Flexible PZT-Integrated, Bilateral Sensors via Transfer-Free Laser Lift-Off for Multimodal Measurements

Fabrication of functional devices that require a high-temperature annealing process on a thin, temperature-sensitive substrate is a long-standing, crucial issue in flexible electronics. Herein, we propose a transfer-free laser lift-off method to directly fabricate lead zirconate titanate (PZT) piezoelectric sensors that commonly undergo a high-temperature annealing (∼650 °C) on ubiquitous flexible substrates, including polyimide (∼300 °C), polyethylene terephthalate (∼120 °C), and polydimethylsiloxane (∼150 °C). The method includes the steps of fabricating sensors, encapsulating a flexible substrate, and peeling off the device by melting the sacrificial PZT layer at the interface with a sapphire glass. The appropriate fluence of laser energy has been figured out to avoid inadequate stripping or damage of the device. In addition, a process window for reliable stripping of the device has been established among the laser fluence and the thickness of the sacrificial layer and the supporting substrate. Furthermore, the capability of the newly proposed technique has been verified and expanded by successfully integrating several sensors that need skillful low-temperature heating treatment on top of a flexible supporting substrate accordingly before stripping. Finally, a PZT-integrated, bilateral multimodal sensor on a PI substrate has been fabricated, and the device demonstrates excellent performance and stability toward perceiving distributed dynamic pressure and temperature stimuli, revealing its high potential for the fabrication of high-performance devices for multimodal sensing applications.