Transient Electronic Research Articles

Electrochemically triggered degradation of silicon membranes for smart on-demand transient electronic devices

Transient electronics is an emerging technology that enables unique functional transformation or the physical disappearance of electronic devices, and is attracting increasing attention for potential applications in data secured hardware as an ultimate solution against data breaches. Developing smart triggered degradation modalities of silicon (Si) remain the key challenge to achieve advanced non-recoverable on-demand transient electronics. Here, we present a novel electrochemically triggered transience mechanism of Si by lithiation, allowing complete and controllable destruction of Si devices. The depth and microstructure of the lithiation-affected zone over time is investigated in detail and the results suggest a few hours of lithiation is sufficient to create microcracks and significantly promote lithium penetration. Finite element models are proposed to confirm the mechanism. Electrochemically triggered degradation of thin film Si ribbons and Si integrated circuit chips with metal-oxide-semiconductor field-effect transistors from a commercial 0.35 micrometer complementary metal-oxide-semiconductor technology node is performed to demonstrate the potential applications for commercial electronics. This work opens new opportunities for versatile triggered transience of Si-based devices for critical secured information systems and green consumer electronics.

Self-Assembled Functionally Graded Graphene Films with Tunable Compositions and Their Applications in Transient Electronics and Actuation.

The facile fabrication of functionally graded all-graphene films using a single-step casting process is reported. The films consist of a self-assembled graphene oxide (GO) precursor that can be reduced to different levels on an active metal substrate. Control of processing conditions such as the underlying substrate metal and the film-drying environment results in an ability to tailor the internal architecture of the films as well as to functionally grade the reduction of GO. A gradient arrangement within each film, where one side is electrically conductive reduced GO (rGO) and the other side is insulating GO, was confirmed by scanning electron microscopy, Raman, X-ray diffraction, Fourier transform infrared, and X-ray photoelectron spectroscopy characterization studies. All-graphene-based freestanding films with selectively reduced GO were used in transient electronic applications such as flexible circuitry and RFID tag antennas, where their decommissioning is easily achieved by capitalizing on GO's ability to readily dissociate and create a stable suspension in water. Furthermore, the functionally graded structure was found to exhibit differential swelling behavior, and its potential applications in graphene-based actuators are outlined.

Biodegradable photolithography compatible substrate for transparent transient electronics and flexible energy storage devices

Transient electronic devices (TED) can disappear with non-traceable or minimal remains once their intended lifetime is over, and hence form a growing area of research in defence and healthcare industry. However, due to the incompatibility of the TED substrates with high throughput micro-fabrication processes like UV lithography, they are obligated to rely on slow and low resolution processes like transfer printing and stencil printing. Therefore, the development of a substrate that is compatible with UV lithography would not only enable micro-fabrication but would also allow for a smooth transition of TED from lab to shelf.In this study, we demonstrate the suitability of agarose, a carbohydrate, as a substrate for transient electronics. Agarose is chemically modified with HMDS that imparts a hydrophobic character to otherwise hydrophilic agarose. Consequently, unlike other available biodegradable substrates that are incompatible with water based processing during UV lithography, these silylated agarose substrates provide a compatible window for aqueous processing steps. After establishing suitable thermal and optical properties of such a substrate, its compatibility with UV lithography is demonstrated by micropatterning antibody and aluminium patterns. Additionally, in order to demonstrate its wider applicability in the area of energy storage, a flexible-biodegradable battery is stencil printed on it that can sustain a small electronic device in both relaxed and flexed state.

Controllably degradable transient electronic antennas based on water-soluble PVA/TiO2 films

Transient electronic is an emerging field that designed electronic devices can be fleetly and partially (or completely) degraded when transiency is triggered. Here, a class of PVA-based degradable composite film was synthesized, whose physical properties allow it to be used as substrate material for transient electronic devices. We found the dielectric properties and dissolution rate of the composite film can be tuned by controlling the TiO2 nanoparticle addition. Based on the as-synthesized PVA/TiO2 composite film, patch antennas were further designed and fabricated. The antennas were found to possess excellent radiation performances at a frequency of 2.5 GHz. Most importantly, the antennas could be physically degraded within 1 h when immersed in pure water. This study shows that the PVA-based film is a good candidate substrate or supporting material for transient electronics. In addition, the design and manufacture methods reported here provide a reference for other transient devices with complex structure and function.

Triggered degradation of 250 μm-thick Mg targets using acetic acid for transient electronic applications.

Transient electronics are becoming a hot topic due to the rapid development of bioelectronics, self-destructive devices and environmental sensors. This letter reports a novel scheme for triggering degradation of 250 μm-thick Mg target using acetic acid regarding transient electronics applications. The triggered transience has also been demonstrated using commercial vinegar. To achieve programmable transience as well as device protection, polypropylene carbonate (PPC) was investigated as passivation layer. The proposed method has demonstrated simplicity, high safety, low cost and low trigger temperature.

Materials and processing approaches for foundry-compatible transient electronics

Foundry-based routes to transient silicon electronic devices have the potential to serve as the manufacturing basis for "green" electronic devices, biodegradable implants, hardware secure data storage systems, and unrecoverable remote devices. This article introduces materials and processing approaches that enable state-of-the-art silicon complementary metal-oxide-semiconductor (CMOS) foundries to be leveraged for high-performance, water-soluble forms of electronics. The key elements are (i) collections of biodegradable electronic materials (e.g., silicon, tungsten, silicon nitride, silicon dioxide) and device architectures that are compatible with manufacturing procedures currently used in the integrated circuit industry, (ii) release schemes and transfer printing methods for integration of multiple ultrathin components formed in this way onto biodegradable polymer substrates, and (iii) planarization and metallization techniques to yield interconnected and fully functional systems. Various CMOS devices and circuit elements created in this fashion and detailed measurements of their electrical characteristics highlight the capabilities. Accelerated dissolution studies in aqueous environments reveal the chemical kinetics associated with the underlying transient behaviors. The results demonstrate the technical feasibility for using foundry-based routes to sophisticated forms of transient electronic devices, with functional capabilities and cost structures that could support diverse applications in the biomedical, military, industrial, and consumer industries.

Composites Formed from Thermoresponsive Polymers and Conductive Nanowires for Transient Electronic Systems.

The disintegration of transient electronic systems after a preprogrammed time or a particular stimulus (e.g., water, light, or temperature) is fundamentally linked to the properties and behavior of the materials used for their construction. Herein, we demonstrate that polymers exhibiting lower critical solution temperature (LCST) behavior can work as thermoresponsive substrates for circuitry and that these materials can be coupled with conductive nanowires to form a transient electronics platform with unique, irreversible temperature-responsive behavior. The transient systems formed from composites of LCST polymers and conductive nanowires exhibit stable electrical performance in solution (Tsolution > LCST) for over 24 h until a cooling stimulus triggers a rapid (within 5 min) and gigantic (3-4 orders of magnitude) transition in electrical conductance due to polymer dissolution. Using a parylene mask, we are able to fabricate thermoresponsive electrical components, such as conductive traces and parallel-plate capacitors, demonstrating the versatility of this material and patterning technique. With this unique stimulus-responsive transient system and polymers with LCSTs above room temperature (e.g., poly(N-isopropylacrylamide), methyl cellulose), we have developed a platform in which a circuit requires a source of heat to remain viable and is destroyed and vanishes once this heat source is lost.

Transient Electronics: Dry Transient Electronic Systems by Use of Materials that Sublime (Adv. Funct. Mater. 12/2017)

Transient Electronics: Dry Transient Electronic Systems by Use of Materials that Sublime (Adv. Funct. Mater. 12/2017)

Kinetics and mechanism of the thermal degradation for the synthesis of poly(norbornene sulfone)s by two different polymerization methods

The recent development of sulfur dioxide (SO2) polymerization has seen a renaissance in its chemistry, especially poly(olefin sulfone)s from the copolymerization of SO2, and unsaturated hydrocarbons can be found to have many applications, including transient electronic packaging, drug delivery, and electron beam‐resistant materials. In this work, a type of functional poly(norbornene sulfone) was synthesized via two different polymerization methods. Aiming to understanding the effects of different polymerization methods on poly(olefin sulfone)s and gain further understanding on the kinetics of poly(olefin sulfone)s's thermal instability, we investigated their detailed thermal degradation behaviors using thermogravimetry and analyzed the resultant kinetics in accordance with three kinetic models. The results supported the conclusion that although the poly(norbornene sulfone)s obtained have different activation energy, the thermal degradation kinetics are the same and also obey the Dn type. Copyright © 2017 John Wiley & Sons, Ltd.

Flammable carbon nanotube transistors on a nitrocellulose paper substrate for transient electronics

Transient electronics represent an emerging class of technology comprising materials that can vanish in a controlled manner in response to stimuli. In contrast to conventional electronic devices that are designed to operate over the longest possible period, transient electronics are defined by operation typically over a short and well-defined period; when no longer needed, transient electronics undergo self-deconstruction and disappear completely. In this work, we demonstrate the fabrication of thermally triggered transient electronic devices based on a paper substrate, specifically, a nitrocellulose paper. Nitrocellulose paper is frequently used in acts of magic because it consists of highly flammable components that are formed by nitrating cellulose by exposure to nitric acid. Therefore, a complete and rapid destruction of electronic devices fabricated on nitrocellulose paper is possible without producing any residue (i.e., ash). The transience rates can be modified by controlling radio frequency signal-induced voltages that are applied to a silver (Ag) resistive heater, which is stamped on the backside of the nitrocellulose paper. The Ag resistive heater was prepared by a simple, low-cost stamping fabrication, which requires no harsh chemicals or complex thermal treatments. For the electronics on the nitrocellulose paper substrate, we employed semiconducting carbon nanotube (CNT) network channels in the transistor for superior electrical and mechanical properties.

Transient Electronics: Materials and Devices

Transient technology is an emerging field that requires materials, devices, and systems to be capable of disappearing with minimal or non-traceable remains over a period of stable operation. Electronics with the capability of disintegrating or vanishing after stable operation are becoming an interesting research topic and have attracted increasing attentions. In recent years, transience technology has been extended to intelligence applications, bioelectronics and environmental monitoring systems, and energy harvesters and storage. Although the transient concept has only a few years of development, this emerging transient technology is believed to find more opportunities in the fast development of advanced electronics. In this review, we will examine recent progress in the development of transient electronics. First, an overview of various transient materials, including metals, polymers, and semiconductor materials, is described. Second, recent progress in the design and development of transient electronic...

Recent progress in transient electronics

Fabrication of durable and long-lasting electronics is well established and desirable in traditional electronic devices. On the contrary, transient electronics is a new concept based on rapid and demand degradation of electronics after a programmed set period of operations. It represents a novel class of electronics that can physically and/or functionally disappear in part or as a whole when they are subjected to certain stimulus. Traditional electronics usually requires functionally stable even under extreme conditions. Such characteristic, however, renders current electronic devices that are malfunctioned or destroyed possess a great threat to our environment and become one of the major sources of environmental pollution. In contrast, transient electronic devices that can degrade or disintegrate after stable operation for a desired period under certain conditions may avert this problem while its performance can be comparable with current devices. Meanwhile, transient electronics could supplement the limitation of traditional electronics and potentially could be of great interest for applications in biomedical implants, secure memory devices, disposable environmental sensors, and zero-waste consumer electronic devices. For example, the transient electronics could be used for implantable medical diagnostic and therapeutic devices that resorb in the body to avoid adverse long-term effects. Transient electronic devices could also be used as environmental sensors that could dissolve to eliminate the need for their retrieval. Moreover, transient electronics could be integrated in portable consumer devices that decompose to minimize the costs and health risks that associated with recycling and the management of hazardous waste streams. Obviously, transient electronics is a subject that is interdisciplinary and cross-disciplinary, involving materials science, electronics, mechanics, biology and other subjects. The progress in transient electronics is tremendous recently. In this paper, we summarize the recent progress in transient electronics including the materials, devices and fabrication procedures that are developed in this field. We also introduce the potential applications of various transient electronics with the hope to inspire more application-defined fabrication of transient electronics.

Thermally triggered degradation of transient electronic devices.

Thermally triggered transient electronics using wax-encapsulated acid, which enable rapid device destruction via acidic degradation of the metal electronic components are reported. Using a cyclic poly(phthalaldehyde) (cPPA) substrate affords a more rapid destruction of the device due to acidic depolymerization of cPPA.

Diverse photoinduced dynamics in an organic charge-transfer complex having strong electron-phonon interactions.

CONSPECTUS: Phenomena that occur in nonequilibrium states created by photoexcitation differ qualitatively from those that occur at thermal equilibrium, and various physical theories developed for thermal equilibrium states can hardly be applied to such phenomena. Recently it has been realized that understanding phenomena in nonequilibrium states in solids is important for photoenergy usage and ultrafast computing. Consequently, much effort has been devoted to revealing such phenomena by developing various ultrafast observation techniques and theories applicable to nonequilibrium states. This Account describes our recent studies of diverse photoinduced dynamics in a strongly correlated organic solid using various ultrafast techniques. Solids in which the electronic behavior is affected by Coulomb interactions between electrons are designated as strongly correlated materials and are known to exhibit unique physical properties even at thermal equilibrium. Among them, many organic charge-transfer (CT) complexes have low dimensionality and flexibility in addition to strong correlations; thus, their physical properties change sensitively in response to changes in pressure or electric field. Photoexcitation is also expected to drastically change their physical properties and would be useful for ultrafast photoswitching devices. However, in nonequilibrium states, the complicated dynamics due to these characteristics prevents us from understanding and using these materials for photonic devices. The CT complex (EDO-TTF)2PF6 (EDO-TTF = 4,5-ethylenedioxytetrathiafulvalene) exhibits unique photoinduced dynamics due to strong electron-electron and electron-phonon interactions. We have performed detailed studies of the dynamics of this complex using transient electronic spectroscopy at the 10 and 100 fs time scales. These studies include transient vibrational spectroscopy, which is sensitive to the charges and structures of constituent molecules, and transient electron diffraction, which provides direct information on the crystal structure. Photoexcitation of the charge-ordered low-temperature phase of (EDO-TTF)2PF6 creates a new photoinduced phase over 40 fs via the Franck-Condon state, in which electrons and vibrations are coherently and strongly coupled. This new photoinduced phase is assigned to an insulator-like state in which the charge order differs from that of the initial state. In the photoinduced phase, translations of component molecules proceed before the rearrangements of intramolecular conformations. Subsequently, the charge order and structure gradually approach those of the high-temperature phase over 100 ps. This unusual two-step photoinduced phase transition presumably originates from steric effects due to the bent EDO-TTF as well as strong electron-lattice interactions.

Dissolution Behaviors and Applications of Silicon Oxides and Nitrides in Transient Electronics

Silicon oxides and nitrides are key materials for dielectrics and encapsulation layers in a class of silicon‐based high performance electronics that has ability to completely dissolve in a controlled fashion with programmable rates, when submerged in bio‐fluids and/or relevant solutions. This type of technology, referred to as “transient electronics”, has potential applications in biomedical implants, environmental sensors, and other envisioned areas. The results presented here provide comprehensive studies of transient behaviors of thin films of silicon oxides and nitrides in diverse aqueous solutions at different pH scales and temperatures. The kinetics of hydrolysis of these materials depends not only on pH levels/ion concentrations of solutions and temperatures, but also on the morphology and chemistry of the films, as determined by the deposition methods and conditions. Encapsulation strategies with a combination of layers demonstrate enhancement of the lifetime of transient electronic devices, by reducing water/vapor permeation through the defects.

25th Anniversary Article: Materials for High‐Performance Biodegradable Semiconductor Devices

We review recent progress in a class of silicon-based electronics that is capable of complete, controlled dissolution when immersed in water or bio-fluids. This type of technology, referred to in a broader sense as transient electronics, has potential applications in resorbable biomedical devices, eco-friendly electronics, environmental sensors, secure hardware systems and others. New results reported here include studies of the kinetics of hydrolysis of nanomembranes of single crystalline silicon in bio-fluids and aqueous solutions at various pH levels and temperatures. Evaluations of toxicity using live animal models and test coupons of transient electronic materials provide some evidence of their biocompatibility, thereby suggesting potential for use in bioresorbable electronic implants.

Ultrafast inter-ionic charge transfer of transition-metal complexes mapped by femtosecond X-ray powder diffraction.

The transient electronic and molecular structure arising from photoinduced charge transfer in transition metal complexes is studied by X-ray powder diffraction with a 100 fs temporal and atomic spatial resolution. Crystals containing a dense array of Fe(II)-tris(bipyridine) ([Fe(bpy)3](2 +)) complexes and their [Formula: see text] counterions display pronounced changes of electron density that occur within the first 100 fs after two-photon excitation of a small fraction of the [Fe(bpy)3](2 +) complexes. Transient electron density maps derived from the diffraction data reveal a transfer of electronic charge from the Fe atoms and-so far unknown-from the [Formula: see text] counterions to the bipyridine units. Such charge transfer (CT) is connected with changes of the inter-ionic and the Fe-bipyridine distances. An analysis of the electron density maps demonstrates the many-body character of charge transfer which affects approximately 30 complexes around a directly photoexcited one. The many-body behavior is governed by the long-range Coulomb forces in the ionic crystals and described by the concept of electronic polarons.

Short-Time Electron Transfer Processes in Ionic Aqueous Solution: Counterion and H/D Isotope Effects on Electron−Atom Pairs Relaxation

Counterion and H/D isotope substitution effects on early electron transfer steps in aqueous sodium chloride solution (X2O/NaCl = 55, X = H,D) have been investigated by femtosecond absorption spectroscopy of short-lived electron−chlorine atom pairs in the 18500−8000 cm-1 spectral range. The frequency dependence of the overall signal rise time and early signal decay (geminate recombination process) from 1.77 to 2.29 eV has been analyzed in the framework of inhomogeneous populations of hydrated electron for which the absorption bands overlap in the visible spectral region. By use of a kinetic model, two well-defined electron hydration channels have been discriminated. The spectral signature of a delayed hydration channel (e-hyd‘) is fully developed 4.5 ps after the initial energy deposition in the sample against 1.4 ps for the fastest electron hydration channel (e-hyd). Compared to the absorption band of the hydrated electron ground state (e-hyd), which peaks around 1.7 eV, the e-Hyd‘ population exhibits a spectral blue shift of about 0.15 eV. This electronic ground state is assigned to a polaron-like state, i.e., an electron localized in the vicinity of sodium ion: {e-···Na+}hyd. The time-resolved spectroscopic experiments demonstrate that this electron localization process can be triggered by short-range counterion effects on transient electron−chlorine atom pairs ({Cl:e-}pair:Na+). The existence of selective H/D isotope substitution effects on short-lived electronic configurations of aqueous Cl- (electron−Cl atom)pairs provides direct evidence that solvent cage dynamics around Cl- can differently interfere with multiple electron transfer channels. Contrary to infrared presolvated electron relaxation (p-like excited hydrated electron), early electron−chlorine atom pair relaxation (Cl:e- → Cl-) or 1D geminate recombination of fully hydrated electron with chlorine atom (Cl + e-hyd → Cl-) for which no significant isotope effect is observed, the electron transfer process involving the deactivation of {Cl:e-}pair:(Na+) population is drastically influenced by a change of intramolecular OH/OD vibrational mode frequency. In aqueous NaCl solution, the electron photodetachment from these transient electronic configurations [{Cl:e-}pair:(Na+)] → {Cl}, {e-···Na+}hyd] takes place with a characteristic time of 750 fs in H2O and 980 fs in D2O. The complete buildup of a polaron-like state (second electron hydration channel) is delayed by a factor of 1.6 (4.5 ps in H2O and 7.4 ps in D2O) when the energetic vibrational modes of water molecules (OH vs OD) are decreased by √2. The conjugate effects of very fast responses and slower cooperative motions of water molecules during short-range (electron−atom)pairs−Na+ couplings and a second electron hydration channel are discussed.