Medical implants based on microsystems

Mokwa, W.

doi:10.1088/0957-0233/18/5/r01

Cited by 62 publications

(41 citation statements)

References 62 publications

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“…This methodology enables straightforward IOP sensing without involving further calculations which are derived from ocular mechanics as are used in applanation tonometry and which have large variation due to different dimensions and mechanical properties of individual eyes [7], [8]. In contrast to active sensing in which power transfer, size, and cost of the device are critical concerns [9], [10], passive sensing approaches have relatively flexible design constraints on the device side [11]. Works from many research groups have demonstrated the possibility of using miniaturized LC sensors (sensors with electrical LC resonant circuit) to enable passive wireless pressure sensing for various applications, including transcutaneous pressure monitoring, intracranial pressure monitoring, and pressure monitoring of abdominal aortic aneurysms in addition to the proposed IOP monitoring [12]- [17].…”

mentioning

confidence: 99%

Wireless Intraocular Pressure Sensing Using Microfabricated Minimally Invasive Flexible-Coiled LC Sensor Implant

Chen

Saati

Varma

et al. 2010

J. Microelectromech. Syst.

237

127

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Abstract-This paper presents an implant-based wireless pressure sensing paradigm for long-range continuous intraocular pressure (IOP) monitoring of glaucoma patients. An implantable parylene-based pressure sensor has been developed, featuring an electrical LC-tank resonant circuit for passive wireless sensing without power consumption on the implanted site. The sensor is microfabricated with the use of parylene C (poly-chlorop-xylylene) to create a flexible coil substrate that can be folded for smaller physical form factor so as to achieve minimally invasive implantation, while stretched back without damage for enhanced inductive sensor-reader coil coupling so as to achieve strong sensing signal. A data-processed external readout method has also been developed to support pressure measurements. By incorporating the LC sensor and the readout method, wireless pressure sensing with 1-mmHg resolution in longer than 2-cm distance is successfully demonstrated. Other than extensive on-bench characterization, device testing through six-month chronic in vivo and acute ex vivo animal studies has verified the feasibility and efficacy of the sensor implant in the surgical aspect, including robust fixation and long-term biocompatibility in the intraocular environment. With meeting specifications of practical wireless pressure sensing and further reader development, this sensing methodology is promising for continuous, convenient, direct, and faithful IOP monitoring.[ 2009-0111]Index Terms-Implantable microdevice, intraocular pressure (IOP), LC pressure sensor, parylene, wireless sensing.

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mentioning

confidence: 99%

Wireless Intraocular Pressure Sensing Using Microfabricated Minimally Invasive Flexible-Coiled LC Sensor Implant

Chen

Saati

Varma

et al. 2010

J. Microelectromech. Syst.

237

127

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“…93, and the role of microsystems is described in Ref. 97. Many implanted devices require a wireless communication system with the outside environment 98 .…”

Section: Medical Implant/cathetersmentioning

confidence: 99%

Precision in harsh environments

2016

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Microsystems are increasingly being applied in harsh and/or inaccessible environments, but many markets expect the same level of functionality for long periods of time. Harsh environments cover areas that can be subjected to high temperature, (bio)-chemical and mechanical disturbances, electromagnetic noise, radiation, or high vacuum. In the field of actuators, the devices must maintain stringent accuracy specifications for displacement, force, and response times, among others. These new requirements present additional challenges in the compensation for or elimination of cross-sensitivities. Many state-of-the-art precision devices lose their precision and reliability when exposed to harsh environments. It is also important that advanced sensor and actuator systems maintain maximum autonomy such that the devices can operate independently with low maintenance. The next-generation microsystems will be deployed in remote and/or inaccessible and harsh environments that present many challenges to sensor design, materials, device functionality, and packaging. All of these aspects of integrated sensors and actuator microsystems require a multidisciplinary approach to overcome these challenges. The main areas of importance are in the fields of materials science, micro/nano-fabrication technology, device design, circuitry and systems, (first-level) packaging, and measurement strategy. This study examines the challenges presented by harsh environments and investigates the required approaches. Examples of successful devices are also given.

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“…The use of passive telemetry in implantable medical devices is common (Mokwa 2007) and enables the realization of active implants with no power constraints.…”

Section: Development Of a Novel Sensormentioning

confidence: 99%