Assembly and packaging of a three-axis micro accelerometer used for detection of heart infarction

Abstract

In coronary artery bypass grafting there is a risk of graft occlusion which may result in myocardial infarction. A three-axis acceleration sensor may give additional information about heart function during surgery and the first postoperative days. This paper describes the assembly and packaging of a three-axis micro acceleration sensor for use in clinical trials. The sensor was connected to a cable for power supply and signal output and moulded in silicone. Testing of the encapsulation showed leakage currents well below the 10 muA limit for direct cardiac applications. A hydrogen peroxide gas plasma method was used for sterilization. In animal experiments the sensor was sutured to the heart and no fatigue failures ensued due to the cycling strain forces from the heart. The sensor has been qualified for clinical trials.

Detection of intraoperative myocardial dysfunction by accelerometer during aortic valve replacement

“…A silicon-encapsulated 3D accelerometer (KXM52-1040, Kionix, Inc., NY, USA) with outer dimensions 11.0 × 14.5 × 5.2 mm was used [16]. Accelerations and the electrocardiogram (ECG) (500 samples/s) were recorded synchronously.…”

Implantable MEMS acceleration sensor for heart monitoring recent development and outlook

“…We have used the same material for encapsulation as in the previous design, the biocompatible silicone Elastosil R 4001/40 (Wacker Chemie AG, Germany). And the same press moulding technique [5]. Silicone is a well-established biocompatible material and is easy to prototype and process.…”

“…Previously, an implantable 3-axis acceleration MEMS sensor for continuous monitoring of cardiac function has been developed [5]. In experiments, both on animals and on patients, the sensor was sutured to the heart surface, see Figure 1.…”

A miniaturized bulk micromachined triaxial accelerometer fabricated using deep reactive etching through a multilevel thickness membrane

“…Although a number of accelerometers with even smaller sizes recently have become commercially available, for instance the CMA3000 series from VTI (2011), the biocompatible packaging required for capacitive accelerometers for in vivo use adds several millimeters in all directions (Imenes et al 2007). For the 5 9 5 9 1.8 mm 3 accelerometer described in (Imenes et al 2007), the packaged sensor system was 14 9 11.5 9 5.2 mm 3 , mainly due to the required near-chip capacitors and their substrate.…”

“…For the 5 9 5 9 1.8 mm 3 accelerometer described in (Imenes et al 2007), the packaged sensor system was 14 9 11.5 9 5.2 mm 3 , mainly due to the required near-chip capacitors and their substrate. It is therefore desirable to have a piezoresistive accelerometer which does not require any additional components in the immediate vicinity and has a shape and size similar to the requirement.…”