Here we report the first demonstration of a biopolymer protonic field-effect transistor with proton-transparent PdH(x) contacts. In maleic-chitosan nanofibres, the. ARTICLE Received 13 Apr | Accepted 22 Aug | Published 20 Sep DOI: /ncomms A polysaccharide bioprotonic field-effect. Prof. Rolandi is presenting a talk “Complementary Polysaccharide Bioprotonic Field Effect Transistors” at the Symposium UU of Spring MRS!.
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Documents Flashcards Grammar checker. Artificial devices that can control and monitor ionic and protonic currents are thus an ideal means for interfacing with biological systems. Here we report the first demonstration of a biopolymer protonic field-effect transistor with proton-transparent PdHx contacts.
In maleic-chitosan nanofibres, the flow of protonic current is turned on or off by an electrostatic potential applied to a gate electrode. This study introduces a new class of biocompatible solid-state devices, which can control and monitor the flow of protonic current. This represents a step towards bionanoprotonics. Correspondence and requests for materials should be addressed to M.
Preeminent examples include ATP oxidative phosphorylation in mithochondria2, the HCVN1 voltage-gated proton channel3, light-activated proton pumping in bacteriorhodopsin4, and the proton-conducting single water file in the antibiotic gramicidin5.
In living systems, electrical signals are communicated and processed by modulating ionic6 and protonic currents7. In contrast, the development of computing has mainly focused on devices that control electronic currents such as vacuum tubes, solid-state fieldeffect transistors FETand nanoscale molecular structures8— Few examples of protonic-based devices exist, and include an ice FET working with AC current12, and a water bipolar junction transistor At the nanoscale, ionic and protonic conductivity has attracted increasing interest with the advent of resistive ionic memories14, memristors15,16, synaptic transistors17, and nanofluidics18— In hybrid bionanodevices, biological multifunctionality has been added to carbon nanotubes21 or silicon nanowires22 with transmembrane proton conductive proteins.
Bionanoelectronic devices23 that can control the current of ions and protons—a more appropriate language than electrons in nature24—are uniquely positioned. In this regard, nanofluidics devices are particularly attractive. However, these require microscopic liquid reservoirs, and current control at physiological concentration is limited to difficult-to-fabricate nanometer channels Recently, conducting polymer ion bipolar junction transistor devices have been demonstrated25, Most chitin derivatives are biodegradable, nontoxic, and physiologically inert Palladium is chosen as the contact material for its ability to form proton-conducting PdHx on exposure to hydrogen PdHx affords proton exchange between the contacts and the maleic—chitosan channel without electrolysis.
The SiO2 nm gate dielectric insulates the maleic—chitosan and the contacts from the Si electrostatic back gate.
When a bias is applied between the contacts, the current increases with relative humidity and polysaccharide hydration level Fig. Measurements using hydrogen-depleted Pd or Au contacts—both proton blocking—record a considerably smaller current Supplementary Fig.
It is important to note that both Au and Pd are significantly better electronic conductors than PdHx. Increase in protonic conductivity with hydration level is common in other biological macromolecules such as collagen29, cellulose30 and keratin A higher level of water absorption creates more proton-conducting hydrogen-bond chains HBC that serve as proton wires2 for Grotthus type transfer to occur Fig.
In maleic—chitosan, we propose that the protons responsible for the current as hydronium ions in the HBC originate from the polysaccharide maleic acid groups, some of which are deprotonated Fig.
The protonic conductivity in chitin Supplementary Fig. S1which has no maleic groups, is significantly lower than in the maleic—chitosan derivative. As expected for a semiconducting FET with predominantly positive charge carriers, a negative Vgs results in a higher sourcedrain current for the same Vds, whereas a positive Vgs almost turns Ids off. In most materials, protons have to overcome activation energy in the range of 0. This behaviour is often referred to as protonic semi-conductivity.
A polysaccharide bioprotonic field-effect transistor. – Semantic Scholar
However, in highly conducting proton wires, such as in gramicidin, the activation energy associated with transport is very small5. This suggests that highly efficient biopritonic wires are formed in the material. The intra- and inter-molecular hydrogen bonds as well as the hydrogen bonds between the water of hydration and the polar parts of the molecule form a continuous network comprised by hydrogen-bond chains.
For device with PdHx contacts shown in Figure 1. The charge per unit area induced onto the channel is directly proportional to Vgs through the gate capacitance per unit area, Cg. To create that charge, excess protons are injected into the maleic—chitosan via the proton transparent contacts.
The data in Figure 3b corroborates this description. Given that this model involves several assumptions and approximate estimates of the maleic—chitosan channel volume, this data is in good, even fortuitous, agreement.
Measurements performed on a thicker device show a significantly smaller Ids modulation from Vgs, as predicted by our description Supplementary Fig. This is transistlr unique property of having proton transparent contacts and reduces fabrication constraints.
From these polysaccgaride, it is clear that, for a negative Vgs, the proton density is drastically increased at the polysaccharide—dielectric interface to form a highly conducting region. Plots of current density show that the majority of Ids flows in the same area Supplementary Fig. An analogous Vgs effect on the charge density and current density distribution has been observed in thin-film organic transistors From these plots, it is also clear that in significantly thinner devices the expected charge modulation will be higher.
Such devices may be fabricated with individual maleic—chitosan nanofibres and should offer a greatly improved on-off ratio.
We also estimate Ids as a function of Vds for different Polyysaccharide Fig. The simulations are in good agreement with the experimental data at low Vds, while the nonlinear dependence of Ids on Vds for higher Vds is not reproduced.
We have assumed the contacts to be completely proton transparent. A small contact barrier neglected in our model may cause charge accumulation or depletion at the maleic—chitosan PdHx interface.
This charge, in turn, may reduce the strength of the electric field at the contacts, thus effectively limiting the current. When the bias is reversed, the charge should be released and cause hysteresis in fleld-effect Ids—Vds dependence. The causes for hysteresis and the non-linear behaviour of Ids for high Vds are still not fully understood and merit further investigation. PdHx bioptotonic allow for indiscriminate measurement of the protonic current.
A voltage applied to the electrostatic gate controls the maleic—chitosan channel proton density and the channel conductivity. Current modulation occurs even for devices thicker than the Debye length. This allows for current control in highly concentrated electrolytes at any aa scale. In the future, several nanostructured biological and organic materials can be measured in these devices.
The demonstrated ability to control protonic currents in nanostructured biocompatible solid-state devices bionanoprotonics may open exciting opportunities for interfacing with living systems.
These opportunities include biomedical applications where protonic currents are important such as the in-vivo study and stimulation of proton selective ion-channels. Maleic—chitosan nanofibres were prepared following previously published procedures The maleic—chitosan hydration level was determined with a thermogravimetric analyser TA Instruments, model Photolithography and lift-off was used to define the contacts.
After dialysis and freeze drying, maleic—chitosan was prepared in a DI water solution. This procedure eliminates any salt and thus potential salt effects on the conductivity. Devices were mounted on a chip, and wire bonded. Measurements were performed with a semiconductor parameter analyser Agilent C.
This was done to ensure that the measured device current was from the maleic—chitosan channel and not from water condensed on the top of the SiO2. Atomic force microscopy Polysacchariee was employed to measure device dimensions. We defined a silicon Si based metal—oxide—semiconductor transistor with the same dimensions as polysacchariide experiment. We used a 8. We replaced the properties of silicon with those of the channel material. Mobility was varied to fit the data.
In addition, we assigned the mobility of electrons to a value that is orders of magnitude smaller than that of protons. This minimizes the role of electrons in the electrical response of the device.
To calculate the gate capacitance, we first obtained the interface charge at different gate biases; whereas the two other contacts were kept at zero bias. Chance and design – proton transfer in water, channels and bioenergetic proteins. Theory of hydrogen-bonded chains in bioenergetics. Ph regulation and beyond: Molecular mechanism of vectorial proton translocation by bacteriorhodopsin. Nature— Gramicidin forms multi-state rectifying channels.
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A polysaccharide bioprotonic field-effect transistor.
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