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CAMP December Newsletter: Page 4

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 Pacemaker Powered by Implantable Biofuel Cell Operating Under Conditions Mimicking Human Blood Circulatory System – Battery Not Included

Professor Evgeny Katz, Professor William D. Jemison, MD Robert Lobel (Fletcher Allen Cardiology) and a group of postdocs and students are powering pacemakers using implantable biofuel cells that operate under conditions mimicking the circulatory system of blood in humans. Implantable devices harvesting energy from biological sources and based on electrochemical, mechanical and other energy transducers are currently receiving high attention. The energy collected from the body can be utilized to activate various microelectronic devices. While some microelectronic devices can work over a fairly broad range of electrical operating conditions, others (such as a pacemaker) require precise voltage levels and voltage regulation to operate correctly.  Thus certain classes of electronic devices (powered by implantable energy sources) will require careful attention to not only energy and power considerations, but also to voltage scaling and voltage regulation. This requires appropriate interfacing between the energy harvesting device and the microelectronic device. The research team, for the first time, demonstrated the continuous operation of a pacemaker powered by a single implantable biofuel cell operating under conditions mimicking the human blood circulatory system. In this case, the voltage level regulation for the correct pacemaker operation was adjusted by an interface circuit consisting of a charge pump and DC-DC converter combination. Biocatalytic electrodes made of buckypaper were modified with PQQ-dependent glucose dehydrogenase on the anode and with laccase on the cathode and were assembled in a flow biofuel cell filled with serum solution mimicking the human blood circulatory system. The biofuel cell generated open circuitry voltage, Voc, ca. 470 mV and short circuitry current, Isc, ca. 5 mA (current density 0.83 mA/cm2). The power generated by the implantable biofuel cell was used to activate a pacemaker connected to the cell via a charge pump and DC-DC converter interface circuit (to adjust the voltage produced by the biofuel cell to the value required by the pacemaker). The voltage-current dependencies were analyzed for the biofuel cell connected to an Ohmic load and to the electronic loads composed of the interface circuit, or power converter, and pacemaker to study their operation. The correct pacemaker operation was confirmed using a medical device – implantable loop recorder. Sustainable operation of the pacemaker was achieved with the system closely mimicking human physiological conditions using a single biofuel cell. This first demonstration of the pacemaker, activated by the physiologically produced electrical energy, shows promise for future electronic implantable medical devices powered by electricity harvested from the human body. Future implantable medical devices powered by implanted biofuel cells extracting electrical energy directly from a human body are possible, resulting in bionic human hybrids. The present study is a step on the long path to the design of bioelectronic self-powered “cyborgs” which can autonomously operate using power from biological sources. See Figure 3.

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FIGURE 3:  (A) Experimental setup which includes (from left to right): (a) sensor device for the Medtronic CareLink Programmer, Model 2090, (b) Medtronic Reveal XT, Model 9529, implantable loop recorder (ILR), (c) Affinity DR 5330L, St. Jude Medical, pacemaker, (d) the charge pump–DC-DC interface circuit, (e) the flow biofuel cell with the inlet/outlet connected to a peristaltic pump (not shown in the scheme). (B) Registered pulses generated by the pacemaker when it is powered by the standard battery. (C) Registered pulses generated by the pacemaker when it is powered by the biofuel cell.

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 Wireless and Ultrasonic Real Time In-Die Monitoring of Pharmaceutical Manufacturing of Solid Dosages

Professor Cetin Cetinkaya and his group have carried out research to demonstrate the feasibility and effectiveness of a special in-die real time tablet monitoring system.  They integrated the traditional die-punch set with an ultrasonic pulse-echo measurement system.  It includes an ultrasonic transducer mounted inside the upper punch of the compaction apparatus.  This upper punch is used to get ultrasonic pressure wave phase velocity waveforms and extract the time of flight of pressure waves travelling within the compact at a number of compaction force levels during compaction. The reflection coefficients, for the waves reflecting from the punch tip –powder bed interface, are extracted from the acquired waveforms. The reflection coefficient decreases with an increase in compaction force, indicating solidification. A monitoring system employing such methods is capable of determining material properties and the integrity of the tablet during compaction. The performance characteristics of tablets depend on various mechanical properties such as hardness and particle size.  Also today tablets are the most common method of drug delivery in medicine. The current focus is on transmitting the acoustic waves wirelessly to a nearby computer for real-time non-invasive monitoring of pharmaceutical manufacturing.

Professor Cetinkaya (of Clarkson University’s Department of Mechanical & Aeronautical Engineering) is the Director and Co-director, respectively, of the Photo-Acoustic Research and Nanomechanics / Nanomaterials Laboratories.  For more information about Professor Cetinkaya and his work you can contact him at the following email address: cetin@clarkson.edu