Polymer-based miniature flexible capacitive pressure sensor for intraocular pressure (IOP) monitoring inside a mouse eye

Abstract

This paper presents an ultra-thin and flexible polymer-based capacitive pressure sensor for intraocular pressure (IOP) monitoring in a mouse eye. Due to the size limitation of the anterior chamber in the mouse eye, a volume of approximately 700 × 700 × 150 μm(3) on a small substrate is available for the MEMS capacitive pressure sensor. Moreover, the sensor would ideally be easily injectable into place. Further complicating the sensing is the need to operate the device on the curved surface of the anterior chamber with minimum damage to the eye tissue. Therefore, a thin and flexible substrate is required. We fabricate sensors by exploiting Parylene as a biocompatible structural material in a suitable form factor and 25 μm thick liquid crystal polymer (LCP) as a soft and flexible host substrate. Using our approach, the flexibility and small form factor necessary for a mouse eye implant is achieved, along with the sensitivity required to monitor IOP fluctuations. This device will allow better study of glaucoma through close monitoring in mice after integration with other components.

Emerging flexible and wearable physical sensing platforms for healthcare and biomedical applications

“…This group of flexible elastomers provides a high degree of deformability and conformability on different surfaces with varied textures and geometries, rendering them viable candidates for use as one of the fundamental components of stretchable and wearable sensing devices. Furthermore, these flexible silicone elastomers are generally chemically inert and biocompatible, making them excellent for use in implantable flexible sensors 59,60 . Table 1 (A) summarizes the polymeric substrates and soft elastomeric materials typically employed for the fabrication of the soft templates of flexible and stretchable physical sensing devices.…”

Wearable Flexible Sensors: A Review

“…OLAE process is currently used to develop wearable health and medical devices. Use of PDMS [14,15], PEN [16], PI [17], P(VDF-TrFE) [18], Parylene [19] and Polypyrrole [20] have been commonly done to develop flexible sensors [21] for different applications. The electrode part of the sensor has been developed from different conducting materials like carbon-based nanomaterials and metallic nanoparticles.…”

Mechanical Characterization of PDMS Films for the Optimization of Polymer Based Flexible Capacitive Pressure Microsensors

“…This kind of sensors is basically constituted of metallic electrodes deposited on or imbedded in dielectric polymer films. Among the existing polymers, polydimethylsiloxane (PDMS) is a primary reference material, hence suitable for wearable use [2], especially when coated with suitable highly biocompatible material [3,4]. Besides, PDMS is a dielectric material [5]; it is appropriate to be used in capacitive sensing applications.…”

“…Indeed, associated with metallic electrodes, the deformation of the PDMS films under pressure induces capacitance changes between electrodes that can be read out for pressure measurement purposes. For that reason, PDMSbased capacitive sensors are found in many medical applications involving pressure monitoring, such as implanted pressure sensors [4], tactile sensing [10,11], gesture, or gait analysis [12]. Since PDMS films are deformable under shear 2 Journal of Sensors and normal forces, three-axis pressure capacitive microsensor arrays can be developed with appropriate electrode design [13].…”