Rapid advances in medical technologies are revolutionizing the way we fight
disease. Microsystems with embedded sensors and actuators have an enormous
potential to play a key role in minimally invasive diagnosis and therapy
that are increasingly playing a critical role in medicine. Highly miniaturized
"smart" implantables and surgical tools are the key devices in
this area. We explore how MEMS and micro/nanofabrication technologies can contribute
to realizing such devices and innovating medical technologies.
Implantable Wireless Drug Delivery Chips
MEMS technology is enabling pinpoint drug delivery to localized disease that is expected to maximize the efficacy of chemotherapy while drastically
reducing its side effects compared with the case of systemic administration.
We are developing implantable wireless drug delivery devices (DDD) packaged
in a form of miniaturized chip. The device shown below was developed to
have a drug reservoir in it, and controlled drug release from the reservoir
was achieved with the photo-defined microvalve structures of PNIPAM hydrogel by thermally actuating them via wireless power transfer using
external RF fields (refer to Micromachined Actuators), which opened/closed the micro nozzles created in the reservior wall through
which the drug could diffuse out.
Another DDD chip that has embedded a microfluidic pump has been developed
to achieve forced and faster drug ejection with higher temporal release
controllability. The chip was integrated with the Nitinol micro-coil actuator
(refer to Micromachined Actuators) to drive the micro pump wirelessly, coupled with micromachined check
valves to produce regulated drug flow in the device.
Stents are tubular mechanical devices implanted into arteries to scaffold
the channels narrowed by plaque deposition. Stents are playing vital roles
in the treatment of both vascular and non-vascular diseases, with its main
application being cardiovascular disease for stenosis management. However,
stenting often causes restenosis, i.e., re-narrowing of the vessel. We
are developing a new class of stent devices, "smart" stents,
that are integrated with MEMS transducers to realize advanced diagnosis
and treatment of restenosis via implanted stents. These devices are based
on custom-designed alloy-based stents that function as RF antennae to enable
wireless operation of the devices. One type of them was integrated with
micromachined capacitive pressure sensors based on medical-grade stainless
steel (refer to Micromachined Sensors) for wireless detection of local blood pressure shifting caused by re-narrowing.
The fabricated devices were tested with pig models to demonstrate its targeted
We are also investigating another type of smart stent, active stent, RF
powered to perform moderate heating of the implanted site toward realizing
endohyperthermia treatment of restenosis. A stent-based resonant circuit
serves as a frequency-selective wireless heater, applying local thermal
stress to the vessel tissue to suppress in-stent restenosis. The biocompatible
MEMS circuit breaker chip (refer to Micromachined Sensors) is integrated with the stent to prevent it from overheating, enabling
safeguarded wireless operation of hyperthermia treatment via the implant.
This work has demonstrated wireless heating and temperature regulation
using fabricated prototypes, which will be further optimized toward their
Catheter-Based Micro Rotary Motor for 3-D Viewing Microendoscopy
We have demonstrated the first micro rotary motor enabled with a novel
ferrofluid-based levitation mechanism, with a specific application focus
on advanced microendoscopes that enable circumferential scanning of probing
beam. The ferrofluid in the micro motor serves as an extremely simple,
miniaturized bearing that sustains on the magnet rotor and levitate it
inside a tubular substrate, an endoscope catheter (ferrofluid micro bearing
- refer to Micromachined Actuators). The rotor is electromagnetically driven by micropatterned stator coils
formed around the outer walls of the catheter, enabling 90°-step angular
actuation of the rotor. The fabricated prototypes were successfully operated
for continuous rotation of the prism mirrors coupled with the rotors. The
results indicate a promising potential of the device for 3-D viewing microendoscopy
with different modalities including ultrasound and optical coherence tomography.
Radio Controlled Micro Gripper
Miniaturized grippers with high gripping force, high robustness, and biocompatibility
are a key component that will advance microsurgical tools and techniques.
For such devices, eliminating mechanical interface and electrical wiring
can significantly simplifies the device archetecture, which in turn minimizes
the space occupied by them and eases surgical procedures. Future surgery
is looking at the use of swallowable microsurgical robots, in which wireless
control of micro tools for gripping, cutting, burning, etc. is an essential
requirement. Toward these applications, we have developed a micro gripper
based on Nitinol, a biocompatible shape-memory alloy, that can be radio
controlled via RF power transfer to the wireless heater circuit on which
the Nitinol gripper structure is integrated for its thermal actuation.
Jump to other research theme:
Carbon Nanotube Forest: Process and Application
The main page of Research