Betacel is considered to be the first commercially successful betavoltaic battery."Nuclear-Fueled Cardiac Pacemakers," Fred N. Huffman and John C. Norman, CHEST 65, page 667 - 672 (1974). It was developed in the early 1970s by Larry C. Olsen at the American corporation

McDonnell Douglas McDonnell Douglas Corporation was a major American Aerospace manufacturer, aerospace manufacturing corporation and defense contractor, formed by the merger of McDonnell Aircraft and the Douglas Aircraft Company in 1967. Between then and its own ...

, using the radioisotope

promethium-147 Promethium (61Pm) is an artificial element, except in trace quantities as a product of spontaneous fission of 238U and 235U and alpha decay of 151Eu, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no s ...

as the beta-electron source coupled to silicon

semiconductor A semiconductor is a material with electrical conductivity between that of a conductor and an insulator. Its conductivity can be modified by adding impurities (" doping") to its crystal structure. When two regions with different doping level ...

cells. This power source was incorporated in the Betacel-Biotronik heart pacemaker. The device was not widely adopted because of its limited lifespan and doubts over the use of

radioactive Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is conside ...

material.

Development

The betavoltaic program along with the development of the Betacel was led by Dr. Olsen and a team of researchers at Donald W. Douglas Laboratories (DWDL), McDonnell Douglas Corporation, in the early 1970s. As the first (and only) viable betavoltaic power source ever developed, it was immediately used to power heart pacemakers. Betacel powered cardiac pacemakers were implanted in numerous patients in the 1970s. Biotronik GmbH & Co., Ingenieurburo, Berlin, adapted its chemical battery-powered pacemakers to accept the promethium-fueled Betacel battery. The Betacel powered Biotronik pacemakers were considered to have useful lives of 7 to 10 years. Clinical investigation of the Betacel-Biotronik pacemaker began in Europe in 1972 and was extended to the United States under State of Washington license in 1973. By early 1973, over 60 implanted Betacel-Biotronik pacemakers were being monitored as part of the clinical investigation. By mid-1974, the USAEC had authorized the licensing in the United States of a Clinical Investigation Program that allowed the implantation of 50 Betacel-Biotronik pacemakers per month in major clinics in the U.S.

Original technology

Betacels utilized Pm-147 beta sources that were combined with custom designed silicon p-n junctions. Operational configurations involved stacking unidirectional sources with Si p-n junctions in a series arrangement. The power output of the Betacel was approximately 400

μW The watt (symbol: W) is the unit of power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantify the rate of energy transfer. The watt is named in honor of ...

. The

power density Power density, defined as the amount of power (the time rate of energy transfer) per unit volume, is a critical parameter used across a spectrum of scientific and engineering disciplines. This metric, typically denoted in watts per cubic meter ...

of the battery was approximately 0.025 mW/cm³. The battery itself was approximately one cubic inch in volume (16 cm³). Most of the volume was used for shielding, to contain the

gamma radiation A gamma ray, also known as gamma radiation (symbol ), is a penetrating form of electromagnetic radiation arising from high energy interactions like the radioactive decay of atomic nuclei or astronomical events like solar flares. It consists o ...

that was emitted from the Pm-146 contaminant within the Pm-147."Betacel Nuclear Batteries for Biomedical Applications," L.C. Olsen and S.E Seeman, 8th Intersociety Energy Conversion Engineering Conference, Philadelphia, PA, page 451, August 13–17, 1973. These Betacel batteries presented an

efficiency Efficiency is the often measurable ability to avoid making mistakes or wasting materials, energy, efforts, money, and time while performing a task. In a more general sense, it is the ability to do things well, successfully, and without waste. ...

of approximately 4%. However, more efficient devices were in the development process utilizing bidirectional beta sources. These bi-directional source devices would have yielded efficiencies approaching 8%. However, these higher efficiency devices were never realized since pacemaker manufacturers focused on the use of

lithium-ion A lithium-ion or Li-ion battery is a type of rechargeable battery that uses the reversible Intercalation (chemistry), intercalation of Li+ ions into electronically Electrical conductor, conducting solids to store energy. Li-ion batteries are c ...

batteries which did not utilize radioactive material, and could power pacemakers for 5 to 7 years. Although previous betavoltaic devices degraded rapidly due to radiation damage, the Betacel showed no deleterious effects from radiation. The power levels decreased as expected. In particular, the battery power decreased exponentially with a

half-life Half-life is a mathematical and scientific description of exponential or gradual decay. Half-life, half life or halflife may also refer to: Film * Half-Life (film), ''Half-Life'' (film), a 2008 independent film by Jennifer Phang * ''Half Life: ...

of 2.62 years, the same as that for Pm-147.

Limitations and demise

Pm-147 is not an ideal source since the half-life is only 2.62 years and the contaminant Pm-146 emits gamma rays that require batteries to be well shielded. The material is toxic and not readily available. Moreover, at the time there was a certain stigma associated with the use of nuclear power and radioactive materials: the public was fearful and leery of any nuclear technology. This stigma, combined with advances in (and the lower cost of) lithium-ion battery technology, eventually overshadowed aspirations of a more lucrative future for the Betacel, relegating betavoltaic batteries to the realm of academic research in the years that immediately followed.

Later developments in betavoltaic technology

The Betacel did not last but it provided a foundation for future betavoltaic technology research and sparked a resurgence of interest in betavoltaic power generation. Other sources such as

tritium Tritium () or hydrogen-3 (symbol T or H) is a rare and radioactive isotope of hydrogen with a half-life of ~12.33 years. The tritium nucleus (t, sometimes called a ''triton'') contains one proton and two neutrons, whereas the nucleus of the ...

have been considered and implemented in the development of betavoltaic batteries. Between 2001 and 2010, four commercial companies (City Labs, Inc., BetaBatt Inc., Qynergy, Inc. and Widetronix, Inc.) have ventured into betavoltaic power cell development, while university research on the subject is still actively being conducted. Rapid advances in semiconductor and materials science technology, integrated circuit design and fabrication, and micro-/nano-scale

microelectromechanical system MEMS (micro-electromechanical systems) is the technology of microscopic devices incorporating both electronic and moving parts. MEMS are made up of components between 1 and 100 micrometres in size (i.e., 0.001 to 0.1 mm), and MEMS devices ...

s (MEMS), have converged to the extent that extremely small devices with diminutive power requirements are becoming more and more routine. These devices are ideally suited for betavoltaic power sources that can easily and safely offer nanowatt-to-microwatt power levels with enduring 20-year lifetimes.

References

{{Reflist Battery types