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International Journal of Bioprinting 3D printing and 3D-printed electronics in smart drug delivery devices

Figure 8. (a) 3D-printed rigid and hard stereolithography-printed body with a soft and flexible thermoplastic polyurethane (TPU) blister being 3D printed
on top. (b) Photo of the hybrid soft and hard multi-material microfluidic pump with fingered power actuation. (Reprinted with permission from [129] .)

methods of triggering drug release through the use of delivery system with locally incorporated drug depots,
special 3D-printed designs. In one such example, 3D which can be selectively placed within a printed drug
printing was used to fabricate oral drug capsule, which was delivery matrix, was fabricated using hybrid 3D printing.
designed to safely break and release the stored drug under Vat-based 3D printing was used to fabricate the drug
the physiological pressures of the antropyloric region in the delivery matrix, and droplet-based 3D printing was used to
gastrointestinal tract [127] . This allows for the drug release deposit the drug depots. This drug delivery system allowed
to be targeted at that region. The customizability of the for the customization of the drug release profile as well as
dimensions and design of the printed capsule through the multiple drug releases by controlling the position, size and
use of 3D printing allows for pressure at which the capsule type of drug depots [131] . The use of hybrid 3D printing in
will break to be easily changed for other purposes [128] . smart drug delivery devices, however, has been limited.
However, currently the use of 3D printing has mostly been Hybrid 3D printing has also been applied to the fabrication
limited to single material or single 3D printing process of some electronic healthcare devices. However, most of the
fabrication. This has limited the type of components that electronic components are not printed but are placed on to
can be fabricated. A way to overcome this is the use of the device [132] . These pick-and-place methods of fabricating
multi-material or multiple different 3D printing processes, 3D-printed electronics devices use the traditional hard
also known as hybrid or multi-process 3D printing, in a and rigid electronic components. By using this method,
singular fabrication process. Hybrid 3D printing allows for not only would the customizability of the design of the
the printing and fabrication of multiple different materials product be limited, but it would also negatively impact the
and designs, some of which are difficult for a singular 3D flexibility and conformity of the devices as the electronic
process to achieve. This allows for the combination of the components might delaminate from the substrate [133] . Thus,
different advantages brought about by using different 3D 3D-printed electronics could be used in order to overcome
printing methods. The use of different 3D printing methods such issues. The future trends or direction of the use of
also allows for materials with drastically different properties, 3D-printed electronics in smart drug delivery devices will
such as a soft, flexible material and a hard, rigid material, to be explored in the next section.
be fabricated into a single product (Figure 8) [129] . This allows 4.2. Future trends in smart drug delivery devices for
for a higher degree of customization in terms of the design 3D-printed electronics
and application of the printed part as a greater number of As discussed in previous sections, flexible electronics
different materials can be used. The use of hybrid and multi- has clearly demonstrated rapid progress and its unique
material 3D printing also allows for more parts of a product advantages for a plethora of drug delivery applications.
to be fabricated using 3D printing due to the improved These features have offered several benefits, such
customization and freedom in material selection and design.
as minimally invasive acute delivery methods for
Currently, hybrid 3D printing has some applications in implantation, small size, easy manipulation, enhanced
traditional drug delivery devices, such as the fabrication of performance, reduced immune response as well as
liquid-filled solid capsules using alternating extrusion and greater compatibility with the in vivo systems. However,
droplet-based 3D printing [130] . In another example, a drug a few aspects need to be carefully considered. In case of

Volume 9 Issue 4 (2023) 157 https://doi.org/10.18063/ijb.725