A Swallowable diagnostic capsule with a direct access sensor using anisotropic conductive adhesive Pio Jesudoss, Alan Mathewson, Karen Twomey and Frank Stam Heterogeneous System Integration Group, Microelectronics Applications Integration Tyndall National Institute Cork, Ireland +353214904441, pio.jesudoss@tyndall.ie William M.D. Wright Department of Electrical and Electronic Engineering University College Cork Cork, Ireland Abstract— Technological developments in biomedical microsystems are opening up new opportunities to improve healthcare procedures. Swallowable diagnostic sensing capsules are an example of this. In this paper, a novel direct access sensor (DAS) has been demonstrated which uses Flip Chip (FC) technology to expose the sensor to the liquid medium. An electrochemical study showed that the Anisotropic Conductive Adhesive (ACA) joint provides good connection and does not impair the sensor functionality. The reliability test results showed that most of the samples survived the humidity aging test and that only 2 out of 9 ACA connections of the same electrode failed. For the failed samples, the failure analysis showed that the tensile stress at the chip/epoxy interface caused a delamination at this interface. Keywords-component; Anisotropic conuctive ahesive (ACA); Flip hip Over Hole (FCOH); Direct Access Sensor (DAS); reliability; swallowable diagnostic sensing capsule. I. INTRODUCTION In medicine, Inflammatory Bowel Disease (IBD) is a group of inflammatory conditions that affect the Gastro-Intestinal (GI) tract [1]. Although the IBD can be divided into several categories, the two major forms of IBD are Crohn’s disease (CD) and ulcerative colitis (UC) [2]. There has been a rapid growth of IBD in Europe and North America during the second half of the twentieth century and it is becoming more prevalent in the rest of the world as they adopt the western life style [3]. CD and UC are chronic disease which can lead to long-term and sometime irreversible impairment of the GI tract [1]. One of the conventional methods to investigate any suspected pathology is to use an endoscope which is inserted through patient’s mouth, nose or rectum. These procedures provide some information: gastroscopy provides information about the Oesophagus and the stomach while the colonoscopy helps investigate the large intestine. These procedures are not only unpleasant for the patients but are also unable to provide information from the small intestine. With recent advances in microelectronics, wireless communication and sensor development, the limitations of endoscopy is overcome in the format of a biomedical swallowable capsule [4]. The swallowable capsule is an autonomous system which contains a sensor, the associated electronics for signal conditioning and amplifying and a radio transmitter all encapsulated in a biocompatible material. The swallowable capsule involves a non-invasive technique which can provide information about the whole GI tract. The concept of first radio telemetry ingestible capsule was put forward by R.Stuart Mackay and Bertil Jacobson in 1957 [4, 5].The swallowable capsules can be classified into families of imaging (PillCam, Olympus Optical) [5-7], drug delivery systems [5, 7, 8] and sensing capsules [4, 5, 7-15]. Unlike the imaging and the drug delivery capsules where none of the parts are exposed, the chemical sensing capsules have one or more sensors that measures biochemical variables related to the gut ecosystem through exposed sensors. But in none of the diagnostic sensing capsules, the sensor attachment -the first level packaging of the 978-1-4244-9111-7/11/$26.00 ©2011 IEEE 3B.3.1 IRPS11-224