Ultrastretchable Kirigami Bioprobes

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 mu m thick parylene film with 5 x 91 slits exhibits a film strain of approximate to 250% at 9 mN strain-force (0.08 MPa in stress) with a Young's modulus of 23 kPa, while the 3 x 91-slit film shows a Young's modulus of 3.6 kPa. The maximum strains of these devices are approximate to 470% and approximate to 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.