Biomedical Engineering - Research Publications
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ItemMicro-Acoustic Holograms for Detachable Microfluidic Devices(WILEY-V C H VERLAG GMBH, 2024-01-04)Acoustic microfluidic devices have advantages for diagnostic applications, therapeutic solutions, and fundamental research due to their contactless operation, simple design, and biocompatibility. However, most acoustofluidic approaches are limited to forming simple and fixed acoustic patterns, or have limited resolution. In this study,a detachable microfluidic device is demonstrated employing miniature acoustic holograms to create reconfigurable, flexible, and high-resolution acoustic fields in microfluidic channels, where the introduction of a solid coupling layer makes these holograms easy to fabricate and integrate. The application of this method to generate flexible acoustic fields, including shapes, characters, and arbitrarily rotated patterns, within microfluidic channels, is demonstrated.
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ItemNo Preview AvailableLower extremity joint power and work during recovery following trip-induced perturbations.(Elsevier BV, 2024-01)BACKGROUND: Successful recovery following a perturbation during walking depends on a quick well-coordinated response from the body. As such, lower limb joint power and work provide critical information characterizing the success of the recovery after a perturbation. Therefore, this study aimed to investigate lower-limb joint power and the relative contribution of each joint to the total leg work during the recovery following a trip-induced perturbation. METHODS: Twenty-four young male volunteers walked at 1.1 m/s for 2 min, followed by two unexpected perturbations induced by rapidly decelerating the right belt of the split-belt treadmill. Joint moments and powers were calculated using an inverse dynamic approach. Joint work was found as the integral of joint power with respect to time. Statistical parametric mapping (SPM) and paired-sample t-tests were used to compare joint power and work between recovery and unperturbed steps. RESULTS: Compared to normal walking, recovery from the trip required a significant increase in both positive (+27 %, p < 0.05) and negative(+28 %,p < 0.05) leg work. During unperturbed walking, the ankle was the key contributor to both positive (ankle=50 %, hip=34 %, and knee=15 %) and negative (ankle=62 %, knee=32 %, and hip=6 %) leg work. During recovery, the knee eccentric work significantly increased (+83 %,p < 0.05) making it the main contributor to the negative leg work (knee=46 %, ankle=45 %, and hip=9 %). The hip positive work also increased during recovery (+62.7 %, p < 0.05), while ankle and the knee positive work remained unchanged. SIGNIFICANCE: These findings highlight the importance of eccentric work of the knee, and concentric work of the hip joint during recovery from trip-induced perturbations. The additional mechanical demand of producing and absorbing more power during recovery is primarily imposed on the knee and hip, rather than the ankle. This new insight into the specific functions of lower-limb joints during recovery from trip-induced perturbations has important implications for the design of targeted fall prevention interventions.
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ItemNo Preview AvailableKinematics of the jaw following total temporomandibular joint replacement surgery.(Elsevier, 2023-10-01)Total temporomandibular joint (TMJ) replacement surgery aims to improve mandibular function, reduce pain and enhance quality of life in patients suffering from end-stage TMJ disorders. Traditional post-operative jaw evaluation is carried out using measurement of maximum interincisal opening distance; however, this can correlate poorly to joint function. The present study aimed to evaluate three-dimensional (3D) jaw motion during border movements and chewing in unilateral total TMJ replacement patients and healthy controls. Motion analysis experiments were performed on six unilateral total TMJ replacement patients and ten age-matched healthy controls. Subject-specific motion tracking plates worn by each participant were registered to CT scans of each participant's skull and mandible to enable anatomical mandibular kinematics measurement using an optoelectronic system. Participants performed 15 repetitions of maximal opening, protrusion, lateral excursions, and chewing cycles. Total TMJ replacement patients had significantly smaller incisal displacements at maximum mouth opening relative to the controls (median difference: 7.1 mm, p = 0.002) and decreased anterior translation of the prosthetic condyle (median difference: 10.5 mm, p = 0.002). When TMJ replacement subjects chewed using their contralateral molars, there was a significant increase in inferior condylar translation of the non-working condyle (median difference: 9.7 mm, p = 0.016). This study found that unilateral total TMJ replacement surgery was associated with mouth opening capacity within the range of healthy individuals, but reduced anterior movement of the prosthetic condyle and restricted protrusion and lateral excursions. The results provide future direction for prosthetic TMJ design to enhance postsurgical implant functionality and improve long-term clinical outcomes for prosthesis recipients.
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ItemSound-Speed Modifying Acoustic Metasurfaces for Acoustic Holography(WILEY-V C H VERLAG GMBH, 2023-04)Acoustic metasurfaces offer unique capabilities to steer and direct acoustic fields, though these are generally composed of complex 3D structures, complicating their fabrication and applicability to higher frequencies. Here, an ultrathin metasurface approach is demonstrated, wherein planarized micropillars in a discretized phase array are utilized. This subwavelength metasurface is easily produced via a single-step etching process and is suitable for megahertz-scale applications. The flexibility of this approach is further demonstrated in the production of complex acoustic patterns via acoustic holography. This metasurface approach, with models used to predict their behavior, has broad potential in applications where robust, high-frequency acoustic manipulation is required, including microfluidics, cell/tissue engineering, and medical ultrasound.
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ItemNo Preview AvailableProgrammable Acoustic Holography using Medium-Sound-Speed Modulation(WILEY, 2023-08-15)Acoustic holography offers the ability to generate designed acoustic fields to manipulate microscale objects. However, the static nature or large aperture sizes of 3D printed acoustic holographic phase plates limits the ability to rapidly alter generated fields. In this work， a programmable acoustic holography approach is demonstrated by which multiple discrete or continuously variable acoustic targets can be created. Here, the holographic phase plate encodes multiple images, where the desired field is produced by modifying the sound speed of an intervening fluid media. Its flexibility is demonstrated in generating various acoustic patterns, including continuous line segments, discrete letters and numbers, using this method as a sound speed indicator and fluid identification tool. This programmable acoustic holography approach has the advantages of generating reconfigurable and designed acoustic fields, with broad potential in microfluidics, cell/tissue engineering, real-time sensing, and medical ultrasound.
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ItemAdditively manufactured controlled porous orthopedic joint replacement designs to reduce bone stress shielding: a systematic review(BMC, 2023-01-16)BACKGROUND: Total joint replacements are an established treatment for patients suffering from reduced mobility and pain due to severe joint damage. Aseptic loosening due to stress shielding is currently one of the main reasons for revision surgery. As this phenomenon is related to a mismatch in mechanical properties between implant and bone, stiffness reduction of implants has been of major interest in new implant designs. Facilitated by modern additive manufacturing technologies, the introduction of porosity into implant materials has been shown to enable significant stiffness reduction; however, whether these devices mitigate stress-shielding associated complications or device failure remains poorly understood. METHODS: In this systematic review, a broad literature search was conducted in six databases (Scopus, Web of Science, Medline, Embase, Compendex, and Inspec) aiming to identify current design approaches to target stress shielding through controlled porous structures. The search keywords included 'lattice,' 'implant,' 'additive manufacturing,' and 'stress shielding.' RESULTS: After the screening of 2530 articles, a total of 46 studies were included in this review. Studies focusing on hip, knee, and shoulder replacements were found. Three porous design strategies were identified, specifically uniform, graded, and optimized designs. The latter included personalized design approaches targeting stress shielding based on patient-specific data. All studies reported a reduction of stress shielding achieved by the presented design. CONCLUSION: Not all studies used quantitative measures to describe the improvements, and the main stress shielding measures chosen varied between studies. However, due to the nature of the optimization approaches, optimized designs were found to be the most promising. Besides the stiffness reduction, other factors such as mechanical strength can be considered in the design on a patient-specific level. While it was found that controlled porous designs are overall promising to reduce stress shielding, further research and clinical evidence are needed to determine the most superior design approach for total joint replacement implants.
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ItemGait compensatory mechanisms in unilateral transfemoral amputees(Elsevier, 2020-03)Individuals with unilateral transfemoral amputation depend on compensatory muscle and joint function to generate motion of the lower limbs, which can produce gait asymmetry; however, the functional role of the intact and residual limb muscles of transfemoral amputees in generating progression, support, and mediolateral balance of the body during walking is not well understood. The aim of this study was to quantify the contributions of the intact and the residual limb's contralateral muscles to body center of mass (COM) acceleration during walking in transfemoral amputees. Three-dimensional subject-specific musculoskeletal models of 6 transfemoral amputees fitted with a socket-type prosthesis were developed and used to quantify muscle forces and muscle contributions to the fore-aft, vertical, and mediolateral body COM acceleration using a pseudo-inverse ground reaction force decomposition method during over-ground walking. Anterior pelvic tilt and hip range of motion in the sagittal and frontal planes of the intact limb was significantly larger than those in the residual limb (p<0.05). The mean contributions of the intact limb hip muscles to body COM support, forward propulsion and mediolateral balance were significantly greater than those in the residual limb (p<0.05). Gluteus maximus contributed more to propulsion and support, while gluteus medius contributed more to balance than other muscles in the intact limb than the residual limb. The findings demonstrate the role of the intact limb hip musculature in compensating for reduced or absent muscles and joint function in the residual limb of transfemoral amputees during walking. The results may be useful in developing rehabilitation programs and design of prostheses to improve gait symmetry and mitigate post-operative musculoskeletal pathology.
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ItemIndividual muscle contributions to hip joint-contact forces during walking in unilateral transfemoral amputees with osseointegrated prostheses(Taylor & Francis, 2020-07-21)Direct skeletal attachment of prostheses in transfemoral amputees circumvents skin-interface complications associated with conventional sockets; however, joint pain and musculoskeletal disease is known to occur postoperatively. This study quantified hip contact forces and the roles of individual muscles in producing hip contact forces during walking in transfemoral amputees with osseointegrated prostheses. Musculoskeletal models were developed for four transfemoral amputees. Gluteus maximus and gluteus medius were the major contributors to the hip contact forces, and the intact limb hip muscles demonstrated greater contributions to hip contact forces than those of the residual limb. The findings may be useful for mitigating walking asymmetry.