There is considerable interest in the design and development of conjugated polymers for interfacing a variety of electronic biomedical devices. These materials are able to accommodate both electronic ...and ionic transport. We discuss some of the issues associated with these materials, and consider opportunities for future developments.
Pushing the boundaries: The design and development of conjugated polymers for interfacing a variety of electronic biomedical devices continues to garner a lot of research interest. These materials are able to accommodate both electronic and ionic transport, but there remains to be some issues associated with such materials, as discussed in this Concept article.
This paper presents the development of alkali metal ion selective small molecules and conjugated polymers for optical ion sensing. A crown ether bithiophene unit is chosen as the detecting unit, as ...both a small molecule and incorporated into a conjugated aromatic structure. The complex formation and the resulting backbone twist of the detector unit is investigated by UV–vis and NMR spectroscopy where a remarkable selectivity toward sodium or potassium ions is found. X‐ray diffraction analysis of single crystals with and without alkali metal ions is carried out and a difference of the dihedral angle of more than 70° is observed. In a conjugated polymer structure, the detector unit has a higher sensitivity for alkali metal ion detection than its small molecule analog. Ion selectivity is retained in polymers with solubility in polar solvents facilitated by the attachment of polar ethylene glycol side chains. This design concept is further evolved to develop a sodium‐salt solid state sensor based on blends of the detecting polymer with a polyvinyl alcohol matrix where the detection of sodium ions is achieved in aqueous salt solutions with concentrations similar to biologically important environments.
Let's twist: Ion selective small molecules and conjugated polymers undergo a backbone twist in sodium‐ or potassium‐salt solutions. The color change of the polymers is detectable by the human eye and conjugated polymers have a higher sensitivity for ion detection compared to their analogous small molecule. Solid state sensors based on these polymers can detect alkali metal ions in aqueous solutions.
Abstract
Cochlear implants restore hearing in patients with severe to profound deafness by delivering electrical stimuli inside the cochlea. Understanding stimulus current spread, and how it ...correlates to patient-dependent factors, is hampered by the poor accessibility of the inner ear and by the lack of clinically-relevant in vitro, in vivo or in silico models. Here, we present 3D printing-neural network co-modelling for interpreting electric field imaging profiles of cochlear implant patients. With tuneable electro-anatomy, the 3D printed cochleae can replicate clinical scenarios of electric field imaging profiles at the off-stimuli positions. The co-modelling framework demonstrated autonomous and robust predictions of patient profiles or cochlear geometry, unfolded the electro-anatomical factors causing current spread, assisted on-demand printing for implant testing, and inferred patients’ in vivo cochlear tissue resistivity (estimated mean = 6.6 kΩcm). We anticipate our framework will facilitate physical modelling and digital twin innovations for neuromodulation implants.
Devices interfacing with biological tissues can provide valuable insights into function, disease, and metabolism through electrical and mechanical signals. However, certain neuromuscular tissues, ...like those in the gastrointestinal tract, undergo significant strains of up to 40%. Conventional inextensible devices cannot capture the dynamic responses in these tissues. This study introduces electrodes made from poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and polydimethylsiloxane (PDMS) that enable simultaneous monitoring of electrical and mechanical responses of gut tissue. The soft PDMS layers conform to tissue surfaces during gastrointestinal movement. Dopants, including Capstone FS-30 and polyethylene glycol, are explored to enhance the conductivity, electrical sensitivity to strain, and stability of the PEDOT:PSS. The devices are fabricated using shadow masks and solution-processing techniques, providing a faster and simpler process than traditional clean-room-based lithography. Tested on ex vivo mouse colon and human stomach, the device recorded voltage changes of up to 300 µV during contraction and distension consistent with muscle activity, while simultaneously recording resistance changes of up to 150% due to mechanical strain. These devices detect and respond to chemical stimulants and blockers, and can induce contractions through electrical stimulation. They hold great potential for studying and treating complex disorders like irritable bowel syndrome and gastroparesis.
Spinal cord injuries have devastating consequences for humans, as mammalian neurons of the central nervous system (CNS) cannot regenerate. In the peripheral nervous system (PNS), however, neurons may ...regenerate to restore lost function following injury. While mammalian CNS tissue softens after injury, how PNS tissue mechanics changes in response to mechanical trauma is currently poorly understood. Here we characterised mechanical rat nerve tissue properties before and after in vivo crush and transection injuries using atomic force microscopy-based indentation measurements. Unlike CNS tissue, PNS tissue significantly stiffened after both types of tissue damage. This nerve tissue stiffening strongly correlated with an increase in collagen I levels. Schwann cells, which crucially support PNS regeneration, became more motile and proliferative on stiffer substrates in vitro, suggesting that changes in tissue stiffness may play a key role in facilitating or impeding nervous system regeneration.
Organic electrochemical transistors (OECTs) are receiving a great deal of attention as amplifying transducers for electrophysiology. A key limitation of this type of transistors, however, lies in the ...fact that their output is a current, while most electrophysiology equipment requires a voltage input. A simple circuit is built and modeled that uses a drain resistor to produce a voltage output. It is shown that operating the OECT in the saturation regime provides increased sensitivity while maintaining a linear signal transduction. It is demonstrated that this circuit provides high quality recordings of the human heart using readily available electrophysiology equipment, paving the way for the use of OECTs in the clinic.
The working principle of a voltage amplifier based on an organic electrochemical transistor is demonstrated. By implementing a drain load resistor, a voltage to voltage transduction can be achieved with an amplification of up to 30 V/V, paving the way for a direct implementation in the clinic as an active organic electrode for electrophysiological activity.
Electrophoretic drug delivery devices are able to deliver drugs with exceptional temporal and spatial precision. This technology has emerged as a promising platform for treating pathologies ranging ...from neuropathic pain to epilepsy. As the range of applications continues to expand, there is an urgent need to understand the underlying physics and estimate materials and device parameters for optimal performance. Here, computational modeling of the electrophoretic drug delivery device is carried out. Three critical performance indices, namely, the amount of drug transported, the pumping efficiency and the ON/OFF ratio are investigated as a function of initial drug concentration in the device and fixed charge concentration in the ion exchange membrane. The results provide guidelines for future materials and device design with an eye towards tailoring device performance to match disease-specific demands.
The field‐effect mobility of pentacene transistors saturates when six monolayers of pentacene are deposited on the gate dielectric. This saturation is not caused by the formation of islands, as the ...early stages of growth have been found to take place in a layer‐by‐layer fashion, and layer completion continues well past six monolayers (see Figure).
Recent interest in bioelectronics has prompted the exploration of properties of conducting polymer films at the interface with biological milieus. Poly(3,4-ethylenedioxythiophene) doped with ...poly(styrenesulfonate) (PEDOT:PSS) from a commercially available source has been used as a model system for these studies. Different cross-linking schemes have been used to stabilize films of this material against delamination and redispersion, but the cost is a decrease in the electrical conductivity and/or additional heat treatment. Here we introduce divinylsulfone (DVS) as a new cross-linker for PEDOT:PSS. Thanks to the higher reactiveness of the vinyl groups of DVS, the cross-linking can be performed at room temperature. In addition, DVS does not reduce electronic conductivity of PEDOT:PSS but rather increases it by acting as a secondary dopant. Cell culture studies show that PEDOT:PSS:DVS films are cytocompatible and support neuroregeneration. As an example, we showed that this material improved the transconductance value and stability of an organic electrochemical transistor (OECT) device. These results open the way for the utilization of DVS as an effective cross-linker for PEDOT:PSS in bioelectronics applications.
Recording neural activity during neurosurgical interventions is an invaluable tool for both improving patient outcomes and advancing our understanding of neural mechanisms and organization. However, ...increasing clinical electrodes' signal‐to‐noise and spatial specificity requires overcoming substantial physical barriers due to the compromised metal electrochemical interface properties. The electrochemical properties of poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) based interfaces surpass those of current clinical electrocorticography electrodes. Here, robust fabrication process of PEDOT:PSS microelectrode arrays is demonstrated for safe and high fidelity intraoperative monitoring of human brain. PEDOT:PSS microelectrodes measure significant differential neural modulation under various clinically relevant conditions. This study reports the first evoked (stimulus‐locked) cognitive activity with changes in amplitude across pial surface distances as small as 400 µm, potentially enabling basic neurophysiology studies at the scale of neural micro‐circuitry.
The superiority of organic electrodes in mapping human brain activity under various clinical conditions is demonstrated. The improved electrode characteristics allow recording of changes in cognitive activity on the sub‐millimeter scale. The great spatial specificity possible with poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) microelectrodes and the reliable discrimination between and within language modalities underscore PEDOT:PSS's potential for standard electrocorticography clinical practice to maximize outcome for patient care.
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