A technical review and evaluation of implantable sensors for hearing devices

• Published in: Biomedical engineering online Vol. 17; no. 1; p. 23
• Main Authors: Calero, Diego, Paul, Stephan, Gesing, André, Alves, Fabio, Cordioli, Júlio A
• Format: Journal Article
• Language: English
• Published: England BioMed Central Ltd 13-02-2018; BioMed Central; BMC
• Subjects: Accelerometer; Care and treatment; Cochlear implant; Hearing Aids; Hearing loss; Humans; Implantable transducers; Piezoelectric sensor; Prosthesis Design; Prosthesis Implantation - instrumentation; Review; Sensors; Subcutaneous microphone; Subcutaneous microphone; Implantable transducers; Piezoelectric sensor; Accelerometer; Cochlear implant; Hearing aids; MEMS sensor
• ISSN: 1475-925X; 1475-925X
• DOI: 10.1186/s12938-018-0454-z

Most commercially available cochlear implants and hearing aids use microphones as sensors for capturing the external sound field. These microphones are in general located in an external element, which is also responsible for processing the sound signal. However, the presence of the external element is the cause of several problems such as discomfort, impossibility of being used during physical activities and sleeping, and social stigma. These limitations have driven studies with the goal of developing totally implantable hearing devices, and the design of an implantable sensor has been one of the main challenges to be overcome. Different designs of implantable sensors can be found in the literature and in some commercial implantable hearing aids, including different transduction mechanisms (capacitive, piezoelectric, electromagnetic, etc), configurations microphones, accelerometers, force sensor, etc) and locations (subcutaneous or middle ear). In this work, a detailed technical review of such designs is presented and a general classification is proposed. The technical characteristics of each sensors are presented and discussed in view of the main requirements for an implantable sensor for hearing devices, including sensitivity, internal noise, frequency bandwidth and energy consumption. The feasibility of implantation of each sensor is also evaluated and compared.