Microsystem technologies for implantable applications

Abstract

Microsystem technologies (MST) have become the basis of a large industry. The advantages of MST compared to other technologies provide opportunities for application in implantable biomedical devices. This paper presents a general and broad literature review of MST for implantable applications focused on the technical domain. A classification scheme is introduced to order the examples, basic technological building blocks relevant for implantable applications are described and finally a case study on the role of microsystems for one clinical condition is presented. We observe that the microfabricated parts span a wide range for implantable applications in various clinical areas. There are 94 active and 67 commercial 'end items' out of a total of 142. End item refers to the total concept, of which the microsystem may only be a part. From the 105 active end items 18 (13% of total number of end items) are classified as products. From these 18 products, there are only two for chronic use. The number of active end items in clinical, animal and proto phase for chronic use is 17, 13 and 20, respectively. The average year of first publication of chronic end items that are still in the animal or clinical phase is 1994 (n = 7) and 1993 (n = 11), respectively. The major technology-market combinations are sensors for cardiovascular, drug delivery for drug delivery and electrodes for neurology and ophthalmology. Together these form 51% of all end items. Pressure sensors form the majority of sensors and there is just one product (considered to be an implantable microsystem) in the neurological area. Micro-machined ceramic packages, glass sealed packages and polymer encapsulations are used. Glass to metal seals are used for feedthroughs. Interconnection techniques such as flip chip, wirebonding or conductive epoxy as used in the semiconductor packaging and assembly industry are also used for manufacturing of implantable devices. Coatings are polymers or metal. As an alternative to implantable primary batteries, rechargeable batteries were introduced or concepts in which energy is provided from the outside based on inductive coupling. Long-term developments aiming at autonomous power are, for example, based on electrostatic conversion of mechanical vibrations. Communication with the implantable device is usually done using an inductive link. A large range of materials commonly used in microfabrication are also used for implantable microsystems.

Implantable microchip: the futuristic controlled drug delivery system

“…Many researchers have been reported that, implantable drug delivery systems can be divided into two classes (Figure 3; Grayson et al, 2003;Staples et al, 2006;Nisar et al, 2008;Receveur et al, 2007;Daniel et al, 2009;Sakamoto et al, 2010;Stevenson et al, 2012) (a) Active device or solid-state silicon microchip -controlled drug releasing system after implantation using mechanical, electrical, magnetic, laser or other means. (b) Passive device or resorbable polymeric microchip -predetermined drug releasing system by the materials, fabrication methods or drug formulation and cannot be controlled after implantation.…”

A New Concept of a Drug Delivery System with Improved Precision and Patient Safety Features

“…This defined level may vary in a narrow therapeutic window [1][2][3][4][5]. Therefore conventional injections start with a higher concentration cmax to keep the drug in the therapeutic window over a certain time [3].…”

Detuning Study of Implantable Antennas Inside the Human Body

“…The number of microsystems designed to be implanted into the human body has increased in recent years [1]. A wide variety of sensors, microelectrodes, drug delivery devices, micro-machined transducers, micro actuators, surgical tools, etc.…”