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Editorial

J. Med. Devices. 2016;10(2):020201-020201-1. doi:10.1115/1.4033281.

The following technical briefs were submitted, peer reviewed, and accepted for presentation at the 2016 University of Minnesota's Design of Medical Devices (DMD) Conference (www.dmd.umn.edu) held April 11–14, 2016 at The Commons Hotel and McNamara Alumni Center in Minneapolis, MN.

Commentary by Dr. Valentin Fuster

Special Section Technical Briefs

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2016;10(2):020903-020903-2. doi:10.1115/1.4033115.
Topics: Muscle , Blood
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
J. Med. Devices. 2016;10(2):020915-020915-2. doi:10.1115/1.4033206.
Commentary by Dr. Valentin Fuster
J. Med. Devices. 2016;10(2):020917-020917-2. doi:10.1115/1.4033208.
Topics: X-rays , Motors , Sensors
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
J. Med. Devices. 2016;10(2):020919-020919-2. doi:10.1115/1.4033219.
Commentary by Dr. Valentin Fuster
J. Med. Devices. 2016;10(2):020921-020921-2. doi:10.1115/1.4033221.
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
J. Med. Devices. 2016;10(2):020926-020926-2. doi:10.1115/1.4033121.
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
J. Med. Devices. 2016;10(2):020934-020934-2. doi:10.1115/1.4033166.

We demonstrate laser microfabrication of transparent fluoric polymer using a conventional green laser. Fluoric polymers have unique characteristics such as high transparency, chemical resistance, and low refractive index and are expected to overcome many problems which conventional polymers have for biochip applications. We developed crack-free surface microfabrication of commercially available fluoric polymer commercially available fluoric polymer CYTOP (Asahi Glass Co., Ltd., Tokyo) using a conventional green laser. The laser ablation with successive wet etching by fluorine solution and annealing achieves high-quality microfluidics on the surface of the polymer substrate. In addition, we demonstrate the fabrication of a biochip with a three-dimensional fluid structure by bonding two pieces of CYTOP substrates for clear microscopic observation of swimming aquatic microorganism at the sidewall of the fluidics.

Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
J. Med. Devices. 2016;10(2):020936-020936-2. doi:10.1115/1.4033169.
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
J. Med. Devices. 2016;10(2):020961-020961-2. doi:10.1115/1.4033278.
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
J. Med. Devices. 2016;10(2):020963-020963-2. doi:10.1115/1.4033284.
Topics: Lung
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster

Research Papers

J. Med. Devices. 2016;10(2):021001-021001-7. doi:10.1115/1.4032868.

Cancellous bone screws are used to achieve good pull-out characteristics when connected to cancellous bone. This study examines some screw characteristics, including pitch and inner diameter, using a model of cancellous bone with a range of bone apparent densities (ADs). This was achieved using bone geometry based on microCT-scanned cancellous bone and converted into a geometric model using mimics® software. The finite element (FE) models were produced in ansys®. The calculated reaction force for pull-out of 0.2 mm shows the influence of design parameters. Change in the proximal half angle increased the stiffness by about 15% in line with the experimental findings of others. An increase in pull-out reaction force with an increase in bone AD was also observed. However, when a particular screw geometry in lower AD bone was modeled and then rotated through 180 deg on plan, a significant reduction in reaction force was noted. Further models with screws of similar geometry in the same location showed similar reductions in reaction force and hence pull-out stiffness. Examination of the geometry of the bone/screw interface indicates that in certain positions there is little cancellous bone to support the implant—leading to low pull-out reaction forces, which is very difficult to predict. The study also examined the effect of increasing the bone stiffness adjacent to the implant, and concluded that, even in bone of low AD, increases in pull-out stiffness might be achieved.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2016;10(2):021002-021002-8. doi:10.1115/1.4032813.

Instruments used in endoscopic surgery (colonoscopy surgery or natural orifice transluminal endoscopic surgery (NOTES)) are flexible to be advanced in human body. However, when the end of the instrument reaches the target, the instrument should be rigid enough to hold its shape against external forces for better surgical accuracy. In order to obtain these two properties, a variable stiffness over tube based on low-melting-point-alloy (LMPA) is proposed in this paper. The structure exploits the phase transformation property of the LMPA which enables the stiffness change of the over tube by heating and cooling. A prototype was fabricated using a special molding method, and experiments were carried out to evaluate its variable stiffness property and response characteristics. According to experimental results, it costs 17 s to make the over tube transform from rigid state to flexible state and 18 s to make the over tube transform from flexible state to rigid state. The experimental results also indicated that the over tube is very rigid in rigid state and flexible in compliant state. A heat insulation layer was assembled to prevent human tissue from thermal damage. The temperature of the outer wall of the over tube was 42.5 °C when hot water of 80 °C was pumped into the over tube continually with the help of the heat insulation layer.

Topics: Stiffness , Surgery
Commentary by Dr. Valentin Fuster

Technical Brief

J. Med. Devices. 2016;10(2):024501-024501-5. doi:10.1115/1.4032867.

A novel and frugal self-transfer device has been developed for transferring a user, with disabilities in lower limbs, from a wheel chair to a toilet commode or any other surface. The device does not require any external power for the transfer operation, as it utilizes the available physical strength of the upper body of the user. It is designed to raise the user, turn, and place on top of a toilet seat. Lockable gas springs are employed for raising, while a turntable with epicyclic gear train facilitates rotary transfer. Trials were carried out to optimize the ergonomic aspects of the design. Overall acceptability of the system has also been studied, and the results show that the device is capable of transferring a subject from a wheel chair to another surface with less effort.

Topics: Design , Wheels
Commentary by Dr. Valentin Fuster
J. Med. Devices. 2016;10(2):024502-024502-6. doi:10.1115/1.4032870.

Cutting the kneecap (patella) in knee replacement surgery is challenging and can lead to pain and reduced function when done incorrectly. The presented device allows the surgeon to check the three-dimensional symmetry and thickness of the bone remnant before the operation is complete. Observations and measurements made on 36 resected artificial patellae and 16 resected cadaveric patellae matched well with computed tomography (CT) scans of the patellae with few exceptions; the exceptions should be addressable by changes in design and use. Average time to apply the device was 1 min.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2016;10(2):024503-024503-7. doi:10.1115/1.4032869.

It is difficult to achieve a stably delicate operation in manual microsurgery, and the aim of this paper is to evaluate the robotic trephination that can open a promising perspective for the development of robotic microsurgical system for keratoplasty. A robot for corneal trephination integrating a force/torque sensor is designed based on manual trephine action. The manual experiments and the robotic experiments about penetrating trephination are performed in porcine eyes. The expected values of operational parameters that are references to the robotic trephination are obtained from the manual experiments using probability density functions (PDFs), including linear velocity, angular velocity, and rotating angle. Considering the meanings of the forces/torques, the results of the manual and robotic experiments such as trephine forces/torques and photomicrographs are compared to evaluate the effectiveness of robotic trephination. The manual trephination shows some randomness and this leads to large fluctuations in the trephine forces/torques during the surgery, but the robot may improve overall outcome of the graft, as it is able to carry out the operation stably and produce a uniform cutting margin. There is potential to improve the biomechanical properties in the delicate microsurgery by using the trephine robot and such devices can assist the surgeon to achieve a consistently high-quality result.

Commentary by Dr. Valentin Fuster

Design Innovation Paper

J. Med. Devices. 2016;10(2):025001-025001-9. doi:10.1115/1.4032866.

An ankle–foot prosthesis designed to mimic the missing physiological limb generates a large sagittal moment during push off which must be transferred to the residual limb through the socket connection. The large moment is correlated with high internal socket pressures that are often a source of discomfort for the person with amputation, limiting prosthesis use. In this paper, the concept of active alignment is developed. Active alignment realigns the affected residual limb toward the center of pressure (CoP) during stance. During gait, the prosthesis configuration changes to shorten the moment arm between the ground reaction force (GRF) and the residual limb. This reduces the peak moment transferred through the socket interface during late stance. A tethered robotic ankle prosthesis has been developed, and evaluation results are presented for active alignment during normal walking in a laboratory setting. Preliminary testing was performed with a subject without amputation walking with able-bodied adapters at a constant speed. The results show a 33% reduction in the peak resultant moment transferred at the socket limb interface.

Commentary by Dr. Valentin Fuster

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