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PRESS RELEASE
August 2, 2007

Arrowhead Subsidiary Unidym Signs Joint Development Agreement for Printable Conductors with Interphases' Thin-Film Solar Cells

PASADENA, California – August 2, 2007 – Arrowhead Research Corporation (NASDAQ:ARWR) announced today that its majority-owned subsidiary, Unidym, Inc., has signed a joint development agreement with InterPhases Research, a developer of novel thin-film solar cell technology. The joint development effort will focus on using Unidym's proprietary transparent electrodes with InterPhases' solar cells made from copper indium selenide (CIS) films. InterPhases' CIS cells are among the emerging thin-film solar cell technologies that promise to be highly competitive in the overall solar cell product market, which was worth $10.6 billion in 2006 and is expected to grow to $18.5 billion by 2011 according to Solarbuzz, an international solar energy research and consulting company.

“Unidym’s transparent electrodes provide a better match to InterPhases’ unconventional CIS solar cells,” explained Shalini Menezes, Director of Research and Development at InterPhases Research. "Additionally, because Unidym's transparent electrodes are printable with a low-temperature solution-based process, they offer a significant cost advantage relative to alternative transparent electrodes."

“We are excited to work with InterPhases Research to integrate Unidym's printable transparent electrodes with their thin-film CIS technology, stated Art Swift, President and CEO of Unidym. “We anticipate that Unidym’s transparent electrode technology will have superior performance and reduced cost, relative to transparent conducting oxides for InterPhases’ CIS solar cells, thus accelerating the commercialization of this exciting and potentially valuable technology.”

About Arrowhead Research Corporation

Arrowhead Research Corporation (www.arrowheadresearch.com) is a publicly-traded nanotechnology company commercializing new technologies in the areas of life sciences, electronics, and energy. Arrowhead is building value for shareholders through the progress of majority owned subsidiaries founded on nanotechnologies originally developed at universities. The company works closely with universities to source early stage deals and to generate rights to intellectual property covering promising new nanotechnologies. Currently, Arrowhead has four subsidiaries commercializing nanotech products and applications, including anti-cancer drugs, RNAi therapeutics, carbon-based electronics and compound semiconductor materials.

About Unidym, Inc.

Unidym (www.unidym.com) is a leader in the manufacture and application of carbon nanotubes (CNTs), a novel material with extraordinary electrical, thermal, and mechanical properties. Unidym provides bulk materials, CNT-enabled products, and intellectual property to a wide range of customers and business partners. As a result of its recent merger with CNI, Unidym possesses a foundational patent portfolio that covers nearly every aspect of CNT manufacturing and processing as well as multiple product applications.

Unidym is focused on the electronics industry where its initial products include transparent electrodes for touch screens, flat panel displays, solar cells, and solid state lighting; electrodes for fuel cells; and thin film transistors for printable electronics. Unidym is also pursuing a cross-industry partnership strategy to capture value from the wide ranging uses of CNTs. Unidym’s licensing program, technical expertise and manufacturing facilities can enable partners to rapidly develop CNT solutions for their specific applications.

About InterPhases Research

InterPhases Research (www.interphases.com) is developing economically viable photovoltaic energy solutions for the global market. With a vision to revolutionize power generation, it seeks to propel solar power into mainstream electricity market via technological breakthroughs in materials, device design and module fabrication. InterPhases is uniquely positioned with the cheapest, safest and simplest method to mass-produce efficient solar cells that can achieve near term grid parity.

Safe Harbor Statement under the Private Securities Litigation Reform Act of 1995:

This news release contains forward-looking statements within the meaning of the "safe harbor" provisions of the Private Securities Litigation Reform Act of 1995. These statements are based upon our current expectations and speak only as of the date hereof. Our actual results may differ materially and adversely from those expressed in any forward-looking statements as a result of various factors and uncertainties, including the recent economic slowdown affecting technology companies, the future success of our scientific studies, our ability to successfully develop products, rapid technological change in our markets, changes in demand for our future products, legislative, regulatory and competitive developments and general economic conditions. Our Annual Report on Form 10-K and 10-K/A, recent and forthcoming Quarterly Reports on Form 10-Q and 10-Q/A, recent Current Reports on Forms 8-K and 8-K/A, our Registration Statement on Form S-3, and other SEC filings discuss some of the important risk factors that may affect our business, results of operations and financial condition. We undertake no obligation to revise or update publicly any forward-looking statements for any reason.

Contacts

Art L. Swift, CEO Unidym, Inc.
Telephone: 650.462.1935
Email: aswift@unidym.com