Method and system for designing a biomechanical interface contacting a biological body segment
A method and associated system for designing a biomechanical interface of a device contacting a biological body segment of a subject includes forming a quantitative model of the biological body segment from subject specific data, conducting a biophysical analysis, such as a finite element analysis, to thereby establish a relationship, such as a functional relationship, between the quantitative model and at least one feature of the biomechanical interface contacting the biological body segment, and applying the relationship to the at least one feature of the biomechanical interface contacting the biological body segment to thereby obtain an interface design for the mechanical interface of the device. The subject-specific data can include geometry of the biological body segment and the at least one feature can be associated with physiological benefit of the biological body segment.
1 . A method for computer design and manufacture of a biomechanical interface of a wearable device interfacing an external surface of a biological body segment of a subject, comprising:
with a computer:
forming a quantitative model of the biological body segment from subject-specific data, the subject-specific data including geometry of the biological body segment;
conducting a biophysical analysis using the quantitative model of the biological body segment, the biophysical analysis including simulation of a response to a donning condition, the simulation including:
forming a single combined model using a finite element analysis (FEA) representation of the quantitative model of the biological body segment and an interface design, wherein the interface design is derived from and meshed with the quantitative model in order to simulate interaction between the quantitative model of the biological body segment and the interface design, the combined model comprising shared nodes, each of the shared nodes representing a portion of both the biological body segment model and the interface design,
morphing the combined model in response to application of a fitting pressure, the morphing including adjusting an equilibrium shape of the interface design,
assigning mechanical properties of the interface design to the morphed combined model, the assigning mechanical properties being generation dependent in the following way:
c
=
{
c
soft
1000
γ
=
1
c
true
γ
=
2
wherein γ is a generation index, c soft denotes the c parameter for soft tissue, and c true denotes a physically realistic c parameter, and
decreasing the fitting pressure applied to the morphed combined model, the combined model responsively undergoing a relaxation phase, wherein following the relaxation phase, both the quantitative model of the biological body segment and the interface design components of the combined model are in a pre-stressed state to simulate the response to the donning condition, and
exporting a final interface design for manufacture by a computer-controlled fabricator, the final interface design based on the morphed combined model.
2 . The method of claim 1 , wherein the biophysical analysis includes at least one member selected from the group of numerical methods consisting of finite element analysis, finite difference methods, finite volume methods, isogeometric analysis, boundary element methods, and meshfree methods.
3 . The method of claim 1 , further including optimizing at least one feature of the biomechanical interface for a physiological benefit of the biological body segment in the biomechanical interface by the biophysical analysis.
4 . The method of claim 1 , further including fabricating the biomechanical interface.
5 . The method of claim 1 , wherein the forming the quantitative model includes at least one non-invasive imaging method selected from the group consisting of magnetic resonance, x-ray, ultrasound, optical methods, tomography, thermography, and elastography, to form a non-invasive image.
6 . The method of claim 5 , including imaging tissue of the biological body segment.
7 . The method of claim 5 , wherein forming the quantitative model further includes employing the non-invasive imaging method to form an external tissue geometry and an internal tissue geometry of the biological body segment.
8 . The method of claim 5 , wherein forming the quantitative model includes employing the non-invasive imaging method to form an external tissue geometry and further includes statistical shape modeling to form an inferred internal geometry of the biological body segment.
9 . The method of claim 1 , wherein forming the quantitative model further includes performing a biomechanical material property analysis of the biological body segment.
10 . The method of claim 9 , wherein the biomechanical material property analysis includes a contact method.
11 . The method of claim 10 , wherein the contact method includes at least one method selected from the group consisting of indentation analysis, pressurization analysis, and vibration analysis.
12 . The method of claim 9 , wherein the biomechanical material property analysis includes a non-contact method.
13 . The method of claim 12 , wherein the non-contact method includes at least one method selected from the group consisting of ultrasound and magnetic resonance imaging.
14 . The method of claim 13 , wherein the non-contact method includes magnetic resonance elastography.
15 . The method of claim 13 , wherein the non-contact method includes ultrasound elastography.
16 . The method of claim 9 , wherein the biomechanical material property analysis includes analysis of at least one biomechanical property selected from the group consisting of impedance, damping, stiffness, the shear and bulk modulus (or any other stiffness or compliance tensor component), and other elastic, hyperelastic, viscoelastic, and poroelastic properties or constitutive parameters of the tissues.
17 . The method of claim 16 , wherein the at least one biomechanical property is mapped against the external tissue geometry.
18 . A system for designing and manufacturing a biomechanical interface of a wearable device interfacing an external surface of a biological body segment of a subject, the system comprising:
a computer comprising:
a modeler that generates a quantitative model of the biological body segment from subject-specific data, the subject-specific data including geometry of the biological body segment;
an analyzer that conducts a biophysical analysis using the quantitative model of the biological body segment, the biophysical analysis including simulation of a response to a donning condition, the simulation including:
forming a single combined model using a finite element analysis FEA) representation of the quantitative model of the biological body segment and an interface design, wherein the interface design is derived from and meshed with the quantitative model, in order to simulate interaction between the quantitative model of the biological body segment and the interface design, the combined model comprising shared nodes, each of the shared nodes representing a portion of both the biological body segment model and the interface design such that the biological body segment model and the interface design are always tied together,
morphing the combined model in response to a fitting pressure, the morphing including adjusting an equilibrium shape of the interface design,
assigning mechanical properties of the interface design to the morphed combined model, the assigning mechanical properties being generation dependent in the following way:
c
=
{
c
soft
1000
γ
=
1
c
true
γ
=
2
wherein γ is a generation index, c soft denotes the c parameter for soft tissue, and c true denotes a physically realistic c parameter, and
decreasing the fitting pressure applied to the morphed combined model, the combined model responsively undergoing a relaxation phase, wherein following the relaxation phase, both the quantitative model of the biological body segment and the interface design components of the combined model are in a pre-stressed state to simulate the response to the donning condition, and
an exporter that exports a final interface design for manufacture by a computer-controlled fabricator, the final interface design based on the morphed combined model.
19 . The method of claim 1 , wherein the biomechanical interface includes a liner and a socket, and wherein the final interface design is for the socket or the liner and socket.
20 . The method of claim 1 , wherein the biomechanical interface includes a liner and a socket, and wherein the donning condition includes liner donning induced pre-loads and socket donning induced pre-loads.
21 . The method of claim 1 , wherein conducting the biophysical analysis further comprises simulation of a response to a functional loading condition, the functional loading condition applied generally to the combined model along a length direction of the body segment to evaluate tissue loading expected during a functional use of the biomechanical interface.
22 . The method of claim 21 , wherein the method further comprises adjusting at least one feature of the biomechanical interface interfacing the biological body segment based on the response of the combined model to the functional loading condition to thereby obtain the final interface design for the biomechanical interface, the at least one feature associated with a physiological benefit of the biological body segment.
23 . The system of claim 18 , wherein conducting the biophysical analysis further comprises simulation of a response to a functional loading condition, the functional loading condition applied generally to the combined model along a length direction of the body segment to evaluate tissue loading expected during a functional use of the biomechanical interface.
24 . The system of claim 23 , wherein the system further comprises an evaluator that adjusts at least one feature of the biomechanical interface interfacing the biological body segment based on the response of the combined model to the functional loading condition to thereby obtain the final interface design for the biomechanical interface of the device, the at least one feature associated with a physiological benefit of the biological body segment.
25 . The method of claim 1 , wherein the morphing the combined model in response to application of a fitting pressure is performed before the assigning mechanical properties of the interface design to the morphed combined model.
26 . The method of claim 25 , wherein the assigning mechanical properties of the interface design to the morphed combined model is performed before the decreasing the fitting pressure applied to the morphed combined model.
27 . The method of claim 26 , wherein conducting the biophysical analysis further comprises simulation of a response to a functional loading condition, the functional loading condition applied generally to the combined model along a length direction of the body segment to evaluate tissue loading expected during a functional use of the biomechanical interface, wherein the decreasing the fitting pressure applied to the morphed combined model is performed before the simulation of a response to a functional loading condition.
28 . The method of claim 1 , further comprising applying a fitting pressure to the combined model when the interface design lacks mechanical strength such that the interface design is freely carried along with motion of the quantitative model of the biological body segment without developing stresses.