Page 26 - IJB-10-2

International Journal of Bioprinting PEDOT/PSS-based sensors

of the material’s properties, researchers explored toward exploring and optimizing multi-component
techniques such as screen printing, which allowed for printing inks. This progression involved the incorporation
controlled deposition of PEDOT:PSS patterns, enabling of additional components, such as CNTs and graphene, to
the fabrication of more intricate and tailored sensors. enhance various aspects of the sensors. The integration of
Coincidentally, the breakthrough occurred with the CNTs into PEDOT:PSS formulations leads to the creation
advent of 3D printing technology, which revolutionized of composite inks that offer improved sensing repeatability
the sensor fabrication process in a few ways: (i) allowing and enhanced bending stability. These enhancements
the deposition of PEDOT:PSS in controlled patterns and stem from the unique properties of CNTs, such as their
precise locations, (ii) fabricating sensors with improved excellent electrical conductivity and mechanical strength.
spatial resolution, (iii) reducing waste, and (iii) allowing Likewise, graphene/PEDOT:PSS composite inks have
on-demand fabrication. Direct ink writing, inkjet printing, been developed to leverage the exceptional electrical,
and DLP techniques have found promising applications in mechanical, and thermal properties of graphene. The
the realm of PEDOT:PSS-based sensors. These techniques synergistic effects of combining graphene with PEDOT:PSS
enable the rapid creation of intricate sensor patterns with contribute to sensors with enhanced sensitivity, response
high resolution and versatility in design. As 3D printing time, and stability. The shift from single-component
technologies continue to evolve, it is expected that sensor to multi-component ink formulations highlights the
performance, resolution, and complexity will continue drive to harness the strengths of various materials for
to improve. Innovations in material formulations, ink optimized sensor performance. This evolution showcases
development, and integration with emerging technologies the innovative approach in sensor development, where the
like Internet of Things (IoT) and flexible electronics judicious selection and combination of materials lead to
will likely drive the next wave of PEDOT:PSS-based sensors with advanced capabilities and improved reliability.
sensor applications.
5.4. Function: from single function to multi-function
5.2. Substrate: from polymer to flexible paper The functionalities of PEDOT:PSS-based sensors have
The substrate for PEDOT:PSS-based sensors has undergone a remarkable evolution from singular capabilities
undergone notable evolution over time. In the early stages, to multi-functional versatility. Initially, these sensors
conventional substrates like polyethylene terephthalate started as single-purpose devices, such as pressure and
were commonly used. However, as the focus shifted strain sensors, providing specific insights into mechanical
toward creating flexible and wearable sensors, there was interactions. However, advancements in technology have
a transition to substrates that offered both hydrophilicity driven a leap toward multi-functionality. From the early
and flexibility. Hydrophilic and flexible paper-based pressure and strain sensors, the field expanded to include
substrates emerged as a preferred choice. This shift to paper stretchable versions of these sensors, enabling them to
substrates not only enhances the adaptability of the sensors withstand deformation while retaining their sensing
for wearable applications but also aligns with the growing capabilities. This development marked a significant
interest in eco-friendly and biodegradable materials. The breakthrough in wearable and flexible electronics,
utilization of paper substrates not only contributes to allowing sensors to be seamlessly integrated into various
the comfort and conformance of the sensors to different applications. Furthermore, the expansion into multiple
surfaces but also reflects the broader trend of integrating parameters has been a noteworthy trend. Sensors that were
sustainable materials into sensor fabrication processes. once limited to single measurements, such as temperature
This evolution in substrate selection demonstrates the or humidity, have now evolved into dual-response sensors,
dynamic nature of PEDOT:PSS-based sensor technology, simultaneously detecting both temperature and humidity
driven by the pursuit of enhanced functionality, comfort, changes. This expanded functionality is particularly useful
and environmental consciousness. in applications where correlated data provides a more
comprehensive understanding of the environment. In the
5.3. Materials composition: from single to realm of biometric sensing, PEDOT:PSS-based sensors
multi-component have exhibited a similar trend toward multi-functionality.
The composition of PEDOT:PSS-based printing inks has Some sensors are engineered to simultaneously monitor
also undergone substantial changes, evolving from single- multiple biochemical markers, enabling the comprehensive
component formulations to more sophisticated multi- assessment of physiological conditions. For instance,
component formulations. In the early stages, PEDOT:PSS sensors are designed to detect glucose, glutamate, and
with inherent conductivity was commonly used as the lactate simultaneously, enabling comprehensive metabolic
primary component for sensor fabrication. As the demand insights. Moreover, the integration of different sensing
for improved sensor performance grew, there was a shift modalities has led to the development of sensors capable

Volume 10 Issue 2 (2024) 18 doi: 10.36922/ijb.1725