Precision Compliant Systems Laboratory (PCSL)

The purpose of this research is to generate the knowledge required to synthesize, model and manufacture new six axis, nano-, micro- and macro-scale nanopositioners. These nanopositioners are relevant to (a) instruments that enable us to measure/understand, and (b) equipment that enables us to manipulate/affect, that which happens at the micrometer and nanometer scales. The long-term impact of this work is aimed at increasing the type/pace of scientific discoveries (via instrumentation) and the pace/quality with which these discoveries may be converted into tangible goods (via manufacturing equipment). We focus on problems wherein performance requirements and/or geometric constraints demand unusually small machine envelopes. For example in vivo biomedical devices require mm-scale devices. Nanomanufacturing equipment requires devices that may only obtain viable speed, cost and stability requirements if they are centimeters to 10s of nanometers in size.

We utilize the principles of mechanical design, precision engineering, applied physics and manufacturing – in combination with invention – to synthesize new machine element concepts; and the models, tools and fabrications processes that enable their creation:
(1) Physics-based concept synthesis tools that enable engineers to create many new machine architecture concepts, compare them, and then select the best architecture.
(2) Compliant structure/bearing and actuator concepts that enable the conversion of machine architecture concepts into functional machines with nm-level resolution.
(3) Micro- and nanofabrication processes that enable the creation and integration of the machine elements into nanopositioning systems.

We draw case studies fromareas that are of high scientific and/or economic impact. At present, the scientific and practical applications of this work are focused on the following fields:

Nano-scale science and engineering:
- Nanopositioning
- Nanoinstrumentation
- Nanomechanical devices

Precision engineering:
- Compliant machine elements
- Exact constraint design theory
- Mechanism design

Biomedical:
- Micro-optical scanners
- 3D invivo tissue imaging
- Two-photon endoscopy

New machine element concepts, synthesis methods and design tools are required to realize small-scale MNS. The PCSL aims to create and grow a body of knowledge that supports the design and fabrication of small-scale MNS. Six-axis systems present the most challenging problems and therefore they serve as platforms for validating the research. Although this work is inspired by specific applications, the results are applicable to a wide array of small-scale MNS problems.

Two current research focuses are: (1) the development of a high force, high speed, and long stroke micro-scale thermomechanical actuator (TMA) for a three-axis millimeter scale compliant endoscopic scanner, and (2) the design of small scale non-linear optics for an endomicroscope capable of performing optical biopsy based two-photon excitation (in collaboration with Prof. Peter So’s research group). Two-photon microscopic imaging is based on the non-linear excitation of fluorophores using infrared radiation. A two-photon fluorescence microscope has the advantage of having inherent 3-D resolution, allowing fluorescence contrast to identify tissue biochemical signatures, providing deep image penetration into highly turbid tissues, and minimizing tissue photodamage.

In 2003, the µ-HexFlex, a PCSL invention, was awarded a R&D 100 Award, and a US patent in conjunction with MIT is pending. The µ-HexFlex is a six-axis micro-mechanism with nanometer level resolution, composed of stacked layers of silicon and silicon dioxide. The integrated TMAs are capable of exerting in-plane and out-of-plane forces on the central stage and flexure bearings.