| 1. |
- Antfolk, Christian, et al.
(författare)
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Transfer of tactile input from an artificial hand to the forearm: experiments in amputees and able-bodied volunteers
- 2013
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Ingår i: Disability and Rehabilitation: Assistive Technology. - : Informa UK Limited. - 1748-3115 .- 1748-3107. ; 8:3, s. 249-254
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Tidskriftsartikel (refereegranskat)abstract
- Abstract in UndeterminedPurpose:This study explores the possibilities of transferring peripheral tactile stimulations from an artificial hand to the forearm skin.Method:A tactile display applied to the forearm skin was used to transfer tactile input to the forearm from various locations on a hand displayed on a computer screen. Discernment of location, levels of pressure and a combination of the two in simulated functional grips was tested to quantify the participants' ability to accurately perceive the tactile stimulations presented. Ten participants (5 forearm amputees and 5 able-bodied volunteers) unfamiliar with the equipment participated in the three-stage experiments comprising a learning session with vision, a reinforced learning session without vision and a validation session without vision.Results:The location discernment accuracy was high in both groups (75.2% and 89.6% respectively). The capacity to differentiate between three different levels of pressure was also high (91.7% and 98.1% respectively in the two groups). Recognition of simulated grip was slightly more difficult with the groups scoring 58.7% and 68.0% respectively for accuracy in the validation session.Conclusions:This study demonstrates that it is possible, following a brief training period, to transfer tactile input from an artificial hand to the forearm skin. The level of accuracy was lower for the more complex task, simulated grip recognition, possibly because this represents a more complex task requiring higher order brain functions. These results could form the basis for developing sensory feedback in hand prostheses. [Box: see text].
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| 2. |
- Cipriani, Christian, et al.
(författare)
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A novel concept for a prosthetic hand with bidirectional non-invasive interface: a feasibility study
- 2009
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Ingår i: IEEE Transactions on Biomedical Engineering. - 1558-2531. ; 56:11, s. 2739-2743
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Tidskriftsartikel (refereegranskat)abstract
- Abstract in Undetermined A conceptually novel prosthesis consisting of a mechatronic hand, an electromyographic classifier, and a tactile display has been developed and evaluated by addressing problems related to controllability in prosthetics: intention extraction, perception, and feeling of ownership. Experiments have been performed, and encouraging results for a young transradial amputee are reported.
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| 3. |
- Antfolk, Christian, et al.
(författare)
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A Tactile Display System for Hand Prostheses to Discriminate Pressure and Individual Finger Localization
- 2010
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Ingår i: Journal of Medical and Biological Engineering. - : Taiwanese Society of Biomedical Engineering. - 1609-0985. ; 30:6, s. 355-359
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Tidskriftsartikel (refereegranskat)abstract
- No current commercially available myoelectrically controlled prosthetic hands provide conscious sensory feedback to the user. A system aiming at relocation of sensory input from a prosthetic hand equipped with force sensors to the forearm skin of amputees, a tactile display, has been developed and constructed. The system consists of five piezoresistive force sensors or, alternatively, a prosthetic hand equipped with force sensors, five digital servomotors with a lever and a circular plastic disk pushing on the skin, control electronics based on an MSP430 microcontroller and a test application implemented in LabVIEW running on a PC. The tactile display system is intended to be integrated into the socket of a hand prosthesis and used as a conscious sensory feedback system for hand amputees using a myoelectrically controlled hand prosthesis. The system will provide continuous force feedback from sensors in the fingertips of each prosthetic finger and will likely improve the users' controllability and perception of the prosthetic hand. Here we report on tests made on "a five site" localization discrimination task and three pressure level discrimination tasks on the forearm of five healthy participants (non-amputees) using the LabView application to generate the stimulations. A mean five-finger discrimination accuracy of 86% and a mean three-level pressure discrimination accuracy of 93% were achieved, indicating the system to be a viable method of producing sensory feedback on the level of individual fingers.
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| 4. |
- Antfolk, Christian, et al.
(författare)
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Artificial Redirection of Sensation From Prosthetic Fingers to the Phantom Hand Map on Transradial Amputees: Vibrotactile Versus Mechanotactile Sensory Feedback
- 2013
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Ingår i: IEEE Transactions on Neural Systems and Rehabilitation Engineering. - 1534-4320. ; 21:1, s. 112-120
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Tidskriftsartikel (refereegranskat)abstract
- This work assesses the ability of transradial amputees to discriminate multi-site tactile stimuli in sensory discrimination tasks. It compares different sensory feedback modalities using an artificial hand prosthesis in: 1) a modality matched paradigm where pressure recorded on the five fingertips of the hand was fed back as pressure stimulation on five target points on the residual limb; and 2) a modality mismatched paradigm where the pressures were transformed into mechanical vibrations and fed back. Eight transradial amputees took part in the study and were divided in two groups based on the integrity of their phantom map; group A had a complete phantom map on the residual limb whereas group B had an incomplete or nonexisting map. The ability in localizing stimuli was compared with that of 10 healthy subjects using the vibration feedback and 11 healthy subjects using the pressure feedback (in a previous study), on their forearms, in similar experiments. Results demonstrate that pressure stimulation surpassed vibrotactile stimulation in multi-site sensory feedback discrimination. Furthermore, we demonstrate that subjects with a detailed phantom map had the best discrimination performance and even surpassed healthy participants for both feedback paradigms whereas group B had the worst performance overall. Finally, we show that placement of feedback devices on a complete phantom map improves multi-site sensory feedback discrimination, independently of the feedback modality.
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| 5. |
- Antfolk, Christian, et al.
(författare)
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Design and technical construction of a tactile display for sensory feedback in a hand prosthesis system
- 2010
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Ingår i: BioMedical Engineering Online. - 1475-925X. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Background: The users of today's commercial prosthetic hands are not given any conscious sensory feedback. To overcome this deficiency in prosthetic hands we have recently proposed a sensory feedback system utilising a "tactile display" on the remaining amputation residual limb acting as man-machine interface. Our system uses the recorded pressure in a hand prosthesis and feeds back this pressure onto the forearm skin. Here we describe the design and technical solution of the sensory feedback system aimed at hand prostheses for trans-radial/humeral amputees. Critical parameters for the sensory feedback system were investigated. Methods: A sensory feedback system consisting of five actuators, control electronics and a test application running on a computer has been designed and built. Firstly, we investigate which force levels were applied to the forearm skin of the user while operating the sensory feedback system. Secondly, we study if the proposed system could be used together with a myoelectric control system. The displacement of the skin caused by the sensory feedback system would generate artefacts in the recorded myoelectric signals. Accordingly, EMG recordings were performed and an analysis of the these are included. The sensory feedback system was also preliminarily evaluated in a laboratory setting on two healthy non-amputated test subjects with a computer generating the stimuli, with regards to spatial resolution and force discrimination. Results: We showed that the sensory feedback system generated approximately proportional force to the angle of control. The system can be used together with a myoelectric system as the artefacts, generated by the actuators, were easily removed using a simple filter. Furthermore, the application of the system on two test subjects showed that they were able to discriminate tactile sensation with regards to spatial resolution and level of force. Conclusions: The results of these initial experiments in non-amputees indicate that the proposed tactile display, in its simple form, can be used to relocate tactile input from an artificial hand to the forearm and that the system can coexist with a myoelectric control systems. The proposed system may be a valuable addition to users of myoelectric prosthesis providing conscious sensory feedback during manipulation of objects.
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| 6. |
- Antfolk, Christian, et al.
(författare)
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Exploring the conditions for PhD-students to develop abilities to independently formulate research questions
- 2015
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Rapport (populärvet., debatt m.m.)abstract
- Developing an ability to independently formulate research questions is an important goal in doctoral education. During a seminar in the “Docent course”, accredited by Genombrottet at Lund University, the authors behind this paper ended up in a discussion on the actual conditions for developing such ability. During the discussions, the authors, based on their own experiences, identified several conditions that could hamper the PhD-students’ abilities to develop the skills required to independently formulate research questions. Examples of such conditions were: involvement in projects where objectives and deliverables already were stated by a funder, a lack of discussions with supervisors early in the PhD-process, and/or a lack of proper training. The authors also discussed if working with a compilation thesis automatically lead to contrived overall research questions, which resulted primarily as an afterthought at a very late stage in the process.
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| 7. |
- Antfolk, Christian, et al.
(författare)
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Sensory feedback in upper limb prosthetics.
- 2013
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Ingår i: Expert Review of Medical Devices. - : Informa UK Limited. - 1745-2422 .- 1743-4440. ; 10:1, s. 45-54
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Tidskriftsartikel (refereegranskat)abstract
- One of the challenges facing prosthetic designers and engineers is to restore the missing sensory function inherit to hand amputation. Several different techniques can be employed to provide amputees with sensory feedback: sensory substitution methods where the recorded stimulus is not only transferred to the amputee, but also translated to a different modality (modality-matched feedback), which transfers the stimulus without translation and direct neural stimulation, which interacts directly with peripheral afferent nerves. This paper presents an overview of the principal works and devices employed to provide upper limb amputees with sensory feedback. The focus is on sensory substitution and modality matched feedback; the principal features, advantages and disadvantages of the different methods are presented.
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| 8. |
- Antfolk, Christian, et al.
(författare)
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SmartHand tactile display: A new concept for providing sensory feedback in hand prostheses.
- 2010
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Ingår i: Scandinavian Journal of Plastic and Reconstructive Surgery and Hand Surgery. - : Medical Journals Sweden AB. - 1651-2073. ; 44, s. 50-53
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Tidskriftsartikel (refereegranskat)abstract
- Abstract A major drawback with myoelectric prostheses is that they do not provide the user with sensory feedback. Using a new principle for sensory feedback, we did a series of experiments involving 11 healthy subjects. The skin on the volar aspect of the forearm was used as the target area for sensory input. Experiments included discrimination of site of stimuli and pressure levels at a single stimulation point. A tactile display based on digital servomotors with one actuating element for each of the five fingers was used as a stimulator on the forearm. The results show that the participants were able to discriminate between three fingers with an accuracy of 97%, between five fingers with an accuracy of 82%, and between five levels with an accuracy of 79%. The tactile display may prove a helpful tool in providing amputees with sensory feedback from a prosthetic hand by transferring tactile stimuli from the prosthetic hand to the skin at forearm level.
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| 9. |
- Antfolk, Christian, et al.
(författare)
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Using EMG for Real-time Prediction of Joint Angles to Control a Prosthetic Hand Equipped with a Sensory Feedback System
- 2010
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Ingår i: Journal of Medical and Biological Engineering. - : Taiwanese Society of Biomedical Engineering. - 1609-0985. ; 30:6, s. 399-405
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Tidskriftsartikel (refereegranskat)abstract
- All commercially available upper limb prosthesis controllers only allow the hand to be commanded in an open and close fashion without any sensory feedback to the user. Here the evaluation of a multi-degree of freedom hand controlled using a real-time EMG pattern recognition algorithm and incorporating a sensory feedback system is reported. The hand prosthesis, called SmartHand, was controlled in real-time by using 16 myoelectric signals from the residual limb of a 25-year old male transradial amputee in a two day long evaluation session. Initial training of the EMG pattern recognition algorithm was performed with a dataglove fitted to the contralateral hand recording joint angle positions of the fingers and mapping joint angles of the fingers to the EMG data. In the following evaluation sessions, the myoelectric signals were classified using local approximation and lazy learning, producing finger joint angle outputs and consequently controlling the prosthetic hand. Sensory information recorded from force sensors in the artificial hand was relayed to actuators, integrated in the socket of the prosthesis, continuously delivering force sensory feedback stimulations to the stump of the amputee. The participant was able to perform several dextrous movements as well as functional grip tasks after only two hours of training and increased his controllability during the two day session. In the final evaluation session a mean classification accuracy of 86% was achieved.
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| 10. |
- Antfolk, Maria, et al.
(författare)
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A single inlet two-stage acoustophoresis chip enabling tumor cell enrichment from white blood cells
- 2015
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Ingår i: Lab on a Chip. - 1473-0189. ; 15:9, s. 2102-2109
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Tidskriftsartikel (refereegranskat)abstract
- Metastatic disease is responsible for most cancer deaths, and hematogenous spread through circulating tumor cells (CTC) is a prerequisite for tumor dissemination. CTCs may undergo epithelial–mesenchymal transition where many epithelial cell characteristics are lost. Therefore, CTC isolation systems relying on epithelial cell markers are at risk of losing important subpopulations of cells. Here, a simple acoustophoresis-based cell separation instrument is presented. Cells are uniquely separated while maintained in their initial suspending medium, thus eliminating the need for a secondary cell-free medium to hydrodynamically pre-position them before the separation. When characterizing the system using polystyrene particles, 99.6 ± 0.2% of 7 μm diameter particles were collected through one outlet while 98.8 ± 0.5% of 5 μm particles were recovered through a second outlet. Prostate cancer cells (DU145) spiked into blood were enriched from white blood cells at a sample flow rate of 100 μL min−1 providing 86.5 ± 6.7% recovery of the cancer cells with 1.1 ± 0.2% contamination of white blood cells. By increasing the acoustic intensity a recovery of 94.8 ± 2.8% of cancer cells was achieved with 2.2 ± 0.6% contamination of white blood cells. The single inlet approach makes this instrument insensitive to acoustic impedance mismatch; a phenomenon reported to importantly affect accuracy in multi-laminar flow stream acoustophoresis. It also offers a possibility of concentrating the recovered cells in the chip, as opposed to systems relying on hydrodynamic pre-positioning which commonly dilute the target cells.
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