Inventors University of California Irvine Associate Professor Peter J. Burke (Irvine, CA) and Christopher M. Rutherglen (Tustin, CA) developed an in vivoRFID chipto be implanted in a patient's body.The RFID chip comprises an integrated antenna formed on the chip, and a CMOS-compatible circuitry adapted for biosensing andtransmitting information out of the patient's body. The CMOS-compatible circuitry is adapted to sense a chemical and/or physical quantity from a local environment in the patient's body and to control drug release from the drug reservoirs based on the quantity sensed, according to U.S. Patent Application 20100171596
Many current implantable biosensors require a wire coming out of the patient, or a battery to be implanted. Also, typical biosensors are large and unsuited for a variety of applications that require minimal invasiveness. With respect to wireless transfer of information, antennas are either external, which add to the size of the system, or too big for applications in interrogation of biological systems. Efforts in reducing the size of antennas beyond a certain point are met by known technical drawbacks, which are discussed in further detail below.
Burke and Rutherglen developed a CMOS-compatible radio frequency identification("RFID") chip, thinned from the backside, with an integrated antenna, as a platform for biosensing. A transmit function is built into the RFID chip using CMOS-compatible circuitry so the chip can send information back out of the body. The chip is physically small enough for non-invasive monitoring of patient heath as an implanted device. Power is provided by a power source from outside the body, so that the implantation can be permanent and requires no battery. Many different sensors can be integrated onto the chip. The chip can also be used to control the release of drugs, or to stimulate electrically biological function for either therapeutic or diagnostic purposes. The chip can be small enough that control at the single-cell level is possible.
Using an electrically-small on-chip antenna integrated on a single-chip radio, some antenna gain may be sacrificed for small radio size. The benefits of a small single-chip platform, however, outweigh the disadvantages associated with textbook antenna metrics, especially in the technology vector for implantable biomedical microdevices, where small size is critical and communications occur over a short range.
FIG. 4 is a schematic of a carbon nanotube antenna.
The chip can also be used to control the release of drugs, or to stimulate electrically biological function for either therapeutic or diagnostic purposes. Drug reservoirs can be integrated onto the RFIDchip, allowing for intelligent or externally-controlled release of drugs. An exemplary application would be the use of glucose sensors fordiabetes monitoring. Glucose sensors can be implanted in a patient to monitor blood sugar levels, and then control the release of insulin from an on-chip reservoir. This application allows the monitoring of blood sugar to occur on a more frequent (or even continuous) basis than the conventional method of testing that involves pricking the patient's finger and putting a drop of blood on a test strip once a day.
FIG. 5 is a schematic of a system using an antenna and a diode to receive radio. signals and to convert RF power to direct current.
Available conventional RFID technology does not adequately address the need for a biosensing platform that is small enough for non-invasive monitoring of patient health as an implanted device. In general RFID applications, a battery is typically required to power the RFID tag for two-way communications, and the antennas are either external to the chip (which adds to the size of the system) or fabricated with an eye toward antenna efficiency (i.e., a "good" antenna according to textbook antenna metrics would broadcast efficiently over a long range), rather than size. In contrast, a single-chip RFID platform as described herein provides a solution to the small size required for biomedical implants.
The RFID chip can have any number of nanotube antennas configured to receive, transmit or both. In embodiments where each nanotube antenna is tuned to a separate resonant frequency, the number of nanotube antennas available to receive data on separate channels is limited only by the available bandwidth. The internal structure of the chip can range from simple nanotubes or nanoelectrodes to more complex integrated nanosystems having nanotubes, nanowires, nanotransistors, self-assembling DNA and the like.
The nanostructure-based antennas can be formed from any nanoscale structure that acts as an antenna. In a preferred embodiment, nanostructure-based antennas are formed from carbon single-walled nanotubes (SWNTs). Each carbon SWNT antenna can be tuned to a resonant frequency by adjustment of its length. Additional exemplary embodiments of wireless interconnects for nanodevices and nanosystems are described in greater detail in co-pending application Ser. No. 11/573,443 (entitled "Interconnected Nanosystems"), which is incorporated herein by reference.
FIG. 7 is a schematic of a system incorporating integrated nanosystems
According to this embodiment, nanotube antennas and frequency domain multiplexing are used for high-bandwidth communication with integrated nanosystems, which comprises nanowires and nanotubes. Referring to FIG. 7, long nanotube antennas of different lengths, each resonant at a different frequency, are coupled to the integrated nanosystem. The CMOS-compatible RFID chip 70 has multiple nanostructure-based antennas 76, such as nanotube antennas, that together form antenna arrays 71 extending from each of the four sides of the chip 70.