Ultra-precise reactions
As the researchers explain, DSP is based on chemical reactions created by fluctuating pressure inside small bubbles suspended in a liquid polymer solution.
“We have found that if we use a certain type of ultrasound with a certain frequency and power, we can create very local and very focused chemically reactive regions,” says Habibi. “Basically, bubbles can be used as reactors to drive chemical reactions to transform liquid resin into solids or semi-solids.”
The reactions caused by the oscillation directed by ultrasonic waves inside the micro-sized bubbles are intense, although they only last a few seconds. The temperature inside the cavity rises to about 15,000 Kelvin and the pressure exceeds 1,000 bar (the pressure of the Earth’s surface at sea level is around one bar). The reaction time is so short that the surrounding material is not affected.
The researchers experimented with a polymer used in additive manufacturing called polydimethylsiloxane (PDMS). They used a transducer to generate an ultrasonic field that passes through the shell of the building material and solidifies the target liquid resin and deposits it on a platform or other previously solidified object. The transducer moves along a predetermined path, eventually creating the desired product pixel by pixel. The microstructure parameters can be manipulated by adjusting the frequency of the ultrasound wave frequency and the viscosity of the material used.
Versatile and specific
The authors believe that the versatility of DSP will benefit industries that depend on very specific and delicate equipment. PDMS polymer, for example, is widely used in the microfluidics industry, where manufacturers require controlled environments (clean rooms) and sophisticated lithographic technique to create medical devices and biosensors.
Aerospace engineering and repair can also benefit from DSP, as ultrasonic waves penetrate opaque surfaces such as metal shells. This can allow maintenance teams to service parts located in the depths of an aircraft’s fuselage that would be inaccessible to printing techniques that rely on photoactivated reactions. DSP could even have medical applications for remote body printing for humans and other animals.
“We have shown that we can print a variety of materials, including polymers and ceramics,” says Packirisamy. “Then we will test the polymer-metal compounds and finally we want to get to print metal using this method.”
The study received funding from ALIGO INNOVATION, Concordia and the Quebec Research Fund – Nature and Technology (FRQNT).
Read the quoted document: “Direct sound printing. ”