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Research Papers

Toward Medical Devices With Integrated Mechanisms, Sensors, and Actuators Via Printed-Circuit MEMS

[+] Author and Article Information
Joshua Gafford

John A. Paulson School of Engineering
and Applied Sciences,
Harvard University,
Cambridge, MA 02138
e-mail: jgafford@seas.harvard.edu

Tommaso Ranzani, Sheila Russo, Samuel Kesner

Wyss Institute for
Biologically-Inspired Engineering,
Boston, MA 02115

Alperen Degirmenci

John A. Paulson School of
Engineering and Applied Sciences,
Harvard University,
Cambridge, MA 02138

Robert Howe, Robert Wood, Conor Walsh

John A. Paulson School of
Engineering and Applied Sciences,
Harvard University,
Cambridge, MA 02138;
Wyss Institute for
Biologically-Inspired Engineering,
Boston, MA 02115

1Corresponding author.

Manuscript received July 31, 2016; final manuscript received November 9, 2016; published online January 11, 2017. Assoc. Editor: Rita M. Patterson.

J. Med. Devices 11(1), 011007 (Jan 11, 2017) (12 pages) Paper No: MED-16-1291; doi: 10.1115/1.4035375 History: Received July 31, 2016; Revised November 09, 2016

Recent advances in medical robotics have initiated a transition from rigid serial manipulators to flexible or continuum robots capable of navigating to confined anatomy within the body. A desire for further procedure minimization is a key accelerator for the development of these flexible systems where the end goal is to provide access to the previously inaccessible anatomical workspaces and enable new minimally invasive surgical (MIS) procedures. While sophisticated navigation and control capabilities have been demonstrated for such systems, existing manufacturing approaches have limited the capabilities of millimeter-scale end-effectors for these flexible systems to date and, to achieve next generation highly functional end-effectors for surgical robots, advanced manufacturing approaches are required. We address this challenge by utilizing a disruptive 2D layer-by-layer precision fabrication process (inspired by printed circuit board manufacturing) that can create functional 3D mechanisms by folding 2D layers of materials which may be structural, flexible, adhesive, or conductive. Such an approach enables actuation, sensing, and circuitry to be directly integrated with the articulating features by selecting the appropriate materials during the layer-by-layer manufacturing process. To demonstrate the efficacy of this technology, we use it to fabricate three modular robotic components at the millimeter-scale: (1) sensors, (2) mechanisms, and (3) actuators. These modules could potentially be implemented into transendoscopic systems, enabling bilateral grasping, retraction and cutting, and could potentially mitigate challenging MIS interventions performed via endoscopy or flexible means. This research lays the ground work for new mechanism, sensor and actuation technologies that can be readily integrated via new millimeter-scale layer-by-layer manufacturing approaches.

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References

Figures

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Fig. 1

Conceptual LESS dissection procedure, with callouts illustrating end-effector modules developed in this research

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Fig. 2

PCMEMS layer-by-layer manufacturing process

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Fig. 3

(top) 355 nm Nd:YVO4 laser modeled as a Gaussian beam, and associated ablation rate dependence on depth of cut, (bottom) manufacturing timing diagram (hatched requires constant supervision/attention, solid requires no intervention) with qualitative graphs showing how the processing time scales with the number of layers in the laminate

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Fig. 4

Deterministic design and analysis process flow used to build three-axis PCMEMS force sensor, (top) numerical and analytical modeling of the simplified structure, (middle) CAD generation of toolpaths, (bottom) fabrication using process outlined in Sec. 2.1

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Fig. 5

Various transduction modalities demonstrated via PCMEMS: (a)–(c) strain gage-based force sensor modeling, fabricated prototype, and validation (reconstructed tissue stiffness profile obtained via robotic palpation), (d)–(f) light intensity modulation force sensor modeling, fabricated prototypes, and calibration profile, (g)–(i) capacitance force sensor modeling, fabricated prototype, and calibration profile

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Fig. 6

Conceptual representation of force-sensing microsurgical forceps integrated into a flexible system, with an image of a conventional 5 mm laparoscopic forcep for scale

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Fig. 7

(a) Origami-inspired assembly of force-sensing microsurgical forceps and (b) fabricated device on a U.S. penny for scale and an associated kinematics diagram, showing internal Sarrus linkage and planar return spring

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Fig. 8

(a) Torsion failure results and (b) peel failure results, both of which show a sufficiently linear dependence on hinge geometry, and insets show 3D renderings of test samples, (c) torsion failure results for different hinge materials (Reprinted with permission from Gafford et al. [23]. Copyright 2013 by ASME).

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Fig. 9

(a) Force-sensing microsurgical forceps and associated wiring and signal conditioning, where the inset shows on-board half-bridge with the locations of the measuring and compensating gages highlighted, (b) (left) results of needle driving experiment showing a clear distinction between initial grip force and needle driving force, (right) results of tissue retraction experiment, where a number of discrete states (contact, grasping, retraction, and release) can be discerned based on the recorded force profile

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Fig. 10

Dexterous manipulation demonstration on a 6DoF robotic micromanipulation platform, (a) robotic platform shown with gripper and modular servo/signal conditioning attachment, (b) still frame of gripper assembling a pyramid from 1 mm steel bearing balls, and (c) representative force reading for eight different ball displacements (Reprinted with permission from Degirmenci et al. [28]. Copyright 2015 by IEEE).

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Fig. 11

(a) Kinematic representation of reciprocating cutting head and associated driving scheme and (b) mechanical representation of structural loop with relevant parameters

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Fig. 12

Active cutting device manufacturing process: (a) exploded view of laminate, showing sublaminates for actuators and mechanisms, and (b) cross section of the laminated structure

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Fig. 13

(a) Fabricated tissue removal device actuated by on-board piezoelectric bimorphs, (b) test setup for kinematic evaluation of tissue cutting device, showing a detail of the sensor interface, and (c) testing results where the measured jaw displacement is compared with the displacement predicted by the dynamic model

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Fig. 14

Mechanical debridement results: (a) test setup (inset shows blade penetrating tissue), (b) force/displacement curve for oscillating blade on pig intestine, and (c) force/displacement curve for oscillating blade on pig stomach

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