Owing to the growing demand for highly integrated electronics, anisotropic heat dissipation of thermal management material is a challenging and promising technique. Moreover, to satisfy the needs for advancing flexible and stretchable electronic devices, maintaining high thermal conductivity during the deformation of electronic materials is at issue. Presented here is an effective assembly technique to realize a continuous array of boron nitride (BN) nanosheets on tetrahedral structures, creating 3D thermal paths for anisotropic dissipation integrated with deformable electronics. The tetrahedral structures, with a fancy wavy shaped cross‐section, guarantee flexibility and stretchability, without the degradation of thermal conductivity during the deformation of the composite film. The structured BN layer in the composites induces a high thermal conductivity of 1.15 W m−1 K−1 in the through‐plane and 11.05 W m−1 K−1 in the in‐plane direction at the low BN fraction of 16 wt%, which represent 145% and 83% increases over the randomly mixing method, respectively. Furthermore, this structured BN composite maintains thermal dissipation property with 50% strain of the original length of composite. Various electronic device demonstrations provide exceptional heat dissipation capabilities, including thin film silicon transistor and light‐emitting diode on flexible and stretchable composite, respectively.

When a circular magnetostrictive patch bonded to a plate is subjected to static biasing and dynamic actuating magnetic fields, the patch deformation generates guided waves in the plate. To fully understand the characteristics of the circular patch-based transducer, the radiation pattern of the Lamb waves for arbitrary relative orientations of the two fields was experimentally investigated. The largest Lamb wave in an aluminum plate was generated when the two field directions make some oblique angle around 70°, not when they are parallel. The experimental findings were explained by a theoretical analysis.

When an alternating magnetic field by a figure-of-eight coil is applied to a circular magnetostrictive patch bonded to a plate, ultrasonic guided waves can be effectively generated and measured. Wave experiments with two transducers consisting of the coil and the patch show that the magnitude and type of the measured waves depend on the magnetic field directions of the wave transmitting and receiving coils; a first-order theory was derived to explain the direction-dependent phenomena. The relation between the patch size and the frequency of the maximum signal output was also investigated.

The rapid pace of progress in implantable electronics driven by novel technology has created devices with unconventional designs and features to reduce invasiveness and establish new sensing and stimulating techniques. Among the designs, injectable forms of biomedical electronics are explored for accurate and safe targeting of deep‐seated body organs. Here, the classes of biomedical electronics and tools that have high aspect ratio structures designed to be injected or inserted into internal organs for minimally invasive monitoring and therapy are reviewed. Compared with devices in bulky or planar formats, the long shaft‐like forms of implantable devices are easily placed in the organs with minimized outward protrusions via injection or insertion processes. Adding flexibility to the devices also enables effortless insertions through complex biological cavities, such as the cochlea, and enhances chronic reliability by complying with natural body movements, such as the heartbeat. Diverse types of such injectable implants developed for different organs are reviewed and the electronic, optoelectronic, piezoelectric, and microfluidic devices that enable stimulations and measurements of site‐specific regions in the body are discussed. Noninvasive penetration strategies to deliver the miniscule devices are also considered. Finally, the challenges and future directions associated with deep body biomedical electronics are explained.

We present electrophysiological (EP) signals correlated with cellular cell activities in the adrenal cortex and medulla using an adrenal gland implantable flexible EP probe. With such a probe, we could observe the EP signals from the adrenal cortex and medulla in response to various stress stimuli, such as enhanced hormone activity with adrenocorticotropic hormone, a biomarker for chronic stress response, and an actual stress environment, like a forced swimming test. This technique could be useful to continuously monitor the elevation of cortisol level, a useful indicator of chronic stress that potentially causes various diseases.