Correction: Printable and flexible electronics: from TFTs to bioelectronic devices

Correction for 'Printable and flexible electronics: from TFTs to bioelectronic devices' by M. Magliulo et al., J. Mater. Chem. C, 2015, 3, 12347–12363

Enhanced stability of organic field-effect transistor biosensors bearing electrosynthesized ZnO nanoparticles

Herein electrosynthesized ZnO nanoparticles (ZnO NPs) agents to largely improve functional bio-interlayer organic field-effect transistor (FBI-OFET) biosensors stability are investigated. For a proof-of-principle, streptavidin (SA) was chosen as the capturing biomolecule to sense biotin and poly-3-hexylthiophene (P3HT) served as channel material. The ZnO NPs were prepared and integrated into the FBI-OFET architecture by means of a straightforward and versatile procedure. To this end, ZnO NPs were mixed with an SA solution and the resulting aqueous suspension was readily spin-coated onto the SiO2gate dielectric. The P3HT film was spin-coated on the SA-ZnO NPs layer afterwards with the whole fabrication procedure taking no more than 30 min. The FBI-OFET biosensors bearing the ZnO NPs exhibited a shelf life exceeding one year, while the bare ones failed to work after few weeks. Moreover, the ZnO NPs enabled a two orders of magnitude increase in field-effect mobility while the already proven very good sensing performances were retained. The electrical and XPS characterization of the ZnO NPs based functional bio-interlayer provided information about the role of the nanostructured oxide on the improved device stability and a plausible mechanism for this occurrence is derived accordingly

Organic bioelectronics probing conformational changes in surface confined proteins

The study of proteins confined on a surface has attracted a great deal of attention due to its relevance in the development of bio-systems for laboratory and clinical settings. In this respect, organic bio-electronic platforms can be used as tools to achieve a deeper understanding of the processes involving protein interfaces. In this work, biotin-binding proteins have been integrated in two different organic thin-film transistor (TFT) configurations to separately address the changes occurring in the protein-ligand complex morphology and dipole moment. This has been achieved by decoupling the output current change upon binding, taken as the transducing signal, into its component figures of merit. In particular, the threshold voltage is related to the protein dipole moment, while the field-effect mobility is associated with conformational changes occurring in the proteins of the layer when ligand binding occurs. Molecular Dynamics simulations on the whole avidin tetramer in presence and absence of ligands were carried out, to evaluate how the tight interactions with the ligand affect the protein dipole moment and the conformation of the loops surrounding the binding pocket. These simulations allow assembling a rather complete picture of the studied interaction processes and support the interpretation of the experimental results

About the amplification factors in organic bioelectronic sensors

A systematic comparison between electrochemical and organic bioelectronic sensors reveals a unified rational description for a transistor amplified detection

Vapor sortion in the polymeric films

Sorption of Volatile Organic Compounds (VOCs) in polymer films and the ensuing physicochemical interactions between polymer and analyte are important phenomena in applications concerning chemical sensors. The principle of various sensors is based on the swelling of polymers in the presence of VOCs resulting in a change of a physical property. The main objective of this work is the evaluation of the sorption properties of a series of polymers since the need for proper sensing layer is very important in gas sensing applications. Thickness changes of polymers in the form of supported films due to absorption of vapors by applying white light reflectance spectroscopy (WLRS) was studied. The polymers tested include three members of a homologous series of relatively hydrophobic poly (alkyl methacrylates), the hydrophilic poly (2-hydroxyethyl methacrylate) and two poly (dimethylsiloxane-co-diphenylsiloxane) copolymers. The thickness expansion of supported films upon exposure to different activities of four vapors of varying polarity and hydrogen bonding ability (methanol, ethanol, ethyl acetate and water) was studied. The deduced sorption isotherms were fitted to the Flory-Huggins equation and interaction parameters χ, as well as solubility coefficients S at infinite solute dilution were deduced for each binary system. After the evaluation of the swelling behavior of the polymeric materials, four of them have been chosen to be used as sensitive layers in capacitance type chemical sensors. The selected polymers used in the array are PBMA, P(DMS-co-DPhS) -OH PHEMA PEI. Chemocapacitive sensors are based on changes in the dielectric properties of the sensing material due to sorption of analytes. The capacitance responses of a four InterDigital Chemocapacitive (IDC) sensor array upon exposure to various concentrations of four analytes and of their binary mixtures are presented. Reproducible and reversible changes were found for the exposure to all vapors. At low vapor concentrations and/or low analyte sorption in the polymer layer the capacitance response of each sensor may be considered linear with vapor concentration. The normalized capacitance response was correlated with estimated values of the capacitance change based on the permittivities ε of each mixture component (polymer/analyte) and the volume fractions of the sorbed analytes using Clausius Mossoti mixing rule equation. The volume fractions derived from the interaction parameters. The theoretical model is capable of predicting the response of the sensors. The capacitance response AC of the sensor array to binary mixtures of the four analytes was also studied showing that it could be approximated by the sum of the pure components responses. The responses are fairly reproducible and reversible thus, allowing detection of each components removal from the mixture. The behavior of sensors based on PBMA and PHEMA filled with BaTiΟ₃ was studied. The deposited polymer/BaTiΟ₃ films were characterized by microscopy showing that nanoparticles are better dispersed into the PBMA matrix. In all cases the ε of the composite increased with the increase of the filler following the Lichtenecker “loglaw” relationship. This indicates that the logarithm of the composite’s ε is linearly proportional to the volume fraction of BaTiΟ₃. The initial capacitance values for each composite used as sensitive layers on the chemocapacitors showed the same trend. Incorporation of BaTiΟ₃ in the sensing layer results in increased initial capacitance CP. With increasing amount of BaTiΟ₃ load the response ΔC to each analyte is increased.Η εργασία αφορά στη μελέτη ρόφησης οργανικών ατμών και υδρατμών σε πολυμερικά υμένια και στην εφαρμογή των φαινομένων αυτών στην ανάπτυξη και αξιολόγηση της λειτουργίας χημικών αισθητήρων. Η αρχή λειτουργίας πολλών τύπων χημικών αισθητήρων αερίων βασίζεται στην διάχυση του αερίου στο πολυμερές. Η εργασία επιχειρεί να συμβάλλει στην εκλογικευμένη ανάπτυξη αισθητήρων αερίων τύπου χημειοπυκνωτών και περιλαμβάνει τα έξης στάδια: (i) Χαρακτηρισμό της ροφητικής ικανότητας μιας σειράς πολυμερών σε τέσσερεις αναλυτές. (ii) Επιλογή, με βάση την παραπάνω μελέτη πολυμερών για την κατασκευή συστοιχίας τεσσάρων χημειοπυκνωτών και αξιολόγηση των αποκρίσεών τους σε διάφορες συγκεντρώσεις των αναλυτών. (iii) Συσχέτιση των πειραματικών αποκρίσεων με τις αναμενόμενες μεταβολές στην χωρητικότητα του πυκνωτή βάσει της υπολογιζόμενης διηλεκτρικής σταθεράς του μίγματος πολυμερούς-αναλυτή. (iv) Ανάπτυξη σύνθετων πολυμερικών υλικών με τον εμπλουτισμό των ΡΗΕΜΑ και ΡΒΜΑ με BaTiΟ₃ και μελέτη των υλικών αυτών ως αισθητήρια υλικά. i) Ο χαρακτηρισμός της ροφητικής ικανότητας των πολυμερικών υλικών παρουσία ατμών οργανικών ενώσεων και υδρατμών πραγματοποιήθηκε με την μέθοδο της οπτικής συμβολομετρίας ευρέος φάσματος. Τα πολυμερή που μελετήθηκαν είναι ΡΜΜΑ, ΡΒΜΑ, PiBMA, ΡΗΕΜΑ [P(DMS co DPhS) - OH και P(DMS co DPhS) –vinyl. Οι αναλυτές είναι νερό μεθανόλη, αιθανόλη, οξεικός Αιθυλεστέρας. Ο χαρακτηρισμός κάθε συστήματος βασίστηκε στις ισόθερμες ροφήσεως. Στις ισόθερμες έγινε προσαρμογή της εξίσωσης Flory-Huggins. Προσδιορίσθηκε για κάθε σύστημα ο παράγοντας αλληλεπίδρασης χ ο συντελεστής διαλυτότητας σε άπειρη αραίωση S. O S αυξάνεται με τη μείωση της διαφοράς μεταξύ των παραμέτρων διαλυτότητας αναλυτή πολυμερούς (δαναλύτη-δπολυμερούς). Επίσης συγκρίθηκαν τα αποτελέσματα της οπτικής συμβολομετρίας με κλασικές σταθμικές μεθόδους. ii) Επιλέγοντας τέσσερα πολυμερή (ΡΒΜΑ P(DMS-co-DPhS)-OH ΡΗΕΜΑ, PEI) κατασκευάστηκε συστοιχία 4 αισθητήρων χωρητικότητας αλληλεπικαλυπτομένων ηλεκτροδίων με τεχνικές μικροηλεκτρονικής. Οι πειραματικές τιμές των αρχικών χωρητικοτήτων των χημειοπυκvωτών συμφωνούν ικανοποιητικά με θεωρητικό υπολογισμό της χωρητικότητας πυκνωτών τέτοιου τύπου. Πραγματοποιήθηκαν μετρήσεις χωρητικότητας σε ένα εύρος συγκεντρώσεων (1000 20000ppm) για όλους τους αναλυτές. Οι αισθητήρες παρουσίασαν αναπαραγωγιμότητα, αντιστρεψιμότητα, επαναληπτικότητα, σταθερότητα με το χρόνο και γραμμική συμπεριφορά με τη συγκέντρωση του αναλυτή στην περιοχή των χαμηλών συγκεντρώσεων. iii) Οι αποκρίσεις των αισθητήρων συσχετίσθηκαν με αναμενόμενες μεταβολές στην χωρητικότητα του πυκνωτή βάσει της υπολογιζόμενης διηλεκτρικής σταθεράς του μίγματος πολυμερούς αναλυτή λόγω ρόφησης του αναλυτή. Με την επεξεργασία αυτή είδαμε ότι αναπαράγεται: α) η σειρά εκλεκτικότητας των αισθητήρων ως προς 3 αναλυτές, β) η αύξηση της απόκρισης με την συγκέντρωση του αναλυτή. Η συστοιχία μετρήθηκε παρουσία ισομοριακών δυαδικών μιγμάτων των αναλυτών. Οι αισθητήρες αντιλαμβάνονται την παρουσία/απουσία του κάθε συστατικού και οι αποκρίσεις στα μίγματα ήταν ίσες με το άθροισμα των αποκρίσεων των καθαρών συστατικών. iv) BaTiΟ₃ ενσωματώθηκε στην πολυμερική μήτρα για να αυξήσει την αρχική χωρητικότητα τουαισθητήρα και κατ’ επέκταση την απόκρισή του. Ο χαρακτηρισμός της μορφολογίας των υμενίων των σύνθετων έδειξε ότι το BaTiΟ₃ διασπείρεται καλύτερα στο ΡΒΜΑ απ’ ότι στο ΡΗΕΜΑ. Οι πειραματικές τιμές της διηλεκτρικής σταθεράς των σύνθετων ακολουθούν τη λογαριθμική εξίσωση Lichtenecker. Ο λογάριθμος της ε του σύνθετου έχει γραμμική σχέση με την συγκέντρωση του BaTiΟ₃. Ανάλογη συμπεριφορά παρατηρήθηκε και στις αρχικές χωρητικότητες των πυκνωτών με σύνθετα αισθητήρια υλικά. Οι αποκρίσεις AC των αισθητήρων με σύνθετα παρουσία των τεσσάρων αναλυτών αυξάνονται με την αύξηση της συγκέντρωσης του BaTiΟ₃

Electronic biosensors based on EGOFETs

There is an increasing interest for low cost, ultrasensitive, time saving yet reliable, point-of-care bioelectronic sensors. Electrolyte gated organic field effect transistors (EGOFETs) are proven compelling transducers for various sensing applications, offering direct electronic, label-free transduction of bio-recognition events along with miniaturization, fast data handling and processing. Given that field effect transistors act as intrinsically signal amplifiers, even a small change of a chemical or biological quantity may significantly alter the output electronic signal. In EGOFETs selectivity can be guaranteed by the immobilization of bioreceptors able to bind specifically a target analyte. The layer of receptors can be linked to one of the electronic active interfaces of the transistor, and the interactions with a target molecule affect the electronic properties of the device. The present chapter discusses main aspects of EGOFETs transducers along with detailed examples of how to tailor the device interfaces with desired functionality. The development of an “electronic tongue” based on an EGOFET device coupled to odorant binding proteins (OBPs) for enantiomers differentiation is presented

Organic field-effect transistor sensors: a tutorial review

The functioning principles of electronic sensors based on organic semiconductor field-effect transistors (OFETs) are presented. The focus is on biological sensors but also chemical ones are reviewed to address general features. The field-induced electronic transport and the chemical and biological interactions for the sensing, each occurring at the relevant functional interface, are separately introduced. Once these key learning points have been acquired, the combined picture for the FET electronic sensing is proposed. The perspective use of such devices in point-of-care is introduced, after some basics on analytical biosensing systems are provided as well. This tutorial review includes also a necessary overview of the OFET sensing structures, but the focus will be on electronic rather than electrochemical detection. The differences among structures are highlighted along with the implications on the performance level in terms of key analytical figure of merits such as: repeatability, sensitivity and selectivit

Tailoring Functional Interlayers in Organic Field-Effect Transistor Biosensors

This review aims to provide an update on the development involving dielectric/organic semiconductor (OSC) interfaces for the realization of biofunctional organic field-effect transistors (OFETs). Specific focus is given on biointerfaces and recent technological approaches where biological materials serve as interlayers in back-gated OFETs for biosensing applications. Initially, to better understand the effects produced by the presence of biomolecules deposited at the dielectric/OSC interfacial region, the tuning of the dielectric surface properties by means of self-assembled monolayers is discussed. Afterward, emphasis is given to the modification of solid-state dielectric surfaces, in particular inorganic dielectrics, with biological molecules such as peptides and proteins. Special attention is paid on how the presence of an interlayer of biomolecules and bioreceptors underneath the OSC impacts on the charge transport and sensing performance of the device. Moreover, naturally occurring materials, such as carbohydrates and DNA, used directly as bulk gating materials in OFETs are reviewed. The role of metal contact/OSC interface in the overall performance of OFET-based sensors is also discussed

Electrolyte-gated organic transistors for biosensing applications

The interfacing of biomaterials to electronic devices is one of the most challenging research fields that has relevance to both fundamental studies and the development of highly performing biosensors. Important aspects connected to the field of biosensors based on electrolyte-gated organic transistors are discussed. The main features of biomolecules used as recognition elements along with the strategies reported so far for their deposition on the biosensors transducer surface are presented. An introduction of the involving surface interactions such as covalent binding, physical adsorption, self-assembly and bio-affinity binding strategy is given. Besides, the most relevant surface materials for electronic biosensors development are analysed. In the last part, different electronic biosensors based on electrolyte-gated organic transistors are presented. Particular attention is paid to the biosensors operation mechanism and to the analytical figure of merits. Specific applications such as DNA and proteins detection are also discussed