Researchers at the University of Houston have released a paper highlighting research into micro-scale printing of organic electronics, which has applications in flexible electronics and bioelectronics.
The researchers have used multiphoton lithography (MPL) and materials mostly composed of acrylate-based polymers/monomers or epoxy-based photoresists, and they have embedded the resin with organic semiconductor (OS) materials.
Multiphoton lithography
Multiphoton lithography is based on two-photon polymerization, which is an optical process based on the simultaneous absorption of two photons in a photosensitive material (the photoresist). This process leads to polymerization by activating photo-initiators in the resist. It is an incredibly accurate method of photopolymerizing resins, hence why it is used in these microelectronic applications.
“In this paper we introduced a new photosensitive resin doped with an organic semiconductor material to fabricate highly conductive 3D microstructures with high-quality structural features via MPL process,” said Mohammad Reza Abidian, associate professor of Biomedical Engineering at the university.
“The excellent electrical conductivity can be attributed to the presence of OS in the cross-linked polymer chains, providing both ionic and electronic conduction pathways along the polymer chains.”
Using the organic semiconductor resins, the team were able to produce a range of microelectronic devices including a circuit board consisting of several elements including the board, and an array of micro capacitors.
According to the paper, by including 0.5% (by weight) OS in the resin they were able to enhance the electrical conductivity of the composite polymer by about 10 orders of magnitude when compared to other MPL-based methods.
In addition to making the photo-chemicals electrically conductive, they researchers have successfully added bioactive molecules such as laminin and glucose oxidase into the OS composite microstructures (OSCMs).
To confirm that the bioactivity of laminin was retained throughout the entire MPL process, primary mouse endothelial cells were cultured on organic semiconductor composite microstructures. Cells seeded on laminin incorporated structures displayed evidence of adherence to substrate, proliferation, and enhanced survival.
The team has also been able to manufacture a glucose biosensor. Glucose oxidase, an enzyme for the specific recognition of glucose, was encapsulated within the solidified organic semiconductor composite microelectrodes via the MPL process.
The biosensor offered a highly sensitive glucose sensing platform with nearly 10-fold higher sensitivity compared to previous glucose biosensors.
“We anticipate that the presented MPL-compatible OS composite resins will pave the path towards production of soft, bioactive, and conductive microstructures for various applications in the emerging fields of flexible bioelectronics, biosensors, nanoelectronics, organ-on-chips, and immune cell therapies,” said Abidian.
The paper has been published with the title “Multiphoton Lithography of Organic Semiconductor Devices for 3D Printing of Flexible Electronic Circuits, Biosensors, and Bioelectronics” and can be found in the Advanced Materials journal at this link, if you’d like to read more about it.
