Flexible and Transparent Aluminum‐Nitride‐Based Surface‐Acoustic‐Wave Device on Polymeric Polyethylene Naphthalate

Abstract

The development of wearable technology increasingly requires bendable sensing devices operating across multiple domains for opto‐electro‐mechanical and biochemical transduction. Piezoelectric materials integrated into flexible and transparent device architectures can enable multiple‐sensing platforms. It is shown that flexible and compliant surface‐acoustic‐wave (SAW) piezoelectric devices include all these features and can be applied to the human body. A flexible and transparent aluminum‐nitride‐(AlN)‐based SAW device on a thermoplastic polyethylene naphthalate (PEN) substrate, fabricated by low‐temperature sputtering deposition of a multilayered AlN‐based stack, is reported for the first time. Two resonant modes, corresponding to Rayleigh and Lamb wave propagation, are shown and compared with a control SAW device on a silicon substrate. A large transmission‐signal amplitude, up to 20 dB, is achieved for the Lamb resonance mode around 500 MHz at an acoustic velocity of 10 500 m s−1. The technology is applied to the fabrication of a wearable temperature sensor. Compared to the same piezoelectric stack and SAW technology onto silicon substrates, the AlN/PEN SAW shows better performance and a temperature coefficient frequency as high as ≈810 ppm °C−1. The potential of this flexible SAW device as a wearable temperature sensor based on Rayleigh modes is demonstrated.

Acoustic Biosensors and Microfluidic Devices in the Decennium: Principles and Applications

“…A Love wave biosensor using 36 • YX LiTaO 3 with Al IDT and 500 nM SiO 2 guiding layer operating at 325 MHz, was reported to detect the human immunodeficiency virus (HIV) with the capability to differentiate between the two serotypes (HIV-1 and HIV-2) from human serum [313]. A Lamb wave device utilizing a thin AlN film of 4.5 µm thickness on a flexible substrate of 125 µm thick polyethylene naphthalate (PEN) with Al IDT, operating at a Lamb wave frequency of 500 MHz, was demonstrated for the detection of E. coli [56,317]. The fabricated flexible device is given in Figure 35a.…”

Biosensors Based on Mechanical and Electrical Detection Techniques

“…An example of this comes from the work of Ji et al producing a SAW biosensor for the detection of bacterial endotoxin with a high sensitivity of 3.5 ug L −1 [ 126 ]. An alternative is the design developed by Lamanna et al using a thin molybdenum layer on AlN instead of gold on quartz [ 114 , 127 ]. The advantage here is that the thin AlN layer is better able to accommodate strain, and hence the device is made flexible.…”

Progress in lead-free piezoelectric nanofiller materials and related composite nanogenerator devices

“…It has been importantly studied for micro-electromechanical systems (MEMS) and biomedical devices because AlN has high biocompatibility and chemical resistivity as well as facile thin lm processability with the feature of well crystalline texturing and lowtemperature fabrication. [111][112][113] Relatively, AlN syntheses of nanopowder and nanostructures have not been studied deeply in elds of piezoelectric properties and applications. Because the syntheses and fabrications of wurtzite materials are relatively easy and very broadly known, it is not the main topic in this review.…”