Direct Measurement of Mass Transport in Actuation of Conducting Polymers Nanotubes. Annu Int Conf IEEE Eng Med Biol Soc 2018;2018:4472-4475. [PMID: 30441344 DOI: 10.1109/embc.2018.8513214]

Organic Semiconductor Nanotubes for Electrochemical Devices

Electrochemical devices that transform electrical energy to mechanical energy through an electrochemical process have numerous applications ranging from soft robotics and micropumps to autofocus microlenses and bioelectronics. To date, achievement of large deformation strains and fast response times remains a challenge for electrochemical actuator devices operating in liquid wherein drag forces restrict the actuator motion and electrode materials/structures limit the ion transportation and accumulation. We report results for electrochemical actuators, electrochemical mass transfers, and electrochemical dynamics made from organic semiconductors (OSNTs). Our OSNTs electrochemical device exhibits high actuation performance with fast ion transport and accumulation and tunable dynamics in liquid and gel-polymer electrolytes. This device demonstrates an excellent performance, including low power consumption/strain, a large deformation, fast response, and excellent actuation stability. This outstanding performance stems from enormous effective surface area of nanotubular structure that facilitates ion transport and accumulation resulting in high electroactivity and durability. We utilize experimental studies of motion and mass transport along with the theoretical analysis for a variable-mass system to establish the dynamics of the electrochemical device and to introduce a modified form of Euler-Bernoulli's deflection equation for the OSNTs. Ultimately, we demonstrate a state-of-the-art miniaturized device composed of multiple microactuators for potential biomedical application. This work provides new opportunities for next generation electrochemical devices that can be utilized in artificial muscles and biomedical devices.

Femtosecond Laser 3D-printing of Conductive Microelectronics for Potential Biomedical Applications

Development of soft and conductive micro devices represents a demanding research topic in various biomedical applications, particularly organic bioelectronics. Among various fabrication methods, two-photon polymerization (2PP) using a wide range of photocurable inks is a promising 3D printing technique for construction of structures in submicron resolution. Herein, we introduce a novel conductive photosensitive resin by using poly (3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) and poly(ethylene glycol) diacrylate), and fabricate 3D conductive polymeric microstructures via 2PP. In the developed resin, presence of PEDOT:PSS significantly enhances the electrical conductivity of microstructures (~ 10 orders of magnitude).Clinical Relevance- Conductive microdevices based on the PEDOT:PSS-doped resin open new avenues in a broad range of biomedical research areas including neural interfaces, biosensors, and bioelectronics.

Conducting Polymer Microtubes for Bioactuators

Conducting polymer (CP) actuators are promising devices for biomedical applications such as artificial muscles and drug delivery systems. Here, we report a tri-layer actuator based on poly(pyrrole) (PPy) microtubes (PPy MTs) doped with poly(sodium-p-styrenesulfonate) (PSS) and constructed on a passive layer of gold-coated poly-propylene (PP) film. The PPy MTs were fabricated using electrochemical deposition of PPy around poly(lactic-co-glycolic acid) (PLGA) fiber templates, followed by template removal. The PPy MTs were subjected to a redox process using cyclic voltammetry in 0.1 M NaPSS electrolyte solution as the potential was swept between -0.8 V and +0.4 V for 5 cycles at the scan rates of 10, 50, 100, and 200 mV/s. The bending behavior of the PPy MTs actuator was investigated by measuring the deflection of actuator tip resulting from the expansion/contraction strain of PPy MTs. The PPy MTs actuator showed a reversible bending movement during each potential cycle. The maximum deflection of actuator decreased by increasing the scan rate that was confirmed by calculating the actuation strain generated during each cycle at various scan rates.