Related Application

[001] The present invention claims priority to Singapore patent application no. 10202251440A filed on 20 October 2022, the disclosure of which is incorporated in its entirety. Also incorporated by reference is International patent application no. PCT/SG2023/05407 or Taiwan patent application no. TW112121318.

Field of Invention

[002] The present invention relates to force feedback actuators deployable in a wearable apparel to generate sensation in virtual reality, augmented reality, mixed reality, extended reality applications. The apparel can be a vest, a glove or a belt, with the actuators being operable to simulate blunt force, point-impact force, amplified force or moving force sensations.

Background

[003] Virtual reality (VR), augmented reality, mixed reality or extended reality applications often lack desired sensation of touch to give a more immersive experience. Touch sensation helps to provide a greater understanding of the physical world around us; such tactile sensation augments visual or audio inputs, and can be configured to give a more immersive experience, such as, simulated sharp, blunt or impact force sensations. In addition, such point forces on a user’s skin are operable to generate moving-force sensations, such as, simulated massaging.

[004] A tactile wearable gaming vest by Cel Kom LLC as disclosed in US patent 7,967,679 is known. A disadvantage of this gaming vest is that it is tethered to a pneumatic power source powered by an air compressor.

[005] Desirably, this invention is configured by 3D printed pneumatic actuators to provide force feedback or sensation for virtual reality (VR), augmented reality (AR), mixed reality (MR), extended reality (xD), haptics or massaging applications; these 3D printed force feedback actuators are pneumatically actuated, for example by very small volume bladders that are operable at safe pressure levels meant for wearables; they are thus very compact, relative small in sizes, easy to customise into a wearable apparel, fast response time, and so on. Advantageously, these compact pneumatic force feedback actuators do not require an air compressor to supply compressed air. In addition, the simulated force can be configured for sharp, blunt, impact or amplified force sensations, or for multiple-points or moving point forces for massaging applications.

Summary

[006] The following presents a simplified summary to provide a basic understanding of the present invention. This summary is not an extensive overview of the present invention, and is not intended to identify key features of the invention. Rather, it is to present some of the inventive concepts of this invention in a generalised form as a prelude to the detailed description that is to follow.

[007] The present invention seeks to provide force feedback actuators to generate force sensations for virtual reality, such as force sensation being a blunt force, a point-impact force, an amplified force or moving-force sensation; desirably, the force feedback actuators are 3D-printed; these force feedback actuators are thus small and compact in dimensions; in addition, they are suitable to be operable at a safe pneumatic actuation pressure and thus are suitable for use in a wearable apparel.

[008] In one embodiment, the present invention provides a force feedback actuator (FFA) which comprises: a base layer; an internal cavity formed inside the base layer, with the internal cavity in fluid communication with a port; a flange ring formed on top of the base layer; a first tape disposed across an inside of the flange ring; and a skin layer formed on the first tape and across the inside of the flange ring; wherein the base layer, the flange ring and the skin layer are formed by 3D-printing to form the internal cavity into an air-tight chamber, with the port for supplying a fluid pressure to deform the skin layer during actuation of the FFA or for releasing the fluid pressure for the skin layer to return to an undeformed state during de-actuation of the FFA.

[009] Preferably, the base layer is formed with a thermoplastic urethane (TPU) of Shore hardness higher than a Shore harness of a TPU for forming the skin layer. [0010] Preferably, the FFA further comprises a bladder that can be fitted inside the internal cavity to contain the fluid pressure supplied through the port. Alternatively, the FFA further comprises a groove formed on a bottom surface of the base layer located inside the internal cavity, a second tape is disposed over the groove, and a bladder membrane is formed over the second tape, with the bladder membrane being formed across the internal cavity.

[0011] Preferably, the FFA further comprises a plurality of spaced apart petal members projecting from an inside edge of the flange ring into the skin layer. Preferably, a top surface of the flange ring is formed with crenellations, with the crenellations formed by merlons and crenelles, and the plurality of spaced petal members project from the merlons into the skin layer.

[0012] Preferably, the FFA further comprises an extension ring projecting a predetermined height h from the flange ring, and the skin layer is formed on the extension ring. The FFA may comprise a plurality of extension rings and associated skin layers, wherein axes of the extension rings and the associated skin layers are substantially parallel or diverging. When actuated, the skin layer bulges outwardly and a perceived pressure at a tip of the bulged skin layer is given by n x P, where n is a ratio of an area A of the FFA across the skin layer to an area TA across an individual tip of the bulged skin layer, and P is a pressure across area A of a FFA without the extension ring. In addition, when actuated, an amplified perceived force at the tips of an actuated FFA is given by m x F, wherein m is the number of bulged skin layers and F is the perceived force sensed at a tip of an individual bulged skin layer.

[0013] Preferably, the FFAs are located inside a wearable apparel, which comprises a glove, a buckle member associated with a belt, a body band, a headgear or a vest, to simulate tactile force sensations.

[0014] In another embodiment, the present invention provides a method for generating tactile force sensation comprising: supplying fluid pressure to the above FFAs; controlling the fluid pressure supply according to any desired pattern and any desired groups of the FFAs; and simulating blunt force, point-impact force or amplified force sensation.

[0015] In yet another embodiment, the present invention provides a method for generating a moving-force sensation comprising: arranging the FFAs according to a desired pattern; supplying fluid pressure to a first group of FFAs in the desired pattern; releasing the fluid pressure to the first group of FFAs and supplying fluid pressure to a next group of FFAs; and sequentially supplying fluid pressure and releasing fluid pressure to progress through all groups of the FFAs to generate a moving-force sensation.

Brief Description of the Drawings

[0016] This invention will be described by way of non-limiting embodiments of the present invention, with reference to the accompanying drawings, in which:

[0017] FIG. 1 illustrates a force feedback actuator formed according to an embodiment of the present invention, whilst FIG. 2 illustrates a sectional view of the actuator shown in FIG. 1 and FIG. 3 illustrates a shape of the actuator when actuated;

[0018] FIG. 4 illustrates a force feedback actuator formed according to another embodiment of the present invention;

[0019] FIG. 5 illustrates a force feedback actuator formed according to another embodiment of the present invention, whilst FIG. 6 illustrates a sectional view of the actuator shown in FIG. 5, whilst FIG. 7 illustrates a shape of the actuator when actuated;

[0020] FIG. 8 illustrates a force feedback actuator formed with a skin layer of silicone DS 10, and FIG. 9 illustrates a shape of the skin layer when the actuator is actuated;

[0021] FIG. 10 illustrates a force feedback actuator formed with a skin layer of TPU Shore harness 60A, whilst FIG. 11 illustrates a shape of the skin layer when the actuator is actuated;

[0022] FIG. 12 illustrates a force feedback actuator formed with a skin of TPU shore harness 85 A, whilst FIG. 13 illustrates a shape of the skin layer when the actuator is actuated;

[0023] FIG. 14 illustrates a force feedback actuator formed with a skin of TPU Shore harness

95 A, whilst FIG. 15 illustrates a shape of the skin layer when the actuator is actuated; [0024] FIG. 16 illustrates a graph showing comparative force output variation with actuation pressure with the skin layer being made from various types of TPU Shore hardness;

[0025] FIG. 17 illustrates a graph showing comparative material extensions of the skin layer with variations in actuation pressure;

[0026] FIG. 18 illustrates a force feedback actuator formed to simulate blunt force output according to another embodiment of the present invention; FIG. 19 illustrates a force feedback actuator formed to simulate a point impact force output; whilst FIG. 20 illustrates a section view of the actuator shown in FIG. 18 or 19;

[0027] FIG. 21 illustrates a force feedback actuator formed to simulate force amplification according to another embodiment of the present invention; FIGs. 22-23 illustrate sectional views of the actuator shown in FIG. 21 being formed according to two variations;

[0028] FIG. 24 illustrates a force feedback actuator formed according to a variation of the embodiment shown in FIG. 21, whilst FIG. 25 illustrates the actuator in FIG. 24 being located inside a glove;

[0029] FIG. 26 illustrates the above force feedback actuator for use with a belt to provide tactile force sensation; and

[0030] FIGs. 27-28 illustrate the above force feedback actuator for use with a vest to provide a method of generating-moving force sensation.

Detailed Description

[0031] One or more specific and alternative embodiments of the present invention will now be described with reference to the attached drawings. It shall be apparent to one skilled in the art, however, that this invention may be practised without such specific details. Some of the details may not be described at length so as not to obscure the invention. For ease of reference, common reference numerals or series of numerals will be used throughout the figures when referring to the same or similar features common to the figures. [0032] FIG. 1 shows a force feedback actuator (FFA) 100 according to an embodiment of the present invention. FIG. 2 shows the FFA in a sectional view, whilst FIG. 3 shows the FFA after it is actuated with a pressurized fluid, such as, compressed air. As shown in FIGs. 2 and 3, the FFA 100 is made up of a base layer 102, an internal cavity 106 connected to a port 104, and a flange ring 110 formed at a top of the base layer 102. On an inside edge of the flange ring 110, spaced apart petal members 112 project from the inner edge; the centre void space of the flange ring 110 is then formed over with a skin layer 140, so that the internal cavity 106 bound by the base layer 102, the flange ring 110 and the skin layer 140 becomes an air-tight chamber, with the air-tight chamber being in fluid communication with the port 104. A tubing T connected to the port 104 supplies pressurized fluid for actuation of the FFA 100. In one embodiment, the FFA 100 is formed by 3D printing, such as, by fused deposition modelling (FDM). In one embodiment, the base layer 102 and the flange ring 110 are made of a thermoplastic urethane (TPU) of a relatively high hardness, such as, Shore hardness 95A, whilst the skin layer 140 is made of a relatively lower Shore harness material; in one embodiment, the skin layer 140 may be made of pure silicone (DS10), a TPU of lower Shore hardness (such as 60A or 85A) or even a TPU of Shore hardness 95A but of a relatively thinner dimension compared to that of the base layer 102.

[0033] Disposed inside the internal cavity 106 of the FFA is a bladder 120. As shown in the figures, the internal cavity 106 is connected to the port 104. To allow 3D-printing of the skin over the internal cavity 106, a tape 109 is provided over the internal cavity 106; in use the bladder 120, such as a pre-formed element, is inserted into the internal cavity 106 and a mouth of the bladder 120 is sealingly connected to the port 104. FIG. 3 is a sectional view after the FFA is actuated by a pressurized fluid supplied into the bladder 120 (the bladder is not shown in FIG. 3), with the skin layer 140 being shown to bulge outwardly; when the fluid supply is released of its pressure, the skin layer 140 reverts to its unactuated state.

[0034] FIG. 4 shows a sectional view of a FFA 100a similar in construction as the above FFA 100 except that an internal cavity 106a is relatively thinner and more compact; in one embodiment, the internal cavity 106a is formed with a thin, flat groove 105 formed at a bottom surface of the base layer located inside the internal cavity. To 3D-print a bladder membrane 120a over the flat groove 105, a tape 107 is disposed over the flat groove 105; in the same manner, to 3D-print the skin layer 140 over the internal cavity 120a, another tape 109 is disposed over the bladder membrane 120a. In one embodiment, the bladder membrane 120a is formed with a thickness range of substantially 0.4 mm to 0.8 mm. The bladder membrane 120a may be made of a soft material, such as, silicone rubber, which is more ductile or of a lower stiffness material than TPU Shore hardness 60A. With this construction, the FFA 100a can be formed with the internal cavity 106a that is thinner in dimension, compared to that of the above internal cavity 106. Advantageously, the bladder membrane 120a is snuggly fitted inside the internal cavity 106a and the FFA can transfer force quickly in response to a pressurized fluid supplied through the port 104; in contrast, in the above FFA 100, the bladder 120 has to expand at an initial stage for inflating the bladder 120 and to fill up any void space inside the internal cavity 106 before the bladder 120 contacts the skin layer 140.

[0035] In the above embodiments, the bladder 120 and bladder membrane 120a are formed from a softer material compared to the material of the skin layer 140; when formed the bladder 120 or the bladder member 120a acts inside the internal cavity 106,106a as a seamless, hermetic seal, whilst the skin layer 140 acts as a controlling constraint to the bladder 120 or bladder membrane 120a; with this FFA construction, the skin layer 140 minimises strain or rupture on the bladder/bladder membrane; advantageously, the skin layer 140 increases the pressure tolerance of the FFA, thus enabling the FFA to reach an actuation pressure of substantially over 200kPa; this FFA construction configuration has been proven to be more reliable than a configuration using any bladder formed with seams.

[0036] FIG. 5 shows a FFA 100b according to another embodiment of the present invention. FIG. 6 shows a sectional view of the FFA 100b, whilst FIG. 7 shows a skin layer 140b of the FFA being bulged outwardly by a pressured fluid supplied to the port 104 via a tubing T. The FFA 100b is 3D-printed according to the description relating to FIG. 2 or to the description relating to FIG. 4, except that a top surface of a flange ring 110b is now formed with crenellations 114, which resemble surface structure on top of a castle. Each crenellation 114 is formed with a projected member or merlon and a groove or crenelle. In one embodiment, a petal member 112b extends from each merlon; the crenellations and the petal members 112b can be more clearly visualised in FIG. 5 or FIGs. 8-15. The above description on the construction of the FFA 100,100a are applicable to similar features of the FFA 100b and no further description is thus provided. [0037] In the above embodiments, the base layer 102 or the flange ring 110,110b are shown to be substantially round in shape; it is possible that the base layer 102, the flange ring 110,110b and outline shape of the FFA 100, 100a, 100b are formed in a polygonal or oval shape, according to a desired pattern of force output. In one embodiment, the base layer 102 or the flange ring 110,110b may be formed with a diagonal dimension of substantially 10- 20 mm, but this dimension is not so restricted; in another embodiment, the base layer 102 may be formed with a thickness dimension of substantially 10 mm or less; the thickness dimension of the base layer 102 may also depend on the sizes of the port 104, the tubing T and a type of suitable port connection (such as, male or female connection with the tubing T). Also the thickness of the bladder membrane 120a or the skin layer 140,140b also depends on the nozzle size of a selected 3D-printer, selected material of the skin layer, and life expectancy of the FFA 100, 100a, 100b.

[0038] In the above description, the skin layer 140,140b may be formed with a thickness range of substantially 0.4 to 0.8 mm when using a nozzle size of substantially 0.3mm for 3D printing, whilst thickness of the flange ring 110 may be substantially 1 mm. The petal members 112,112b are provided to increase the fusion length between the flange ring 110 and the skin layer 140,140b; with the petal members 112,112b, the FFAs 100, 100a, 100b are expected to have longer operating lives, in relation to fatigue on the material of the skin layer caused by repeated inflation and deflation of the FFAs.

[0039] Also, in the above description, the FFAs 100b are formed with crenellations 114. The crenellations 114 are formed to add stiffness to the flange ring 110b, so as to maintain dimensional integrity of the flange ring 110b, also the dimensional integrity the entire FFAs.

[0040] FIGs. 8-9 show the above FFA 100b has been formed with a skin layer 140b of pure silicone, grade DS10; pure silicone, grade DS10 is obtainable as type DragonSkin- 10, from Smooth-On, USA. In FIGs. 8-9, the skin layer 140b formed from pure silicone, grade DS10 is very soft and exhibits very large extensions, as seen in FIG. 9. With an inflation tolerance of substantially less than 40kPa, as seen from FIGs. 16 and 17, the corresponding force simulation using FFA with pure silicone, grade DS 10 is too low. [0041] FIGs. 10-15 show the above FFAs 100b have been formed with skin layer 140b of TPU Shore hardness 60A, 85A and 95A; from these figures, extensions of the skin layer 140 are seen to depend on the Young’s modulus, which is proportional to substantially the Shore harness of the TPU. Tests were carried out and graphs of force output from the FFAs and extensions of the skin layer 140b against actuation pressure were plotted in FIGs. 16-17. The FFAs 100b made with the skin layer 140 of TPU Shore hardness 85A and 95A have been shown to reliably withstand an inflation pressure of over 270 kPa. For force simulation with wearable FFAs, the safe working pressure of substantially 200 kPa has been adopted; accordingly, FFAs with skin layer 140b made of TPU Shore hardness 60A meets the safe working pressure for wearable FFAs.

[0042] A closer examination of the graph in FIG. 17 shows that the TPU extension ratios varied with the Young Modulus, which is proportional to substantially the Shore hardness. However, the extension ratios of TPU Shore hardness 95A, in FIG. 17, are shown to lay between those of TPU 60A and 85 A; this might be caused by, possibly variations in the TPU materials obtained from different sources. When assessing the FFAs of the present invention, the Young Modulus of TPU Shore harness 95 A (Polyflex 95 A obtained from Polymaker) lies between those of TPU Shore hardness 60A and 85A (with TPU Shore harness 60A being material X60 obtained from Diabase, and TPU Shore hardness 85A being Ninjaflex 85A obtained from Ninjatek).

[0043] A limitation of known wearable FFA is the limited force output operating at the safe working pressure of substantially 200 kPa. To increase the force output of wearable FFA for simulating tactile sensations, increasing the compressed air chambers of such FFA is not suitable for use in a wearable apparel, such as, a vest or glove. An advantage of the present invention is that the FFAs 100, 100a, 100b have very compact air actuation internal cavities 106,106a; accordingly these FFAs provide correspondingly quick actuation response time, of substantially 0.2-0.3 s for each FFA to inflate and self-deflate. A further development of these advantages is to simulate a higher perceived force using these FFAs 100, 100a, 100b, as will be described below:

[0044] FIGs. 18-19 show two FFAs 200 formed according to another embodiment of the present invention. FIG. 20 illustrates a sectional view of the FFA 200 shown in FIG. 18 or 19. As in the above embodiments, each of the FFA 200 is made up of a base layer 102, formed with an internal cavity 206 to receive a bladder 120 or a bladder membrane 120a, a port 104 fluidly connected to the internal cavity 206, a flange ring 110 and a skin layer 240, except that the skin layer 240 is now formed on an extension ring 215 of a predetermined height h extending from a top of the flange ring 110. In FIG. 18, the skin layer 240 has a relatively larger area than that of the skin layer 240 in FIG. 19, so that when actuated, the bulged skin layer 240 in FIG. 18 simulates a blunt force output; whereas, the bulged skin layer 240 in FIG. 19 simulates a point impact force. The base layer 102, the internal cavity 206, the bladder 120 or the bladder membrane 120a, the port 104, the flange ring 110, the skin layer 240 are formed according to similar corresponding elements described above, and no further descriptions of these elements are thus provided. As represented in FIG. 20, the extension ring 215 is formed as an integral part of the flange ring 110. The extension ring 215 thus allows a force sensation F to be perceived at a predetermined height h located above the flange ring 110; in one embodiment, the height h may be substantially 5 mm.

[0045] In FIG. 20, an area of the FFA 200 across the flange ring is denoted as A, whilst a tip area at the bulged skin layer is TA. Assuming a perceived pressure P is sensed across the area A (that is, at the FFA without the extension ring), and n is the ratio of the area A to the tip area TA of the bulged skin layer, the pressure perceived at the tip area of the bulged skin layer is n x P; the perceived pressure at the tip area of the FFA shown in FIG. 18 is therefore lower than the perceived pressure at the tip area of the FFA shown in FIG. 19; in other words, the perceived force sensed at a smaller tip area of the FFA shown in FIG. 19 is higher than that of the perceived force at a bigger tip area of the FFA shown in FIG. 18. The perceived force at an individual tip area of the FFA is now denoted F in FIG. 20.

[0046] FIG. 21 shows a FFA 200a formed according to a variation of the above FFA 200. In FIG. 21, the FFA 200a is shown to include 5 extension rings 215 and corresponding skin layers 240al, 240a2... 250a5 raised on the associated extension rings, with 5 numbers being an example. With the perceived force F at an individual tip area of the bulged skin layer, the force perceived by a user at an actuated FFA 200a is m x F, where m represents the number of tips of bulged skin layers.

[0047] When the numbers m of the tips of the bulged skin layers 240 of a FFA are configured in close proximity to each other, our human touch response cannot perceive individual simulated point forces, according to a two-point discrimination (2PD) principle. In other words, multiple simulated point forces on a user epidermis are perceived or sensed as an amplified force sensation of magnitude m x F; this means that, by simulating a number m of point forces in close proximity, the user perceives or senses an amplified force of magnitude m x F from an actuated FFA 200a, without having to increase the fluid pressure applied to the port 104.

[0048] In FIG. 22, the extension rings 215 are shown to be arranged substantially vertically from the flange ring 110; accordingly, axes of the extension rings 215 and the associated bulged skin layers 240 appear to be substantially parallel. However, in another embodiment 200b of the FFA shown in FIG. 23, the axes of the extension rings 215 and the associated bulged skin layers 240 are shown to be diverging at an angle a. This embodiment is advantageous in that tips of the bulged skin layers 240 can be adjusted by the angle a to provide a desired spatial density of force F simulation; For example, when a plurality of FFAs is located in close proximity to each other, the perceived forces F at the tips can be adjusted to be more regularly spaced apart.

[0049] The 2PD technique to simulate increased sensible force perception occurs in other body regions. For example, in a sensory dense area, such as, in the palm, the amplified force magnitude n x F is more pronounced. FIG. 24 shows a FFA 300 according to another embodiment of the present invention. The FFA 300 is constructed in similar manners as the above FFAs, except that the base layer 102 now extends up to surround the flange ring 110. In use to provide tactile force sensation, a plurality of FFAs 300 is located inside a glove WG worn over a palm of a user; these FFAs 300 may be linked or grouped for actuation in a desired pattern by sequentially supplying fluid pressure to associated groups of tubings T (which are not shown).

[0050] In another embodiment to simulate force amplification, it is possible that individual FFAs are located in close proximity, with each FFA being provided with a single skin layer 140, 140b, 240; this is made possible due to the small outline dimension of the above FFAs.

[0051] FIG. 26 shows another implementation of the FFA of the present invention. As shown in FIG. 26, the FFA is located on a buckle member 350 and is wearable around a waist of a user; in one embodiment, a plurality of FFAs is located on the buckle member 350; the FFA can be any configuration of the above force feedback actuator 100, 100a, 100b, 200, 200a, 200b, 300 that are described above.

[0052] FIGs. 27-28 show yet another implementation of the FFAs of the present invention. The FFAs shown in FIGs. 27-28 are located inside a wearable vest WV. For illustration purposes, the FFAs are arranged in two vertical rows inside the wearable vest WV; when donned on, the FFAs may be located over the abdominal muscles or the spinal muscles of a user. For illustration, the FFAs are laterally arranged in 4 rows; when a lateral row of FFAs is supplied with fluid pressure via the ports 104, they are described as “active” FFAs. When the fluid pressure is released, the FFAs are described as “inactive”. By sequentially actuating lateral rows of the FFAs, for example, according to arrows M, a pattern of force simulation is generated by the FFAs; the force simulation may follow a desired pattern of moving-force sensation. The pattern of moving-force simulation may be useful for a massaging application; such massaging applications may help to relieve aching muscles, to help improve blood circulation in a therapy, and so on. This embodiment may be re-configured inside an arm band, a waist band, a thigh band, a head-gear, and so on, for simulating tactile force sensation on or for massaging other body regions.

[0053] The above wearable vest WV with the FFAs has been described in a simplified manner. In addition to providing reality tactile force sensation, the wearable vest WV can also be used to simulate contact forces in other applications, such as, boxing, mixed martial arts, shooting, fencing, and similar virtual games, to simulate blunt force sensation or amplified force sensation. The area of the skin layer can also be reduced, as in FIG. 19, to simulate point-impact force sensation.

[0054] In use, the wearable vest is controlled by system donned on the back of a user. The control system includes a power system, fluid control valves, fluid pressure source (such as, a pressurized pneumatic cannister) and a microcontroller. Advantageously, ultra-low volume of the internal cavities 106, 106a, 206 allow the above FFAs to exhibit fast response time of substantially 0.3s to inflate and self-deflate, besides generating high output forces at a fluid pressure of substantially 200kPa. The ultra-low volume internal cavities also consume little compressed air; for example, a wearable pneumatic cannister can support operating 6 FFAs for substantially 45 minutes. By providing a wearable pneumatic cannister, the wearable vest WV becomes free from tethering from an external fluid power source (such as, a pneumatic compressor). Advantageously, the wearable vest WV provides adjustability to fit different users. In addition, the present invention is made in modules, ranging from the control system to the FFAs, thus allowing users to change the FFAs placement to simulate different desired force sensations, ease of FFAs or components replacement, or for any upgrading of the FFA and its control system. The modules also allow the components to be taken out for the wearable vest WV for washing or cleaning.

[0055] While specific embodiments have been described and illustrated, it is understood that many changes, modifications, variations and combinations of variations disclosed in the text description and drawings thereof could be made to the present invention without departing from the scope of the present invention. For example, whilst FDM has been described, some other 3D-printing techniques, such as, stereolithography (SLA) or powder bed fusion (PBF) can also be employed to print the above FFAs, with considerations for available forms and costs of TPU materials.