Smart Medical Devices

End-effectors at mm scale

The small scale of minimally-invasive surgical procedures presents significant challenges to developing robust, smart, and dexterous tools and end-effectors for manipulating millimeter and sub-millimeter anatomical structures (e.g. vessels or nerves) and surgical equipment (e.g. sutures or staples). To meet the demand, we are developing a versatile fabrication process, based on printed circuit board manufacturing techniques, to create monolithic, kinematically complex, three-dimensional machines in parallel at the millimeter to centimeter scales. During lamination, precisely aligned material layers are combined in different ways to create functional layers that serve a specific purpose, including structural layers, flexure layers that enable rotary joints and articulated structures, printed circuit board (PCB) layers, metal spring layers, or low-friction sliding bearing layers. Finally, various functional layers combine to create multi-structure, multi-material, quasi-2D laminates capable of folding into complex 3D structures.

Assured safety drill

We have developed an assured safety drilling mechanism that is compatible with a large range of bit diameters and provides safe, reliable access to the inside of the skull. This is accomplished through a dynamic bi-stable linkage that supports drilling when force is applied against the skull but retracts upon penetration when the reaction force is diminished. In the initial design retraction was achieved when centrifugal forces from rotating masses overpower the axial forces, thus changing the state of the bi-stable mechanism. The current design iteration features a torsional spring loaded mechanism that overpowers axial forces upon penetration, thus triggering the change in the bi-stable mechanism. Testing on ex-vivo animal structures has demonstrated that the device can withdraw the drill bit in sufficient time to eliminate the risk of soft tissue damage. Ease of use and portability of the device will enable its use in unregulated environments such as hospital emergency rooms and emergency disaster relief areas.

Associated Papers

A Light-Reflecting Balloon Catheter for Atraumatic Tissue Defect Repair
Roche ET, Fabozzo A, Lee Y, Polygerinos P, Friehs I, Schuster L, Whyte W, Casar Berazaluce AM, Bueno A, Lang N, et al. A Light-Reflecting Balloon Catheter for Atraumatic Tissue Defect Repair. Science Translational Medicine [Internet]. 2015;7 (306) :306ra149. Publisher's VersionAbstract

Closing small defects in the body typically requires stitching of tissues during surgery. Toward a minimally invasive approach, Roche et al. engineered a balloon catheter with a reflective surface coating that could be used to adhere biodegradable patches to tissues. The device unfolds the patch and its adhesive, delivers ultraviolet (UV) light, and then applies pressure to stabilize the adhesive as the light cures the polymer. The authors demonstrated catheter-mediated application of the photocurable polymer patch in vivo in rat tissue, with minimal inflammation and complete animal survival, as well as in a challenging septal defect in the beating hearts of pigs. The device was also used to seal porcine stomach ulcers and abdominal hernias ex vivo, suggesting versatility of this approach in repairing defects more easily and atraumatically than sutures.A congenital or iatrogenic tissue defect often requires closure by open surgery or metallic components that can erode tissue. Biodegradable, hydrophobic light-activated adhesives represent an attractive alternative to sutures, but lack a specifically designed minimally invasive delivery tool, which limits their clinical translation. We developed a multifunctional, catheter-based technology with no implantable rigid components that functions by unfolding an adhesive-loaded elastic patch and deploying a double-balloon design to stabilize and apply pressure to the patch against the tissue defect site. The device uses a fiber-optic system and reflective metallic coating to uniformly disperse ultraviolet light for adhesive activation. Using this device, we demonstrate closure on the distal side of a defect in porcine abdominal wall, stomach, and heart tissue ex vivo. The catheter was further evaluated as a potential tool for tissue closure in vivo in rat heart and abdomen and as a perventricular tool for closure of a challenging cardiac septal defect in a large animal (porcine) model. Patches attached to the heart and abdominal wall with the device showed similar inflammatory response as sutures, with 100% small animal survival, indicating safety. In the large animal model, a ventricular septal defect in a beating heart was reduced to <1.6 mm. This new therapeutic platform has utility in a range of clinical scenarios that warrant minimally invasive and atraumatic repair of hard-to-reach defects.

Self-Assembling, Low-Cost, and Modular mm-Scale Force Sensor
Gafford JB, Wood RJ, Walsh CJ. Self-Assembling, Low-Cost, and Modular mm-Scale Force Sensor. IEEE Sensors Journal [Internet]. 2016;16 (1) :69-76. [Cover Article]. Publisher's VersionAbstract

The innovation in surgical robotics has seen a shift toward flexible systems that can access remote locations inside the body. However, a general reliance on the conventional fabrication techniques ultimately limits the complexity and the sophistication of the distal implementations of such systems, and poses a barrier to further innovation and widespread adoption. In this paper, we present a novel, self-assembling force sensor manufactured using a composite lamination fabrication process, wherein linkages pre-machined in the laminate provide the required degrees-of-freedom and fold patterns to facilitate self-assembly. Using the purely 2-D fabrication techniques, the energy contained within a planar elastic biasing element directly integrated into the laminate is released post-fabrication, allowing the sensor to self-assemble into its final 3-D shape. The sensors are batch-fabricated, further driving down the production costs. The transduction mechanism relies on the principle of light intensity modulation, which allows the sensor to detect axial forces with millinewton-level resolution. The geometry of the sensor was selected based on the size constraints inherent in minimally invasive surgery, as well as with a specific focus on optimizing the sensor's linearity. The sensor is unique from the fiber-based force sensors in that the emitter and the detector are encapsulated within the sensor itself. The bare sensor operates over a force range of 0-200 mN, with a sensitivity of 5 V/N and a resolution of 0.8 mN. The experimental results show that the sensor's stiffness can be tuned using a thicker material for the spring layer and/or encapsulation/integration with soft materials. The empirical validation shows that the sensor has the sensitivity and the resolution necessary to discern the biologically relevant forces in a simulated cannulation task.

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