An ultrastretchable film device is developed that can follow the shape of spherical and large deformable biological samples such as heart and brain tissues. Although the film is composed of biocompatible parylene for the device substrate and metal layers of platinum (Pt)/titanium (Ti), which are unstretchable materials, the film shows a high stretchability by patterning slits as a "Kirigami" design. A Pt/Ti-microelectrode array embedded in 11 µm thick parylene film with 5 × 91 slits exhibits a film strain of ≈250% at 9 mN strain-force (0.08 MPa in stress) with a Young's modulus of 23 kPa, while the 3 × 91-slit film shows a Young's modulus of 3.6 kPa. The maximum strains of these devices are ≈470% and ≈840%, respectively. It is demonstrated that the Kirigami-based microelectrode device can simultaneously record in vivo electrocorticogram signals from the visual and barrel cortices of a mouse by stretching the film and tuning the electrode gap. Moreover, wrapping the Kirigami device around a beating mouse's heart, which shows large and rapid changes in the volume and the surface area, can record the in vivo epicardial electrocardiogram signals. Such a small Young's modulus for a stretchable device reduces the device's strain-force, minimizing the device-induced stress to soft biological tissues.

Electronic devices used to record biological signals are important in neuroscience, brain–machine interfaces, and medical applications. Placing electronic devices below the skin surface and recording the muscle offers accurate and robust electromyography (EMG) recordings. The device stretchability and flexibility must be similar to the tissues to achieve an intimate integration of the electronic device with the biological tissues. However, conventional elastomer‐based EMG electrodes have a Young's modulus that is ≈20 times higher than that of muscle. In addition, these stretchable devices also have an issue of displacement on the tissue surface, thereby causing some challenges during accurate and robust EMG signal recordings. In general, devices with kirigami design solve the issue of the high Young's modulus of conventional EMG devices. In this study, donut‐shaped kirigami bioprobes are proposed to reduce the device displacement on the muscle surface. The fabricated devices are tested on an expanding balloon and they show no significant device (microelectrode) displacement. As the package, the fabricated device is embedded in a dissolvable material‐based scaffold for easy‐to‐use stretchable kirigami device in an animal experiment. Finally, the EMG signal recording capability and stability using the fabricated kirigami device is confirmed in in vivo experiments without significant device displacements.

The most remarkable features of Kirigami are that unstretchable materials can gain stretchability and that its strain force is very small compared to other elastomer‐based stretchable materials. These features are suitable for applications related to deformable soft biological samples. In article number https://doi.org/10.1002/adhm.201701100, Takeshi Kawano and co‐workers propose the ultrastretchable bioprobe device using a ‘Kirigami’ design and demonstrate the recordings of biological signals in mouse brain and heart.

No abstract

No abstract