A revolutionary photoresist for 3D printing allows precise removal of materials post-production, enabling customisable microstructures in a printed object.
In 3D printing, it may seem odd to print materials only to remove them later. However, making changes to a 3D structure after the polymer is cured, or hardened, is necessary for building more complex micro- and nanoscale designs. More intricate 3D objects may require temporary supports, or scaffolds, that are essential for forming certain structures but must be removed once their job is done.
Another reason for modifying a final product is to fix mistakes that occur during the manufacturing process, as even small defects can lead to wasted time and resources. The ability to precisely erase and reprint parts of a design ensures that the final product meets exact specifications, saving both time and materials.
Direct laser writing (DLW) is an additive manufacturing technique used to create customisable 3D micro- and nanoscale objects. In the two-photon polymerisation (2PP) process used in DLW, a pulsed, ultra-fast laser beam interacts with a photoresist material. Two photon absorption creates what’s called a voxel, the smallest unit of material that can be manipulated or solidified by the laser. These voxels can be controlled at an incredibly small scale, allowing generation of highly detailed and complex 3D structures that are difficult to achieve with other manufacturing methods.
Conventional photoresists typically exhibit binary behaviour, meaning they either harden completely, or not at all, depending on the printing conditions. This irreversible cross-linking process renders the material photochemically inactive. However, there is a growing demand for incorporating dynamic functionalities into printed structures, ideally in a single printing process.
A major advancement in DLW is the ability to erase parts of 3D structures after they are printed.
Traditionally, removing parts of a 3D structure has been achieved mechanically or through chemical processes, but these methods can be inefficient and imprecise. A more sophisticated approach involves using materials, called cleavable photoresists, that can break down in response to specific triggers. These materials can even be designed to degrade on their own, without the need for an external erasing tool.
Queensland University of Technology’s Dr Steven Gauci, Prof Christopher Barner-Kowollik and their colleagues have developed a new type of photoresist that offers variable degradability. By adjusting the laser intensity during DLW 2PP printing, scientists can control which parts of the structure remain stable and which ones break down triggered by the mildest triggers of all – darkness.
Before, creating degradable structures required switching between different materials, making the process more complicated. Now, a single material can be used to print structures with both permanent and darkness-triggered degradable sections.
The potential applications are wide-ranging. In drug delivery, controlled degradation could be used to release medication in a targeted and precise manner. In tissue engineering, this resist could be utilised to create scaffolds for cell cultures that can be removed without damaging the surrounding cells. In regenerative medicine, scaffolds can be designed to break down naturally over time, aiding in tissue formation. These advancements open new possibilities in biomedical engineering.
This innovative research showcases how advancements in materials chemistry can overcome the limitations of traditional manufacturing. It demonstrates how curiosity-driven science can lead to new technologies with real-world applications that were previously unimaginable.
Published 15 October in ANFF’s 2024 Casebook ‘ANFF NEXT‘
Posted 19 August 2025