap method of dealloying increases the practicality of np-Pt and makes further research possible,” the scientist said.

Specifically, dealloying is a process of selective leaching or corrosion where one component of an alloy, or material blend, is selectively removed from the material. Before the dealloying process, the material is a uniform blend. After the selective leaching process, the more chemically active blended materials are partially removed from the material, leaving tiny pores behind.

In this case, np-Pt was manufactured by selectively leaching copper from a platinum-copper alloy (Pt15Cu85) using sulfuric acid (H2SO4). Prior to this study, np-Pt had never been manufactured in larger bulk quantities.

The research team suggests that the successful performance of bulk np-Pt serves as a model for the development of other nanoporous metals that may be investigated for their suitability as potential actuator materials, strain sensors or chemical reaction catalysts.