Recent years have witnessed the rapid development of sustainable materials. Along this line, developing biodegradable or recyclable soft electronics is challenging yet important due to their versatile applications in biomedical devices, soft robots, and wearables. Although some degradable bulk hydrogels are directly used as the soft electronics, the sensing performances are usually limited due to the absence of distributed conducting circuits. Here, sustainable hydrogel‐based soft electronics (HSE) are reported that integrate sensing elements and patterned liquid metal (LM) in the gelatin–alginate hybrid hydrogel. The biopolymer hydrogel is transparent, robust, resilient, and recyclable. The HSE is multifunctional; it can sense strain, temperature, heart rate (electrocardiogram), and pH. The strain sensing is sufficiently sensitive to detect a human pulse. In addition, the device serves as a model system for iontophoretic drug delivery by using patterned LM as the soft conductor and electrode. Noncontact detection of nearby objects is also achieved based on electrostatic‐field‐induced voltage. The LM and biopolymer hydrogel are healable, recyclable, and degradable, favoring sustainable applications and reconstruction of the device with new functions. Such HSE with multiple functions and favorable attributes should open opportunities in next‐generation electronic skins and hydrogel machines.
Degradable electronics represent a rapidly emerging field of science and technology with the potential to serve short‐term medical implantation applications where the device disappears once its function is complete. Despite many efforts in developing new types of degradable electronics, many of such systems are nonelastic and incompatible with the dynamic motion of native soft/elastic biological tissues. Herein, a photo‐crosslinkable hydrogel with integrated electronics that are highly stretchable and degradable in liquid environments is demonstrated. The fabrication process takes advantage of facile laser micromachining of conductive patterns directly onto the hydrogel under ambient conditions and permanent hydrogel–hydrogel bonding. The robustness and degradation rate of hydrogel and the laser‐processed encapsulated stretchable circuits is systematically investigated in different solutions under various conditions. Biocompatibility tests with non‐neoplastic cells (HMT 3522 S1) and cancer cells (T4‐2 and MDA‐MB‐231) are performed in 2D and 3D cell culture systems to confirm instead of evaluate the safety of the hydrogel and its byproducts during degradation as well as the zinc metal used in this technology. As a proof of concept, a stretchable hydrogel‐based device that can be used for remote/wireless delivery of thermal energy into the tissue in contact with the hydrogel is fabricated.
more » « less- NSF-PAR ID:
- 10061864
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Healthcare Materials
- Volume:
- 7
- Issue:
- 16
- ISSN:
- 2192-2640
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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By mimicking biomimetic synaptic processes, the success of artificial intelligence (AI) has been astounding with various applications such as driving automation, big data analysis, and natural-language processing.[1-4] Due to a large quantity of data transmission between the separated memory unit and the logic unit, the classical computing system with von Neumann architecture consumes excessive energy and has a significant processing delay.[5] Furthermore, the speed difference between the two units also causes extra delay, which is referred to as the memory wall.[6, 7] To keep pace with the rapid growth of AI applications, enhanced hardware systems that particularly feature an energy-efficient and high-speed hardware system need to be secured. The novel neuromorphic computing system, an in-memory architecture with low power consumption, has been suggested as an alternative to the conventional system. Memristors with analog-type resistive switching behavior are a promising candidate for implementing the neuromorphic computing system since the devices can modulate the conductance with cycles that act as synaptic weights to process input signals and store information.[8, 9]
The memristor has sparked tremendous interest due to its simple two-terminal structure, including top electrode (TE), bottom electrode (BE), and an intermediate resistive switching (RS) layer. Many oxide materials, including HfO2, Ta2O5, and IGZO, have extensively been studied as an RS layer of memristors. Silicon dioxide (SiO2) features 3D structural conformity with the conventional CMOS technology and high wafer-scale homogeneity, which has benefited modern microelectronic devices as dielectric and/or passivation layers. Therefore, the use of SiO2as a memristor RS layer for neuromorphic computing is expected to be compatible with current Si technology with minimal processing and material-related complexities.
In this work, we proposed SiO2-based memristor and investigated switching behaviors metallized with different reduction potentials by applying pure Cu and Ag, and their alloys with varied ratios. Heavily doped p-type silicon was chosen as BE in order to exclude any effects of the BE ions on the memristor performance. We previously reported that the selection of TE is crucial for achieving a high memory window and stable switching performance. According to the study which compares the roles of Cu (switching stabilizer) and Ag (large switching window performer) TEs for oxide memristors, we have selected the TE materials and their alloys to engineer the SiO2-based memristor characteristics. The Ag TE leads to a larger memory window of the SiO2memristor, but the device shows relatively large variation and less reliability. On the other hand, the Cu TE device presents uniform gradual switching behavior which is in line with our previous report that Cu can be served as a stabilizer, but with small on/off ratio.[9] These distinct performances with Cu and Ag metallization leads us to utilize a Cu/Ag alloy as the TE. Various compositions of Cu/Ag were examined for the optimization of the memristor TEs. With a Cu/Ag alloying TE with optimized ratio, our SiO2based memristor demonstrates uniform switching behavior and memory window for analog switching applications. Also, it shows ideal potentiation and depression synaptic behavior under the positive/negative spikes (pulse train).
In conclusion, the SiO2memristors with different metallization were established. To tune the property of RS layer, the sputtering conditions of RS were varied. To investigate the influence of TE selections on switching performance of memristor, we integrated Cu, Ag and Cu/Ag alloy as TEs and compared the switch characteristics. Our encouraging results clearly demonstrate that SiO2with Cu/Ag is a promising memristor device with synaptic switching behavior in neuromorphic computing applications.
Acknowledgement This work was supported by the U.S. National Science Foundation (NSF) Award No. ECCS-1931088. S.L. and H.W.S. acknowledge the support from the Improvement of Measurement Standards and Technology for Mechanical Metrology (Grant No. 22011044) by KRISS.
References [1] Young
et al. ,IEEE Computational Intelligence Magazine, vol. 13, no. 3, pp. 55-75, 2018.[2] Hadsell
et al. ,Journal of Field Robotics, vol. 26, no. 2, pp. 120-144, 2009.[3] Najafabadi
et al. ,Journal of Big Data, vol. 2, no. 1, p. 1, 2015.[4] Zhao
et al. ,Applied Physics Reviews, vol. 7, no. 1, 2020.[5] Zidan
et al. ,Nature Electronics, vol. 1, no. 1, pp. 22-29, 2018.[6] Wulf
et al., SIGARCH Comput. Archit. News, vol. 23, no. 1, pp. 20–24, 1995.[7] Wilkes,
SIGARCH Comput. Archit. News, vol. 23, no. 4, pp. 4–6, 1995.[8] Ielmini
et al., Nature Electronics, vol. 1, no. 6, pp. 333-343, 2018.[9] Chang
et al., Nano Letters, vol. 10, no. 4, pp. 1297-1301, 2010.[10] Qin
et al. , Physica Status Solidi (RRL) - Rapid Research Letters, pssr.202200075R1, In press, 2022. -
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