Use of 2-(6-mercaptohexyl) malonic acid to adjust the morphology and electret properties of cyclic olefin copolymer and its application to flexible loudspeakers

Abstract

Recent uses of flexible electret loudspeakers in futuristic applications have garnered much interest for these novel loudspeakers. In this paper, a novel thin film processing method was developed to improve the performance of an electret diaphragm. This paper discusses the relationship between the charge storage and the additive concentration. A cyclic olefin copolymer (COC) thin film containing an additive such as 2-(6-mercaptohexyl) malonic acid was prepared using a spin-coating process. Furthermore, attention was directed towards the processing conditions which were found to have an important role and are related to the self-assembly and micelle formation behavior of the additives in the COC. In the present study, thin films of 13 μm thickness were charged by a corona method. Compared with a reference thin film of pure COC, results indicated that when a 3497 mg kg −1 additive was added to the COC matrix, the obtained surface potential was 71% higher. Thus, the results show that a COC + additive thin film leads to a much improved charge storage. It appears to be an inexpensive and relatively easy way to form a thin structure for developing novel flexible electret loudspeakers.

A Review of Cyclic Olefin Copolymer Applications in Microfluidics and Microdevices

“…One of these numerous advantages is the material's good electret properties, which refer to its ability to retain its electric polarization after being subjected to an electric field. [206] COC also has a low cost, good electrical insulation, flexibility, a high glass transition temperature, and good chemical stability.…”

Modeling and experimental verification on directivity of an electret cell array loudspeaker

“…Figure 1 shows an electret-based diaphragm placed beside a perforated electrode and separated with an air gap by a grid spacer. The electret-based diaphragm was developed using a PTFE/COC composite film (Ko et al, 2010), where a 2-µm thick COC was spun onto a 20-µm thick PTFE film. The electret-based diaphragm contained nano and sub-micron pores to enhance the charge stability and density.…”

A Review of Acoustic Impedance Matching Techniques for Piezoelectric Sensors and Transducers

“…As thin films ranging from few micrometers to nanometers, they have seen growing use in applications such as force microscopy [ 15 ], nano-positioning [ 16 ], micromechanical systems (MEMS) [ 17 , 18 , 19 ] and nanoelectromechanical systems (NEMS) [ 20 , 21 ], energy harvesters [ 22 , 23 ], etc. Some well-known applications of thin films are MEMS microphone [ 24 ], headphone [ 24 ], loudspeaker [ 24 , 25 , 26 ], acoustic emission sensor [ 27 , 28 ], vibration sensor [ 10 , 14 ], inertial sensor [ 19 ], tactile sensors [ 29 , 30 , 31 ], power harvesting [ 32 , 33 ], ultrasound transducers [ 34 , 35 , 36 , 37 , 38 ], and guided wave sensors [ 39 , 40 , 41 ]. Thin films are preferably made of nontoxic piezopolymers or piezocomposites.…”