A Physically Transient Form of Silicon Electronics

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Science  28 Sep 2012:
Vol. 337, Issue 6102, pp. 1640-1644
DOI: 10.1126/science.1226325

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  1. Fig. 1

    Demonstration platform for transient electronics, with key materials, device structures, and reaction mechanisms. (A) Image of a device that includes transistors, diodes, inductors, capacitors, and resistors, with interconnects and interlayer dielectrics, all on a thin silk substrate. (B) Exploded-view schematic illustration, with a top view in the lower right inset. (C) Images showing the time sequence of dissolution in DI water. (D) Chemical reactions for each of the constituent materials with water.

  2. Fig. 2

    Experimental studies of transient electronic materials and devices and corresponding theoretical analysis. (A) Atomic force microscope topographical images of a Si NM (initial dimensions: 3 μm × 3 μm × 70 nm) at various stages of hydrolysis in PBS at 37°C. (B) Diagram of the processes of reactive diffusion used in models of transience. (C) Experimental (symbols) and theoretical (lines) results for time-dependent dissolution of Si NMs (35 nm, black; 70 nm, blue; 100 nm, red) in PBS at 37°C. (D) Optical microscope images of the dissolution of a serpentine trace of Mg (150 nm thick) on top of a layer of MgO (10 nm thick) in DI water at room temperature. (E) Experimental (symbols) and theoretical (lines) results of dissolution kinetics of similar traces of Mg (300 nm thick) with different encapsulating layers: MgO (400 nm, red; 800 nm, blue) and silk (condition i, cyan; condition ii, purple). (F) Measurements of transience in operational characteristics of n-channel transistors encapsulated by MgO and crystallized silk (picture in the inset on the left) and then immersed in DI water. The results show the drain current (Id) at Vd = 0.1 V as a function of Vg at various times (left) and at Vg = 5 V as a function of time (right).

  3. Fig. 3

    Images and electrical properties of transient electronic components, circuits, and sensors, including simple integrated circuits and sensor arrays. (A) Image of an LC (inductor-capacitor) oscillator fabricated with Mg electrodes and MgO dielectric layers (left) and an array of Si NM diodes with serpentine Mg resistors (right). (B) Measurements of the S21 scattering parameter of an inductor (blue), capacitor (black), and LC oscillator (red) at frequencies up to 3 GHz (left). Current-voltage (I-V) characteristics of diodes connected to three different Mg resistors (right) are shown. (C) Images of an array of p-channel (left) MOSFETs and a logic gate (inverter; right) composed of n-channel MOSFETs. The MOSFETs use Mg source (S), drain (D), and gate (G) electrodes; MgO gate dielectrics; and Si NM semiconductors. The inverter uses Mg for interconnects and Au for source, drain, and gate electrodes, in a circuit configuration shown in the diagram. (D) I-V characteristics of a representative n-channel MOSFET [left, channel length (Lch) and width (W) are 20 μm and 900 μm, respectively]. Transfer characteristic for the inverter (right, Lch and W are 20 μm and 700 μm for the input transistor and 500 μm and 40 μm for the load transistor, respectively). The voltage gain is ~8. (E) Image of strain sensors based on Si NM resistors (left) and an addressable array of Si NM photodetectors with blocking diodes. In both cases, Mg serves as contact and interconnection electrodes and MgO as the dielectric. (F) Fractional change in resistance of a representative strain gauge as a function of time during cyclic loading (left). R, bent; R0, flat. Bending induces tensile (red) and compressive (blue) strains uniaxially up to ~0.2%. Right, image of a logo collected with the photodetector array. The inset shows the logo design.

  4. Fig. 4

    In vivo evaluations and example of a transient bioresorbable device for thermal therapy. (A) Images of an implanted (left) and sutured (right) demonstration platform for transient electronics located in the subdermal dorsal region of a BALB/c mouse. (B) Implant site after 3 weeks (left). (Right) Histological section of tissue at the implant site, excised after 3 weeks, showing a partially resorbed region of the silk film. (A, subcutaneous tissue; B, silk film; C, muscle layer). (C) Resonant responses of an implanted transient rf metamaterial structure before and after placement in a silk package, immediately after implantation and at several time intervals thereafter. (D) Measured and calculated Q factor for the metamaterial. The results indicate transience dominated by the diffusion of biofluids through the silk package. (E) Transient wireless device for thermal therapy, consisting of two resistors (red outline) connected to a first wireless coil (70 MHz; outer coil) and a second resistor (blue outline) connected to a second, independently addressable, wireless coil (140 MHz; inner coil). The inset shows a thermal image of this device coupled with a primary coil operating at two frequencies, to drive both the inner and outer coils simultaneously. (F) Primary coil next to a sutured implant site for a transient thermal therapy device. The inset shows an image of a device. (G) Thermal image collected while wirelessly powering the device through the skin; the results show a hot spot (5°C above background) at the expected location, with a magnified view in the inset.

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