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

typically use material removal methods from a larger block This is to facilitate the delivery of drugs into chronic
to fabricate the products, leading to material wastage and wounds. The thickness of the crust and necrotic tissue of
increased cost. The layer-by-layer fabrication method of a chronic wound differs with time, type and stage of the
3D printing only deposits printing material as needed. wound. By having customizable length of microneedle, the
This leads to minimal waste generated from the fabrication needles could pierce and deliver drugs under the wound
process. 3D printing has also been used for prototyping or crust and necrotic tissue. This would help increase the
testing of product design . As 3D printing can be used for bioavailability of the drugs within the deeper layers of the
[39]
the fabrication of small quantity of products on demand, wound, improving the treatment of chronic wounds.
it allows for prototypes or products with different design The customizability of 3D printing has also been used
changes to be easily fabricated. These products can be used to fabricate specially designed features to be used with
for testing or for physical visualization of how the final microneedles for smart drug delivery. In one such example,
product would be. vat-based 3D printing was used to fabricate a microneedle
[42]
2.2. 3D-printed parts for integration with electronics patch which contained microfluidic channels . The
3D printing can be applied to smart drug delivery devices microfluidic channels were connected to a specialized
which contain electronics in various ways. These includes mixing channel which would allow for the content flowing
the use of 3D printing to fabricate different parts, casings from the different microfluidic channels to mix before being
or shells which are used with the electronic components delivered through the microneedles (Figure 1). For the
in smart drug delivery devices. This section covers 3D purposes of drug delivery, this would allow the mixing and
printing fabricated parts that are used for integration with combination of different drug compounds to be delivered
electronic components for smart drug delivery. The next to the patient. The patient would be able to receive multiple
section will cover casings and shells that are fabricated different drug treatment simultaneously without having
using 3D printing for containing electronic components in to go through complicated process of taking several drugs
smart drug delivery devices. separately. Additionally, by controlling the input flow rate of
the individual microfluidic channels, the final composition
There are a few different types of 3D-printed parts that
are fabricated to be integrated with electronic components of the mixed fluid can be changed. The mixed fluid can
then be transdermally delivered to the patient through the
which are used for smart drug delivery. One of them is microneedle patch attached to the end of the mixing channel.
3D-printed microneedles. These microneedles are often The 3D-printed microfluidic and mixing channels can also
used with microelectronic control systems or micropumps be used for drug testing of different drug compositions for
in order to control the on-demand release of drugs. In one development of drug therapies. In another work regarding
such example, a hollow microneedle array, which could 3D-printed microfluidic channels, 3D printing was used to
be attached to micro-electromechanical systems (MEMS) fabricate different microfluidic chips with varying channel
with integrated electronics and pumps, was fabricated using geometries and dimensions . Due to the customizability
[43]
vat-based 3D printing . This allows accurate control of of 3D printing, the different geometries and designs of the
[40]
the amount of drugs delivered through the microneedles. microfluidic chips can be easily fabricated. These differently
The hollow microneedle patch was specially designed and designed microfluidic chips were used to investigate and
fabricated using stereolithography. The microneedles were optimize the use of electrotactic drug delivery for drug-
designed to have an internal reservoir which is used to store loaded ionic liquid microdroplets. These ionic liquid
the liquid drug before distribution through the hollow microdroplets would then be used for drug delivery.
microneedles. The patch was also fabricated with a tubular
opening for connection to the pump. The microneedle 2.3. 3D-printed casing for containing electronics
combined with the MEMS allows for the controlled 3D printing has also been used to fabricate different casing
delivery of microliter volumes of drugs though a non- and shells for containing electronics for smart drug delivery
invasive transdermal route. In another example, hollow purposes. The customizability of 3D printing allows for
microneedle patches, which were integrated with wireless unique design of the casing which would be used to house
electronic control system and pumps, were fabricated the components of the drug delivery device, such as the
using extrusion-based 3D printing . The system is also drug reservoir, electronic sensors, and triggers. One area of
[41]
equipped with two separate reservoirs which can be used applications of these 3D-printed casings is in smart pills. Smart
to store and deliver different drugs. The wireless electronic pills use various different types of electronic components to
system allows for the control and delivery of separate sense and trigger the release of drugs from the pill. In one
release profile from the two different drugs. Through the such example, 3D printing was used to fabricate a pill which
use of 3D printing, the design of the microneedles, such as contained a miniature electrolytic pump connected to a drug
the needle length and spacing, can be easily customized. reservoir . When the drug is to be released from the pill, the
[44]

Volume 9 Issue 4 (2023) 147 https://doi.org/10.18063/ijb.725