The development of various flexible and stretchable materials has attracted interest for promising applications in biomedical engineering and electronics industries. This interest in wearable electronics, stretchable circuits, and flexible displays has created a demand for stable, easily manufactured, and cheap materials. However, the construction of flexible and elastic electronics, on which commercial electronic components can be mounted through simple and cost-effective processing, remains challenging. We have developed a nanocomposite of carbon nanotubes (CNTs) and polydimethylsiloxane (PDMS) elastomer. To achieve uniform distributions of CNTs within the polymer, an optimized dispersion process was developed using isopropyl alcohol (IPA) and methyl-terminated PDMS in combination with ultrasonication. After vaporizing the IPA, various shapes and sizes can be easily created with the nanocomposite, depending on the mold. The material provides high flexibility, elasticity, and electrical conductivity without requiring a sandwich structure. It is also biocompatible and mechanically stable, as demonstrated by cytotoxicity assays and cyclic strain tests (over 10,000 times). We demonstrate the potential for the healthcare field through strain sensor, flexible electric circuits, and biopotential measurements such as EEG, ECG, and EMG. This simple and cost-effective fabrication method for CNT/PDMS composites provides a promising process and material for various applications of wearable electronics.

The long-term, continuous, inconspicuous, and noiseless monitoring of bioelectrical signals is critical to the early diagnosis of disease and monitoring health and wellbeing. However, it is a major challenge to record the bioelectrical signals of patients going about their daily lives because of the difficulties of integrating skin-like conducting materials, the measuring system, and medical technologies in a single platform. In this study, we developed a thin epidermis-like electronics that is capable of repeated self-adhesion onto skin, integration with commercial electronic components through soldering, and conformal contact without serious motion artifacts. Using well-mixed carbon nanotubes and adhesive polydimethylsiloxane, we fabricated an epidermal carbon nanotube electronics which maintains excellent conformal contact even within wrinkles in skin, and can be used to record electrocardiogram signals robustly. The electrode is biocompatible and can even be operated in water, which means patients can live normal lives despite wearing a complicated recording system.

ObjectiveTo evaluate the effect of extracorporeal shock wave therapy (ESWT) on lower limb spasticity in subacute stroke patients.MethodsWe studied thirty hemiplegic subacute stroke patients with ankle plantar flexor spasticity. ESWT was applied for 1 session/week, with a total of 3 sessions at the musculotendinous junction of medial and lateral gastrocnemius muscles. Patients were evaluated both clinically and biomechanically at baseline, after sham stimulation, and at immediately 1 week and 4 weeks after ESWT. For clinical assessment, Modified Ashworth Scale (MAS), clonus score, passive range of motion of ankle, and Fugl-Myer Assessment for the lower extremity were used. A biomechanical assessment of spasticity was conducted by an isokinetic dynamometer. Two parameters, peak eccentric torque (PET) and torque threshold angle (TTA), were analyzed at the velocities of 60°/sec, 180°/sec, and 240°/sec.ResultsAfter sham stimulation, there were no significant changes between each assessment. MAS and PET (180°/sec and 240°/sec) were significantly improved immediately and 1 week after ESWT. However, these changes were not significant at 4 weeks after ESWT. PET (60°/sec) and TTA (60°/sec, 180°/sec, and 240°/sec) were significantly improved immediately after ESWT. Yet, these changes were not significant at 1 week and 4 weeks after ESWT as well.ConclusionLower limb spasticity in subacute stroke patients was significantly improved immediately after ESWT. Although the therapeutic effect of ESWT reduced with time and therefore was not significant at 4 weeks after ESWT, the degree of spasticity was lower than that of the baseline. Future studies with a larger sample of patients are warranted in order to verify the protocols which can optimize the effect of ESWT on spasticity.

Implantable devices have provided various potential diagnostic options and therapeutic methods in diverse medical fields. A variety of hard-material-based implantable electrodes have been developed. However, several limitations for their chronic implantation remain, including mechanical mismatches at the interface between the electrode and the soft tissue, and biocompatibility. Soft-material-based implantable devices are suitable candidates for complementing the limitations of hard electrodes. Advances in microtechnology and materials science have largely solved many challenges, such as optimization of shape, minimization of infection, enhancement of biocompatibility and integration with components for diverse functions. Significant strides have also been made in mechanical matching of electrodes to soft tissue. In this review, we provide an overview of recent advances in soft-material-based implantable electrodes for medical applications, categorized according to their implantation site and material composition. We then review specific applications in three categories: neuroprosthetics, neural signal recording, and neuromodulation. Finally, we describe various strategies for the future development and application of implantable, soft-material-based devices.

of wastes. [4] Furthermore, self-destructive property induced by external stimuli such as moisture, light, and heat can expand its potential application to security-related electronics for protecting private and confidential information. [5-7] Combined uses of natural or synthesized biodegradable polymers with non-transient electronic materials were examples of early research direction of water-soluble electronic devices, which allowed to partially disintegrate into fragmentation due to collapse of the substrates. [8-10] Recognition of chemical reactivity of monocrystalline silicon nanomembranes (Si NMs) in aqueous solutions reached a turning point in transient system through integration with other inorganicbased conductors and insulators, enabling to fabricate almost any types of existing silicon-based electronic devices in a transient form with moderate modifications. [11] Demonstrated examples included device components, sensors, actuators, and energy sources with electrical behaviors comparable to those of state-ofthe-art devices. Successful follow-ups to initial works provided various interpretations of the dissolution kinetics and versatile organic-and inorganic-based materials and devices to accomplish a wide spectrum of this technology for potential applications in biological researches to clinical medicine and other possible areas. In the following, we discuss various types of biodegradable inorganic/organic materials along with their degradation mechanisms and biocompatible properties, diverse manufacturing processes for electronic devices and systems, examples of basic transient electronic components, and different strategies/concepts of transience. Representative applications in the fields of bioengineering, green-electronics, security systems, and others are reviewed, and concluding remarks address some challenges and perspectives for the future of transient electronics. 2. Bioresorbable Materials 2.1. Inorganic Materials Figure 1a shows a representative example of water-soluble electronic devices that contained electronic components, involving a transistor, diode, inductor, capacitor, resistor, and interconnects. [11] All components consisted of various inorganic biodegradable constituents such as Si NMs, magnesium oxide (MgO), and magnesium (Mg) for semiconductors, gate and interlayer dielectrics, and conductors, that can be degraded into benign and biocompatible end products. In addition, many other inorganic Transient electronics refers to an emerging class of advanced technology, defined by an ability to chemically or physically dissolve, disintegrate, and degrade in actively or passively controlled fashions to leave environmentally and physiologically harmless by-products in environments, particularly in bio-fluids or aqueous solutions. The unusual properties that are opposite to operational modes in conventional electronics for a nearly infinite time frame offer unprecedented opportunities in research areas of eco-friendly electronics, temporary biomedical implants, data-secure hardware system...