Callum Lamont

University College London

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Ahmad Shah Idil

University College London

Nick Donaldson

University College London

Kambiz Nanbakhsh

Delft University of Technology

Vasiliki Giagka

Fraunhofer Institute for Reliability and Microintegration

Anne Vanhoestenberghe

King's College London

Federico Mazza

Imperial College London

Csaba Dücső

Centre for Energy Research

Magda Sachs

Royal College of Paediatrics and Child Health

Mary Broadfoot

Royal Hospital for Children

Timothy G. Constandinou

Imperial College London

Cooperative Institutions

University College London

University of Melbourne

Holst Centre (Netherlands)

Delft University of Technology

Hungarian Academy of Sciences

HUN-REN Research Centre for Natural Sciences

Pázmány Péter Catholic University

Institute of Child Health

BioElectronics (United States)

Menzies School of Health Research

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Silicone encapsulation of thin-film SiO_x, SiO_xN_y and SiC for modern electronic medical implants: a comparative long-term ageing study

Journal of Neural Engineering (2021)

Callum Lamont Thomas C Grego Kambiz Nanbakhsh Ahmad Shah Idil Vasiliki Giagka

Objective.Ensuring the longevity of implantable devices is critical for their clinical usefulness. This is commonly achieved by hermetically sealing the sensitive electronics in a water impermeable housing, however, this method limits miniaturisation. Alternatively, silicone encapsulation has demonstrated long-term protection of implanted thick-film electronic devices. However, much of the current conformal packaging research is focused on more rigid coatings, such as parylene, liquid crystal polymers and novel inorganic layers. Here, we consider the potential of silicone to protect implants using thin-film technology with features 33 times smaller than thick-film counterparts.Approach.Aluminium interdigitated comb structures under plasma-enhanced chemical vapour deposited passivation (SiOx, SiOxNy, SiOxNy+ SiC) were encapsulated in medical grade silicones, with a total of six passivation/silicone combinations. Samples were aged in phosphate-buffered saline at 67 ∘C for up to 694 days under a continuous ±5 V biphasic waveform. Periodic electrochemical impedance spectroscopy measurements monitored for leakage currents and degradation of the metal traces. Fourier-transform infrared spectroscopy, x-ray photoelectron spectroscopy, focused-ion-beam and scanning-electron- microscopy were employed to determine any encapsulation material changes.Main results.No silicone delamination, passivation dissolution, or metal corrosion was observed during ageing. Impedances greater than 100 GΩ were maintained between the aluminium tracks for silicone encapsulation over SiOxNyand SiC passivations. For these samples the only observed failure mode was open-circuit wire bonds. In contrast, progressive hydration of the SiOxcaused its resistance to decrease by an order of magnitude.Significance.These results demonstrate silicone encapsulation offers excellent protection to thin-film conducting tracks when combined with appropriate inorganic thin films. This conclusion corresponds to previous reliability studies of silicone encapsulation in aqueous environments, but with a larger sample size. Therefore, we believe silicone encapsulation to be a realistic means of providing long-term protection for the circuits of implanted electronic medical devices.

Passivation

10.1088/1741-2552/abf0d6

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Citations (19)

Early diet in preterm babies and later intelligence quotient

BMJ (1999)

D. Behrman Mary Broadfoot Phyll Buchanan Callum Lamont Magda Sachs

Is there a rationale for rationing chronic dialysis? Two points need clarificationEditor-I agree with Chandna et al that late referral is an important factor in the survival of patients receiving dialysis. 1I am unaware, however, of the source of their information that an NHS consensus statement recommends that nephrology referrals be made at a serum creatinine concentration > 135 mol/l in women and > 180 mol/l in men.The workload generated by this practice would be so enormous that British renal units under present conditions would be unable to cope.I am also concerned that of the authors' 292 patients receiving dialysis, 26 (admittedly high risk) patients spent 44% of their lives in hospital.The costs of inpatient treatment for these high risk patients would be substantially higher than the average cost of £250 a day that the authors quote.

10.1136/bmj.318.7198.1625

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A Bayesian Demonstration of Reliability for Encapsulated Implanted Electronics

Callum Lamont Federico Mazza Nick Donaldson

The long term performance of implanted medical devices is critically affected by their packaging materials. Traditional hermetic enclosures are a hindrance to miniaturisation which might be avoided by polymer encapsulation. However, much uncertainty remains regarding such an approach for chronic implants. It is difficult to extract meaning from lifetime experiments performed on arbitrary test structures and before many highly reliable devices have actually failed. In this study, we describe an accelerated aging experiment on devices that employ test structures fabricated on a silicone encapsulated 0.35 μm CMOS technology. Samples are aged at 47, 67 and 87 °C under a constant 5V DC bias. After over 300 days of aging, of the 36 samples under test, there have only been four failures. Three failures are attributed to the interconnect to the measurement system, with the remaining failure due to delamination of the silicone encapsulant over wirebonds. By employing a Bayesian reliability analysis of the near-zero failure data we demonstrate a 1 ^st failure percentile for the CMOS components of greater than 92 days when aged at 87 °C, calculated at a 95% confidence level, which approximately corresponds to over 8 years at 37 °C.

10.1109/ner.2019.8717034

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On the longevity and inherent hermeticity of silicon-ICs: evaluation of bare-die and PDMS-coated ICs after accelerated aging and implantation studies

Nature Communications (2025)

Kambiz Nanbakhsh Ahmad Shah Idil Callum Lamont Csaba Dücső Ömer Can Akgun

Abstract Silicon integrated circuits (ICs) are central to the next-generation miniature active neural implants, whether packaged in soft polymers for flexible bioelectronics or implanted as bare die for neural probes. These emerging applications bring the IC closer to the corrosive body environment, raising reliability concerns, particularly for chronic use. Here, we evaluate the inherent hermeticity of bare die ICs, and examine the potential of polydimethylsiloxane (PDMS), a moisture-permeable elastomer, as a standalone encapsulation material. For this aim, the electrical and material performance of ICs sourced from two foundries was evaluated through one-year accelerated in vitro and in vivo studies. ICs featured custom-designed test structures and were partially PDMS coated, creating two regions on each chip, uncoated “bare die” and “PDMS-coated”. During the accelerated in vitro study, ICs were electrically biased and periodically monitored. Results revealed stable electrical performance, indicating the unaffected operation of ICs even when directly exposed to physiological fluids. Despite this, material analysis revealed IC degradation in the bare regions. PDMS-coated regions, however, revealed limited degradation, making PDMS a suitable IC encapsulant for years-long implantation. Based on the new insights, guidelines are proposed that may enhance the longevity of implantable ICs, broadening their applications in the biomedical field.

Polydimethylsiloxane

Bioelectronics

10.1038/s41467-024-55298-4

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Author Correction: On the longevity and inherent hermeticity of silicon-ICs: evaluation of bare-die and PDMS-coated ICs after accelerated aging and implantation studies

Nature Communications (2025)

Kambiz Nanbakhsh Ahmad Shah Idil Callum Lamont Csaba Dücső Ömer Can Akgun

10.1038/s41467-025-57175-0

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Tuning the viscosity of halogen free bulk heterojunction inks for inkjet printed organic solar cells

Organic Electronics (2014)

Callum Lamont Tamara M. Eggenhuisen Michiel J. J. Coenen Thijs W.L. Slaats Ronn Andriessen

Polystyrene

Hildebrand solubility parameter

10.1016/j.orgel.2014.10.052

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Citations (29)

SUCCESSFUL PREGNANCY IN A 44‐YEAR‐OLD HAEMODIALYSIS PATIENT

BJOG An International Journal of Obstetrics & Gynaecology (1978)

M.H.R. Sheriff M Hardman Callum Lamont Robert K. Shepherd David J. Warren

A 44-year-old patient had been treated by intermittent haemodialysis for almost three years when she presented with a 28-week pregnancy. Successful delivery of a healthy but small infant was achieved by Caesarean section at 36 weeks. The successful outcome of this pregnancy was attributed to close control of the haemoglobin concentration and blood chemistry, and to increased frequency of dialysis. The relative value of various chemical tests of fetal maturity in the presence of maternal renal failure are discussed.

Fetal monitoring

10.1111/j.1471-0528.1978.tb14900.x

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Citations (31)

A conductive stretchable PEDOT–elastomer hybrid with versatile processing and properties

Journal of Materials Chemistry B (2015)

Callum Lamont Orawan Winther‐Jensen Bjørn Winther‐Jensen

Herein we describe the use of vapour phase polymerisation (VPP) to form an elastomeric conducting hybrid, via the combination of poly(3,4-ethylene dioxythiophene) (PEDOT) and poly(glycerol sabecate) (PGS). The extent of PGS curing inversely affected the degree of PEDOT penetration in the material. At longer cure times, samples exhibited a negligible strain-resistance relationship. However, by reducing cure times and allowing greater penetration of PEDOT into PGS, more stable properties were observed over repeated deformation. The isolation of the PEDOT towards the surface allowed the use of laser engraving to pattern conducting tracks with ease. Such a benefit points to its potential for uninvolved, rapid manufacture of electrode arrays for biomedical devices or to allow precision cell interaction in tissue engineering.

Stretchable electronics

10.1039/c5tb02009c

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Citations (9)

Protecting breast feeding from breast milk substitutes

BMJ (1998)

Harvey Marcovitch Mary Lynch Katherine Dodd Anthony Costello Harshpal Singh Sachdev

Editor—In its submission to the Acheson inquiry on poverty and health (the findings of which are expected to be published in autumn 1998) the Royal College of Paediatrics and Child Health proposed interventions to increase the number of women breast feeding their babies. At the college’s 1998 annual general meeting Unicef accepted an invitation to set up a stand at the trade exhibition to provide information on its baby friendly initiative, which was designed to help establish breast feeding and was launched in 1991. Also at that meeting members and fellows reaffirmed their unequivocal support for the practice and promotion of breast feeding in a policy statement. This was policy states that “women should be encouraged to practice exclusive breastfeeding for the first 4-6 months of their infant’s life. Thereafter, infants should be enabled to breastfeed while receiving appropriate and adequate weaning food for as long as this meets with their mothers’ wishes and convenience.”1 Therefore, we were surprised and disappointed to read some of the sentiments expressed in the editorial by Costello and Sachdev on encouraging breast feeding which reminded doctors that manufacturers of infant milk substitutes may attempt to seek “endorsement by association” or “passivity towards their products.”2 They cited as examples the failure of the Royal College of Paediatrics and Child Health to join the interagency group on monitoring breast feeding and the fact that the college accepts research funds from manufacturers of breast milk substitutes. In fact, the college declined to join the group not because it was opposed to its aims but because of legitimate concerns about the proposed research methodology. The college takes the issue of commercial sponsorship seriously, not only in the area of breast milk substitutes. At the 1997 annual general meeting the college’s ethics committee was asked to investigate the marketing of breast milk substitutes and provide recommendations for action. Its report will be ready later this year. In the meantime no further research funding or donations have been or will be accepted from manufacturers of infant formula.

Promotion (chess)

10.1136/bmj.317.7163.949a

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Citations (4)

Protecting breast feeding from breast milk substitutes. Health workers must be protected from conflicts of interest.

PubMed (1998)

Mary Broadfoot Jane Britten Phyll Buchanan Karen Hogg Callum Lamont

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Citations (1)