Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
, 110 (17), 6694-9

Multifunctional Three-Dimensional Macroporous Nanoelectronic Networks for Smart Materials

Affiliations

Multifunctional Three-Dimensional Macroporous Nanoelectronic Networks for Smart Materials

Jia Liu et al. Proc Natl Acad Sci U S A.

Abstract

Seamless and minimally invasive integration of 3D electronic circuitry within host materials could enable the development of materials systems that are self-monitoring and allow for communication with external environments. Here, we report a general strategy for preparing ordered 3D interconnected and addressable macroporous nanoelectronic networks from ordered 2D nanowire nanoelectronic precursors, which are fabricated by conventional lithography. The 3D networks have porosities larger than 99%, contain approximately hundreds of addressable nanowire devices, and have feature sizes from the 10-μm scale (for electrical and structural interconnections) to the 10-nm scale (for device elements). The macroporous nanoelectronic networks were merged with organic gels and polymers to form hybrid materials in which the basic physical and chemical properties of the host were not substantially altered, and electrical measurements further showed a >90% yield of active devices in the hybrid materials. The positions of the nanowire devices were located within 3D hybrid materials with ∼14-nm resolution through simultaneous nanowire device photocurrent/confocal microscopy imaging measurements. In addition, we explored functional properties of these hybrid materials, including (i) mapping time-dependent pH changes throughout a nanowire network/agarose gel sample during external solution pH changes, and (ii) characterizing the strain field in a hybrid nanoelectronic elastomer structures subject to uniaxial and bending forces. The seamless incorporation of active nanoelectronic networks within 3D materials reveals a powerful approach to smart materials in which the capabilities of multifunctional nanoelectronics allow for active monitoring and control of host systems.

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Fig. 1.
Fig. 1.
Strategy for preparing 3D macroporous nanoelectronic networks and integration with host materials. (A) Different nanowire nanoelectronic elements (from left to right): kinked nanowire, nanotube, core-shell, straight, and branched nanowire. (B) Free-standing 2D macroporous nanowire nanoelectronic precursor. Blue, nanoelectronic element; orange, passivation polymer; black, metal contact and input/output. (C) The 3D macroporous nanoelectronic networks integrated with host materials (gray).
Fig. 2.
Fig. 2.
Organized 2D and 3D macroporous nanoelectronic networks. (A) Schematics of nanowire registration by contact printing and SU-8 patterning. Gray, silicon wafer; blue, Ni sacrificial layer; black ribbon, nanowire; green, SU-8; red, metal contact. (Upper) Top view. (Lower) Side view. (I) Contact printing nanowire on SU-8. (II) Regular SU-8 structure was patterned by lithography to immobilize nanowires. Extra nanowires were washed away during the development process of SU-8. (III) Regular bottom SU-8 structure was patterned by spin-coating and lithography. (IV) Regular metal contact was patterned by lithography and thermal evaporation, followed by top SU-8 passivation. (B) Dark-field optical images corresponding to each step of schematics in A. The nanowire and SU-8 features appear green in these images. The small red features on the right and lower edges of the image in II correspond to metal lithography markers used in alignment. The red dashed line highlights metal contacts/interconnects in IV. (C) SEM image of a 2D macroporous nanoelectronic network before release from the substrate. (Inset) Zoom-in of the region enclosed by the small red dashed box containing a single nanowire device. (D) Photograph of wire-bonded free-standing 2D macroporous nanoelectronic network in Petri dish chamber for aqueous solution measurements. The red dashed box highlights the free-standing portion of the nanoelectronic network, and the white-dashed box encloses the wire-bonded interface between the input/output and printed circuit board connector board. (E) Zoom-in of the region enclosed by the red dashed box in D. (F) Histogram nanowire device conductance in the free-standing 2D macroporous nanoelectronic networks. (G) Photograph of a manually scrolled-up 3D macroporous nanoelectronic network. (H) 3D reconstructed confocal fluorescence images of self-organized 3D macroporous nanoelectronic network viewed along the x-axis. Nonsymmetrical Cr/Pd/Cr metal layers (Materials and Methods), which are stressed, were used to drive self-organization. The SU-8 ribbons were doped with rhodamine 6G for imaging.
Fig. 3.
Fig. 3.
The 3D macroporous photodetectors and device localization. (A) Schematics of the single 3D macroporous nanowire photodetector characterization. Green ellipse, laser spot; blue cylinder, nanowire; orange, SU-8 mesh network. The illumination of the laser spot generated from confocal microscope on the nanowire device (I) makes the conductance change of nanowire, which could be (II) correlated with laser spot position. Green spots in II correlate to the laser spot positions in I. (B) High-resolution (1 nm per pixel) photocurrent image (I) from a single nanowire device (2 µm channel length) on substrate recorded with focused laser spot scanned in xy plane. The black dash lines indicate the boundary of metal contact in the device. (II) The 20× photocurrent measurements from the central region (red dash box) of the nanowire device with high resolution (the distance for each trace in x direction is 1 nm). (C) A 3D reconstructed photocurrent imaging overlapped with confocal microscopy imaging shows the spatial correlation between nanowire photodetectors with SU-8 framework in 3D. Green, false color of the photocurrent signal; orange (rhodamine 6G), SU-8 mesh network. Dimensions in I, x: 317 μm; y: 317 μm; z: 53 μm; II, x: 127 μm; y: 127 μm; z: 65 μm. The white numbers in II indicate the heights of the nanowire photodetectors.
Fig. 4.
Fig. 4.
The 3D macroporous chemical sensors. (A) The xz views of 3D reconstructed image of the 3D macroporous nanoelectronic network in gel. Red (rhodamine 6G), SU-8 mesh network; blue (DAPI), agarose gel. Dimensions: x = 317 μm; y = 317 μm; and z = 144 μm. (B) Schematics of the experimental setup. (C) The projection of four nanowire devices in the yz plane. Red dashed line corresponds to the approximate gel boundary, and the red and blue areas correspond to aqueous solution and agarose gel, respectively. (D) Representative change in calibrated voltage over time with pH change for 3D macroporous nanowire chemical sensors (I) in solution and (II) embedded in agarose gel. (E) Calibrated voltage with one pH value change in solution for four different devices located in 3D space. (I) Four devices without gel and (II) four devices embedded in agarose gel.
Fig. 5.
Fig. 5.
The 3D macroporous strain sensors embedded in elastomer. (A) Micro-CT 3D reconstruction of the macroporous strain sensor array embedded in a piece of elastomer. Pseudocolors are applied: orange, metal; purple, elastomer. (B) Dark-field microscopy image of a typical nanowire device indicated by red dash circle in A. All of the functional nanowires are intentionally aligned parallel to the axial axis of the elastomer cylinder. The white arrow points to a nanowire. (C) A bending strain field was applied to the elastomer piece. The 3D strain field was mapped by the nanowire strain sensors using the sensitivity calibration of the nanowire devices. The detected strains are labeled in the cylinder image at the device positions.

Similar articles

See all similar articles

Cited by 12 PubMed Central articles

See all "Cited by" articles

Publication types

LinkOut - more resources

Feedback