If implants could be injected into the body in liquid form and then made solid on the spot, operations would become less invasive. The new 3D printing technique will allow creating implants inside the body using biocompatible ink activated by ultrasonic waves. It works like this: a special ink is injected into the desired area of the body to create an implant, ultrasonic waves activate its polymerization inside the body, and then the remaining ink is removed with a syringe. This approach may have great potential in the field of surgery and therapy.
There are two main methods of 3D printing. The first method is based on the sequential application of layers of viscous material that hardens to create three-dimensional objects. This method is the most common in 3D printing.
The second method, known as three-dimensional printing, uses a light-sensitive jelly-like resin that is placed in a container. Beams or patterns of light are projected through the transparent sides of the container, causing the resin to polymerize in the areas exposed to the light, while the rest of the resin remains gel-like. By moving the light source, you can gradually create a complex three-dimensional object.
One of the limitations of three-dimensional printing is that the container and resin must be transparent to transmit light. However, human skin and biological tissues are almost opaque. This means that light penetrates them only to a shallow depth, usually a few millimeters. Therefore, for now, volume printing cannot be used to create implants inside the body.
Scientists from Duke University and Harvard Medical School have invented a new sound-based technique called deep acoustic volumetric printing or DAVP.
Instead of photosensitive resin, a biocompatible ultrasonically treated “ink” known as sono-ink is used here, which heats up and then solidifies when absorbing ultrasound pulses.
It is assumed that the viscous ink can be injected into the desired area of the body to create an implant. Then, by using ultrasound waves from an external transducer in a targeted manner, their polymerization and formation inside the body can be activated. After the implant itself has polymerized and acquired the desired shape, the remaining ink can be removed from the body with a syringe. Depending on the intended use, sono-ink can be durable or biodegradable, and can mimic different types of biological tissue, such as bone.
During laboratory tests, scientists have used DAVP technology to seal a section of a goat’s heart (which is needed to treat non-valvular atrial fibrillation), repair a bone defect in a chicken leg, and create hydrogels that can distribute chemotherapy drugs inside liver tissue.
The ability to print through tissue opens up a wide range of potential applications in surgery and therapy, which often require invasive approaches.
