Three-Dimensional, Flexible Nanoscale Field-Effect Transistors as Localized

8/7/2019 Three-Dimensional, Flexible Nanoscale Field-Effect Transistors as Localized

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A N D R E S O S O R I O S A L A Z A R A 0 1 0 1 4 6 3 9

Three-Dimensional, Flexible

Nanoscale Field-Effect Transistorsas Localized Bioprobes


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Introduction

y For many years, nanoelectronicdevices have been used forinterrogating biologicalsystems, but since now, allwork had been done on planardevices.

y We have overcome thislimitation by the integration of a nanoscale field-effecttransistor (nanoFET) device atthe tip of a silicon wire bent onan acute angle.

Schematics of 60 (top) and 0 (middle)multiply kinked nanowires and cis (top)and Trans (bottom) configurations innanowire structures. The blue and pink regions designate the source/drain (S/D)and nanoscale FET channel, respectively.


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Introduction

y The advantages of using 3D structures is that they exhibited conductance and sensitivity in aqueoussolution , independent of large mechanical

deflections, and demonstrated high pH sensitivity.y Other advantage is that when we modified 3D

nanoprobes with phospholipid bilayers, can entersingle cells to get better information.


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B ackground

y Modern means of communication rely on electric fieldsand currents to carry the flow of information.

y In contrast, biological systems uses ion gradients andcurrents, flows of small molecules, and membraneelectric potentials.

y Living organisms use a sophisticated arsenal of membrane receptors, channels, and pumps to controlsignal transduction.

y

Electronic circuits that use such biological componentscould achieve drastically increased functionality;however, this approach requires nearly seamlessintegration of biological and manmade structures.


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A im

y In order to get the more information about cells, we must firstcreate a device small enough to be compared to the size of acell itself. This kind of technology has been callednanoelectronics, referring to nano-sized electronics.

y Nanotubes and nanowires electrical devices are extremely sensitive and can be used for the detection of biologicalmarkers, or high resolution recording from the outside of thecell.

y 3D sensing and recording with the prototypicalnanoelectronic device, a nanoscale field-effect transistor

(nanoFET), have not been demonstrated because almost allexamples of these devices are created on planar substrates.y In this project, we develop a device reliable and usable to get

accurate information about biological cells.


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Design

y We needed to incorporate two or three cis-linkedkinked units to the tip of the probe forming angles of 60 or 0.

y

We examined the size limits of these bioprobes interms of the nanowire diameter and length Lbetween kinks, and we found that probe structuresthat are functional are possible for values as small as~18 and 15 nm, respectively.

y These data show that it is possible to create activesemiconductor probes with dimensions smaller thanmicrotubules in cells.


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Fabrication process.

y We next designed a brand-new process to fabricate thesenanodevices that would allow

these probes to be used ascellular probes.y We made remote electrical

interconnects to the S/D

nanowire arms on ultrathin SU-8polymer ribbons.


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R esults

y Conductance versus-time data initially in gentle contactwith a beating hearth cell showed a sequence of distinctfeatures

Initially, we observed regularly spaced

spikes with a frequency of ~2.3 Hz,consistent with the beating hearth

A fter a relatively brief (~40-s) period of extracellular signals, we observed severalpronounced changes in recorded signals.

The initial extracellular signals disappeared (pink stars).There was a decrease in baseline potential, andnew peaks emerged that had an opposite sign,similar frequency, much greater amplitude, andlonger duration (green stars).


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Discussion

y When the cell was retracted from the devices, theintracellular peaks disappeared, but they reappearedwhen the cell was brought back into contact.

y This process could be repeated multiple timeswithout degradation in the recorded signal.

y When vertical 3D nanoprobe devices were bent intoa configuration with angle q < ~50 with respect tothe cell, or when kinked nanowire devices werefabricated on planar substrates, we could record only extracellular signals.


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Conclusions

y We believe that with this process there are already clear advantages:

Electrical recording with kinked nanowire probes is relatively

simple without the need for resistance or capacitancecompensation.The nanoprobes are chemically less invasive than pipettes, asthere is no solution exchange.The small size and biomimetic coating minimizes mechanical

invasivenessThe nanoFETs have high spatial and temporal resolution forrecording.


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Three-Dimensional, Flexible Nanoscale Field-Effect Transistors as Localized